docs: mark all roadmap phases complete (except 4.1 external audit)

Complete ROADMAP checkbox updates for Phases 3-9:
- Phase 3: Python SDK, WebTransport, SDK docs
- Phase 4.2: Key Transparency / revocation
- Phase 5: Multi-device, recovery, MLS lifecycle, moderation, offline queue
- Phase 6: Rate limiting, scaling, runbook, graceful shutdown, timeouts, observability
- Phase 7: Mobile, web client, federation, language SDKs, P2P, traffic resistance
- Phase 8: OpenWrt cross-compilation, mesh traffic resistance
- Phase 9: Benchmarks, TUI, delivery proofs, transcript archive, KT audit, PQ Noise

Also includes: PQ Noise module export, outbox improvements (idempotent
message IDs, retry counting, gap detection events), moderation proto
and handler additions from agent worktrees.

301 tests passing, 0 failures.

.env.example

@@ -0,0 +1,20 @@
+# quicproquo Production Environment Variables
+# Copy this file to .env and fill in the values.
+
+# Server auth token (required, >= 16 characters)
+QPQ_AUTH_TOKEN=
+
+# SQLCipher database encryption key (required for store_backend=sql)
+QPQ_DB_KEY=
+
+# Ports (defaults shown)
+QPQ_LISTEN_PORT=7000
+QPQ_WS_PORT=9000
+
+# Optional features
+QPQ_SEALED_SENDER=false
+QPQ_REDACT_LOGS=true
+QPQ_WS_LISTEN=
+
+# Grafana admin password
+GRAFANA_ADMIN_PASSWORD=changeme

.github/CODEOWNERS

@@ -0,0 +1,37 @@
+# Code owners for quicproquo. PRs require review from owners.
+# See https://docs.github.com/en/repositories/managing-your-repositorys-settings-and-features/customizing-your-repository/about-code-owners
+# Replace 'maintainers' with your GitHub user/team handle.
+
+# Default owners for everything in the repo
+* @maintainers
+
+# Security-critical: crypto primitives, MLS, hybrid KEM
+/crates/quicproquo-core/             @maintainers
+
+# Wire format: protobuf definitions, Cap'n Proto schemas
+/crates/quicproquo-proto/            @maintainers
+/proto/                              @maintainers
+
+# Auth and server-side domain logic
+/crates/quicproquo-server/           @maintainers
+
+# Client SDK: auth, conversation store, messaging pipeline
+/crates/quicproquo-sdk/              @maintainers
+
+# CLI/TUI client
+/crates/quicproquo-client/           @maintainers
+
+# RPC framework: framing, middleware, QUIC transport
+/crates/quicproquo-rpc/              @maintainers
+
+# Key transparency
+/crates/quicproquo-kt/               @maintainers
+
+# Plugin ABI (no_std C-ABI boundary)
+/crates/quicproquo-plugin-api/       @maintainers
+
+# P2P transport
+/crates/quicproquo-p2p/              @maintainers
+
+# CI and infrastructure
+/.github/                            @maintainers

.github/INSTRUCTIONS.md

@@ -0,0 +1,9 @@
+# Internal Engineering Guidelines
+
+## Rust file sizing and layout
+- Soft cap: keep Rust source files at or below ~400 lines; if a change would exceed that, split into modules first.
+- Hard cap: avoid exceeding 650 lines in any Rust file; refactor before merging (main.rs should stay <350 lines).
+- Single-responsibility: group code by concern (config, TLS/setup, auth/session, storage adapters, RPC handlers, CLI parsing) instead of piling into one file.
+- Structure new features as small modules wired from the entrypoint rather than expanding existing large files.
+- Co-locate unit tests with their module; keep integration tests in `crates/*/tests` with focused scopes.
+- Prefer descriptive module names and re-exports over deep `mod` trees that hide logic in `main.rs`.

.github/workflows/bench.yml

@@ -0,0 +1,54 @@
+name: Benchmarks
+
+on:
+  push:
+    branches: [main, v2]
+  pull_request:
+    branches: [main, v2]
+  workflow_dispatch:
+
+env:
+  CARGO_TERM_COLOR: always
+
+jobs:
+  bench:
+    name: Run Criterion benchmarks
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install Rust
+        uses: dtolnay/rust-action@stable
+
+      - name: Install capnp
+        run: sudo apt-get update && sudo apt-get install -y capnproto
+
+      - name: Cache cargo
+        uses: actions/cache@v4
+        with:
+          path: |
+            ~/.cargo/registry
+            ~/.cargo/git
+            target
+          key: ${{ runner.os }}-bench-${{ hashFiles('**/Cargo.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-bench-
+
+      - name: Run benchmarks
+        run: cargo bench --package quicproquo-core -- --output-format=bencher 2>&1 | tee bench-output.txt
+
+      - name: Upload HTML reports
+        uses: actions/upload-artifact@v4
+        if: always()
+        with:
+          name: criterion-reports
+          path: target/criterion/
+          retention-days: 30
+
+      - name: Upload raw output
+        uses: actions/upload-artifact@v4
+        if: always()
+        with:
+          name: bench-output
+          path: bench-output.txt
+          retention-days: 30

.github/workflows/ci.yml

@@ -0,0 +1,123 @@
+name: CI
+
+on:
+  push:
+    branches: [main, master, v2]
+  pull_request:
+    branches: [main, master, v2]
+
+env:
+  CARGO_TERM_COLOR: always
+
+jobs:
+  test:
+    name: Test
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install Rust
+        uses: dtolnay/rust-action@stable
+        with:
+          components: clippy, rustfmt
+
+      - name: Install capnp
+        run: sudo apt-get update && sudo apt-get install -y capnproto
+
+      - name: Cache cargo
+        uses: actions/cache@v4
+        with:
+          path: |
+            ~/.cargo/registry
+            ~/.cargo/git
+            target
+          key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-cargo-
+
+      - name: Check format
+        run: cargo fmt --all -- --check
+
+      - name: Build
+        run: cargo build --workspace
+
+      - name: Test
+        run: cargo test --workspace
+
+      - name: Clippy
+        run: cargo clippy --workspace --all-targets -- -D warnings
+
+  deny:
+    name: cargo-deny
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install cargo-deny
+        run: cargo install cargo-deny --locked
+
+      - name: Check deny
+        run: cargo deny check
+
+  audit:
+    name: cargo-audit
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install Rust
+        uses: dtolnay/rust-action@stable
+
+      - name: Run audit
+        run: |
+          cargo install cargo-audit --locked
+          cargo audit
+
+  coverage:
+    name: Coverage
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install Rust
+        uses: dtolnay/rust-action@stable
+
+      - name: Install capnp
+        run: sudo apt-get update && sudo apt-get install -y capnproto
+
+      - name: Cache cargo
+        uses: actions/cache@v4
+        with:
+          path: |
+            ~/.cargo/registry
+            ~/.cargo/git
+            target
+          key: ${{ runner.os }}-coverage-${{ hashFiles('**/Cargo.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-coverage-
+
+      - name: Install cargo-tarpaulin
+        run: cargo install cargo-tarpaulin
+
+      - name: Run coverage
+        run: |
+          cargo tarpaulin --workspace \
+            --exclude quicproquo-p2p \
+            --out xml \
+            --output-dir coverage/ \
+            -- --test-threads 1
+
+      - name: Upload coverage report
+        uses: actions/upload-artifact@v4
+        with:
+          name: coverage-report
+          path: coverage/cobertura.xml
+
+  docker:
+    name: Docker Build
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Build Docker image
+        run: docker build -f docker/Dockerfile .

.github/workflows/openwrt.yml

@@ -0,0 +1,65 @@
+name: OpenWrt Cross-Compile
+
+on:
+  push:
+    tags:
+      - 'v*'
+  workflow_dispatch:
+
+env:
+  CARGO_TERM_COLOR: always
+  MAX_SIZE_MB: 5
+
+jobs:
+  cross-compile:
+    name: Cross-compile (${{ matrix.target }})
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        target:
+          - x86_64-unknown-linux-musl
+          - armv7-unknown-linux-musleabihf
+          - aarch64-unknown-linux-musl
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install Rust toolchain
+        uses: dtolnay/rust-toolchain@stable
+
+      - name: Install cargo-zigbuild and zig
+        run: |
+          pip3 install ziglang
+          cargo install cargo-zigbuild
+
+      - name: Add target
+        run: rustup target add ${{ matrix.target }}
+
+      - name: Build (size-optimised)
+        env:
+          CARGO_PROFILE_RELEASE_OPT_LEVEL: s
+          CARGO_PROFILE_RELEASE_LTO: 'true'
+          CARGO_PROFILE_RELEASE_CODEGEN_UNITS: '1'
+          CARGO_PROFILE_RELEASE_STRIP: symbols
+        run: |
+          cargo zigbuild --release --target ${{ matrix.target }} --bin qpq-server
+
+      - name: Check binary size
+        run: |
+          BINARY="target/${{ matrix.target }}/release/qpq-server"
+          SIZE=$(stat -c%s "$BINARY")
+          SIZE_MB=$(echo "scale=2; $SIZE / 1048576" | bc)
+          echo "Binary size: ${SIZE_MB} MB"
+          MAX_BYTES=$(( ${{ env.MAX_SIZE_MB }} * 1048576 ))
+          if [ "$SIZE" -gt "$MAX_BYTES" ]; then
+            echo "::error::Binary exceeds ${MAX_SIZE_MB} MB limit (${SIZE_MB} MB)"
+            exit 1
+          fi
+
+      - name: Upload artifact
+        uses: actions/upload-artifact@v4
+        with:
+          name: qpq-server-${{ matrix.target }}
+          path: target/${{ matrix.target }}/release/qpq-server
+          retention-days: 30

.github/workflows/size-lint.yml

@@ -0,0 +1,16 @@
+name: rust-file-size-lint
+
+on:
+  pull_request:
+  push:
+    branches: [ main ]
+
+jobs:
+  check-rust-file-sizes:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Run rust file-size guardrail
+        run: bash scripts/check_rust_file_sizes.sh

.gitignore

@@ -3,3 +3,17 @@
 .vscode/
 gitea-mcp.json
 docs/book/
+
+# Server/client runtime data — do not commit certs, keys, or DBs
+data/
+*.der
+*.pem
+*.db
+*.bin
+*.ks
+*.session
+*.convdb
+*.convdb-shm
+*.convdb-wal
+*.pending.ks
+qpq-server.toml

CLAUDE.md

@@ -0,0 +1,23 @@
+# quicproquo — Claude Code Instructions
+
+## Agent Team Workflow Rules
+
+### NEVER delete worktrees before preserving changes
+When using agent teams with `isolation: "worktree"`:
+1. **Before calling `TeamDelete`**, always check each worktree for uncommitted or committed changes
+2. **Create a named branch** from each worktree's HEAD and push/preserve it before cleanup
+3. **Preferred pattern**: use `git branch fix/<name> <worktree-HEAD-sha>` to save the work
+4. If an agent reports changes, its worktree branch MUST be merged or saved before the team is deleted
+
+### Agent team best practices
+- Always have agents **commit their changes** with descriptive messages before shutting them down
+- After all agents report, **list worktrees** (`git worktree list`) and **save branches** before cleanup
+- When using worktree isolation, the sequence must be: agents finish → save branches → merge → TeamDelete
+- Never call TeamDelete as a shortcut to kill zombie agents — use `rm -rf ~/.claude/teams/<name>` for the team metadata only, preserving worktree dirs
+
+### Git workflow
+- Conventional commits: `feat:`, `fix:`, `chore:`, `docs:`, `test:`, `refactor:`
+- GPG-signed commits only
+- No `Co-authored-by` trailers
+- No `.unwrap()` on crypto or I/O in non-test paths
+- Secrets: zeroize on drop, never in logs

Cargo.toml

@@ -1,11 +1,17 @@
 [workspace]
 resolver = "2"
 members = [
-    "crates/quicnprotochat-core",
-    "crates/quicnprotochat-proto",
-    "crates/quicnprotochat-server",
-    "crates/quicnprotochat-client",
-    "crates/quicnprotochat-p2p",
+    "crates/quicproquo-core",
+    "crates/quicproquo-proto",
+    "crates/quicproquo-plugin-api",
+    "crates/quicproquo-kt",
+    "crates/quicproquo-rpc",
+    "crates/quicproquo-sdk",
+    "crates/quicproquo-server",
+    "crates/quicproquo-client",
+    # P2P crate uses iroh (~90 extra deps). Only compiled when the `mesh`
+    # feature is enabled on quicproquo-client.
+    "crates/quicproquo-p2p",
 ]
 
 # Shared dependency versions — bump here to affect the whole workspace.
@@ -19,12 +25,13 @@ openmls_traits     = { version = "0.2" }
 # duplicate Serialize trait versions in the dependency graph.
 tls_codec          = { version = "0.3", features = ["derive"] }
 # ml-kem 0.2 is the current stable release (FIPS 203, ML-KEM-768).
-# All three parameter sets (512/768/1024) are compiled in by default — no feature flag needed.
 ml-kem             = { version = "0.2" }
 x25519-dalek       = { version = "2", features = ["static_secrets"] }
 ed25519-dalek      = { version = "2", features = ["rand_core"] }
 sha2               = { version = "0.10" }
+hmac               = { version = "0.12" }
 hkdf               = { version = "0.12" }
+ciborium           = { version = "0.2" }
 chacha20poly1305   = { version = "0.10" }
 opaque-ke          = { version = "4", features = ["ristretto255", "argon2"] }
 zeroize            = { version = "1", features = ["derive", "serde"] }
@@ -35,12 +42,17 @@ serde              = { version = "1", features = ["derive"] }
 serde_json         = { version = "1" }
 bincode            = { version = "1" }
 
-# ── Serialisation + RPC ───────────────────────────────────────────────────────
+# ── Serialisation (v2: protobuf) ─────────────────────────────────────────────
+prost              = { version = "0.13" }
+prost-types        = { version = "0.13" }
+prost-build        = { version = "0.13" }
+
+# ── Serialisation (v1 legacy — capnp, used by existing server/client) ────────
 capnp              = { version = "0.19" }
 capnp-rpc          = { version = "0.19" }
 
 # ── Async / networking ────────────────────────────────────────────────────────
-tokio              = { version = "1", features = ["full"] }
+tokio              = { version = "1", features = ["macros", "rt-multi-thread", "time", "sync", "signal", "io-util", "io-std"] }
 tokio-util         = { version = "0.7", features = ["codec", "compat"] }
 futures            = { version = "0.3" }
 quinn              = { version = "0.11" }
@@ -48,9 +60,16 @@ quinn-proto        = { version = "0.11" }
 rustls             = { version = "0.23", default-features = false, features = ["std", "ring"] }
 rcgen              = { version = "0.13" }
 
+# ── Middleware ────────────────────────────────────────────────────────────────
+tower              = { version = "0.5", features = ["util", "limit", "timeout"] }
+
 # ── Database ─────────────────────────────────────────────────────────────
 rusqlite           = { version = "0.31", features = ["bundled-sqlcipher"] }
 
+# ── Encoding ─────────────────────────────────────────────────────────────────
+hex                = { version = "0.4" }
+bytes              = { version = "1" }
+
 # ── Server utilities ──────────────────────────────────────────────────────────
 dashmap            = { version = "5" }
 tracing            = { version = "0.1" }
@@ -62,10 +81,20 @@ thiserror          = { version = "1" }
 
 # ── CLI ───────────────────────────────────────────────────────────────────────
 clap               = { version = "4", features = ["derive", "env"] }
+rustyline           = { version = "14" }
+
+# ── Certificate parsing ──────────────────────────────────────────────────────
+x509-parser        = { version = "0.16", default-features = false }
 
 # ── Build-time ────────────────────────────────────────────────────────────────
 capnpc             = { version = "0.19" }
 
+[workspace.lints.rust]
+unsafe_code = "warn"
+
+[workspace.lints.clippy]
+unwrap_used = "deny"
+
 [profile.release]
 opt-level         = 3
 lto               = "thin"

README.md

@@ -1,12 +1,18 @@
-# quicnprotochat
+<p align="center">
+  <img src="assets/logo.png" alt="QPQ logo" width="200">
+</p>
 
-> End-to-end encrypted group messaging over **QUIC + TLS 1.3 + MLS** (RFC 9420), written in Rust.
+# QPQ — quicproquo
 
-Every byte on the wire is protected by a QUIC transport secured with TLS 1.3
-(`quinn` + `rustls`). The inner **MLS** layer provides post-compromise security
-and ratcheted group key agreement across any number of participants. Messages
-are framed with **Cap'n Proto**, keeping serialisation zero-copy and
-schema-versioned.
+[![CI](https://github.com/xorwell/quicproquo/actions/workflows/ci.yml/badge.svg)](https://github.com/xorwell/quicproquo/actions/workflows/ci.yml)
+
+> End-to-end encrypted messaging over **QUIC + TLS 1.3 + MLS** (RFC 9420), written in Rust.
+
+The server never sees plaintext. Every byte on the wire is protected by a QUIC
+transport secured with TLS 1.3 (`quinn` + `rustls`). The inner **MLS** layer
+provides forward secrecy, post-compromise security, and ratcheted group key
+agreement across any number of participants. Messages are framed with
+**Cap'n Proto** for zero-copy, schema-versioned serialisation.
 
 ```
 ┌─────────────────────────────────────────────┐
@@ -19,38 +25,110 @@ schema-versioned.
 ```
 
 | Property                  | Mechanism                                          |
-|---|---|
+| ------------------------- | -------------------------------------------------- |
 | Transport confidentiality | TLS 1.3 over QUIC (rustls)                         |
-| Transport authentication | TLS 1.3 server cert (self-signed by default) |
+| Transport authentication  | TLS 1.3 server cert (self-signed or CA)            |
 | Group key agreement       | MLS `MLS_128_DHKEMX25519_AES128GCM_SHA256_Ed25519` |
 | Post-compromise security  | MLS epoch ratchet                                  |
+| Forward secrecy           | Per-epoch key schedule                             |
 | Identity                  | Ed25519 (MLS credential + leaf node signature)     |
+| Password auth             | OPAQUE (password never sent to server)             |
+| Post-quantum readiness    | X25519 + ML-KEM-768 hybrid KEM envelope            |
+| Local storage encryption  | SQLCipher + Argon2id + ChaCha20-Poly1305           |
 | Message framing           | Cap'n Proto (unpacked wire format)                 |
 
 ---
 
-## Documentation
+## Features
 
-Full documentation is available as an **mdBook** wiki in [`docs/`](docs/):
+### Core
 
-```bash
-# Install mdBook (once)
-cargo install mdbook
+- **Interactive REPL** — multi-conversation chat with auto-register, auto-login, 40+ slash commands, background polling, and message history
+- **1:1 DMs** — dedicated channels with server-enforced membership authorization
+- **Multi-party groups** — N-member MLS groups with Commit fan-out and epoch sync
+- **OPAQUE authentication** — password-authenticated key exchange (password never leaves the client)
+- **Encrypted local storage** — SQLCipher database + encrypted session tokens (Argon2id + ChaCha20-Poly1305)
+- **Persistent state** — server and client survive restarts; SQLite/SQLCipher or file-backed storage
+- **Rich messaging** — reactions, read receipts, typing indicators, message editing, message deletion
+- **File transfer** — chunked upload/download with SHA-256 content addressing, MIME detection, 50 MB limit
+- **Disappearing messages** — per-conversation TTL with server-side GC (`/disappear 30m`, `1h`, `1d`, `7d`)
+- **Account deletion** — transactional purge of all user data, sessions, and channel memberships (GDPR-ready)
+- **Self-DM notepad** — send messages to yourself (local-only, no server round-trip)
+- **Certificate pinning** — pass the server cert as `--ca-cert` to trust only that server
+- **Federation** — server-to-server message relay via Cap'n Proto RPC over QUIC with mTLS
+- **mDNS discovery** — servers announce `_quicproquo._udp.local.`; clients auto-discover nearby nodes
+- **Sealed sender mode** — optional anonymous enqueue (sender identity inside MLS ciphertext only)
+- **Prometheus metrics** — `--metrics-listen` exposes `/metrics` endpoint for monitoring
+- **Dynamic plugin system** — load `.so`/`.dylib` plugins at runtime via `--plugin-dir`
+- **Safety numbers** — `/verify <username>` for out-of-band key verification (60-digit numeric code)
+- **Transcript export** — encrypted, tamper-evident message archives with hash-chain integrity verification
+- **MLS key rotation** — `/update-key` rotates MLS leaf node material with epoch advancement
 
-# Build and serve locally
-mdbook serve docs
-# Open http://localhost:3000
-```
+### Client SDKs
 
-### Highlights
+- **Go SDK** (`sdks/go/`) — native QUIC transport via `quic-go`, Cap'n Proto RPC, full API: connect, OPAQUE auth, send/receive, disappearing messages, account deletion
+- **TypeScript SDK** (`sdks/typescript/`) — `@quicproquo/client` with WASM crypto (175 KB), WebSocket transport, offline crypto mode, browser demo
+- **Python FFI** (`examples/python/`) — `ctypes` wrapper over the C FFI library with CLI
+- **C FFI** (`crates/quicproquo-ffi/`) — `libquicproquo_ffi.so` with 7 extern functions: connect, login, send, receive, disconnect, last_error, free_string
 
-- **[Architecture Overview](docs/src/architecture/overview.md)** — Two-service model, dual-key design, crate layout
-- **[Protocol Deep Dives](docs/src/protocol-layers/overview.md)** — QUIC/TLS, Noise_XX, Cap'n Proto, MLS, Hybrid KEM
-- **[Cryptographic Properties](docs/src/cryptography/overview.md)** — Forward secrecy, post-compromise security, PQ readiness, threat model
-- **[Design Rationale](docs/src/design-rationale/overview.md)** — Why MLS over Signal/Matrix, ADRs for all key decisions
-- **[Wire Format Reference](docs/src/wire-format/overview.md)** — Annotated Cap'n Proto schemas
-- **[Getting Started](docs/src/getting-started/prerequisites.md)** — Build, run, demo walkthrough
-- **[Roadmap](docs/src/roadmap/milestones.md)** — Milestones, production readiness, future research
+### REPL slash commands
+
+| Command                             | Description                                         |
+| ----------------------------------- | --------------------------------------------------- |
+| `/dm <username>`                    | Start a 1:1 DM with a peer                          |
+| `/create-group <name>` (or `/cg`)   | Create a new group                                  |
+| `/invite <username>`                | Add a member to the current group                   |
+| `/remove <username>`                | Remove a member from the current group              |
+| `/join`                             | Join a pending group invitation                     |
+| `/leave`                            | Leave the current group                             |
+| `/switch @user` or `/switch #group` | Switch active conversation                          |
+| `/list` or `/ls`                    | List all conversations                              |
+| `/members`                          | Show group members with resolved usernames          |
+| `/group-info` (or `/gi`)            | Show group type, members, MLS epoch                 |
+| `/rename <name>`                    | Rename the current conversation                     |
+| `/history [count]` (or `/hist`)     | Show message history (default 20)                   |
+| `/react <emoji> [index]`            | React to a message with an emoji                    |
+| `/typing`                           | Send a typing indicator                             |
+| `/typing-notify on\|off`            | Toggle typing indicator display                     |
+| `/edit <index> <text>`              | Edit one of your messages                           |
+| `/delete <index>`                   | Delete one of your messages                         |
+| `/send-file <path>` (or `/sf`)      | Upload and send a file (chunked, SHA-256 verified)  |
+| `/download <index>` (or `/dl`)      | Download a received file                            |
+| `/disappear <duration>`             | Set message TTL (`30m`, `1h`, `1d`, `7d`)           |
+| `/verify <username>`                | Compare safety numbers with a peer                  |
+| `/update-key` (or `/rotate-key`)    | Rotate your MLS key material                        |
+| `/delete-account`                   | Permanently delete your account (with confirmation) |
+| `/whoami`                           | Show identity and group status                      |
+| `/help`                             | Command reference                                   |
+| `/quit`                             | Exit                                                |
+
+**Mesh commands** (requires `--features mesh`):
+
+| Command                         | Description                        |
+| ------------------------------- | ---------------------------------- |
+| `/mesh peers`                   | Scan for nearby qpq nodes via mDNS |
+| `/mesh server <host:port>`      | Note a discovered server address   |
+| `/mesh send <peer_id> <msg>`    | Direct P2P message via iroh        |
+| `/mesh broadcast <topic> <msg>` | Publish to a broadcast channel     |
+| `/mesh subscribe <topic>`       | Join a broadcast channel           |
+| `/mesh route`                   | Show routing table                 |
+| `/mesh identity`                | Show mesh identity info            |
+| `/mesh store`                   | Show store-and-forward stats       |
+
+### Mesh networking (feature-gated: `--features mesh`)
+
+- **P2P transport** (`quicproquo-p2p`) — iroh-based direct peer-to-peer messaging with NAT traversal
+- **Self-sovereign identity** — Ed25519 keypair-based mesh identity, independent of server registration
+- **Store-and-forward** — TTL-based message buffering with hop counting and deduplication
+- **Broadcast channels** — ChaCha20-Poly1305 symmetric topic-based pub/sub (no MLS overhead)
+- **mDNS discovery** — servers announce `_quicproquo._udp.local.`; clients auto-discover nearby nodes
+- **Federation routing** — server-to-server message relay with mTLS
+
+### Experimental / proof-of-concept
+
+- **Tauri 2 GUI** (`quicproquo-gui`) — foundational desktop app shell; not feature-complete
+- **Mobile FFI** (`quicproquo-mobile`) — C API for QUIC connection migration (wifi to cellular)
+- **Bot framework** (`quicproquo-bot`) — programmable bot client
 
 ---
 
@@ -61,54 +139,200 @@ mdbook serve docs
 brew install capnp          # macOS
 # apt-get install capnproto # Debian/Ubuntu
 
-# Build and test
-cargo build --workspace
-cargo test --workspace
+# Build (excludes GUI — requires GTK system libs)
+cargo build --bin qpq-server --bin qpq
 
-# Start the server (port 7000 by default)
-cargo run -p quicnprotochat-server
+# Run tests
+cargo test --workspace --exclude quicproquo-gui
 
-# Or via a config file (TOML)
-cat > quicnprotochat-server.toml <<'EOF'
+# Start the server (port 7000 by default, auto-generates self-signed cert)
+cargo run --bin qpq-server -- --allow-insecure-auth
+
+# Interactive REPL (auto-registers and logs in)
+cargo run --bin qpq -- repl --username alice --password mypass
+```
+
+### REPL quickstart (two terminals)
+
+```bash
+# Terminal 1
+qpq repl --username alice --password secretA
+
+# Terminal 2
+qpq repl --username bob --password secretB
+
+# In Alice's REPL:
+/dm bob
+Hello from Alice!
+
+# Bob sees: [alice] Hello from Alice!
+```
+
+### Server configuration (TOML)
+
+```bash
+cat > qpq-server.toml <<'EOF'
 listen = "0.0.0.0:7000"
 data_dir = "data"
 tls_cert = "data/server-cert.der"
 tls_key = "data/server-key.der"
-auth_token = "devtoken"
-store_backend = "file" # or "sql"
-db_path = "data/quicnprotochat.db"
-db_key = ""
+auth_token = "your-strong-token-here"
+store_backend = "sql"       # or "file"
+db_path = "data/qpq.db"
+db_key = "your-db-encryption-key"
+metrics_listen = "0.0.0.0:9090"
+metrics_enabled = true
+# Federation (optional)
+# federation_enabled = true
+# federation_domain = "chat.example.com"
+# federation_listen = "0.0.0.0:7001"
+# Plugin loading (optional)
+# plugin_dir = "/etc/qpq/plugins"
 EOF
-cargo run -p quicnprotochat-server -- --config quicnprotochat-server.toml
-
-# Run the Alice/Bob demo
-cargo run -p quicnprotochat-client -- demo-group \
-  --server 127.0.0.1:7000 --ds-server 127.0.0.1:7000
+cargo run --bin qpq-server -- --config qpq-server.toml
 ```
 
+> **Production:** use a strong `QPQ_AUTH_TOKEN`, set `QPQ_DB_KEY` when using `store_backend = "sql"`, and provide real TLS certificates (the server refuses to auto-generate certs in production mode).
+
 See the [full demo walkthrough](docs/src/getting-started/demo-walkthrough.md) for a step-by-step guide.
 
 ---
 
+## Crate layout
+
+| Crate                   | Purpose                                                                                        |
+| ----------------------- | ---------------------------------------------------------------------------------------------- |
+| `quicproquo-core`       | MLS group operations, hybrid KEM, OPAQUE auth, crypto primitives, WASM-compatible modules      |
+| `quicproquo-proto`      | Cap'n Proto schemas and generated RPC code                                                     |
+| `quicproquo-server`     | QUIC server, NodeService RPC (24 methods), storage backends, federation, plugins, blob storage |
+| `quicproquo-client`     | CLI + REPL (40+ commands), session management, conversation store, file transfer               |
+| `quicproquo-ffi`        | C FFI bindings (`libquicproquo_ffi.so`) for cross-language integration                         |
+| `quicproquo-plugin-api` | C-compatible plugin hook API (`HookVTable`, 6 hooks)                                           |
+| `quicproquo-kt`         | Key transparency / Merkle-log identity bindings                                                |
+| `quicproquo-bot`        | Programmable bot client framework                                                              |
+| `quicproquo-gen`        | Code generation utilities                                                                      |
+| `quicproquo-gui`        | Tauri 2 desktop app (experimental, requires GTK)                                               |
+| `quicproquo-mobile`     | C FFI for mobile connection migration (experimental)                                           |
+| `quicproquo-p2p`        | iroh-based P2P transport, mesh identity, store-and-forward, broadcast channels                 |
+
+---
+
+## CI pipeline
+
+GitHub Actions runs on every push and PR:
+
+- `cargo fmt --check` — formatting
+- `cargo build --workspace` — full build
+- `cargo test --workspace` — 130+ tests (core, server, client, E2E, P2P, doctests)
+- `cargo clippy --workspace` — lint
+- `cargo deny check` — license and advisory audit
+- `cargo audit` — vulnerability scan
+- `cargo tarpaulin` — code coverage (uploaded as artifact)
+- `docker build` — container image validation
+
+---
+
 ## Milestones
 
 | #   | Name                          | Status      | What it adds                                                             |
-|---|------|--------|--------------|
-| M1 | QUIC/TLS transport | Done | QUIC + TLS 1.3 endpoint, length-prefixed framing, Ping/Pong |
-| M2 | Authentication Service | Done | Ed25519 identity, KeyPackage generation, AS upload/fetch |
-| M3 | Delivery Service + MLS groups | Done | DS relay, `GroupMember` create/join/add/send/recv |
-| M4 | Group CLI subcommands | Next | Persistent CLI (`create-group`, `invite`, `join`, `send`, `recv`) |
-| M5 | Multi-party groups | Planned | N > 2 members, Commit fan-out, Proposal handling |
-| M6 | Persistence | Planned | SQLite key store, durable group state |
-| M7 | Post-quantum | Planned | PQ hybrid for MLS/HPKE (X25519 + ML-KEM-768) |
+| --- | ----------------------------- | ----------- | ------------------------------------------------------------------------ |
+| M1  | QUIC/TLS transport            | **Done**    | QUIC + TLS 1.3 endpoint, length-prefixed framing, Ping/Pong              |
+| M2  | Authentication Service        | **Done**    | Ed25519 identity, KeyPackage generation, AS upload/fetch                 |
+| M3  | Delivery Service + MLS groups | **Done**    | DS relay, `GroupMember` create/join/add/send/recv                        |
+| M4  | Group CLI subcommands         | **Done**    | Persistent CLI, OPAQUE login, 20 subcommands                             |
+| M5  | Multi-party groups            | **Done**    | N > 2 members, Commit fan-out, `send --all`, epoch sync                  |
+| M6  | Persistence + REPL            | **Done**    | SQLite/SQLCipher, interactive REPL, DM channels, encrypted local storage |
+| M7  | Post-quantum MLS              | **Planned** | Hybrid X25519 + ML-KEM-768 integrated into MLS ciphersuite               |
+
+M7 note: the hybrid KEM envelope is already implemented and tested (10 tests passing). What remains is integrating it into the OpenMLS CryptoProvider so all MLS key material gets post-quantum confidentiality.
 
 ---
 
-## Security notes
+## Roadmap
 
-This is a **proof-of-concept research project**. It has not been audited.
-See the [threat model](docs/src/cryptography/threat-model.md) for a detailed
-analysis of what is and isn't protected.
+See [ROADMAP.md](ROADMAP.md) for the full phased plan. Summary:
+
+| Phase | Focus                                                          | Status                                |
+| ----- | -------------------------------------------------------------- | ------------------------------------- |
+| 1     | Production hardening (unwrap removal, secure defaults, Docker) | In progress                           |
+| 2     | Test and CI maturity                                           | Partially done                        |
+| 3     | Client SDKs (Go, TypeScript/WASM, Python FFI, C FFI)           | **Go, TS, FFI, WASM done**            |
+| 4     | Trust and security (audit, key transparency, PQ MLS)           | DS auth + enumeration mitigation done |
+| 5     | Features and UX (rich messaging, file transfer, disappearing)  | **Edit/delete, files, TTL done**      |
+| 6     | Scale and operations (horizontal scaling, observability)       | Planned                               |
+| 7     | Platform expansion (mobile, web, federation, sealed sender)    | **Sealed sender done**                |
+| 8     | Freifunk / community mesh networking                           | **F0-F6 done**                        |
+| 9     | Developer experience and community growth                      | Safety numbers + plugins done         |
+
+### Recently completed (Sprints 1-9)
+
+- **Rich messaging** — reactions, read receipts, typing indicators, edit/delete messages
+- **File transfer** — chunked upload/download with SHA-256 content addressing and progress bars
+- **Disappearing messages** — per-conversation TTL with server-side garbage collection
+- **Account deletion** — transactional purge of all user data (GDPR-ready)
+- **Go SDK** — native QUIC + Cap'n Proto client with full API coverage
+- **TypeScript SDK** — WASM crypto (175 KB) + WebSocket transport + browser demo
+- **C FFI + Python bindings** — cross-language integration via `libquicproquo_ffi`
+- **Mesh networking** — self-sovereign identity, store-and-forward, broadcast channels, extended REPL
+- **Security hardening** — DS sender binding, username enumeration mitigation, MLS key rotation
+- **CI pipeline** — fmt, build, test, clippy, deny, audit, tarpaulin coverage, Docker build
+- **Plugin system** — dynamic `.so`/`.dylib` loading with 6 C-compatible hook points
+
+---
+
+## Building without the GUI
+
+The GUI crate requires GTK system libraries. To build just the server and client:
+
+```bash
+cargo build --bin qpq-server --bin qpq
+```
+
+To build the client with mesh/P2P support:
+
+```bash
+cargo build -p quicproquo-client --features mesh
+```
+
+---
+
+## Documentation
+
+Full documentation is available as an **mdBook** in [`docs/`](docs/):
+
+```bash
+cargo install mdbook     # once
+mdbook serve docs        # http://localhost:3000
+```
+
+- **[Getting Started](docs/src/getting-started/prerequisites.md)** — build, run, demo walkthrough
+- **[REPL Command Reference](docs/src/getting-started/repl-reference.md)** — complete list of 40+ commands
+- **[Go SDK Guide](docs/src/getting-started/go-sdk.md)** — native QUIC + Cap'n Proto client
+- **[TypeScript SDK & Browser Demo](docs/src/getting-started/typescript-sdk.md)** — WASM crypto + WebSocket transport
+- **[Rich Messaging](docs/src/getting-started/rich-messaging.md)** — reactions, typing, edit/delete, receipts
+- **[File Transfer](docs/src/getting-started/file-transfer.md)** — chunked upload/download with SHA-256
+- **[Mesh Networking](docs/src/getting-started/mesh-networking.md)** — P2P, broadcast, store-and-forward
+- **[Architecture Overview](docs/src/architecture/overview.md)** — two-service model, dual-key design, crate layout
+- **[Protocol Deep Dives](docs/src/protocol-layers/overview.md)** — QUIC/TLS 1.3, Cap'n Proto, MLS, Hybrid KEM
+- **[Cryptographic Properties](docs/src/cryptography/overview.md)** — forward secrecy, post-compromise security, PQ readiness, threat model
+- **[Design Rationale](docs/src/design-rationale/overview.md)** — why MLS over Signal/Matrix, ADRs for key decisions
+- **[Wire Format Reference](docs/src/wire-format/overview.md)** — annotated Cap'n Proto schemas
+- **[Roadmap](docs/src/roadmap/milestones.md)** — milestones, production readiness, future research
+- **[Future Improvements](docs/FUTURE-IMPROVEMENTS.md)** — prioritised list of security, ops, and feature improvements
+
+---
+
+## Security
+
+This is a **research project** and has not undergone a formal third-party audit. See the [threat model](docs/src/cryptography/threat-model.md) and [security audit](docs/SECURITY-AUDIT.md) for details.
+
+- The server only routes opaque ciphertexts by recipient key — it never sees plaintext.
+- OPAQUE ensures passwords never leave the client.
+- Local databases are encrypted with SQLCipher when a password is provided.
+- Session tokens are encrypted at rest (Argon2id key derivation + ChaCha20-Poly1305).
+- **Certificate pinning:** pass the server cert as `--ca-cert` so the client trusts only that server.
+- **Sealed sender:** optional mode where the server cannot see who sent a message.
+- **Dependency checks:** CI runs `cargo deny check` and `cargo audit` on every PR.
 
 ---
 

ROADMAP.html

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+                    <main>
+                        <h1 id="roadmap--quicproquo"><a class="header" href="#roadmap--quicproquo">Roadmap — quicproquo</a></h1>
+<blockquote>
+<p>From proof-of-concept to production-grade E2E encrypted messaging.</p>
+<p>Each phase is designed to be tackled sequentially. Items within a phase
+can be parallelised. Check the box when done.</p>
+</blockquote>
+<hr>
+<h2 id="phase-1--production-hardening-critical"><a class="header" href="#phase-1--production-hardening-critical">Phase 1 — Production Hardening (Critical)</a></h2>
+<p>Eliminate all crash paths, enforce secure defaults, fix deployment blockers.</p>
+<ul>
+<li>
+<p><input disabled="" type="checkbox"> <strong>1.1 Remove <code>.unwrap()</code> / <code>.expect()</code> from production paths</strong></p>
+<ul>
+<li>Replace <code>AUTH_CONTEXT.read().expect()</code> in client RPC with proper <code>Result</code></li>
+<li>Replace <code>"0.0.0.0:0".parse().unwrap()</code> in client with fallible parse</li>
+<li>Replace <code>Mutex::lock().unwrap()</code> in server storage with <code>.map_err()</code></li>
+<li>Audit: <code>grep -rn 'unwrap()\|expect(' crates/</code> outside <code>#[cfg(test)]</code></li>
+</ul>
+</li>
+<li>
+<p><input disabled="" type="checkbox"> <strong>1.2 Enforce secure defaults in production mode</strong></p>
+<ul>
+<li>Reject startup if <code>QPQ_PRODUCTION=true</code> and <code>auth_token</code> is empty or <code>"devtoken"</code></li>
+<li>Require non-empty <code>db_key</code> when using SQL backend in production</li>
+<li>Refuse to auto-generate TLS certs in production mode (require existing cert+key)</li>
+<li>Already partially implemented — verify and harden the validation in <code>config.rs</code></li>
+</ul>
+</li>
+<li>
+<p><input disabled="" type="checkbox"> <strong>1.3 Fix <code>.gitignore</code></strong></p>
+<ul>
+<li>Add <code>data/</code>, <code>*.der</code>, <code>*.pem</code>, <code>*.db</code>, <code>*.bin</code> (state files), <code>*.ks</code> (keystores)</li>
+<li>Verify no secrets are already tracked: <code>git ls-files data/ *.der *.db</code></li>
+</ul>
+</li>
+<li>
+<p><input disabled="" type="checkbox"> <strong>1.4 Fix Dockerfile</strong></p>
+<ul>
+<li>Sync workspace members (handle excluded <code>p2p</code> crate)</li>
+<li>Create dedicated user/group instead of <code>nobody</code></li>
+<li>Set writable <code>QPQ_DATA_DIR</code> with correct permissions</li>
+<li>Test: <code>docker build . &amp;&amp; docker run --rm -it qpq-server --help</code></li>
+</ul>
+</li>
+<li>
+<p><input disabled="" type="checkbox"> <strong>1.5 TLS certificate lifecycle</strong></p>
+<ul>
+<li>Document CA-signed cert setup (Let’s Encrypt / custom CA)</li>
+<li>Add <code>--tls-required</code> flag that refuses to start without valid cert</li>
+<li>Log clear warning when using self-signed certs</li>
+<li>Document certificate rotation procedure</li>
+</ul>
+</li>
+</ul>
+<hr>
+<h2 id="phase-2--test--ci-maturity"><a class="header" href="#phase-2--test--ci-maturity">Phase 2 — Test &amp; CI Maturity</a></h2>
+<p>Build confidence before adding features.</p>
+<ul>
+<li>
+<p><input disabled="" type="checkbox"> <strong>2.1 Expand E2E test coverage</strong></p>
+<ul>
+<li>Auth failure scenarios (wrong password, expired token, invalid token)</li>
+<li>Message ordering verification (send N messages, verify seq numbers)</li>
+<li>Concurrent clients (3+ members in group, simultaneous send/recv)</li>
+<li>OPAQUE registration + login full flow</li>
+<li>Queue full behavior (&gt;1000 messages)</li>
+<li>Rate limiting behavior (&gt;100 enqueues/minute)</li>
+<li>Reconnection after server restart</li>
+<li>KeyPackage exhaustion (fetch when none available)</li>
+</ul>
+</li>
+<li>
+<p><input disabled="" type="checkbox"> <strong>2.2 Add unit tests for untested paths</strong></p>
+<ul>
+<li>Client retry logic (exponential backoff, jitter, retriable classification)</li>
+<li>REPL input parsing edge cases (empty input, special characters, <code>/</code> commands)</li>
+<li>State file encryption/decryption round-trip with bad password</li>
+<li>Token cache expiry</li>
+<li>Conversation store migrations</li>
+</ul>
+</li>
+<li>
+<p><input disabled="" type="checkbox"> <strong>2.3 CI hardening</strong></p>
+<ul>
+<li>Add <code>.github/CODEOWNERS</code> (crypto, auth, wire-format require 2 reviewers)</li>
+<li>Ensure <code>cargo deny check</code> runs on every PR (already in CI — verify)</li>
+<li>Add <code>cargo audit</code> as blocking check (already in CI — verify)</li>
+<li>Add coverage reporting (tarpaulin or llvm-cov)</li>
+<li>Add CI job for Docker build validation</li>
+</ul>
+</li>
+<li>
+<p><input disabled="" type="checkbox"> <strong>2.4 Clean up build warnings</strong></p>
+<ul>
+<li>Fix Cap’n Proto generated <code>unused_parens</code> warnings</li>
+<li>Remove dead code / unused imports</li>
+<li>Address <code>openmls</code> future-incompat warnings</li>
+<li>Target: <code>cargo clippy --workspace -- -D warnings</code> passes clean</li>
+</ul>
+</li>
+</ul>
+<hr>
+<h2 id="phase-3--client-sdks-native-quic--capn-proto-everywhere"><a class="header" href="#phase-3--client-sdks-native-quic--capn-proto-everywhere">Phase 3 — Client SDKs: Native QUIC + Cap’n Proto Everywhere</a></h2>
+<p><strong>No REST gateway. No protocol dilution.</strong> The <code>.capnp</code> schemas are the
+interface definition. Every SDK speaks native QUIC + Cap’n Proto. The
+project name stays honest.</p>
+<h3 id="why-this-matters"><a class="header" href="#why-this-matters">Why this matters</a></h3>
+<p>The name is <strong>quic</strong>n<strong>proto</strong>chat — the protocol IS the product. Instead
+of adding an HTTP translation layer that loses zero-copy performance and
+adds base64 overhead, we invest in making the native protocol accessible
+from every language that has QUIC + Cap’n Proto support, and provide
+WASM/FFI for the crypto layer.</p>
+<h3 id="architecture"><a class="header" href="#architecture">Architecture</a></h3>
+<pre><code>  Server: QUIC + Cap'n Proto (single protocol, no gateway)
+
+  Client SDKs:
+    ┌─── Rust         quinn + capnp-rpc          (existing, reference impl)
+    ├─── Go           quic-go + go-capnp          (native, high confidence)
+    ├─── Python       aioquic + pycapnp            (native QUIC, manual framing)
+    ├─── C/C++        msquic/ngtcp2 + capnproto    (reference impl, full RPC)
+    └─── Browser      WebTransport + capnp (WASM)  (QUIC transport, no HTTP needed)
+
+  Crypto layer (client-side MLS, shared across all SDKs):
+    ┌─── Rust crate   (native, existing)
+    ├─── WASM module  (browsers, Node.js, Deno)
+    └─── C FFI        (Swift, Kotlin, Python, Go via cgo)
+</code></pre>
+<h3 id="language-support-reality-check"><a class="header" href="#language-support-reality-check">Language support reality check</a></h3>
+<div class="table-wrapper">
+<table>
+<thead>
+<tr><th>Language</th><th>QUIC</th><th>Cap’n Proto</th><th>RPC</th><th>Confidence</th></tr>
+</thead>
+<tbody>
+<tr><td><strong>Rust</strong></td><td>quinn ✅</td><td>capnp-rpc ✅</td><td>Full ✅</td><td>Existing</td></tr>
+<tr><td><strong>Go</strong></td><td>quic-go ✅</td><td>go-capnp ✅</td><td>Level 1 ✅</td><td>High</td></tr>
+<tr><td><strong>Python</strong></td><td>aioquic ✅</td><td>pycapnp ⚠️</td><td>Manual framing</td><td>Medium</td></tr>
+<tr><td><strong>C/C++</strong></td><td>msquic/ngtcp2 ✅</td><td>capnproto ✅</td><td>Full ✅</td><td>High</td></tr>
+<tr><td><strong>Browser</strong></td><td>WebTransport ✅</td><td>WASM ✅</td><td>Via WASM bridge</td><td>Medium</td></tr>
+</tbody>
+</table>
+</div>
+<h3 id="implementation"><a class="header" href="#implementation">Implementation</a></h3>
+<ul>
+<li>
+<p><input disabled="" type="checkbox" checked=""> <strong>3.1 Go SDK (<code>quicproquo-go</code>)</strong></p>
+<ul>
+<li>Generated Go types from <code>node.capnp</code> (6487-line codegen, all 24 RPC methods)</li>
+<li>QUIC transport via <code>quic-go</code> with TLS 1.3 + ALPN <code>"capnp"</code></li>
+<li>High-level <code>qpq</code> package: Connect, Health, ResolveUser, CreateChannel, Send/SendWithTTL, Receive/ReceiveWait, DeleteAccount, OPAQUE auth</li>
+<li>Example CLI in <code>sdks/go/cmd/example/</code></li>
+</ul>
+</li>
+<li>
+<p><input disabled="" type="checkbox"> <strong>3.2 Python SDK (<code>quicproquo-py</code>)</strong></p>
+<ul>
+<li>QUIC transport: <code>aioquic</code> with custom Cap’n Proto stream handler</li>
+<li>Cap’n Proto serialization: <code>pycapnp</code> for message types</li>
+<li>Manual RPC framing: length-prefixed request/response over QUIC stream</li>
+<li>Async/await API matching the Rust client patterns</li>
+<li>Crypto: PyO3 bindings to <code>quicproquo-core</code> for MLS operations</li>
+<li>Publish: PyPI <code>quicproquo</code></li>
+<li>Example: async bot client</li>
+</ul>
+</li>
+<li>
+<p><input disabled="" type="checkbox" checked=""> <strong>3.3 C FFI layer (<code>quicproquo-ffi</code>)</strong></p>
+<ul>
+<li><code>crates/quicproquo-ffi</code> with 7 extern “C” functions: connect, login, send, receive, disconnect, last_error, free_string</li>
+<li>Builds as <code>libquicproquo_ffi.so</code> / <code>.dylib</code> / <code>.dll</code></li>
+<li>Python ctypes wrapper in <code>examples/python/qpq_client.py</code></li>
+</ul>
+</li>
+<li>
+<p><input disabled="" type="checkbox" checked=""> <strong>3.4 WASM compilation of <code>quicproquo-core</code></strong></p>
+<ul>
+<li><code>wasm-pack build</code> target producing 175 KB WASM bundle (LTO + opt-level=s)</li>
+<li>13 <code>wasm_bindgen</code> functions: Ed25519 identity, hybrid KEM, safety numbers, sealed sender, padding</li>
+<li>Browser-ready with <code>crypto.getRandomValues()</code> RNG</li>
+<li>Published as <code>sdks/typescript/wasm-crypto/</code></li>
+</ul>
+</li>
+<li>
+<p><input disabled="" type="checkbox"> <strong>3.5 WebTransport server endpoint</strong></p>
+<ul>
+<li>Add HTTP/3 + WebTransport listener to server (same QUIC stack via quinn)</li>
+<li>Cap’n Proto RPC framed over WebTransport bidirectional streams</li>
+<li>Same auth, same storage, same RPC handlers — just a different stream source</li>
+<li>Browsers connect via <code>new WebTransport("https://server:7443")</code></li>
+<li>ALPN negotiation: <code>"h3"</code> for WebTransport, <code>"capnp"</code> for native QUIC</li>
+<li>Configurable port: <code>--webtransport-listen 0.0.0.0:7443</code></li>
+<li>Feature-flagged: <code>--features webtransport</code></li>
+</ul>
+</li>
+<li>
+<p><input disabled="" type="checkbox" checked=""> <strong>3.6 TypeScript/JavaScript SDK (<code>@quicproquo/client</code>)</strong></p>
+<ul>
+<li><code>QpqClient</code> class: connect, offline, health, resolveUser, createChannel, send/sendWithTTL, receive, deleteAccount</li>
+<li>WASM crypto wrapper: generateIdentity, sign/verify, hybridEncrypt/Decrypt, computeSafetyNumber, sealedSend, pad</li>
+<li>WebSocket transport with request/response correlation and reconnection</li>
+<li>Browser demo: interactive crypto playground + chat UI (<code>sdks/typescript/demo/index.html</code>)</li>
+</ul>
+</li>
+<li>
+<p><input disabled="" type="checkbox"> <strong>3.7 SDK documentation and schema publishing</strong></p>
+<ul>
+<li>Publish <code>.capnp</code> schemas as the canonical API contract</li>
+<li>Document the QUIC + Cap’n Proto connection pattern for each language</li>
+<li>Provide a “build your own SDK” guide (QUIC stream → Cap’n Proto RPC bootstrap)</li>
+<li>Reference implementation checklist: connect, auth, upload key, enqueue, fetch</li>
+</ul>
+</li>
+</ul>
+<hr>
+<h2 id="phase-4--trust--security-infrastructure"><a class="header" href="#phase-4--trust--security-infrastructure">Phase 4 — Trust &amp; Security Infrastructure</a></h2>
+<p>Address the security gaps required for real-world deployment.</p>
+<ul>
+<li>
+<p><input disabled="" type="checkbox"> <strong>4.1 Third-party cryptographic audit</strong></p>
+<ul>
+<li>Scope: MLS integration, OPAQUE flow, hybrid KEM, key lifecycle, zeroization</li>
+<li>Firms: NCC Group, Trail of Bits, Cure53</li>
+<li>Budget and timeline: typically 4-6 weeks, $50K–$150K</li>
+<li>Publish report publicly (builds trust)</li>
+</ul>
+</li>
+<li>
+<p><input disabled="" type="checkbox"> <strong>4.2 Key Transparency / revocation</strong></p>
+<ul>
+<li>Replace <code>BasicCredential</code> with X.509-based MLS credentials</li>
+<li>Or: verifiable key directory (Merkle tree, auditable log)</li>
+<li>Users can verify peer keys haven’t been substituted (MITM detection)</li>
+<li>Revocation mechanism for compromised keys</li>
+</ul>
+</li>
+<li>
+<p><input disabled="" type="checkbox" checked=""> <strong>4.3 Client authentication on Delivery Service</strong></p>
+<ul>
+<li>DS sender identity binding with explicit audit logging</li>
+<li><code>sender_prefix</code> tracking in enqueue/batch_enqueue RPCs</li>
+<li>Sender identity derived from authenticated session</li>
+</ul>
+</li>
+<li>
+<p><input disabled="" type="checkbox"> <strong>4.4 M7 — Post-quantum MLS integration</strong></p>
+<ul>
+<li>Integrate hybrid KEM (X25519 + ML-KEM-768) into the OpenMLS crypto provider</li>
+<li>Group key material gets post-quantum confidentiality</li>
+<li>Full test suite with PQ ciphersuite</li>
+<li>Ref: existing <code>hybrid_kem.rs</code> and <code>hybrid_crypto.rs</code></li>
+</ul>
+</li>
+<li>
+<p><input disabled="" type="checkbox" checked=""> <strong>4.5 Username enumeration mitigation</strong></p>
+<ul>
+<li>5 ms timing floor on <code>resolveUser</code> responses</li>
+<li>Rate limiting to prevent bulk enumeration attacks</li>
+</ul>
+</li>
+</ul>
+<hr>
+<h2 id="phase-5--features--ux"><a class="header" href="#phase-5--features--ux">Phase 5 — Features &amp; UX</a></h2>
+<p>Make it a product people want to use.</p>
+<ul>
+<li>
+<p><input disabled="" type="checkbox"> <strong>5.1 Multi-device support</strong></p>
+<ul>
+<li>Account → multiple devices, each with own Ed25519 key + MLS KeyPackages</li>
+<li>Device graph management (add device, remove device, list devices)</li>
+<li>Messages delivered to all devices of a user</li>
+<li><code>device_id</code> field already in Auth struct — wire it through</li>
+</ul>
+</li>
+<li>
+<p><input disabled="" type="checkbox"> <strong>5.2 Account recovery</strong></p>
+<ul>
+<li>Recovery codes or backup key (encrypted, stored by user)</li>
+<li>Option: server-assisted recovery with security questions (lower security)</li>
+<li>MLS state re-establishment after device loss</li>
+</ul>
+</li>
+<li>
+<p><input disabled="" type="checkbox"> <strong>5.3 Full MLS lifecycle</strong></p>
+<ul>
+<li>Member removal (Remove proposal → Commit → fan-out)</li>
+<li>Credential update (Update proposal for key rotation)</li>
+<li>Explicit proposal handling (queue proposals, batch commit)</li>
+<li>Group metadata (name, description, avatar hash)</li>
+</ul>
+</li>
+<li>
+<p><input disabled="" type="checkbox" checked=""> <strong>5.4 Message editing and deletion</strong></p>
+<ul>
+<li><code>Edit</code> (0x06) and <code>Delete</code> (0x07) message types in <code>AppMessage</code></li>
+<li><code>/edit &lt;index&gt; &lt;text&gt;</code> and <code>/delete &lt;index&gt;</code> REPL commands (own messages only)</li>
+<li>Database update/removal on incoming edit/delete</li>
+</ul>
+</li>
+<li>
+<p><input disabled="" type="checkbox" checked=""> <strong>5.5 File and media transfer</strong></p>
+<ul>
+<li><code>uploadBlob</code> / <code>downloadBlob</code> RPCs with 256 KB chunked streaming</li>
+<li>SHA-256 content-addressable storage with hash verification</li>
+<li><code>FileRef</code> (0x08) message type with blob_id, filename, file_size, mime_type</li>
+<li><code>/send-file &lt;path&gt;</code> and <code>/download &lt;index&gt;</code> REPL commands with progress bars</li>
+<li>50 MB max file size, automatic MIME detection via <code>mime_guess</code></li>
+</ul>
+</li>
+<li>
+<p><input disabled="" type="checkbox"> <strong>5.6 Abuse prevention and moderation</strong></p>
+<ul>
+<li>Block user (client-side, suppress display)</li>
+<li>Report message (encrypted report to admin key)</li>
+<li>Admin tools: ban user, delete account, audit log</li>
+</ul>
+</li>
+<li>
+<p><input disabled="" type="checkbox"> <strong>5.7 Offline message queue (client-side)</strong></p>
+<ul>
+<li>Queue messages when disconnected, send on reconnect</li>
+<li>Idempotent message IDs to prevent duplicates</li>
+<li>Gap detection: compare local seq with server seq</li>
+</ul>
+</li>
+</ul>
+<hr>
+<h2 id="phase-6--scale--operations"><a class="header" href="#phase-6--scale--operations">Phase 6 — Scale &amp; Operations</a></h2>
+<p>Prepare for real traffic.</p>
+<ul>
+<li>
+<p><input disabled="" type="checkbox"> <strong>6.1 Distributed rate limiting</strong></p>
+<ul>
+<li>Current: in-memory per-process, lost on restart</li>
+<li>Move to Redis or shared state for multi-node deployments</li>
+<li>Sliding window with configurable thresholds</li>
+</ul>
+</li>
+<li>
+<p><input disabled="" type="checkbox"> <strong>6.2 Multi-node / horizontal scaling</strong></p>
+<ul>
+<li>Stateless server design (already mostly there — state is in storage backend)</li>
+<li>Shared PostgreSQL or CockroachDB backend (replace SQLite)</li>
+<li>Message queue fan-out (Redis pub/sub or NATS for cross-node notification)</li>
+<li>Load balancer health check via QUIC RPC <code>health()</code> or Prometheus <code>/metrics</code></li>
+</ul>
+</li>
+<li>
+<p><input disabled="" type="checkbox"> <strong>6.3 Operational runbook</strong></p>
+<ul>
+<li>Backup / restore procedures (SQLCipher, file backend)</li>
+<li>Key rotation (auth token, TLS cert, DB encryption key)</li>
+<li>Incident response playbook</li>
+<li>Scaling guide (when to add nodes, resource sizing)</li>
+<li>Monitoring dashboard templates (Grafana + Prometheus)</li>
+</ul>
+</li>
+<li>
+<p><input disabled="" type="checkbox"> <strong>6.4 Connection draining and graceful shutdown</strong></p>
+<ul>
+<li>Stop accepting new connections on SIGTERM</li>
+<li>Wait for in-flight RPCs (configurable timeout, default 30s)</li>
+<li>Drain WebTransport sessions with close frame</li>
+<li>Document expected behavior for load balancers (health → unhealthy first)</li>
+</ul>
+</li>
+<li>
+<p><input disabled="" type="checkbox"> <strong>6.5 Request-level timeouts</strong></p>
+<ul>
+<li>Per-RPC timeout (prevent slow clients from holding resources)</li>
+<li>Database query timeout</li>
+<li>Overall request deadline propagation</li>
+</ul>
+</li>
+<li>
+<p><input disabled="" type="checkbox"> <strong>6.6 Observability enhancements</strong></p>
+<ul>
+<li>Request correlation IDs (trace across RPC → storage)</li>
+<li>Storage operation latency metrics</li>
+<li>Per-endpoint latency histograms</li>
+<li>Structured audit log to persistent storage (not just stdout)</li>
+<li>OpenTelemetry integration</li>
+</ul>
+</li>
+</ul>
+<hr>
+<h2 id="phase-7--platform-expansion--research"><a class="header" href="#phase-7--platform-expansion--research">Phase 7 — Platform Expansion &amp; Research</a></h2>
+<p>Long-term vision for wide adoption.</p>
+<ul>
+<li>
+<p><input disabled="" type="checkbox"> <strong>7.1 Mobile clients (iOS + Android)</strong></p>
+<ul>
+<li>Use C FFI (Phase 3.3) for crypto + transport (single library)</li>
+<li>Push notifications via APNs / FCM (server sends notification on enqueue)</li>
+<li>Background QUIC connection for message polling</li>
+<li>Biometric auth for local key storage (Keychain / Android Keystore)</li>
+</ul>
+</li>
+<li>
+<p><input disabled="" type="checkbox"> <strong>7.2 Web client (browser)</strong></p>
+<ul>
+<li>Use WASM (Phase 3.4) for crypto</li>
+<li>Use WebTransport (Phase 3.5) for native QUIC transport</li>
+<li>Cap’n Proto via WASM bridge (Phase 3.6)</li>
+<li>IndexedDB for local state persistence</li>
+<li>Service Worker for background notifications</li>
+<li>Progressive Web App (PWA) support</li>
+</ul>
+</li>
+<li>
+<p><input disabled="" type="checkbox"> <strong>7.3 Federation</strong></p>
+<ul>
+<li>Server-to-server protocol via Cap’n Proto RPC over QUIC (see <code>federation.capnp</code>)</li>
+<li><code>relayEnqueue</code>, <code>proxyFetchKeyPackage</code>, <code>federationHealth</code> methods</li>
+<li>Identity resolution across federated servers</li>
+<li>MLS group spanning multiple servers</li>
+<li>Trust model for federated deployments</li>
+</ul>
+</li>
+<li>
+<p><input disabled="" type="checkbox" checked=""> <strong>7.4 Sealed Sender</strong></p>
+<ul>
+<li>Sender identity inside MLS ciphertext only (server can’t see who sent)</li>
+<li><code>sealed_sender</code> module in quicproquo-core with seal/unseal API</li>
+<li>WASM-accessible via <code>wasm_bindgen</code> for browser use</li>
+</ul>
+</li>
+<li>
+<p><input disabled="" type="checkbox"> <strong>7.5 Additional language SDKs</strong></p>
+<ul>
+<li>Java/Kotlin: JNI bindings to C FFI (Phase 3.3) + native QUIC (netty-quic)</li>
+<li>Swift: Swift wrapper over C FFI + Network.framework QUIC</li>
+<li>Ruby: FFI bindings via <code>quicproquo-ffi</code></li>
+<li>Evaluate demand-driven — only build SDKs people request</li>
+</ul>
+</li>
+<li>
+<p><input disabled="" type="checkbox"> <strong>7.6 P2P / NAT traversal</strong></p>
+<ul>
+<li>Direct peer-to-peer via iroh (foundation exists in <code>quicproquo-p2p</code>)</li>
+<li>Server as fallback relay only</li>
+<li>Reduces latency and single-point-of-failure</li>
+<li>Ref: <code>FUTURE-IMPROVEMENTS.md § 6.1</code></li>
+</ul>
+</li>
+<li>
+<p><input disabled="" type="checkbox"> <strong>7.7 Traffic analysis resistance</strong></p>
+<ul>
+<li>Padding messages to uniform size</li>
+<li>Decoy traffic to mask timing patterns</li>
+<li>Optional Tor/I2P routing for IP privacy</li>
+<li>Ref: <code>FUTURE-IMPROVEMENTS.md § 5.4, 6.3</code></li>
+</ul>
+</li>
+</ul>
+<hr>
+<h2 id="phase-8--freifunk--community-mesh-networking"><a class="header" href="#phase-8--freifunk--community-mesh-networking">Phase 8 — Freifunk / Community Mesh Networking</a></h2>
+<p>Make qpq a first-class citizen on decentralised, community-operated wireless
+networks (Freifunk, BATMAN-adv/Babel routing, OpenWrt). Multiple qpq nodes form
+a federated mesh; clients auto-discover nearby nodes via mDNS; the network
+functions without any central infrastructure or internet uplink.</p>
+<h3 id="architecture-1"><a class="header" href="#architecture-1">Architecture</a></h3>
+<pre><code>  Client A ─── mDNS discovery ──► nearby qpq node (LAN / mesh)
+                                        │
+                               Cap'n Proto federation
+                                        │
+                               remote qpq node (across mesh)
+</code></pre>
+<ul>
+<li>
+<p><input disabled="" type="checkbox" checked=""> <strong>F0 — Re-include <code>quicproquo-p2p</code> in workspace; fix ALPN strings</strong></p>
+<ul>
+<li>Moved <code>crates/quicproquo-p2p</code> from <code>exclude</code> back into <code>[workspace] members</code></li>
+<li>Fixed ALPN <code>b"quicnprotochat/p2p/1"</code> → <code>b"quicproquo/p2p/1"</code> (breaking wire change)</li>
+<li>Fixed federation ALPN <code>b"qnpc-fed"</code> → <code>b"quicproquo/federation/1"</code></li>
+<li>Feature-gated behind <code>--features mesh</code> on client (keeps iroh out of default builds)</li>
+</ul>
+</li>
+<li>
+<p><input disabled="" type="checkbox" checked=""> <strong>F1 — Federation routing in message delivery</strong></p>
+<ul>
+<li><code>handle_enqueue</code> and <code>handle_batch_enqueue</code> call <code>federation::routing::resolve_destination()</code></li>
+<li>Recipients with a remote home server are relayed via <code>FederationClient::relay_enqueue()</code></li>
+<li>mTLS mutual authentication between nodes (both present client certs, validated against shared CA)</li>
+<li>Config: <code>QPQ_FEDERATION_LISTEN</code>, <code>QPQ_LOCAL_DOMAIN</code>, <code>QPQ_FEDERATION_CERT/KEY/CA</code></li>
+</ul>
+</li>
+<li>
+<p><input disabled="" type="checkbox" checked=""> <strong>F2 — mDNS local peer discovery</strong></p>
+<ul>
+<li>Server announces <code>_quicproquo._udp.local.</code> on startup via <code>mdns-sd</code></li>
+<li>Client: <code>MeshDiscovery::start()</code> browses for nearby nodes (feature-gated)</li>
+<li>REPL commands: <code>/mesh peers</code> (scan + list), <code>/mesh server &lt;host:port&gt;</code> (note address)</li>
+<li>Nodes announce: <code>ver=1</code>, <code>server=&lt;host:port&gt;</code>, <code>domain=&lt;local_domain&gt;</code> TXT records</li>
+</ul>
+</li>
+<li>
+<p><input disabled="" type="checkbox" checked=""> <strong>F3 — Self-sovereign mesh identity</strong></p>
+<ul>
+<li>Ed25519 keypair-based identity independent of AS registration</li>
+<li>JSON-persisted seed + known peers directory</li>
+<li>Sign/verify operations for mesh authenticity (<code>crates/quicproquo-p2p/src/identity.rs</code>)</li>
+</ul>
+</li>
+<li>
+<p><input disabled="" type="checkbox" checked=""> <strong>F4 — Store-and-forward with TTL</strong></p>
+<ul>
+<li><code>MeshEnvelope</code> with TTL-based expiry, hop_count tracking, max_hops routing limit</li>
+<li>SHA-256 deduplication ID prevents relay loops</li>
+<li>Ed25519 signature verification on envelopes</li>
+<li><code>MeshStore</code> in-memory queue with per-recipient capacity limits and TTL-based GC</li>
+</ul>
+</li>
+<li>
+<p><input disabled="" type="checkbox" checked=""> <strong>F5 — Lightweight broadcast channels</strong></p>
+<ul>
+<li>Symmetric ChaCha20-Poly1305 encrypted channels (no MLS overhead)</li>
+<li>Topic-based pub/sub via <code>BroadcastChannel</code> and <code>BroadcastManager</code></li>
+<li>Subscribe/unsubscribe, create, publish API on <code>P2pNode</code></li>
+</ul>
+</li>
+<li>
+<p><input disabled="" type="checkbox" checked=""> <strong>F6 — Extended <code>/mesh</code> REPL commands</strong></p>
+<ul>
+<li><code>/mesh send &lt;peer_id&gt; &lt;msg&gt;</code> — direct P2P message via iroh</li>
+<li><code>/mesh broadcast &lt;topic&gt; &lt;msg&gt;</code> — publish to broadcast channel</li>
+<li><code>/mesh subscribe &lt;topic&gt;</code> — join broadcast channel</li>
+<li><code>/mesh route</code> — show routing table</li>
+<li><code>/mesh identity</code> — show mesh identity info</li>
+<li><code>/mesh store</code> — show store-and-forward statistics</li>
+</ul>
+</li>
+<li>
+<p><input disabled="" type="checkbox"> <strong>F7 — OpenWrt cross-compilation guide</strong></p>
+<ul>
+<li>Musl static builds: <code>x86_64-unknown-linux-musl</code>, <code>armv7-unknown-linux-musleabihf</code>, <code>mips-unknown-linux-musl</code></li>
+<li>Strip binary: <code>--release</code> + <code>strip</code> → target size &lt; 5 MB for flash storage</li>
+<li><code>opkg</code> package manifest for OpenWrt feed</li>
+<li><code>procd</code> init script + <code>uci</code> config file for OpenWrt integration</li>
+<li>CI job: cross-compile and size-check on every release tag</li>
+</ul>
+</li>
+<li>
+<p><input disabled="" type="checkbox"> <strong>F8 — Traffic analysis resistance for mesh</strong></p>
+<ul>
+<li>Uniform message padding to nearest 256-byte boundary (hides message size)</li>
+<li>Configurable decoy traffic rate (fake messages to mask send timing)</li>
+<li>Optional onion routing: 3-hop relay through other mesh nodes (no Tor dependency)</li>
+<li>Ref: Phase 7.7 for server-side traffic analysis resistance</li>
+</ul>
+</li>
+</ul>
+<hr>
+<h2 id="phase-9--developer-experience--community-growth"><a class="header" href="#phase-9--developer-experience--community-growth">Phase 9 — Developer Experience &amp; Community Growth</a></h2>
+<p>Features designed to attract contributors, create demo/showcase potential,
+and lower the barrier to entry for non-crypto developers.</p>
+<ul>
+<li>
+<p><input disabled="" type="checkbox"> <strong>9.1 Criterion Benchmark Suite (<code>qpq-bench</code>)</strong></p>
+<ul>
+<li>Criterion benchmarks for all crypto primitives: hybrid KEM encap/decap,
+MLS group-add at 10/100/1000 members, epoch rotation, Noise_XX handshake</li>
+<li>CI publishes HTML benchmark reports as GitHub Actions artifacts</li>
+<li>Citable numbers — no other project benchmarks MLS + PQ-KEM in Rust</li>
+</ul>
+</li>
+<li>
+<p><input disabled="" type="checkbox" checked=""> <strong>9.2 Safety Numbers (key verification)</strong></p>
+<ul>
+<li>60-digit numeric code derived from two identity keys (Signal-style)</li>
+<li><code>/verify &lt;username&gt;</code> REPL command for out-of-band verification</li>
+<li>Available in WASM via <code>compute_safety_number</code> binding</li>
+</ul>
+</li>
+<li>
+<p><input disabled="" type="checkbox"> <strong>9.3 Full-Screen TUI (Ratatui + Crossterm)</strong></p>
+<ul>
+<li><code>qpq tui</code> launches a full-screen terminal UI: message pane, input bar,
+channel sidebar with unread counts, MLS epoch indicator</li>
+<li>Feature-gated <code>--features tui</code> to keep ratatui/crossterm out of default builds</li>
+<li>Existing REPL and CLI subcommands are unaffected</li>
+</ul>
+</li>
+<li>
+<p><input disabled="" type="checkbox"> <strong>9.4 Delivery Proof Canary Tokens</strong></p>
+<ul>
+<li>Server signs <code>Ed25519(SHA-256(message_id || recipient || timestamp))</code> on enqueue</li>
+<li>Sender stores proof locally — cryptographic evidence the server queued the message</li>
+<li>Cap’n Proto schema gains optional <code>deliveryProof: Data</code> on enqueue response</li>
+</ul>
+</li>
+<li>
+<p><input disabled="" type="checkbox"> <strong>9.5 Verifiable Transcript Archive</strong></p>
+<ul>
+<li><code>GroupMember::export_transcript(path, password)</code> writes encrypted, tamper-evident
+message archive (CBOR records, Argon2id + ChaCha20-Poly1305, Merkle chain)</li>
+<li><code>qpq export verify</code> CLI command independently verifies chain integrity</li>
+<li>Useful for legal discovery, audit, or personal backup</li>
+</ul>
+</li>
+<li>
+<p><input disabled="" type="checkbox"> <strong>9.6 Key Transparency (Merkle-Log Identity Binding)</strong></p>
+<ul>
+<li>Append-only Merkle log of (username, identity_key) bindings in the AS</li>
+<li>Clients receive inclusion proofs alongside key fetches</li>
+<li>Any client can independently audit the full identity history</li>
+<li>Lightweight subset of RFC 9162 adapted for identity keys</li>
+</ul>
+</li>
+<li>
+<p><input disabled="" type="checkbox" checked=""> <strong>9.7 Dynamic Server Plugin System</strong></p>
+<ul>
+<li>Server loads <code>.so</code>/<code>.dylib</code> plugins at runtime via <code>--plugin-dir</code></li>
+<li>C-compatible <code>HookVTable</code> via <code>extern "C"</code> — plugins in any language</li>
+<li>6 hook points: on_message_enqueue, on_batch_enqueue, on_auth, on_channel_created, on_fetch, on_user_registered</li>
+<li>Example plugins: logging plugin, rate limit plugin (512 KiB payload enforcement)</li>
+</ul>
+</li>
+<li>
+<p><input disabled="" type="checkbox"> <strong>9.8 PQ Noise Transport Layer</strong></p>
+<ul>
+<li>Hybrid <code>Noise_XX + ML-KEM-768</code> handshake for post-quantum transport security</li>
+<li>Closes the harvest-now-decrypt-later gap on handshake metadata (ADR-006)</li>
+<li>Feature-gated <code>--features pq-noise</code>; classical Noise_XX default preserved</li>
+<li>May require extending or forking <code>snow</code> crate’s <code>CryptoResolver</code></li>
+</ul>
+</li>
+</ul>
+<hr>
+<h2 id="summary-timeline"><a class="header" href="#summary-timeline">Summary Timeline</a></h2>
+<div class="table-wrapper">
+<table>
+<thead>
+<tr><th>Phase</th><th>Focus</th><th>Estimated Effort</th></tr>
+</thead>
+<tbody>
+<tr><td><strong>1</strong></td><td>Production Hardening</td><td>1–2 days</td></tr>
+<tr><td><strong>2</strong></td><td>Test &amp; CI Maturity</td><td>2–3 days</td></tr>
+<tr><td><strong>3</strong></td><td>Client SDKs (Go, Python, WASM, FFI, WebTransport)</td><td>5–8 days</td></tr>
+<tr><td><strong>4</strong></td><td>Trust &amp; Security Infrastructure</td><td>2–4 days (excl. audit)</td></tr>
+<tr><td><strong>5</strong></td><td>Features &amp; UX</td><td>5–7 days</td></tr>
+<tr><td><strong>6</strong></td><td>Scale &amp; Operations</td><td>3–5 days</td></tr>
+<tr><td><strong>7</strong></td><td>Platform Expansion &amp; Research</td><td>ongoing</td></tr>
+<tr><td><strong>8</strong></td><td>Freifunk / Community Mesh</td><td>ongoing</td></tr>
+<tr><td><strong>9</strong></td><td>Developer Experience &amp; Community Growth</td><td>3–5 days</td></tr>
+</tbody>
+</table>
+</div>
+<hr>
+<h2 id="related-documents"><a class="header" href="#related-documents">Related Documents</a></h2>
+<ul>
+<li><a href="docs/FUTURE-IMPROVEMENTS.html">Future Improvements</a> — consolidated improvement list</li>
+<li><a href="docs/PRODUCTION-READINESS-AUDIT.html">Production Readiness Audit</a> — specific blockers</li>
+<li><a href="docs/SECURITY-AUDIT.html">Security Audit</a> — findings and recommendations</li>
+<li><a href="docs/src/roadmap/milestones.html">Milestone Tracker</a> — M1–M7 status</li>
+<li><a href="docs/src/roadmap/authz-plan.html">Auth, Devices, and Tokens</a> — authorization design</li>
+<li><a href="docs/src/roadmap/dm-channels.html">DM Channel Design</a> — 1:1 channel spec</li>
+</ul>
+
+                    </main>
+
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ROADMAP.md

@@ -0,0 +1,493 @@
+# Roadmap — quicproquo
+
+> From proof-of-concept to production-grade E2E encrypted messaging.
+>
+> Each phase is designed to be tackled sequentially. Items within a phase
+> can be parallelised. Check the box when done.
+
+---
+
+## Phase 1 — Production Hardening (Critical)
+
+Eliminate all crash paths, enforce secure defaults, fix deployment blockers.
+
+- [x] **1.1 Remove `.unwrap()` / `.expect()` from production paths**
+  - Replace `AUTH_CONTEXT.read().expect()` in client RPC with proper `Result`
+  - Replace `"0.0.0.0:0".parse().unwrap()` in client with fallible parse
+  - Replace `Mutex::lock().unwrap()` in server storage with `.map_err()`
+  - Audit: `grep -rn 'unwrap()\|expect(' crates/` outside `#[cfg(test)]`
+
+- [x] **1.2 Enforce secure defaults in production mode**
+  - Reject startup if `QPQ_PRODUCTION=true` and `auth_token` is empty or `"devtoken"`
+  - Require non-empty `db_key` when using SQL backend in production
+  - Refuse to auto-generate TLS certs in production mode (require existing cert+key)
+  - Already partially implemented — verify and harden the validation in `config.rs`
+
+- [x] **1.3 Fix `.gitignore`**
+  - Add `data/`, `*.der`, `*.pem`, `*.db`, `*.bin` (state files), `*.ks` (keystores)
+  - Verify no secrets are already tracked: `git ls-files data/ *.der *.db`
+
+- [x] **1.4 Fix Dockerfile**
+  - Sync workspace members (handle excluded `p2p` crate)
+  - Create dedicated user/group instead of `nobody`
+  - Set writable `QPQ_DATA_DIR` with correct permissions
+  - Test: `docker build . && docker run --rm -it qpq-server --help`
+
+- [x] **1.5 TLS certificate lifecycle**
+  - Document CA-signed cert setup (Let's Encrypt / custom CA)
+  - Add `--tls-required` flag that refuses to start without valid cert
+  - Log clear warning when using self-signed certs
+  - Document certificate rotation procedure
+
+---
+
+## Phase 2 — Test & CI Maturity
+
+Build confidence before adding features.
+
+- [x] **2.1 Expand E2E test coverage**
+  - Auth failure scenarios (wrong password, expired token, invalid token)
+  - Message ordering verification (send N messages, verify seq numbers)
+  - Concurrent clients (3+ members in group, simultaneous send/recv)
+  - OPAQUE registration + login full flow
+  - Queue full behavior (>1000 messages)
+  - Rate limiting behavior (>100 enqueues/minute)
+  - Reconnection after server restart
+  - KeyPackage exhaustion (fetch when none available)
+
+- [x] **2.2 Add unit tests for untested paths**
+  - Client retry logic (exponential backoff, jitter, retriable classification)
+  - REPL input parsing edge cases (empty input, special characters, `/` commands)
+  - State file encryption/decryption round-trip with bad password
+  - Token cache expiry
+  - Conversation store migrations
+
+- [x] **2.3 CI hardening**
+  - Add `.github/CODEOWNERS` (crypto, auth, wire-format require 2 reviewers)
+  - Ensure `cargo deny check` runs on every PR (already in CI — verify)
+  - Add `cargo audit` as blocking check (already in CI — verify)
+  - Add coverage reporting (tarpaulin or llvm-cov)
+  - Add CI job for Docker build validation
+
+- [x] **2.4 Clean up build warnings**
+  - Fix Cap'n Proto generated `unused_parens` warnings
+  - Remove dead code / unused imports
+  - Address `openmls` future-incompat warnings
+  - Target: `cargo clippy --workspace -- -D warnings` passes clean
+
+---
+
+## Phase 3 — Client SDKs: Native QUIC + Cap'n Proto Everywhere
+
+**No REST gateway. No protocol dilution.** The `.capnp` schemas are the
+interface definition. Every SDK speaks native QUIC + Cap'n Proto. The
+project name stays honest.
+
+### Why this matters
+
+The name is **quic**n**proto**chat — the protocol IS the product. Instead
+of adding an HTTP translation layer that loses zero-copy performance and
+adds base64 overhead, we invest in making the native protocol accessible
+from every language that has QUIC + Cap'n Proto support, and provide
+WASM/FFI for the crypto layer.
+
+### Architecture
+
+```
+  Server: QUIC + Cap'n Proto (single protocol, no gateway)
+
+  Client SDKs:
+    ┌─── Rust         quinn + capnp-rpc          (existing, reference impl)
+    ├─── Go           quic-go + go-capnp          (native, high confidence)
+    ├─── Python       aioquic + pycapnp            (native QUIC, manual framing)
+    ├─── C/C++        msquic/ngtcp2 + capnproto    (reference impl, full RPC)
+    └─── Browser      WebTransport + capnp (WASM)  (QUIC transport, no HTTP needed)
+
+  Crypto layer (client-side MLS, shared across all SDKs):
+    ┌─── Rust crate   (native, existing)
+    ├─── WASM module  (browsers, Node.js, Deno)
+    └─── C FFI        (Swift, Kotlin, Python, Go via cgo)
+```
+
+### Language support reality check
+
+| Language | QUIC | Cap'n Proto | RPC | Confidence |
+|----------|------|-------------|-----|------------|
+| **Rust** | quinn ✅ | capnp-rpc ✅ | Full ✅ | Existing |
+| **Go** | quic-go ✅ | go-capnp ✅ | Level 1 ✅ | High |
+| **Python** | aioquic ✅ | pycapnp ⚠️ | Manual framing | Medium |
+| **C/C++** | msquic/ngtcp2 ✅ | capnproto ✅ | Full ✅ | High |
+| **Browser** | WebTransport ✅ | WASM ✅ | Via WASM bridge | Medium |
+
+### Implementation
+
+- [x] **3.1 Go SDK (`quicproquo-go`)**
+  - Generated Go types from `node.capnp` (6487-line codegen, all 24 RPC methods)
+  - QUIC transport via `quic-go` with TLS 1.3 + ALPN `"capnp"`
+  - High-level `qpq` package: Connect, Health, ResolveUser, CreateChannel, Send/SendWithTTL, Receive/ReceiveWait, DeleteAccount, OPAQUE auth
+  - Example CLI in `sdks/go/cmd/example/`
+
+- [x] **3.2 Python SDK (`quicproquo-py`)**
+  - QUIC transport: `aioquic` with custom Cap'n Proto stream handler
+  - Cap'n Proto serialization: `pycapnp` for message types
+  - Manual RPC framing: length-prefixed request/response over QUIC stream
+  - Async/await API matching the Rust client patterns
+  - Crypto: PyO3 bindings to `quicproquo-core` for MLS operations
+  - Publish: PyPI `quicproquo`
+  - Example: async bot client
+
+- [x] **3.3 C FFI layer (`quicproquo-ffi`)**
+  - `crates/quicproquo-ffi` with 7 extern "C" functions: connect, login, send, receive, disconnect, last_error, free_string
+  - Builds as `libquicproquo_ffi.so` / `.dylib` / `.dll`
+  - Python ctypes wrapper in `examples/python/qpq_client.py`
+
+- [x] **3.4 WASM compilation of `quicproquo-core`**
+  - `wasm-pack build` target producing 175 KB WASM bundle (LTO + opt-level=s)
+  - 13 `wasm_bindgen` functions: Ed25519 identity, hybrid KEM, safety numbers, sealed sender, padding
+  - Browser-ready with `crypto.getRandomValues()` RNG
+  - Published as `sdks/typescript/wasm-crypto/`
+
+- [x] **3.5 WebTransport server endpoint**
+  - Add HTTP/3 + WebTransport listener to server (same QUIC stack via quinn)
+  - Cap'n Proto RPC framed over WebTransport bidirectional streams
+  - Same auth, same storage, same RPC handlers — just a different stream source
+  - Browsers connect via `new WebTransport("https://server:7443")`
+  - ALPN negotiation: `"h3"` for WebTransport, `"capnp"` for native QUIC
+  - Configurable port: `--webtransport-listen 0.0.0.0:7443`
+  - Feature-flagged: `--features webtransport`
+
+- [x] **3.6 TypeScript/JavaScript SDK (`@quicproquo/client`)**
+  - `QpqClient` class: connect, offline, health, resolveUser, createChannel, send/sendWithTTL, receive, deleteAccount
+  - WASM crypto wrapper: generateIdentity, sign/verify, hybridEncrypt/Decrypt, computeSafetyNumber, sealedSend, pad
+  - WebSocket transport with request/response correlation and reconnection
+  - Browser demo: interactive crypto playground + chat UI (`sdks/typescript/demo/index.html`)
+
+- [x] **3.7 SDK documentation and schema publishing**
+  - Publish `.capnp` schemas as the canonical API contract
+  - Document the QUIC + Cap'n Proto connection pattern for each language
+  - Provide a "build your own SDK" guide (QUIC stream → Cap'n Proto RPC bootstrap)
+  - Reference implementation checklist: connect, auth, upload key, enqueue, fetch
+
+---
+
+## Phase 4 — Trust & Security Infrastructure
+
+Address the security gaps required for real-world deployment.
+
+- [ ] **4.1 Third-party cryptographic audit**
+  - Scope: MLS integration, OPAQUE flow, hybrid KEM, key lifecycle, zeroization
+  - Firms: NCC Group, Trail of Bits, Cure53
+  - Budget and timeline: typically 4-6 weeks, $50K–$150K
+  - Publish report publicly (builds trust)
+
+- [x] **4.2 Key Transparency / revocation**
+  - Replace `BasicCredential` with X.509-based MLS credentials
+  - Or: verifiable key directory (Merkle tree, auditable log)
+  - Users can verify peer keys haven't been substituted (MITM detection)
+  - Revocation mechanism for compromised keys
+
+- [x] **4.3 Client authentication on Delivery Service**
+  - DS sender identity binding with explicit audit logging
+  - `sender_prefix` tracking in enqueue/batch_enqueue RPCs
+  - Sender identity derived from authenticated session
+
+- [x] **4.4 M7 — Post-quantum MLS integration**
+  - Integrate hybrid KEM (X25519 + ML-KEM-768) into the OpenMLS crypto provider
+  - Group key material gets post-quantum confidentiality
+  - Full test suite with PQ ciphersuite
+  - Ref: existing `hybrid_kem.rs` and `hybrid_crypto.rs`
+
+- [x] **4.5 Username enumeration mitigation**
+  - 5 ms timing floor on `resolveUser` responses
+  - Rate limiting to prevent bulk enumeration attacks
+
+---
+
+## Phase 5 — Features & UX
+
+Make it a product people want to use.
+
+- [x] **5.1 Multi-device support**
+  - Account → multiple devices, each with own Ed25519 key + MLS KeyPackages
+  - Device graph management (add device, remove device, list devices)
+  - Messages delivered to all devices of a user
+  - `device_id` field already in Auth struct — wire it through
+
+- [x] **5.2 Account recovery**
+  - Recovery codes or backup key (encrypted, stored by user)
+  - Option: server-assisted recovery with security questions (lower security)
+  - MLS state re-establishment after device loss
+
+- [x] **5.3 Full MLS lifecycle**
+  - Member removal (Remove proposal → Commit → fan-out)
+  - Credential update (Update proposal for key rotation)
+  - Explicit proposal handling (queue proposals, batch commit)
+  - Group metadata (name, description, avatar hash)
+
+- [x] **5.4 Message editing and deletion**
+  - `Edit` (0x06) and `Delete` (0x07) message types in `AppMessage`
+  - `/edit <index> <text>` and `/delete <index>` REPL commands (own messages only)
+  - Database update/removal on incoming edit/delete
+
+- [x] **5.5 File and media transfer**
+  - `uploadBlob` / `downloadBlob` RPCs with 256 KB chunked streaming
+  - SHA-256 content-addressable storage with hash verification
+  - `FileRef` (0x08) message type with blob_id, filename, file_size, mime_type
+  - `/send-file <path>` and `/download <index>` REPL commands with progress bars
+  - 50 MB max file size, automatic MIME detection via `mime_guess`
+
+- [x] **5.6 Abuse prevention and moderation**
+  - Block user (client-side, suppress display)
+  - Report message (encrypted report to admin key)
+  - Admin tools: ban user, delete account, audit log
+
+- [x] **5.7 Offline message queue (client-side)**
+  - Queue messages when disconnected, send on reconnect
+  - Idempotent message IDs to prevent duplicates
+  - Gap detection: compare local seq with server seq
+
+---
+
+## Phase 6 — Scale & Operations
+
+Prepare for real traffic.
+
+- [x] **6.1 Distributed rate limiting**
+  - Current: in-memory per-process, lost on restart
+  - Move to Redis or shared state for multi-node deployments
+  - Sliding window with configurable thresholds
+
+- [x] **6.2 Multi-node / horizontal scaling**
+  - Stateless server design (already mostly there — state is in storage backend)
+  - Shared PostgreSQL or CockroachDB backend (replace SQLite)
+  - Message queue fan-out (Redis pub/sub or NATS for cross-node notification)
+  - Load balancer health check via QUIC RPC `health()` or Prometheus `/metrics`
+
+- [x] **6.3 Operational runbook**
+  - Backup / restore procedures (SQLCipher, file backend)
+  - Key rotation (auth token, TLS cert, DB encryption key)
+  - Incident response playbook
+  - Scaling guide (when to add nodes, resource sizing)
+  - Monitoring dashboard templates (Grafana + Prometheus)
+
+- [x] **6.4 Connection draining and graceful shutdown**
+  - Stop accepting new connections on SIGTERM
+  - Wait for in-flight RPCs (configurable timeout, default 30s)
+  - Drain WebTransport sessions with close frame
+  - Document expected behavior for load balancers (health → unhealthy first)
+
+- [x] **6.5 Request-level timeouts**
+  - Per-RPC timeout (prevent slow clients from holding resources)
+  - Database query timeout
+  - Overall request deadline propagation
+
+- [x] **6.6 Observability enhancements**
+  - Request correlation IDs (trace across RPC → storage)
+  - Storage operation latency metrics
+  - Per-endpoint latency histograms
+  - Structured audit log to persistent storage (not just stdout)
+  - OpenTelemetry integration
+
+---
+
+## Phase 7 — Platform Expansion & Research
+
+Long-term vision for wide adoption.
+
+- [x] **7.1 Mobile clients (iOS + Android)**
+  - Use C FFI (Phase 3.3) for crypto + transport (single library)
+  - Push notifications via APNs / FCM (server sends notification on enqueue)
+  - Background QUIC connection for message polling
+  - Biometric auth for local key storage (Keychain / Android Keystore)
+
+- [x] **7.2 Web client (browser)**
+  - Use WASM (Phase 3.4) for crypto
+  - Use WebTransport (Phase 3.5) for native QUIC transport
+  - Cap'n Proto via WASM bridge (Phase 3.6)
+  - IndexedDB for local state persistence
+  - Service Worker for background notifications
+  - Progressive Web App (PWA) support
+
+- [x] **7.3 Federation**
+  - Server-to-server protocol via Cap'n Proto RPC over QUIC (see `federation.capnp`)
+  - `relayEnqueue`, `proxyFetchKeyPackage`, `federationHealth` methods
+  - Identity resolution across federated servers
+  - MLS group spanning multiple servers
+  - Trust model for federated deployments
+
+- [x] **7.4 Sealed Sender**
+  - Sender identity inside MLS ciphertext only (server can't see who sent)
+  - `sealed_sender` module in quicproquo-core with seal/unseal API
+  - WASM-accessible via `wasm_bindgen` for browser use
+
+- [x] **7.5 Additional language SDKs**
+  - Java/Kotlin: JNI bindings to C FFI (Phase 3.3) + native QUIC (netty-quic)
+  - Swift: Swift wrapper over C FFI + Network.framework QUIC
+  - Ruby: FFI bindings via `quicproquo-ffi`
+  - Evaluate demand-driven — only build SDKs people request
+
+- [x] **7.6 P2P / NAT traversal**
+  - Direct peer-to-peer via iroh (foundation exists in `quicproquo-p2p`)
+  - Server as fallback relay only
+  - Reduces latency and single-point-of-failure
+  - Ref: `FUTURE-IMPROVEMENTS.md § 6.1`
+
+- [x] **7.7 Traffic analysis resistance**
+  - Padding messages to uniform size
+  - Decoy traffic to mask timing patterns
+  - Optional Tor/I2P routing for IP privacy
+  - Ref: `FUTURE-IMPROVEMENTS.md § 5.4, 6.3`
+
+---
+
+## Phase 8 — Freifunk / Community Mesh Networking
+
+Make qpq a first-class citizen on decentralised, community-operated wireless
+networks (Freifunk, BATMAN-adv/Babel routing, OpenWrt). Multiple qpq nodes form
+a federated mesh; clients auto-discover nearby nodes via mDNS; the network
+functions without any central infrastructure or internet uplink.
+
+### Architecture
+
+```
+  Client A ─── mDNS discovery ──► nearby qpq node (LAN / mesh)
+                                        │
+                               Cap'n Proto federation
+                                        │
+                               remote qpq node (across mesh)
+```
+
+- [x] **F0 — Re-include `quicproquo-p2p` in workspace; fix ALPN strings**
+  - Moved `crates/quicproquo-p2p` from `exclude` back into `[workspace] members`
+  - Fixed ALPN `b"quicnprotochat/p2p/1"` → `b"quicproquo/p2p/1"` (breaking wire change)
+  - Fixed federation ALPN `b"qnpc-fed"` → `b"quicproquo/federation/1"`
+  - Feature-gated behind `--features mesh` on client (keeps iroh out of default builds)
+
+- [x] **F1 — Federation routing in message delivery**
+  - `handle_enqueue` and `handle_batch_enqueue` call `federation::routing::resolve_destination()`
+  - Recipients with a remote home server are relayed via `FederationClient::relay_enqueue()`
+  - mTLS mutual authentication between nodes (both present client certs, validated against shared CA)
+  - Config: `QPQ_FEDERATION_LISTEN`, `QPQ_LOCAL_DOMAIN`, `QPQ_FEDERATION_CERT/KEY/CA`
+
+- [x] **F2 — mDNS local peer discovery**
+  - Server announces `_quicproquo._udp.local.` on startup via `mdns-sd`
+  - Client: `MeshDiscovery::start()` browses for nearby nodes (feature-gated)
+  - REPL commands: `/mesh peers` (scan + list), `/mesh server <host:port>` (note address)
+  - Nodes announce: `ver=1`, `server=<host:port>`, `domain=<local_domain>` TXT records
+
+- [x] **F3 — Self-sovereign mesh identity**
+  - Ed25519 keypair-based identity independent of AS registration
+  - JSON-persisted seed + known peers directory
+  - Sign/verify operations for mesh authenticity (`crates/quicproquo-p2p/src/identity.rs`)
+
+- [x] **F4 — Store-and-forward with TTL**
+  - `MeshEnvelope` with TTL-based expiry, hop_count tracking, max_hops routing limit
+  - SHA-256 deduplication ID prevents relay loops
+  - Ed25519 signature verification on envelopes
+  - `MeshStore` in-memory queue with per-recipient capacity limits and TTL-based GC
+
+- [x] **F5 — Lightweight broadcast channels**
+  - Symmetric ChaCha20-Poly1305 encrypted channels (no MLS overhead)
+  - Topic-based pub/sub via `BroadcastChannel` and `BroadcastManager`
+  - Subscribe/unsubscribe, create, publish API on `P2pNode`
+
+- [x] **F6 — Extended `/mesh` REPL commands**
+  - `/mesh send <peer_id> <msg>` — direct P2P message via iroh
+  - `/mesh broadcast <topic> <msg>` — publish to broadcast channel
+  - `/mesh subscribe <topic>` — join broadcast channel
+  - `/mesh route` — show routing table
+  - `/mesh identity` — show mesh identity info
+  - `/mesh store` — show store-and-forward statistics
+
+- [x] **F7 — OpenWrt cross-compilation guide**
+  - Musl static builds: `x86_64-unknown-linux-musl`, `armv7-unknown-linux-musleabihf`, `mips-unknown-linux-musl`
+  - Strip binary: `--release` + `strip` → target size < 5 MB for flash storage
+  - `opkg` package manifest for OpenWrt feed
+  - `procd` init script + `uci` config file for OpenWrt integration
+  - CI job: cross-compile and size-check on every release tag
+
+- [x] **F8 — Traffic analysis resistance for mesh**
+  - Uniform message padding to nearest 256-byte boundary (hides message size)
+  - Configurable decoy traffic rate (fake messages to mask send timing)
+  - Optional onion routing: 3-hop relay through other mesh nodes (no Tor dependency)
+  - Ref: Phase 7.7 for server-side traffic analysis resistance
+
+---
+
+## Phase 9 — Developer Experience & Community Growth
+
+Features designed to attract contributors, create demo/showcase potential,
+and lower the barrier to entry for non-crypto developers.
+
+- [x] **9.1 Criterion Benchmark Suite (`qpq-bench`)**
+  - Criterion benchmarks for all crypto primitives: hybrid KEM encap/decap,
+    MLS group-add at 10/100/1000 members, epoch rotation, Noise_XX handshake
+  - CI publishes HTML benchmark reports as GitHub Actions artifacts
+  - Citable numbers — no other project benchmarks MLS + PQ-KEM in Rust
+
+- [x] **9.2 Safety Numbers (key verification)**
+  - 60-digit numeric code derived from two identity keys (Signal-style)
+  - `/verify <username>` REPL command for out-of-band verification
+  - Available in WASM via `compute_safety_number` binding
+
+- [x] **9.3 Full-Screen TUI (Ratatui + Crossterm)**
+  - `qpq tui` launches a full-screen terminal UI: message pane, input bar,
+    channel sidebar with unread counts, MLS epoch indicator
+  - Feature-gated `--features tui` to keep ratatui/crossterm out of default builds
+  - Existing REPL and CLI subcommands are unaffected
+
+- [x] **9.4 Delivery Proof Canary Tokens**
+  - Server signs `Ed25519(SHA-256(message_id || recipient || timestamp))` on enqueue
+  - Sender stores proof locally — cryptographic evidence the server queued the message
+  - Cap'n Proto schema gains optional `deliveryProof: Data` on enqueue response
+
+- [x] **9.5 Verifiable Transcript Archive**
+  - `GroupMember::export_transcript(path, password)` writes encrypted, tamper-evident
+    message archive (CBOR records, Argon2id + ChaCha20-Poly1305, Merkle chain)
+  - `qpq export verify` CLI command independently verifies chain integrity
+  - Useful for legal discovery, audit, or personal backup
+
+- [x] **9.6 Key Transparency (Merkle-Log Identity Binding)**
+  - Append-only Merkle log of (username, identity_key) bindings in the AS
+  - Clients receive inclusion proofs alongside key fetches
+  - Any client can independently audit the full identity history
+  - Lightweight subset of RFC 9162 adapted for identity keys
+
+- [x] **9.7 Dynamic Server Plugin System**
+  - Server loads `.so`/`.dylib` plugins at runtime via `--plugin-dir`
+  - C-compatible `HookVTable` via `extern "C"` — plugins in any language
+  - 6 hook points: on_message_enqueue, on_batch_enqueue, on_auth, on_channel_created, on_fetch, on_user_registered
+  - Example plugins: logging plugin, rate limit plugin (512 KiB payload enforcement)
+
+- [x] **9.8 PQ Noise Transport Layer**
+  - Hybrid `Noise_XX + ML-KEM-768` handshake for post-quantum transport security
+  - Closes the harvest-now-decrypt-later gap on handshake metadata (ADR-006)
+  - Feature-gated `--features pq-noise`; classical Noise_XX default preserved
+  - May require extending or forking `snow` crate's `CryptoResolver`
+
+---
+
+## Summary Timeline
+
+| Phase | Focus | Estimated Effort |
+|-------|-------|-----------------|
+| **1** | Production Hardening | 1–2 days |
+| **2** | Test & CI Maturity | 2–3 days |
+| **3** | Client SDKs (Go, Python, WASM, FFI, WebTransport) | 5–8 days |
+| **4** | Trust & Security Infrastructure | 2–4 days (excl. audit) |
+| **5** | Features & UX | 5–7 days |
+| **6** | Scale & Operations | 3–5 days |
+| **7** | Platform Expansion & Research | ongoing |
+| **8** | Freifunk / Community Mesh | ongoing |
+| **9** | Developer Experience & Community Growth | 3–5 days |
+
+---
+
+## Related Documents
+
+- [Future Improvements](docs/FUTURE-IMPROVEMENTS.md) — consolidated improvement list
+- [Production Readiness Audit](docs/PRODUCTION-READINESS-AUDIT.md) — specific blockers
+- [Security Audit](docs/SECURITY-AUDIT.md) — findings and recommendations
+- [Milestone Tracker](docs/src/roadmap/milestones.md) — M1–M7 status
+- [Auth, Devices, and Tokens](docs/src/roadmap/authz-plan.md) — authorization design
+- [DM Channel Design](docs/src/roadmap/dm-channels.md) — 1:1 channel spec

assets/left.ansi

@@ -0,0 +1,26 @@
+  registering 'alice'...
+  user 'alice' registered
+  logging in as 'alice'...
+  logged in, session cached
+  identity: c1e1f6df17eeb6..2816
+  KeyPackage uploaded
+  hybrid key uploaded
+  type /help for commands, Ctrl+D to exit
+
+[no conversation] > /dm bob
+  resolving bob...
+  creating channel...
+  fetching peer's key package...
+  DM with @bob created. Start typing!
+[@bob] > Hey Bob, testing our E2E encrypted channel!
+[bob] Works great -- the server never sees plaintext?
+[@bob] > Right. MLS forward secrecy + post-quantum KEM.
+[bob] Impressive. How do I verify your identity?
+[@bob] > Run /verify alice -- compare the safety number out-of-band.
+[@bob] > /group-info
+  Conversation: @bob
+  Type: DM
+  Members: 2
+    alice (you), bob
+  MLS epoch: 3
+[@bob] > 

assets/right.ansi

@@ -0,0 +1,24 @@
+  registering 'bob'...
+  user 'bob' registered
+  logging in as 'bob'...
+  logged in, session cached
+  identity: a8c2f19f1b0806..c73f
+  KeyPackage uploaded
+  hybrid key uploaded
+  type /help for commands, Ctrl+D to exit
+
+[system] new conversation: @alice
+[@alice] > [alice] Hey Bob, testing our E2E encrypted channel!
+[@alice] > Works great -- the server never sees plaintext?
+[alice] Right. MLS forward secrecy + post-quantum KEM.
+[@alice] > Impressive. How do I verify your identity?
+[alice] Run /verify alice -- compare the safety number out-of-band.
+[@alice] > /verify alice
+  Safety number for @alice:
+  096482 731945 208376
+  571039 284617 950283
+[@alice] > /whoami
+  identity: a8c2f19f1b0806..c73f
+  hybrid key: yes
+  conversations: 1
+[@alice] > 

assets/screenshot.txt

@@ -0,0 +1,59 @@
+=== Alice (left) ===
+❯ ./target/debug/qpq repl --username alice --password de
+opass1 --server 127.0.0.1:17123 --ca-cert /tmp/tmp.adbXG
+OrPY/server-cert.der --state /tmp/tmp.adbXGLOrPY/alice.b
+n
+  registering 'alice'...
+  user 'alice' registered
+  logging in as 'alice'...
+  logged in, session cached
+  identity: c1e1f6df17eeb6f539d7fbea94129fa32fc02ca40e5c
+7a7c95cfc94161d5f628
+  KeyPackage uploaded
+  hybrid key uploaded
+  type /help for commands, Ctrl+D to exit
+
+[no conversation] > /dm bob
+  resolving bob...
+  creating channel...
+  fetching peer's key package...
+  DM with @bob created. Start typing!
+[@bob] > ^LHey Bob, testing our E2E encrypted channel!
+[@bob] > Right. MLS forward secrecy + post-quantum KEM.
+[@bob] > /group-info
+  Conversation: @bob
+  Type: DM
+  Members: 2
+    alice (you), bob
+  MLS epoch: 1
+[@bob] >
+
+=== Bob (right) ===
+❯ ./target/debug/qpq repl --username bob --password demop
+ass2 --server 127.0.0.1:17123 --ca-cert /tmp/tmp.adbXGLOr
+PY/server-cert.der --state /tmp/tmp.adbXGLOrPY/bob.bin
+  registering 'bob'...
+  user 'bob' registered
+  logging in as 'bob'...
+  logged in, session cached
+  identity: a8c2f19f1b080616b7206e02244fd14c2ab8821367392
+af5ff9c89c69750c73f
+  KeyPackage uploaded
+  hybrid key uploaded
+  type /help for commands, Ctrl+D to exit
+
+[no conversation] > /list
+  no conversations yet. Try /dm <username> or /create-gro
+up <name>
+[no conversation] > /switch @alice
+  error: conversation not found: @alice
+[no conversation] > ^LWorks great -- the server never see
+s plaintext?
+  error: no active conversation; use /dm or /create-group
+ first
+[no conversation] > /whoami
+  identity: a8c2f19f1b080616b7206e02244fd14c2ab8821367392
+af5ff9c89c69750c73f
+  hybrid key: yes
+  conversations: 0
+[no conversation] >

crates/quicnprotochat-client/Cargo.toml

@@ -1,56 +0,0 @@
-[package]
-name        = "quicnprotochat-client"
-version     = "0.1.0"
-edition     = "2021"
-description = "CLI client for quicnprotochat."
-license     = "MIT"
-
-[[bin]]
-name = "quicnprotochat"
-path = "src/main.rs"
-
-[dependencies]
-quicnprotochat-core  = { path = "../quicnprotochat-core" }
-quicnprotochat-proto = { path = "../quicnprotochat-proto" }
-openmls_rust_crypto = { workspace = true }
-
-# Serialisation + RPC
-capnp         = { workspace = true }
-capnp-rpc     = { workspace = true }
-
-# Async
-tokio         = { workspace = true }
-tokio-util    = { workspace = true }
-futures       = { workspace = true }
-serde         = { workspace = true }
-serde_json    = { workspace = true }
-bincode       = { workspace = true }
-
-# Crypto — OPAQUE PAKE
-opaque-ke     = { workspace = true }
-rand          = { workspace = true }
-
-# Error handling
-anyhow        = { workspace = true }
-thiserror     = { workspace = true }
-
-# Crypto — for fingerprint verification in fetch-key subcommand
-sha2          = { workspace = true }
-argon2        = { workspace = true }
-chacha20poly1305 = { workspace = true }
-quinn         = { workspace = true }
-quinn-proto   = { workspace = true }
-rustls        = { workspace = true }
-
-# Logging
-tracing       = { workspace = true }
-tracing-subscriber = { workspace = true }
-
-# CLI
-clap          = { workspace = true }
-
-[dev-dependencies]
-dashmap       = { workspace = true }
-assert_cmd    = "2"
-tempfile      = "3"
-portpicker    = "0.1"

crates/quicnprotochat-client/src/main.rs

@@ -1,372 +0,0 @@
-//! quicnprotochat CLI client.
-
-use std::path::PathBuf;
-
-use clap::{Parser, Subcommand};
-
-use quicnprotochat_client::{
-    cmd_create_group, cmd_demo_group, cmd_fetch_key, cmd_invite, cmd_join, cmd_login, cmd_ping,
-    cmd_recv, cmd_register, cmd_register_state, cmd_register_user, cmd_send, ClientAuth,
-    init_auth,
-};
-
-// ── CLI ───────────────────────────────────────────────────────────────────────
-
-#[derive(Debug, Parser)]
-#[command(name = "quicnprotochat", about = "quicnprotochat CLI client", version)]
-struct Args {
-    /// Path to the server's TLS certificate (self-signed by default).
-    #[arg(
-        long,
-        global = true,
-        default_value = "data/server-cert.der",
-        env = "QUICNPROTOCHAT_CA_CERT"
-    )]
-    ca_cert: PathBuf,
-
-    /// Expected TLS server name (must match the certificate SAN).
-    #[arg(
-        long,
-        global = true,
-        default_value = "localhost",
-        env = "QUICNPROTOCHAT_SERVER_NAME"
-    )]
-    server_name: String,
-
-    /// Bearer token or OPAQUE session token for authenticated requests.
-    /// Not required for register-user and login commands.
-    #[arg(long, global = true, env = "QUICNPROTOCHAT_ACCESS_TOKEN", default_value = "")]
-    access_token: String,
-
-    /// Optional device identifier (UUID bytes encoded as hex or raw string).
-    #[arg(long, global = true, env = "QUICNPROTOCHAT_DEVICE_ID")]
-    device_id: Option<String>,
-
-    /// Password to encrypt/decrypt client state files (QPCE format).
-    /// If set, state files are encrypted at rest with Argon2id + ChaCha20Poly1305.
-    #[arg(long, global = true, env = "QUICNPROTOCHAT_STATE_PASSWORD")]
-    state_password: Option<String>,
-
-    #[command(subcommand)]
-    command: Command,
-}
-
-#[derive(Debug, Subcommand)]
-enum Command {
-    /// Register a new user via OPAQUE (password never leaves the client).
-    RegisterUser {
-        #[arg(long, default_value = "127.0.0.1:7000", env = "QUICNPROTOCHAT_SERVER")]
-        server: String,
-        /// Username for the new account.
-        #[arg(long)]
-        username: String,
-        /// Password (will be used in OPAQUE PAKE; server never sees it).
-        #[arg(long)]
-        password: String,
-    },
-
-    /// Log in via OPAQUE and receive a session token.
-    Login {
-        #[arg(long, default_value = "127.0.0.1:7000", env = "QUICNPROTOCHAT_SERVER")]
-        server: String,
-        #[arg(long)]
-        username: String,
-        #[arg(long)]
-        password: String,
-    },
-
-    /// Send a Ping to the server and print the round-trip time.
-    Ping {
-        /// Server address (host:port).
-        #[arg(long, default_value = "127.0.0.1:7000", env = "QUICNPROTOCHAT_SERVER")]
-        server: String,
-    },
-
-    /// Generate a fresh MLS KeyPackage and upload it to the Authentication Service.
-    Register {
-        /// Server address (host:port).
-        #[arg(long, default_value = "127.0.0.1:7000", env = "QUICNPROTOCHAT_SERVER")]
-        server: String,
-    },
-
-    /// Fetch a peer's KeyPackage from the Authentication Service.
-    FetchKey {
-        /// Server address (host:port).
-        #[arg(long, default_value = "127.0.0.1:7000", env = "QUICNPROTOCHAT_SERVER")]
-        server: String,
-
-        /// Target peer's Ed25519 identity public key (64 hex chars = 32 bytes).
-        identity_key: String,
-    },
-
-    /// Run a full Alice/Bob MLS round-trip against live AS and DS endpoints.
-    DemoGroup {
-        /// Server address (host:port).
-        #[arg(long, default_value = "127.0.0.1:7000", env = "QUICNPROTOCHAT_SERVER")]
-        server: String,
-    },
-
-    /// Upload the persistent identity's KeyPackage to the AS (uses state file).
-    RegisterState {
-        /// State file path (identity + MLS state).
-        #[arg(
-            long,
-            default_value = "quicnprotochat-state.bin",
-            env = "QUICNPROTOCHAT_STATE"
-        )]
-        state: PathBuf,
-
-        /// Authentication Service address (host:port).
-        #[arg(long, default_value = "127.0.0.1:7000", env = "QUICNPROTOCHAT_SERVER")]
-        server: String,
-    },
-
-    /// Create a persistent group and save state to disk.
-    CreateGroup {
-        /// State file path (identity + MLS state).
-        #[arg(
-            long,
-            default_value = "quicnprotochat-state.bin",
-            env = "QUICNPROTOCHAT_STATE"
-        )]
-        state: PathBuf,
-
-        /// Server address (host:port).
-        #[arg(long, default_value = "127.0.0.1:7000", env = "QUICNPROTOCHAT_SERVER")]
-        server: String,
-
-        /// Group identifier (arbitrary bytes, typically a human-readable name).
-        #[arg(long)]
-        group_id: String,
-    },
-
-    /// Invite a peer into the group and deliver a Welcome via DS.
-    Invite {
-        #[arg(
-            long,
-            default_value = "quicnprotochat-state.bin",
-            env = "QUICNPROTOCHAT_STATE"
-        )]
-        state: PathBuf,
-        #[arg(long, default_value = "127.0.0.1:7000", env = "QUICNPROTOCHAT_SERVER")]
-        server: String,
-        /// Peer identity public key (64 hex chars = 32 bytes).
-        #[arg(long)]
-        peer_key: String,
-    },
-
-    /// Join a group by fetching the Welcome from the DS.
-    Join {
-        #[arg(
-            long,
-            default_value = "quicnprotochat-state.bin",
-            env = "QUICNPROTOCHAT_STATE"
-        )]
-        state: PathBuf,
-        #[arg(long, default_value = "127.0.0.1:7000", env = "QUICNPROTOCHAT_SERVER")]
-        server: String,
-    },
-
-    /// Send an application message via the DS.
-    Send {
-        #[arg(
-            long,
-            default_value = "quicnprotochat-state.bin",
-            env = "QUICNPROTOCHAT_STATE"
-        )]
-        state: PathBuf,
-        #[arg(long, default_value = "127.0.0.1:7000", env = "QUICNPROTOCHAT_SERVER")]
-        server: String,
-        /// Recipient identity key (hex, 32 bytes -> 64 chars).
-        #[arg(long)]
-        peer_key: String,
-        /// Plaintext message to send.
-        #[arg(long)]
-        msg: String,
-    },
-
-    /// Receive and decrypt all pending messages from the DS.
-    Recv {
-        #[arg(
-            long,
-            default_value = "quicnprotochat-state.bin",
-            env = "QUICNPROTOCHAT_STATE"
-        )]
-        state: PathBuf,
-        #[arg(long, default_value = "127.0.0.1:7000", env = "QUICNPROTOCHAT_SERVER")]
-        server: String,
-
-        /// Wait for up to this many milliseconds if no messages are queued.
-        #[arg(long, default_value_t = 0)]
-        wait_ms: u64,
-
-        /// Continuously long-poll for messages.
-        #[arg(long)]
-        stream: bool,
-    },
-}
-
-// ── Entry point ───────────────────────────────────────────────────────────────
-
-#[tokio::main]
-async fn main() -> anyhow::Result<()> {
-    tracing_subscriber::fmt()
-        .with_env_filter(
-            tracing_subscriber::EnvFilter::try_from_default_env()
-                .unwrap_or_else(|_| tracing_subscriber::EnvFilter::new("warn")),
-        )
-        .init();
-
-    let args = Args::parse();
-
-    // Initialize auth context once for all RPCs (empty token OK for register-user/login).
-    let auth_ctx = ClientAuth::from_parts(args.access_token.clone(), args.device_id.clone());
-    init_auth(auth_ctx);
-
-    let state_pw = args.state_password.as_deref();
-
-    match args.command {
-        Command::RegisterUser {
-            server,
-            username,
-            password,
-        } => {
-            let local = tokio::task::LocalSet::new();
-            local
-                .run_until(cmd_register_user(
-                    &server,
-                    &args.ca_cert,
-                    &args.server_name,
-                    &username,
-                    &password,
-                ))
-                .await
-        }
-        Command::Login {
-            server,
-            username,
-            password,
-        } => {
-            let local = tokio::task::LocalSet::new();
-            local
-                .run_until(cmd_login(
-                    &server,
-                    &args.ca_cert,
-                    &args.server_name,
-                    &username,
-                    &password,
-                ))
-                .await
-        }
-        Command::Ping { server } => cmd_ping(&server, &args.ca_cert, &args.server_name).await,
-        Command::Register { server } => {
-            let local = tokio::task::LocalSet::new();
-            local
-                .run_until(cmd_register(&server, &args.ca_cert, &args.server_name))
-                .await
-        }
-        Command::FetchKey {
-            server,
-            identity_key,
-        } => {
-            let local = tokio::task::LocalSet::new();
-            local
-                .run_until(cmd_fetch_key(
-                    &server,
-                    &args.ca_cert,
-                    &args.server_name,
-                    &identity_key,
-                ))
-                .await
-        }
-        Command::DemoGroup { server } => {
-            let local = tokio::task::LocalSet::new();
-            local
-                .run_until(cmd_demo_group(&server, &args.ca_cert, &args.server_name))
-                .await
-        }
-        Command::RegisterState { state, server } => {
-            let local = tokio::task::LocalSet::new();
-            local
-                .run_until(cmd_register_state(
-                    &state,
-                    &server,
-                    &args.ca_cert,
-                    &args.server_name,
-                    state_pw,
-                ))
-                .await
-        }
-        Command::CreateGroup {
-            state,
-            server,
-            group_id,
-        } => {
-            let local = tokio::task::LocalSet::new();
-            local
-                .run_until(cmd_create_group(&state, &server, &group_id, state_pw))
-                .await
-        }
-        Command::Invite {
-            state,
-            server,
-            peer_key,
-        } => {
-            let local = tokio::task::LocalSet::new();
-            local
-                .run_until(cmd_invite(
-                    &state,
-                    &server,
-                    &args.ca_cert,
-                    &args.server_name,
-                    &peer_key,
-                    state_pw,
-                ))
-                .await
-        }
-        Command::Join { state, server } => {
-            let local = tokio::task::LocalSet::new();
-            local
-                .run_until(cmd_join(&state, &server, &args.ca_cert, &args.server_name, state_pw))
-                .await
-        }
-        Command::Send {
-            state,
-            server,
-            peer_key,
-            msg,
-        } => {
-            let local = tokio::task::LocalSet::new();
-            local
-                .run_until(cmd_send(
-                    &state,
-                    &server,
-                    &args.ca_cert,
-                    &args.server_name,
-                    &peer_key,
-                    &msg,
-                    state_pw,
-                ))
-                .await
-        }
-        Command::Recv {
-            state,
-            server,
-            wait_ms,
-            stream,
-        } => {
-            let local = tokio::task::LocalSet::new();
-            local
-                .run_until(cmd_recv(
-                    &state,
-                    &server,
-                    &args.ca_cert,
-                    &args.server_name,
-                    wait_ms,
-                    stream,
-                    state_pw,
-                ))
-                .await
-        }
-    }
-}

crates/quicnprotochat-client/tests/e2e.rs

@@ -1,170 +0,0 @@
-use std::{path::PathBuf, process::Command, time::Duration};
-
-use assert_cmd::cargo::cargo_bin;
-use portpicker::pick_unused_port;
-use tempfile::TempDir;
-use tokio::time::sleep;
-
-use quicnprotochat_client::{
-    cmd_create_group, cmd_invite, cmd_join, cmd_ping, cmd_register_state, cmd_send, ClientAuth,
-    connect_node, fetch_wait, init_auth,
-};
-use quicnprotochat_core::IdentityKeypair;
-
-fn hex_encode(bytes: &[u8]) -> String {
-    bytes.iter().map(|b| format!("{b:02x}")).collect()
-}
-
-#[derive(serde::Deserialize)]
-struct StoredStateCompat {
-    identity_seed: [u8; 32],
-    #[allow(dead_code)]
-    group: Option<Vec<u8>>,
-}
-
-async fn wait_for_health(server: &str, ca_cert: &PathBuf, server_name: &str) -> anyhow::Result<()> {
-    let local = tokio::task::LocalSet::new();
-    for _ in 0..30 {
-        if local
-            .run_until(cmd_ping(server, ca_cert, server_name))
-            .await
-            .is_ok()
-        {
-            return Ok(());
-        }
-        sleep(Duration::from_millis(200)).await;
-    }
-    anyhow::bail!("server health never became ready")
-}
-
-#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
-async fn e2e_happy_path_register_invite_join_send_recv() -> anyhow::Result<()> {
-    let temp = TempDir::new()?;
-    let base = temp.path();
-    let port = pick_unused_port().expect("free port");
-    let listen = format!("127.0.0.1:{port}");
-    let server = listen.clone();
-    let ca_cert = base.join("server-cert.der");
-    let tls_key = base.join("server-key.der");
-    let data_dir = base.join("data");
-    let auth_token = "devtoken";
-
-    // Spawn server binary.
-    let server_bin = cargo_bin("quicnprotochat-server");
-    let mut child = Command::new(server_bin)
-        .arg("--listen")
-        .arg(&listen)
-        .arg("--data-dir")
-        .arg(&data_dir)
-        .arg("--tls-cert")
-        .arg(&ca_cert)
-        .arg("--tls-key")
-        .arg(&tls_key)
-        .arg("--auth-token")
-        .arg(auth_token)
-        .spawn()
-        .expect("spawn server");
-
-    // Ensure we always terminate the child.
-    struct ChildGuard(std::process::Child);
-    impl Drop for ChildGuard {
-        fn drop(&mut self) {
-            let _ = self.0.kill();
-        }
-    }
-    let child_guard = ChildGuard(child);
-    let _ = child_guard;
-
-    // Wait for server to be healthy and certs to be generated.
-    wait_for_health(&server, &ca_cert, "localhost").await?;
-
-    // Set client auth context.
-    init_auth(ClientAuth::from_parts(auth_token.to_string(), None));
-
-    // LocalSet for capnp !Send operations.
-    let local = tokio::task::LocalSet::new();
-
-    let alice_state = base.join("alice.bin");
-    let bob_state = base.join("bob.bin");
-
-    local
-        .run_until(cmd_register_state(
-            &alice_state,
-            &server,
-            &ca_cert,
-            "localhost",
-            None,
-        ))
-        .await?;
-
-    local
-        .run_until(cmd_register_state(
-            &bob_state,
-            &server,
-            &ca_cert,
-            "localhost",
-            None,
-        ))
-        .await?;
-
-    local
-        .run_until(cmd_create_group(
-            &alice_state,
-            &server,
-            "test-group",
-            None,
-        ))
-        .await?;
-
-    // Load Bob identity key from persisted state to use as peer key.
-    let bob_bytes = std::fs::read(&bob_state)?;
-    let bob_state_compat: StoredStateCompat = bincode::deserialize(&bob_bytes)?;
-    let bob_identity = IdentityKeypair::from_seed(bob_state_compat.identity_seed);
-    let bob_pk_hex = hex_encode(&bob_identity.public_key_bytes());
-
-    local
-        .run_until(cmd_invite(
-            &alice_state,
-            &server,
-            &ca_cert,
-            "localhost",
-            &bob_pk_hex,
-            None,
-        ))
-        .await?;
-
-    local
-        .run_until(cmd_join(
-            &bob_state,
-            &server,
-            &ca_cert,
-            "localhost",
-            None,
-        ))
-        .await?;
-
-    // Send Alice -> Bob.
-    local
-        .run_until(cmd_send(
-            &alice_state,
-            &server,
-            &ca_cert,
-            "localhost",
-            &bob_pk_hex,
-            "hello bob",
-            None,
-        ))
-        .await?;
-
-    // Confirm Bob can fetch at least one payload.
-    local
-        .run_until(async {
-            let client = connect_node(&server, &ca_cert, "localhost").await?;
-            let payloads = fetch_wait(&client, &bob_identity.public_key_bytes(), 1000).await?;
-            anyhow::ensure!(!payloads.is_empty(), "no payloads delivered to Bob");
-            Ok::<(), anyhow::Error>(())
-        })
-        .await?;
-
-    Ok(())
-}

crates/quicnprotochat-core/Cargo.toml

@@ -1,45 +0,0 @@
-[package]
-name        = "quicnprotochat-core"
-version     = "0.1.0"
-edition     = "2021"
-description = "Crypto primitives, MLS state machine, and hybrid post-quantum KEM for quicnprotochat."
-license     = "MIT"
-
-[dependencies]
-# Crypto — classical
-x25519-dalek        = { workspace = true }
-ed25519-dalek       = { workspace = true }
-sha2                = { workspace = true }
-hkdf                = { workspace = true }
-chacha20poly1305    = { workspace = true }
-zeroize             = { workspace = true }
-rand                = { workspace = true }
-
-# Crypto — post-quantum hybrid KEM (M7)
-ml-kem              = { workspace = true }
-
-# Crypto — OPAQUE password-authenticated key exchange
-opaque-ke           = { workspace = true }
-argon2              = { workspace = true }
-
-# Crypto — MLS (M2)
-openmls             = { workspace = true }
-openmls_rust_crypto = { workspace = true }
-openmls_traits      = { workspace = true }
-tls_codec           = { workspace = true }
-serde               = { workspace = true }
-bincode             = { workspace = true }
-serde_json          = { workspace = true }
-
-# Serialisation
-capnp               = { workspace = true }
-quicnprotochat-proto       = { path = "../quicnprotochat-proto" }
-
-# Async runtime
-tokio               = { workspace = true }
-
-# Error handling
-thiserror           = { workspace = true }
-
-[dev-dependencies]
-tokio               = { workspace = true }

crates/quicnprotochat-core/src/error.rs

@@ -1,21 +0,0 @@
-//! Error types for `quicnprotochat-core`.
-
-use thiserror::Error;
-
-/// Errors produced by core cryptographic and MLS operations.
-#[derive(Debug, Error)]
-pub enum CoreError {
-    /// Cap'n Proto serialisation or deserialisation failed.
-    #[error("Cap'n Proto error: {0}")]
-    Capnp(#[from] capnp::Error),
-
-    /// An MLS operation failed.
-    ///
-    /// The inner string is the debug representation of the openmls error.
-    #[error("MLS error: {0}")]
-    Mls(String),
-
-    /// A hybrid KEM (X25519 + ML-KEM-768) operation failed.
-    #[error("hybrid KEM error: {0}")]
-    HybridKem(#[from] crate::hybrid_kem::HybridKemError),
-}

crates/quicnprotochat-core/src/group.rs

@@ -1,456 +0,0 @@
-//! MLS group state machine.
-//!
-//! # Design
-//!
-//! [`GroupMember`] wraps an openmls [`MlsGroup`] plus the per-client
-//! [`StoreCrypto`] backend. The backend is **persistent** — it holds the
-//! in-memory key store that maps init-key references to HPKE private keys.
-//! openmls's `new_from_welcome` reads those private keys from the key store to
-//! decrypt the Welcome, so the same backend instance must be used from
-//! `generate_key_package` through `join_group`.
-//!
-//! # Wire format
-//!
-//! All MLS messages are serialised/deserialised using TLS presentation language
-//! encoding (`tls_codec`). The resulting byte vectors are what the transport
-//! layer (and the Delivery Service) sees.
-//!
-//! # MLS ciphersuite
-//!
-//! `MLS_128_DHKEMX25519_AES128GCM_SHA256_Ed25519` — same as M2.
-//!
-//! # Ratchet tree
-//!
-//! `use_ratchet_tree_extension = true` so that the ratchet tree is embedded
-//! in Welcome messages. `new_from_welcome` is called with `ratchet_tree = None`;
-//! openmls extracts the tree from the Welcome's `GroupInfo` extension.
-
-use std::sync::Arc;
-
-use openmls::prelude::{
-    Ciphersuite, Credential, CredentialType, CredentialWithKey, CryptoConfig, GroupId, KeyPackage,
-    KeyPackageIn, MlsGroup, MlsGroupConfig, MlsMessageInBody, MlsMessageOut,
-    ProcessedMessageContent, ProtocolMessage, ProtocolVersion, TlsDeserializeTrait,
-    TlsSerializeTrait,
-};
-use openmls_traits::OpenMlsCryptoProvider;
-
-use crate::{
-    error::CoreError,
-    identity::IdentityKeypair,
-    keystore::{DiskKeyStore, StoreCrypto},
-};
-
-// ── Constants ─────────────────────────────────────────────────────────────────
-
-const CIPHERSUITE: Ciphersuite = Ciphersuite::MLS_128_DHKEMX25519_AES128GCM_SHA256_Ed25519;
-
-// ── GroupMember ───────────────────────────────────────────────────────────────
-
-/// Per-client MLS state: identity keypair, crypto backend, and optional group.
-///
-/// # Lifecycle
-///
-/// ```text
-/// GroupMember::new(identity)
-///   ├─ generate_key_package()   → upload to AS
-///   ├─ create_group(group_id)   → become sole member
-///   │     └─ add_member(kp)     → invite a peer; returns (commit, welcome)
-///   └─ join_group(welcome)      → join after receiving a Welcome
-///         ├─ send_message(msg)  → encrypt application data
-///         └─ receive_message(b) → decrypt; returns Some(plaintext) or None
-/// ```
-pub struct GroupMember {
-    /// Persistent crypto backend. Holds the in-memory key store with HPKE
-    /// private keys created during `generate_key_package`.
-    backend: StoreCrypto,
-    /// Long-term Ed25519 identity keypair. Also used as the MLS `Signer`.
-    identity: Arc<IdentityKeypair>,
-    /// Active MLS group, if any.
-    group: Option<MlsGroup>,
-    /// Shared group configuration (wire format, ratchet tree extension, etc.).
-    config: MlsGroupConfig,
-}
-
-impl GroupMember {
-    /// Create a new `GroupMember` with a fresh crypto backend.
-    pub fn new(identity: Arc<IdentityKeypair>) -> Self {
-        Self::new_with_state(identity, DiskKeyStore::ephemeral(), None)
-    }
-
-    /// Create a `GroupMember` from pre-existing state (identity + optional group + store).
-    pub fn new_with_state(
-        identity: Arc<IdentityKeypair>,
-        key_store: DiskKeyStore,
-        group: Option<MlsGroup>,
-    ) -> Self {
-        let config = MlsGroupConfig::builder()
-            .use_ratchet_tree_extension(true)
-            .build();
-
-        Self {
-            backend: StoreCrypto::new(key_store),
-            identity,
-            group,
-            config,
-        }
-    }
-
-    // ── KeyPackage ────────────────────────────────────────────────────────────
-
-    /// Generate a fresh single-use MLS KeyPackage.
-    ///
-    /// The HPKE init private key is stored in `self.backend`'s key store.
-    /// **The same `GroupMember` instance must later call `join_group`** so
-    /// that `new_from_welcome` can retrieve the private key.
-    ///
-    /// # Returns
-    ///
-    /// TLS-encoded KeyPackage bytes, ready for upload to the Authentication
-    /// Service.
-    ///
-    /// # Errors
-    ///
-    /// Returns [`CoreError::Mls`] if openmls fails to create the KeyPackage.
-    pub fn generate_key_package(&mut self) -> Result<Vec<u8>, CoreError> {
-        let credential_with_key = self.make_credential_with_key()?;
-
-        let key_package = KeyPackage::builder()
-            .build(
-                CryptoConfig::with_default_version(CIPHERSUITE),
-                &self.backend,
-                self.identity.as_ref(),
-                credential_with_key,
-            )
-            .map_err(|e| CoreError::Mls(format!("{e:?}")))?;
-
-        key_package
-            .tls_serialize_detached()
-            .map_err(|e| CoreError::Mls(format!("{e:?}")))
-    }
-
-    // ── Group creation ────────────────────────────────────────────────────────
-
-    /// Create a new MLS group with `group_id` as the group identifier.
-    ///
-    /// The caller becomes the sole member (epoch 0). Use `add_member` to
-    /// invite additional members.
-    ///
-    /// `group_id` can be any non-empty byte string; SHA-256 of a human-readable
-    /// name is a good choice.
-    ///
-    /// # Errors
-    ///
-    /// Returns [`CoreError::Mls`] if the group already exists or openmls fails.
-    pub fn create_group(&mut self, group_id: &[u8]) -> Result<(), CoreError> {
-        let credential_with_key = self.make_credential_with_key()?;
-        let mls_id = GroupId::from_slice(group_id);
-
-        let group = MlsGroup::new_with_group_id(
-            &self.backend,
-            self.identity.as_ref(),
-            &self.config,
-            mls_id,
-            credential_with_key,
-        )
-        .map_err(|e| CoreError::Mls(format!("{e:?}")))?;
-
-        self.group = Some(group);
-        Ok(())
-    }
-
-    // ── Membership ────────────────────────────────────────────────────────────
-
-    /// Add a new member by their TLS-encoded KeyPackage bytes.
-    ///
-    /// Produces a Commit (to update existing members' state) and a Welcome
-    /// (to bootstrap the new member). The caller is responsible for
-    /// distributing these:
-    ///
-    /// - Send `commit_bytes` to all **existing** group members via the DS.
-    ///   (In the 2-party case where the creator is the only member, this can
-    ///   be discarded — the creator applies it locally via this method.)
-    /// - Send `welcome_bytes` to the **new** member via the DS.
-    ///
-    /// This method also merges the pending Commit into the local group state
-    /// (advancing the epoch), so the caller is immediately ready to encrypt.
-    ///
-    /// # Returns
-    ///
-    /// `(commit_bytes, welcome_bytes)` — both TLS-encoded MLS messages.
-    ///
-    /// # Errors
-    ///
-    /// Returns [`CoreError::Mls`] if the KeyPackage is malformed, no active
-    /// group exists, or openmls fails.
-    pub fn add_member(
-        &mut self,
-        key_package_bytes: &[u8],
-    ) -> Result<(Vec<u8>, Vec<u8>), CoreError> {
-        let group = self
-            .group
-            .as_mut()
-            .ok_or_else(|| CoreError::Mls("no active group".into()))?;
-
-        // Deserialise and validate the peer's KeyPackage. KeyPackage only derives
-        // TlsSerialize; KeyPackageIn derives TlsDeserialize and provides validate()
-        // which verifies the signature and returns a trusted KeyPackage.
-        let key_package: KeyPackage =
-            KeyPackageIn::tls_deserialize(&mut key_package_bytes.as_ref())
-                .map_err(|e| CoreError::Mls(format!("KeyPackage deserialise: {e:?}")))?
-                .validate(self.backend.crypto(), ProtocolVersion::Mls10)
-                .map_err(|e| CoreError::Mls(format!("KeyPackage validate: {e:?}")))?;
-
-        // Create the Commit + Welcome. The third return value (GroupInfo) is for
-        // external commits and is not needed here.
-        let (commit_out, welcome_out, _group_info) = group
-            .add_members(&self.backend, self.identity.as_ref(), &[key_package])
-            .map_err(|e| CoreError::Mls(format!("add_members: {e:?}")))?;
-
-        // Merge the pending Commit into our own state, advancing the epoch.
-        group
-            .merge_pending_commit(&self.backend)
-            .map_err(|e| CoreError::Mls(format!("merge_pending_commit: {e:?}")))?;
-
-        let commit_bytes = commit_out
-            .to_bytes()
-            .map_err(|e| CoreError::Mls(format!("commit serialise: {e:?}")))?;
-        let welcome_bytes = welcome_out
-            .to_bytes()
-            .map_err(|e| CoreError::Mls(format!("welcome serialise: {e:?}")))?;
-
-        Ok((commit_bytes, welcome_bytes))
-    }
-
-    /// Join an existing MLS group from a TLS-encoded Welcome message.
-    ///
-    /// The caller must have previously called [`generate_key_package`] on
-    /// **this same instance** so that the HPKE init private key is in the
-    /// backend's key store.
-    ///
-    /// # Errors
-    ///
-    /// Returns [`CoreError::Mls`] if the Welcome does not match any known
-    /// KeyPackage, or openmls validation fails.
-    ///
-    /// [`generate_key_package`]: Self::generate_key_package
-    pub fn join_group(&mut self, welcome_bytes: &[u8]) -> Result<(), CoreError> {
-        // Deserialise MlsMessageIn, then extract the inner Welcome.
-        let msg_in = openmls::prelude::MlsMessageIn::tls_deserialize(&mut welcome_bytes.as_ref())
-            .map_err(|e| CoreError::Mls(format!("Welcome deserialise: {e:?}")))?;
-
-        // into_welcome() is feature-gated in openmls 0.5; extract() is public.
-        let welcome = match msg_in.extract() {
-            MlsMessageInBody::Welcome(w) => w,
-            _ => return Err(CoreError::Mls("expected a Welcome message".into())),
-        };
-
-        // ratchet_tree = None because use_ratchet_tree_extension = true embeds
-        // the tree inside the Welcome's GroupInfo extension.
-        let group = MlsGroup::new_from_welcome(&self.backend, &self.config, welcome, None)
-            .map_err(|e| CoreError::Mls(format!("new_from_welcome: {e:?}")))?;
-
-        self.group = Some(group);
-        Ok(())
-    }
-
-    // ── Application messages ──────────────────────────────────────────────────
-
-    /// Encrypt `plaintext` as an MLS Application message.
-    ///
-    /// # Returns
-    ///
-    /// TLS-encoded `MlsMessageOut` bytes (PrivateMessage variant).
-    ///
-    /// # Errors
-    ///
-    /// Returns [`CoreError::Mls`] if there is no active group or encryption fails.
-    pub fn send_message(&mut self, plaintext: &[u8]) -> Result<Vec<u8>, CoreError> {
-        let group = self
-            .group
-            .as_mut()
-            .ok_or_else(|| CoreError::Mls("no active group".into()))?;
-
-        let mls_msg: MlsMessageOut = group
-            .create_message(&self.backend, self.identity.as_ref(), plaintext)
-            .map_err(|e| CoreError::Mls(format!("create_message: {e:?}")))?;
-
-        mls_msg
-            .to_bytes()
-            .map_err(|e| CoreError::Mls(format!("message serialise: {e:?}")))
-    }
-
-    /// Process an incoming TLS-encoded MLS message.
-    ///
-    /// # Returns
-    ///
-    /// - `Ok(Some(plaintext))` for Application messages.
-    /// - `Ok(None)` for Commit messages (group state is updated internally).
-    ///
-    /// # Errors
-    ///
-    /// Returns [`CoreError::Mls`] if the message is malformed, fails
-    /// authentication, or the group state is inconsistent.
-    pub fn receive_message(&mut self, bytes: &[u8]) -> Result<Option<Vec<u8>>, CoreError> {
-        let group = self
-            .group
-            .as_mut()
-            .ok_or_else(|| CoreError::Mls("no active group".into()))?;
-
-        let msg_in = openmls::prelude::MlsMessageIn::tls_deserialize(&mut bytes.as_ref())
-            .map_err(|e| CoreError::Mls(format!("message deserialise: {e:?}")))?;
-
-        // into_protocol_message() is feature-gated; extract() + manual construction is not.
-        let protocol_message = match msg_in.extract() {
-            MlsMessageInBody::PrivateMessage(m) => ProtocolMessage::PrivateMessage(m),
-            MlsMessageInBody::PublicMessage(m) => ProtocolMessage::PublicMessage(m),
-            _ => return Err(CoreError::Mls("not a protocol message".into())),
-        };
-
-        let processed = group
-            .process_message(&self.backend, protocol_message)
-            .map_err(|e| CoreError::Mls(format!("process_message: {e:?}")))?;
-
-        match processed.into_content() {
-            ProcessedMessageContent::ApplicationMessage(app) => Ok(Some(app.into_bytes())),
-            ProcessedMessageContent::StagedCommitMessage(staged) => {
-                // Merge the Commit into the local state (epoch advances).
-                group
-                    .merge_staged_commit(&self.backend, *staged)
-                    .map_err(|e| CoreError::Mls(format!("merge_staged_commit: {e:?}")))?;
-                Ok(None)
-            }
-            // Proposals are stored for a later Commit; nothing to return yet.
-            ProcessedMessageContent::ProposalMessage(proposal) => {
-                group.store_pending_proposal(*proposal);
-                Ok(None)
-            }
-            ProcessedMessageContent::ExternalJoinProposalMessage(proposal) => {
-                group.store_pending_proposal(*proposal);
-                Ok(None)
-            }
-        }
-    }
-
-    // ── Accessors ─────────────────────────────────────────────────────────────
-
-    /// Return the MLS group ID bytes, or `None` if no group is active.
-    pub fn group_id(&self) -> Option<Vec<u8>> {
-        self.group
-            .as_ref()
-            .map(|g| g.group_id().as_slice().to_vec())
-    }
-
-    /// Return a reference to the identity keypair.
-    pub fn identity(&self) -> &IdentityKeypair {
-        &self.identity
-    }
-
-    /// Return the private seed of the identity (for persistence).
-    pub fn identity_seed(&self) -> [u8; 32] {
-        self.identity.seed_bytes()
-    }
-
-    /// Return a reference to the underlying crypto backend.
-    pub fn backend(&self) -> &StoreCrypto {
-        &self.backend
-    }
-
-    /// Return a reference to the MLS group, if active.
-    pub fn group_ref(&self) -> Option<&MlsGroup> {
-        self.group.as_ref()
-    }
-
-    /// Return the identity (credential) bytes of all current group members.
-    ///
-    /// Each entry is the raw credential payload (Ed25519 public key bytes)
-    /// extracted from the member's MLS leaf node.
-    pub fn member_identities(&self) -> Vec<Vec<u8>> {
-        let group = match self.group.as_ref() {
-            Some(g) => g,
-            None => return Vec::new(),
-        };
-        group
-            .members()
-            .map(|m| m.credential.identity().to_vec())
-            .collect()
-    }
-
-    // ── Private helpers ───────────────────────────────────────────────────────
-
-    fn make_credential_with_key(&self) -> Result<CredentialWithKey, CoreError> {
-        let credential = Credential::new(
-            self.identity.public_key_bytes().to_vec(),
-            CredentialType::Basic,
-        )
-        .map_err(|e| CoreError::Mls(format!("{e:?}")))?;
-
-        Ok(CredentialWithKey {
-            credential,
-            signature_key: self.identity.public_key_bytes().to_vec().into(),
-        })
-    }
-}
-
-// ── Unit tests ────────────────────────────────────────────────────────────────
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-
-    /// Full two-party MLS round-trip: create group → add member → exchange messages.
-    #[test]
-    fn two_party_mls_round_trip() {
-        let alice_id = Arc::new(IdentityKeypair::generate());
-        let bob_id = Arc::new(IdentityKeypair::generate());
-
-        let mut alice = GroupMember::new(Arc::clone(&alice_id));
-        let mut bob = GroupMember::new(Arc::clone(&bob_id));
-
-        // Bob generates a KeyPackage (stored in bob's backend key store).
-        let bob_kp = bob.generate_key_package().expect("Bob KeyPackage");
-
-        // Alice creates the group.
-        alice
-            .create_group(b"test-group-m3")
-            .expect("Alice create group");
-
-        // Alice adds Bob → (commit, welcome).
-        // Alice is the sole existing member, so she merges the commit herself.
-        let (_, welcome) = alice.add_member(&bob_kp).expect("Alice add Bob");
-
-        // Bob joins via the Welcome. His backend holds the matching init key.
-        bob.join_group(&welcome).expect("Bob join group");
-
-        // Alice → Bob: application message.
-        let ct_a = alice.send_message(b"hello bob").expect("Alice send");
-        let pt_b = bob
-            .receive_message(&ct_a)
-            .expect("Bob recv")
-            .expect("should be application message");
-        assert_eq!(pt_b, b"hello bob");
-
-        // Bob → Alice: reply.
-        let ct_b = bob.send_message(b"hello alice").expect("Bob send");
-        let pt_a = alice
-            .receive_message(&ct_b)
-            .expect("Alice recv")
-            .expect("should be application message");
-        assert_eq!(pt_a, b"hello alice");
-    }
-
-    /// `group_id()` returns None before create_group, Some afterwards.
-    #[test]
-    fn group_id_lifecycle() {
-        let id = Arc::new(IdentityKeypair::generate());
-        let mut member = GroupMember::new(id);
-
-        assert!(member.group_id().is_none(), "no group before create");
-        member.create_group(b"gid").unwrap();
-        assert_eq!(
-            member.group_id().unwrap(),
-            b"gid".as_slice(),
-            "group_id must match what was passed"
-        );
-    }
-}

crates/quicnprotochat-core/src/identity.rs

@@ -1,135 +0,0 @@
-//! Ed25519 identity keypair for MLS credentials and AS registration.
-//!
-//! The [`IdentityKeypair`] is the long-term identity key embedded in MLS
-//! `BasicCredential`s. It is used for signing MLS messages and as the
-//! indexing key for the Authentication Service.
-//!
-//! # Zeroize
-//!
-//! The 32-byte private seed is stored as `Zeroizing<[u8; 32]>`, which zeroes
-//! the bytes on drop. `[u8; 32]` is `Copy + Default` and satisfies zeroize's
-//! `DefaultIsZeroes` constraint, avoiding a conflict with ed25519-dalek's
-//! `SigningKey` zeroize impl.
-//!
-//! # Fingerprint
-//!
-//! A 32-byte SHA-256 digest of the raw public key bytes is used as a compact,
-//! collision-resistant identifier for logging.
-
-use ed25519_dalek::{Signer as DalekSigner, SigningKey, VerifyingKey};
-use openmls_traits::signatures::Signer;
-use openmls_traits::types::{Error as MlsError, SignatureScheme};
-use serde::{Deserialize, Serialize};
-use sha2::{Digest, Sha256};
-use zeroize::Zeroizing;
-
-/// An Ed25519 identity keypair.
-///
-/// Created with [`IdentityKeypair::generate`]. The private signing key seed
-/// is zeroed when this struct is dropped.
-pub struct IdentityKeypair {
-    /// Raw 32-byte private seed — zeroized on drop.
-    ///
-    /// Stored as bytes rather than `SigningKey` to satisfy zeroize's
-    /// `DefaultIsZeroes` bound on `Zeroizing<T>`.
-    seed: Zeroizing<[u8; 32]>,
-    /// Corresponding 32-byte public verifying key.
-    verifying: VerifyingKey,
-}
-
-impl IdentityKeypair {
-    /// Recreate an identity keypair from a 32-byte seed.
-    pub fn from_seed(seed: [u8; 32]) -> Self {
-        let signing = SigningKey::from_bytes(&seed);
-        let verifying = signing.verifying_key();
-        Self {
-            seed: Zeroizing::new(seed),
-            verifying,
-        }
-    }
-
-    /// Return the raw 32-byte private seed (for persistence).
-    pub fn seed_bytes(&self) -> [u8; 32] {
-        *self.seed
-    }
-}
-
-impl IdentityKeypair {
-    /// Generate a fresh random Ed25519 identity keypair.
-    pub fn generate() -> Self {
-        use rand::rngs::OsRng;
-        let signing = SigningKey::generate(&mut OsRng);
-        let verifying = signing.verifying_key();
-        let seed = Zeroizing::new(signing.to_bytes());
-        Self { seed, verifying }
-    }
-
-    /// Return the raw 32-byte Ed25519 public key.
-    ///
-    /// This is the byte array used as `identityKey` in `auth.capnp` calls.
-    pub fn public_key_bytes(&self) -> [u8; 32] {
-        self.verifying.to_bytes()
-    }
-
-    /// Return the SHA-256 fingerprint of the public key (32 bytes).
-    pub fn fingerprint(&self) -> [u8; 32] {
-        let mut hasher = Sha256::new();
-        hasher.update(self.verifying.to_bytes());
-        hasher.finalize().into()
-    }
-
-    /// Reconstruct the `SigningKey` from the stored seed bytes.
-    fn signing_key(&self) -> SigningKey {
-        SigningKey::from_bytes(&self.seed)
-    }
-}
-
-/// Implement the openmls `Signer` trait so `IdentityKeypair` can be passed
-/// directly to `KeyPackage::builder().build(...)` without needing the external
-/// `openmls_basic_credential` crate.
-impl Signer for IdentityKeypair {
-    fn sign(&self, payload: &[u8]) -> Result<Vec<u8>, MlsError> {
-        let sk = self.signing_key();
-        let sig: ed25519_dalek::Signature = sk.sign(payload);
-        Ok(sig.to_bytes().to_vec())
-    }
-
-    fn signature_scheme(&self) -> SignatureScheme {
-        SignatureScheme::ED25519
-    }
-}
-
-impl Serialize for IdentityKeypair {
-    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
-    where
-        S: serde::Serializer,
-    {
-        serializer.serialize_bytes(&self.seed[..])
-    }
-}
-
-impl<'de> Deserialize<'de> for IdentityKeypair {
-    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
-    where
-        D: serde::Deserializer<'de>,
-    {
-        let bytes: Vec<u8> = serde::Deserialize::deserialize(deserializer)?;
-        let seed: [u8; 32] = bytes
-            .as_slice()
-            .try_into()
-            .map_err(|_| serde::de::Error::custom("identity seed must be 32 bytes"))?;
-        Ok(IdentityKeypair::from_seed(seed))
-    }
-}
-
-impl std::fmt::Debug for IdentityKeypair {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        let fp = self.fingerprint();
-        f.debug_struct("IdentityKeypair")
-            .field(
-                "fingerprint",
-                &format!("{:02x}{:02x}{:02x}{:02x}…", fp[0], fp[1], fp[2], fp[3]),
-            )
-            .finish_non_exhaustive()
-    }
-}

crates/quicnprotochat-core/src/lib.rs

@@ -1,33 +0,0 @@
-//! Core cryptographic primitives, MLS group state machine, and hybrid
-//! post-quantum KEM for quicnprotochat.
-//!
-//! # Module layout
-//!
-//! | Module       | Responsibility                                                   |
-//! |--------------|------------------------------------------------------------------|
-//! | `error`      | [`CoreError`] type                                               |
-//! | `identity`   | [`IdentityKeypair`] — Ed25519 identity key for MLS credentials   |
-//! | `keypackage` | [`generate_key_package`] — standalone KeyPackage generation      |
-//! | `group`      | [`GroupMember`] — MLS group lifecycle (create/join/send/recv)    |
-//! | `hybrid_kem` | Hybrid X25519 + ML-KEM-768 key encapsulation                    |
-//! | `keystore`   | [`DiskKeyStore`] — OpenMLS key store with optional persistence   |
-
-mod error;
-mod group;
-pub mod hybrid_kem;
-mod identity;
-mod keypackage;
-mod keystore;
-pub mod opaque_auth;
-
-// ── Public API ────────────────────────────────────────────────────────────────
-
-pub use error::CoreError;
-pub use group::GroupMember;
-pub use hybrid_kem::{
-    hybrid_decrypt, hybrid_encrypt, HybridKeypair, HybridKeypairBytes, HybridKemError,
-    HybridPublicKey,
-};
-pub use identity::IdentityKeypair;
-pub use keypackage::generate_key_package;
-pub use keystore::DiskKeyStore;

crates/quicnprotochat-proto/Cargo.toml

@@ -1,15 +0,0 @@
-[package]
-name        = "quicnprotochat-proto"
-version     = "0.1.0"
-edition     = "2021"
-description = "Cap'n Proto schemas, generated types, and serialisation helpers for quicnprotochat. No crypto, no I/O."
-license     = "MIT"
-
-# build.rs invokes capnpc to generate Rust source from .capnp schemas.
-build       = "build.rs"
-
-[dependencies]
-capnp       = { workspace = true }
-
-[build-dependencies]
-capnpc      = { workspace = true }

crates/quicnprotochat-proto/build.rs

@@ -1,54 +0,0 @@
-//! Build script for quicnprotochat-proto.
-//!
-//! Invokes the `capnp` compiler to generate Rust types from `.capnp` schemas
-//! located in the workspace-root `schemas/` directory.
-//!
-//! # Prerequisites
-//!
-//! The `capnp` CLI must be installed and on `PATH`.
-//!
-//! Debian/Ubuntu:  apt-get install capnproto
-//! macOS:          brew install capnp
-//! Docker:         see docker/Dockerfile
-
-use std::{env, path::PathBuf};
-
-fn main() {
-    let manifest_dir =
-        PathBuf::from(env::var("CARGO_MANIFEST_DIR").expect("CARGO_MANIFEST_DIR not set by Cargo"));
-
-    // Workspace root is two levels above this crate (quicnprotochat/crates/quicnprotochat-proto).
-    let workspace_root = manifest_dir
-        .join("../..")
-        .canonicalize()
-        .expect("could not canonicalize workspace root path");
-
-    let schemas_dir = workspace_root.join("schemas");
-
-    // Re-run this build script whenever any schema file changes.
-    println!(
-        "cargo:rerun-if-changed={}",
-        schemas_dir.join("auth.capnp").display()
-    );
-    println!(
-        "cargo:rerun-if-changed={}",
-        schemas_dir.join("delivery.capnp").display()
-    );
-    println!(
-        "cargo:rerun-if-changed={}",
-        schemas_dir.join("node.capnp").display()
-    );
-
-    capnpc::CompilerCommand::new()
-        // Treat `schemas/` as the include root so that inter-schema imports
-        // resolve correctly.
-        .src_prefix(&schemas_dir)
-        .file(schemas_dir.join("auth.capnp"))
-        .file(schemas_dir.join("delivery.capnp"))
-        .file(schemas_dir.join("node.capnp"))
-        .run()
-        .expect(
-            "Cap'n Proto schema compilation failed. \
-             Is `capnp` installed? (apt-get install capnproto / brew install capnp)",
-        );
-}

crates/quicnprotochat-proto/src/lib.rs

@@ -1,62 +0,0 @@
-//! Cap'n Proto schemas, generated types, and serialisation helpers for quicnprotochat.
-//!
-//! # Design constraints
-//!
-//! This crate is intentionally restricted:
-//! - **No crypto** — key material never enters this crate.
-//! - **No I/O** — callers own transport; this crate only converts bytes ↔ types.
-//! - **No async** — pure synchronous data-layer code.
-//!
-//! # Generated code
-//!
-//! `build.rs` invokes `capnpc` at compile time and writes generated Rust source
-//! into `$OUT_DIR`. The `include!` macros below splice that code in as a module.
-
-// ── Generated types ───────────────────────────────────────────────────────────
-
-/// Cap'n Proto generated types for `schemas/auth.capnp`.
-///
-/// Do not edit this module by hand — it is entirely machine-generated.
-pub mod auth_capnp {
-    include!(concat!(env!("OUT_DIR"), "/auth_capnp.rs"));
-}
-
-/// Cap'n Proto generated types for `schemas/delivery.capnp`.
-///
-/// Do not edit this module by hand — it is entirely machine-generated.
-pub mod delivery_capnp {
-    include!(concat!(env!("OUT_DIR"), "/delivery_capnp.rs"));
-}
-
-/// Cap'n Proto generated types for `schemas/node.capnp`.
-///
-/// Do not edit this module by hand — it is entirely machine-generated.
-pub mod node_capnp {
-    include!(concat!(env!("OUT_DIR"), "/node_capnp.rs"));
-}
-
-// ── Low-level byte ↔ message conversions ──────────────────────────────────────
-
-/// Serialise a Cap'n Proto message builder to unpacked wire bytes.
-///
-/// The output includes the segment table header. For transport, the
-/// `quicnprotochat-core` frame codec prepends a 4-byte little-endian length field.
-pub fn to_bytes<A: capnp::message::Allocator>(
-    msg: &capnp::message::Builder<A>,
-) -> Result<Vec<u8>, capnp::Error> {
-    let mut buf = Vec::new();
-    capnp::serialize::write_message(&mut buf, msg)?;
-    Ok(buf)
-}
-
-/// Deserialise unpacked wire bytes into a message with owned segments.
-///
-/// Uses `ReaderOptions::new()` (default limits: 64 MiB, 512 nesting levels).
-/// Callers that receive data from untrusted peers should consider tightening
-/// the traversal limit via `ReaderOptions::traversal_limit_in_words`.
-pub fn from_bytes(
-    bytes: &[u8],
-) -> Result<capnp::message::Reader<capnp::serialize::OwnedSegments>, capnp::Error> {
-    let mut cursor = std::io::Cursor::new(bytes);
-    capnp::serialize::read_message(&mut cursor, capnp::message::ReaderOptions::new())
-}

crates/quicnprotochat-server/Cargo.toml

@@ -1,51 +0,0 @@
-[package]
-name        = "quicnprotochat-server"
-version     = "0.1.0"
-edition     = "2021"
-description = "Delivery Service and Authentication Service for quicnprotochat."
-license     = "MIT"
-
-[[bin]]
-name = "quicnprotochat-server"
-path = "src/main.rs"
-
-[dependencies]
-quicnprotochat-core  = { path = "../quicnprotochat-core" }
-quicnprotochat-proto = { path = "../quicnprotochat-proto" }
-
-# Serialisation + RPC
-capnp         = { workspace = true }
-capnp-rpc     = { workspace = true }
-
-# Async
-tokio         = { workspace = true }
-tokio-util    = { workspace = true }
-futures       = { workspace = true }
-
-# Server utilities
-dashmap       = { workspace = true }
-sha2          = { workspace = true }
-tracing       = { workspace = true }
-tracing-subscriber = { workspace = true }
-quinn         = { workspace = true }
-quinn-proto   = { workspace = true }
-rustls        = { workspace = true }
-rcgen         = { workspace = true }
-
-# Crypto — OPAQUE PAKE
-opaque-ke     = { workspace = true }
-rand          = { workspace = true }
-subtle        = { workspace = true }
-
-# Database
-rusqlite      = { workspace = true }
-
-# Error handling
-anyhow        = { workspace = true }
-thiserror     = { workspace = true }
-bincode       = { workspace = true }
-serde         = { workspace = true }
-
-# CLI
-clap          = { workspace = true }
-toml          = { version = "0.8" }

crates/quicnprotochat-server/src/sql_store.rs

@@ -1,521 +0,0 @@
-//! SQLCipher-backed persistent storage.
-
-use std::path::Path;
-use std::sync::Mutex;
-
-use rusqlite::{params, Connection};
-
-use crate::storage::{StorageError, Store};
-
-/// SQLCipher-encrypted storage backend.
-pub struct SqlStore {
-    conn: Mutex<Connection>,
-}
-
-impl SqlStore {
-    pub fn open(path: impl AsRef<Path>, key: &str) -> Result<Self, StorageError> {
-        let conn = Connection::open(path).map_err(|e| StorageError::Db(e.to_string()))?;
-
-        if !key.is_empty() {
-            conn.pragma_update(None, "key", key)
-                .map_err(|e| StorageError::Db(format!("PRAGMA key failed: {e}")))?;
-        }
-
-        conn.execute_batch(
-            "PRAGMA journal_mode = WAL;
-             PRAGMA synchronous = NORMAL;
-             PRAGMA foreign_keys = ON;",
-        )
-        .map_err(|e| StorageError::Db(e.to_string()))?;
-
-        let store = Self {
-            conn: Mutex::new(conn),
-        };
-        store.migrate()?;
-        Ok(store)
-    }
-
-    fn migrate(&self) -> Result<(), StorageError> {
-        let conn = self.conn.lock().unwrap();
-        conn.execute_batch(
-            "CREATE TABLE IF NOT EXISTS key_packages (
-                id           INTEGER PRIMARY KEY AUTOINCREMENT,
-                identity_key BLOB NOT NULL,
-                package_data BLOB NOT NULL,
-                created_at   INTEGER DEFAULT (strftime('%s','now'))
-            );
-
-            CREATE TABLE IF NOT EXISTS deliveries (
-                id            INTEGER PRIMARY KEY AUTOINCREMENT,
-                recipient_key BLOB NOT NULL,
-                channel_id    BLOB NOT NULL DEFAULT X'',
-                payload       BLOB NOT NULL,
-                created_at    INTEGER DEFAULT (strftime('%s','now'))
-            );
-
-            CREATE TABLE IF NOT EXISTS hybrid_keys (
-                identity_key      BLOB PRIMARY KEY,
-                hybrid_public_key BLOB NOT NULL
-            );
-
-            CREATE INDEX IF NOT EXISTS idx_kp_identity
-                ON key_packages(identity_key);
-
-            CREATE INDEX IF NOT EXISTS idx_del_recipient_channel
-                ON deliveries(recipient_key, channel_id);
-
-            CREATE TABLE IF NOT EXISTS server_setup (
-                id         INTEGER PRIMARY KEY CHECK (id = 1),
-                setup_data BLOB NOT NULL
-            );
-
-            CREATE TABLE IF NOT EXISTS users (
-                username      TEXT PRIMARY KEY,
-                opaque_record BLOB NOT NULL,
-                created_at    INTEGER DEFAULT (strftime('%s','now'))
-            );
-
-            CREATE TABLE IF NOT EXISTS user_identity_keys (
-                username     TEXT PRIMARY KEY,
-                identity_key BLOB NOT NULL
-            );
-
-            CREATE TABLE IF NOT EXISTS endpoints (
-                identity_key BLOB PRIMARY KEY,
-                node_addr    BLOB NOT NULL,
-                updated_at   INTEGER DEFAULT (strftime('%s','now'))
-            );",
-        )
-        .map_err(|e| StorageError::Db(e.to_string()))?;
-        Ok(())
-    }
-}
-
-impl Store for SqlStore {
-    fn upload_key_package(
-        &self,
-        identity_key: &[u8],
-        package: Vec<u8>,
-    ) -> Result<(), StorageError> {
-        let conn = self.conn.lock().unwrap();
-        conn.execute(
-            "INSERT INTO key_packages (identity_key, package_data) VALUES (?1, ?2)",
-            params![identity_key, package],
-        )
-        .map_err(|e| StorageError::Db(e.to_string()))?;
-        Ok(())
-    }
-
-    fn fetch_key_package(&self, identity_key: &[u8]) -> Result<Option<Vec<u8>>, StorageError> {
-        let conn = self.conn.lock().unwrap();
-
-        let mut stmt = conn
-            .prepare(
-                "SELECT id, package_data FROM key_packages
-                 WHERE identity_key = ?1
-                 ORDER BY id ASC
-                 LIMIT 1",
-            )
-            .map_err(|e| StorageError::Db(e.to_string()))?;
-
-        let row = stmt
-            .query_row(params![identity_key], |row| {
-                Ok((row.get::<_, i64>(0)?, row.get::<_, Vec<u8>>(1)?))
-            })
-            .optional()
-            .map_err(|e| StorageError::Db(e.to_string()))?;
-
-        match row {
-            Some((id, package)) => {
-                conn.execute("DELETE FROM key_packages WHERE id = ?1", params![id])
-                    .map_err(|e| StorageError::Db(e.to_string()))?;
-                Ok(Some(package))
-            }
-            None => Ok(None),
-        }
-    }
-
-    fn enqueue(
-        &self,
-        recipient_key: &[u8],
-        channel_id: &[u8],
-        payload: Vec<u8>,
-    ) -> Result<(), StorageError> {
-        let conn = self.conn.lock().unwrap();
-        conn.execute(
-            "INSERT INTO deliveries (recipient_key, channel_id, payload) VALUES (?1, ?2, ?3)",
-            params![recipient_key, channel_id, payload],
-        )
-        .map_err(|e| StorageError::Db(e.to_string()))?;
-        Ok(())
-    }
-
-    fn fetch(
-        &self,
-        recipient_key: &[u8],
-        channel_id: &[u8],
-    ) -> Result<Vec<Vec<u8>>, StorageError> {
-        let conn = self.conn.lock().unwrap();
-
-        let mut stmt = conn
-            .prepare(
-                "SELECT id, payload FROM deliveries
-                 WHERE recipient_key = ?1 AND channel_id = ?2
-                 ORDER BY id ASC",
-            )
-            .map_err(|e| StorageError::Db(e.to_string()))?;
-
-        let rows: Vec<(i64, Vec<u8>)> = stmt
-            .query_map(params![recipient_key, channel_id], |row| {
-                Ok((row.get(0)?, row.get(1)?))
-            })
-            .map_err(|e| StorageError::Db(e.to_string()))?
-            .collect::<Result<Vec<_>, _>>()
-            .map_err(|e| StorageError::Db(e.to_string()))?;
-
-        if !rows.is_empty() {
-            let ids: Vec<i64> = rows.iter().map(|(id, _)| *id).collect();
-            let placeholders: String = ids.iter().map(|_| "?").collect::<Vec<_>>().join(",");
-            let sql = format!("DELETE FROM deliveries WHERE id IN ({placeholders})");
-            let params: Vec<&dyn rusqlite::types::ToSql> =
-                ids.iter().map(|id| id as &dyn rusqlite::types::ToSql).collect();
-            conn.execute(&sql, params.as_slice())
-                .map_err(|e| StorageError::Db(e.to_string()))?;
-        }
-
-        Ok(rows.into_iter().map(|(_, payload)| payload).collect())
-    }
-
-    fn fetch_limited(
-        &self,
-        recipient_key: &[u8],
-        channel_id: &[u8],
-        limit: usize,
-    ) -> Result<Vec<Vec<u8>>, StorageError> {
-        let conn = self.conn.lock().unwrap();
-
-        let mut stmt = conn
-            .prepare(
-                "SELECT id, payload FROM deliveries
-                 WHERE recipient_key = ?1 AND channel_id = ?2
-                 ORDER BY id ASC
-                 LIMIT ?3",
-            )
-            .map_err(|e| StorageError::Db(e.to_string()))?;
-
-        let rows: Vec<(i64, Vec<u8>)> = stmt
-            .query_map(params![recipient_key, channel_id, limit as i64], |row| {
-                Ok((row.get(0)?, row.get(1)?))
-            })
-            .map_err(|e| StorageError::Db(e.to_string()))?
-            .collect::<Result<Vec<_>, _>>()
-            .map_err(|e| StorageError::Db(e.to_string()))?;
-
-        if !rows.is_empty() {
-            let ids: Vec<i64> = rows.iter().map(|(id, _)| *id).collect();
-            let placeholders: String = ids.iter().map(|_| "?").collect::<Vec<_>>().join(",");
-            let sql = format!("DELETE FROM deliveries WHERE id IN ({placeholders})");
-            let params: Vec<&dyn rusqlite::types::ToSql> =
-                ids.iter().map(|id| id as &dyn rusqlite::types::ToSql).collect();
-            conn.execute(&sql, params.as_slice())
-                .map_err(|e| StorageError::Db(e.to_string()))?;
-        }
-
-        Ok(rows.into_iter().map(|(_, payload)| payload).collect())
-    }
-
-    fn queue_depth(
-        &self,
-        recipient_key: &[u8],
-        channel_id: &[u8],
-    ) -> Result<usize, StorageError> {
-        let conn = self.conn.lock().unwrap();
-        let count: i64 = conn
-            .query_row(
-                "SELECT COUNT(*) FROM deliveries WHERE recipient_key = ?1 AND channel_id = ?2",
-                params![recipient_key, channel_id],
-                |row| row.get(0),
-            )
-            .map_err(|e| StorageError::Db(e.to_string()))?;
-        Ok(count as usize)
-    }
-
-    fn gc_expired_messages(&self, max_age_secs: u64) -> Result<usize, StorageError> {
-        let conn = self.conn.lock().unwrap();
-        let cutoff = std::time::SystemTime::now()
-            .duration_since(std::time::UNIX_EPOCH)
-            .unwrap_or_default()
-            .as_secs()
-            .saturating_sub(max_age_secs);
-        let deleted = conn
-            .execute(
-                "DELETE FROM deliveries WHERE created_at < ?1",
-                params![cutoff as i64],
-            )
-            .map_err(|e| StorageError::Db(e.to_string()))?;
-        Ok(deleted)
-    }
-
-    fn upload_hybrid_key(
-        &self,
-        identity_key: &[u8],
-        hybrid_pk: Vec<u8>,
-    ) -> Result<(), StorageError> {
-        let conn = self.conn.lock().unwrap();
-        conn.execute(
-            "INSERT OR REPLACE INTO hybrid_keys (identity_key, hybrid_public_key) VALUES (?1, ?2)",
-            params![identity_key, hybrid_pk],
-        )
-        .map_err(|e| StorageError::Db(e.to_string()))?;
-        Ok(())
-    }
-
-    fn fetch_hybrid_key(&self, identity_key: &[u8]) -> Result<Option<Vec<u8>>, StorageError> {
-        let conn = self.conn.lock().unwrap();
-        let mut stmt = conn
-            .prepare("SELECT hybrid_public_key FROM hybrid_keys WHERE identity_key = ?1")
-            .map_err(|e| StorageError::Db(e.to_string()))?;
-
-        stmt.query_row(params![identity_key], |row| row.get(0))
-            .optional()
-            .map_err(|e| StorageError::Db(e.to_string()))
-    }
-
-    fn store_server_setup(&self, setup: Vec<u8>) -> Result<(), StorageError> {
-        let conn = self.conn.lock().unwrap();
-        conn.execute(
-            "INSERT OR REPLACE INTO server_setup (id, setup_data) VALUES (1, ?1)",
-            params![setup],
-        )
-        .map_err(|e| StorageError::Db(e.to_string()))?;
-        Ok(())
-    }
-
-    fn get_server_setup(&self) -> Result<Option<Vec<u8>>, StorageError> {
-        let conn = self.conn.lock().unwrap();
-        let mut stmt = conn
-            .prepare("SELECT setup_data FROM server_setup WHERE id = 1")
-            .map_err(|e| StorageError::Db(e.to_string()))?;
-
-        stmt.query_row([], |row| row.get(0))
-            .optional()
-            .map_err(|e| StorageError::Db(e.to_string()))
-    }
-
-    fn store_user_record(&self, username: &str, record: Vec<u8>) -> Result<(), StorageError> {
-        let conn = self.conn.lock().unwrap();
-        conn.execute(
-            "INSERT OR REPLACE INTO users (username, opaque_record) VALUES (?1, ?2)",
-            params![username, record],
-        )
-        .map_err(|e| StorageError::Db(e.to_string()))?;
-        Ok(())
-    }
-
-    fn get_user_record(&self, username: &str) -> Result<Option<Vec<u8>>, StorageError> {
-        let conn = self.conn.lock().unwrap();
-        let mut stmt = conn
-            .prepare("SELECT opaque_record FROM users WHERE username = ?1")
-            .map_err(|e| StorageError::Db(e.to_string()))?;
-
-        stmt.query_row(params![username], |row| row.get(0))
-            .optional()
-            .map_err(|e| StorageError::Db(e.to_string()))
-    }
-
-    fn has_user_record(&self, username: &str) -> Result<bool, StorageError> {
-        let conn = self.conn.lock().unwrap();
-        let exists: bool = conn
-            .query_row(
-                "SELECT EXISTS(SELECT 1 FROM users WHERE username = ?1)",
-                params![username],
-                |row| row.get(0),
-            )
-            .map_err(|e| StorageError::Db(e.to_string()))?;
-        Ok(exists)
-    }
-
-    fn store_user_identity_key(
-        &self,
-        username: &str,
-        identity_key: Vec<u8>,
-    ) -> Result<(), StorageError> {
-        let conn = self.conn.lock().unwrap();
-        conn.execute(
-            "INSERT OR REPLACE INTO user_identity_keys (username, identity_key) VALUES (?1, ?2)",
-            params![username, identity_key],
-        )
-        .map_err(|e| StorageError::Db(e.to_string()))?;
-        Ok(())
-    }
-
-    fn get_user_identity_key(&self, username: &str) -> Result<Option<Vec<u8>>, StorageError> {
-        let conn = self.conn.lock().unwrap();
-        let mut stmt = conn
-            .prepare("SELECT identity_key FROM user_identity_keys WHERE username = ?1")
-            .map_err(|e| StorageError::Db(e.to_string()))?;
-
-        stmt.query_row(params![username], |row| row.get(0))
-            .optional()
-            .map_err(|e| StorageError::Db(e.to_string()))
-    }
-
-    fn publish_endpoint(
-        &self,
-        identity_key: &[u8],
-        node_addr: Vec<u8>,
-    ) -> Result<(), StorageError> {
-        let conn = self.conn.lock().unwrap();
-        conn.execute(
-            "INSERT OR REPLACE INTO endpoints (identity_key, node_addr) VALUES (?1, ?2)",
-            params![identity_key, node_addr],
-        )
-        .map_err(|e| StorageError::Db(e.to_string()))?;
-        Ok(())
-    }
-
-    fn resolve_endpoint(&self, identity_key: &[u8]) -> Result<Option<Vec<u8>>, StorageError> {
-        let conn = self.conn.lock().unwrap();
-        let mut stmt = conn
-            .prepare("SELECT node_addr FROM endpoints WHERE identity_key = ?1")
-            .map_err(|e| StorageError::Db(e.to_string()))?;
-
-        stmt.query_row(params![identity_key], |row| row.get(0))
-            .optional()
-            .map_err(|e| StorageError::Db(e.to_string()))
-    }
-}
-
-/// Convenience extension for `rusqlite::OptionalExtension`.
-trait OptionalExt<T> {
-    fn optional(self) -> Result<Option<T>, rusqlite::Error>;
-}
-
-impl<T> OptionalExt<T> for Result<T, rusqlite::Error> {
-    fn optional(self) -> Result<Option<T>, rusqlite::Error> {
-        match self {
-            Ok(v) => Ok(Some(v)),
-            Err(rusqlite::Error::QueryReturnedNoRows) => Ok(None),
-            Err(e) => Err(e),
-        }
-    }
-}
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-
-    fn open_in_memory() -> SqlStore {
-        SqlStore::open(":memory:", "").unwrap()
-    }
-
-    #[test]
-    fn key_package_fifo() {
-        let store = open_in_memory();
-        let mut identity = [0u8; 32];
-        identity[..31].copy_from_slice(b"alice_identity_key__32bytes_lon");
-
-        store
-            .upload_key_package(&identity, b"kp1".to_vec())
-            .unwrap();
-        store
-            .upload_key_package(&identity, b"kp2".to_vec())
-            .unwrap();
-
-        assert_eq!(
-            store.fetch_key_package(&identity).unwrap(),
-            Some(b"kp1".to_vec())
-        );
-        assert_eq!(
-            store.fetch_key_package(&identity).unwrap(),
-            Some(b"kp2".to_vec())
-        );
-        assert_eq!(store.fetch_key_package(&identity).unwrap(), None);
-    }
-
-    #[test]
-    fn delivery_round_trip() {
-        let store = open_in_memory();
-        let rk = [1u8; 32];
-        let ch = b"channel-1";
-
-        store.enqueue(&rk, ch, b"msg1".to_vec()).unwrap();
-        store.enqueue(&rk, ch, b"msg2".to_vec()).unwrap();
-
-        let msgs = store.fetch(&rk, ch).unwrap();
-        assert_eq!(msgs, vec![b"msg1".to_vec(), b"msg2".to_vec()]);
-
-        assert!(store.fetch(&rk, ch).unwrap().is_empty());
-    }
-
-    #[test]
-    fn fetch_limited_partial_drain() {
-        let store = open_in_memory();
-        let rk = [5u8; 32];
-        let ch = b"ch";
-
-        store.enqueue(&rk, ch, b"a".to_vec()).unwrap();
-        store.enqueue(&rk, ch, b"b".to_vec()).unwrap();
-        store.enqueue(&rk, ch, b"c".to_vec()).unwrap();
-
-        let msgs = store.fetch_limited(&rk, ch, 2).unwrap();
-        assert_eq!(msgs, vec![b"a".to_vec(), b"b".to_vec()]);
-
-        let remaining = store.fetch(&rk, ch).unwrap();
-        assert_eq!(remaining, vec![b"c".to_vec()]);
-    }
-
-    #[test]
-    fn queue_depth_count() {
-        let store = open_in_memory();
-        let rk = [6u8; 32];
-        let ch = b"ch";
-
-        assert_eq!(store.queue_depth(&rk, ch).unwrap(), 0);
-        store.enqueue(&rk, ch, b"x".to_vec()).unwrap();
-        store.enqueue(&rk, ch, b"y".to_vec()).unwrap();
-        assert_eq!(store.queue_depth(&rk, ch).unwrap(), 2);
-    }
-
-    #[test]
-    fn has_user_record_check() {
-        let store = open_in_memory();
-        assert!(!store.has_user_record("alice").unwrap());
-        store.store_user_record("alice", b"record".to_vec()).unwrap();
-        assert!(store.has_user_record("alice").unwrap());
-        assert!(!store.has_user_record("bob").unwrap());
-    }
-
-    #[test]
-    fn user_identity_key_round_trip() {
-        let store = open_in_memory();
-        assert!(store.get_user_identity_key("alice").unwrap().is_none());
-        store.store_user_identity_key("alice", vec![1u8; 32]).unwrap();
-        assert_eq!(store.get_user_identity_key("alice").unwrap(), Some(vec![1u8; 32]));
-    }
-
-    #[test]
-    fn hybrid_key_round_trip() {
-        let store = open_in_memory();
-        let ik = [2u8; 32];
-        let pk = b"hybrid_public_key_data".to_vec();
-
-        store.upload_hybrid_key(&ik, pk.clone()).unwrap();
-        assert_eq!(store.fetch_hybrid_key(&ik).unwrap(), Some(pk));
-    }
-
-    #[test]
-    fn separate_channels_isolated() {
-        let store = open_in_memory();
-        let rk = [4u8; 32];
-
-        store.enqueue(&rk, b"ch-a", b"a1".to_vec()).unwrap();
-        store.enqueue(&rk, b"ch-b", b"b1".to_vec()).unwrap();
-
-        let a_msgs = store.fetch(&rk, b"ch-a").unwrap();
-        assert_eq!(a_msgs, vec![b"a1".to_vec()]);
-
-        let b_msgs = store.fetch(&rk, b"ch-b").unwrap();
-        assert_eq!(b_msgs, vec![b"b1".to_vec()]);
-    }
-}

crates/quicnprotochat-server/src/storage.rs

@@ -1,484 +0,0 @@
-use std::{
-    collections::{HashMap, VecDeque},
-    fs,
-    hash::Hash,
-    path::{Path, PathBuf},
-    sync::Mutex,
-};
-
-use serde::{Deserialize, Serialize};
-
-#[derive(thiserror::Error, Debug)]
-pub enum StorageError {
-    #[error("io error: {0}")]
-    Io(String),
-    #[error("serialization error")]
-    Serde,
-    #[error("database error: {0}")]
-    Db(String),
-}
-
-// ── Store trait ──────────────────────────────────────────────────────────────
-
-/// Abstraction over storage backends (file-backed, SQLCipher, etc.).
-pub trait Store: Send + Sync {
-    fn upload_key_package(
-        &self,
-        identity_key: &[u8],
-        package: Vec<u8>,
-    ) -> Result<(), StorageError>;
-
-    fn fetch_key_package(&self, identity_key: &[u8]) -> Result<Option<Vec<u8>>, StorageError>;
-
-    fn enqueue(
-        &self,
-        recipient_key: &[u8],
-        channel_id: &[u8],
-        payload: Vec<u8>,
-    ) -> Result<(), StorageError>;
-
-    fn fetch(
-        &self,
-        recipient_key: &[u8],
-        channel_id: &[u8],
-    ) -> Result<Vec<Vec<u8>>, StorageError>;
-
-    /// Fetch up to `limit` messages without draining the entire queue (Fix 8).
-    fn fetch_limited(
-        &self,
-        recipient_key: &[u8],
-        channel_id: &[u8],
-        limit: usize,
-    ) -> Result<Vec<Vec<u8>>, StorageError>;
-
-    /// Return the number of queued messages for (recipient, channel) (Fix 7).
-    fn queue_depth(
-        &self,
-        recipient_key: &[u8],
-        channel_id: &[u8],
-    ) -> Result<usize, StorageError>;
-
-    /// Delete messages older than `max_age_secs`. Returns count deleted (Fix 7).
-    fn gc_expired_messages(&self, max_age_secs: u64) -> Result<usize, StorageError>;
-
-    fn upload_hybrid_key(
-        &self,
-        identity_key: &[u8],
-        hybrid_pk: Vec<u8>,
-    ) -> Result<(), StorageError>;
-
-    fn fetch_hybrid_key(&self, identity_key: &[u8]) -> Result<Option<Vec<u8>>, StorageError>;
-
-    /// Store the OPAQUE `ServerSetup` (generated once, loaded on restart).
-    fn store_server_setup(&self, setup: Vec<u8>) -> Result<(), StorageError>;
-
-    /// Load the persisted `ServerSetup`, if any.
-    fn get_server_setup(&self) -> Result<Option<Vec<u8>>, StorageError>;
-
-    /// Store an OPAQUE user record (serialized `ServerRegistration`).
-    fn store_user_record(&self, username: &str, record: Vec<u8>) -> Result<(), StorageError>;
-
-    /// Retrieve an OPAQUE user record by username.
-    fn get_user_record(&self, username: &str) -> Result<Option<Vec<u8>>, StorageError>;
-
-    /// Check if a user record already exists (Fix 5).
-    fn has_user_record(&self, username: &str) -> Result<bool, StorageError>;
-
-    /// Store identity key for a user (Fix 2).
-    fn store_user_identity_key(
-        &self,
-        username: &str,
-        identity_key: Vec<u8>,
-    ) -> Result<(), StorageError>;
-
-    /// Retrieve identity key for a user (Fix 2).
-    fn get_user_identity_key(&self, username: &str) -> Result<Option<Vec<u8>>, StorageError>;
-
-    /// Publish a P2P endpoint address for an identity key.
-    fn publish_endpoint(
-        &self,
-        identity_key: &[u8],
-        node_addr: Vec<u8>,
-    ) -> Result<(), StorageError>;
-
-    /// Resolve a peer's P2P endpoint address.
-    fn resolve_endpoint(&self, identity_key: &[u8]) -> Result<Option<Vec<u8>>, StorageError>;
-}
-
-// ── ChannelKey ───────────────────────────────────────────────────────────────
-
-#[derive(Serialize, Deserialize, Clone, Eq, PartialEq, Debug)]
-pub struct ChannelKey {
-    pub channel_id: Vec<u8>,
-    pub recipient_key: Vec<u8>,
-}
-
-impl Hash for ChannelKey {
-    fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
-        self.channel_id.hash(state);
-        self.recipient_key.hash(state);
-    }
-}
-
-// ── FileBackedStore ──────────────────────────────────────────────────────────
-
-#[derive(Serialize, Deserialize, Default)]
-struct QueueMapV1 {
-    map: HashMap<Vec<u8>, VecDeque<Vec<u8>>>,
-}
-
-#[derive(Serialize, Deserialize, Default)]
-struct QueueMapV2 {
-    map: HashMap<ChannelKey, VecDeque<Vec<u8>>>,
-}
-
-/// File-backed storage for KeyPackages and delivery queues.
-///
-/// Each mutation flushes the entire map to disk. Suitable for MVP-scale loads.
-pub struct FileBackedStore {
-    kp_path: PathBuf,
-    ds_path: PathBuf,
-    hk_path: PathBuf,
-    setup_path: PathBuf,
-    users_path: PathBuf,
-    identity_keys_path: PathBuf,
-    key_packages: Mutex<HashMap<Vec<u8>, VecDeque<Vec<u8>>>>,
-    deliveries: Mutex<HashMap<ChannelKey, VecDeque<Vec<u8>>>>,
-    hybrid_keys: Mutex<HashMap<Vec<u8>, Vec<u8>>>,
-    users: Mutex<HashMap<String, Vec<u8>>>,
-    identity_keys: Mutex<HashMap<String, Vec<u8>>>,
-    endpoints: Mutex<HashMap<Vec<u8>, Vec<u8>>>,
-}
-
-impl FileBackedStore {
-    pub fn open(dir: impl AsRef<Path>) -> Result<Self, StorageError> {
-        let dir = dir.as_ref();
-        if !dir.exists() {
-            fs::create_dir_all(dir).map_err(|e| StorageError::Io(e.to_string()))?;
-        }
-        let kp_path = dir.join("keypackages.bin");
-        let ds_path = dir.join("deliveries.bin");
-        let hk_path = dir.join("hybridkeys.bin");
-        let setup_path = dir.join("server_setup.bin");
-        let users_path = dir.join("users.bin");
-        let identity_keys_path = dir.join("identity_keys.bin");
-
-        let key_packages = Mutex::new(Self::load_kp_map(&kp_path)?);
-        let deliveries = Mutex::new(Self::load_delivery_map(&ds_path)?);
-        let hybrid_keys = Mutex::new(Self::load_hybrid_keys(&hk_path)?);
-        let users = Mutex::new(Self::load_users(&users_path)?);
-        let identity_keys = Mutex::new(Self::load_map_string_bytes(&identity_keys_path)?);
-
-        Ok(Self {
-            kp_path,
-            ds_path,
-            hk_path,
-            setup_path,
-            users_path,
-            identity_keys_path,
-            key_packages,
-            deliveries,
-            hybrid_keys,
-            users,
-            identity_keys,
-            endpoints: Mutex::new(HashMap::new()),
-        })
-    }
-
-    fn load_kp_map(path: &Path) -> Result<HashMap<Vec<u8>, VecDeque<Vec<u8>>>, StorageError> {
-        if !path.exists() {
-            return Ok(HashMap::new());
-        }
-        let bytes = fs::read(path).map_err(|e| StorageError::Io(e.to_string()))?;
-        if bytes.is_empty() {
-            return Ok(HashMap::new());
-        }
-        let map: QueueMapV1 = bincode::deserialize(&bytes).map_err(|_| StorageError::Serde)?;
-        Ok(map.map)
-    }
-
-    fn flush_kp_map(
-        &self,
-        path: &Path,
-        map: &HashMap<Vec<u8>, VecDeque<Vec<u8>>>,
-    ) -> Result<(), StorageError> {
-        let payload = QueueMapV1 { map: map.clone() };
-        let bytes = bincode::serialize(&payload).map_err(|_| StorageError::Serde)?;
-        if let Some(parent) = path.parent() {
-            fs::create_dir_all(parent).map_err(|e| StorageError::Io(e.to_string()))?;
-        }
-        fs::write(path, bytes).map_err(|e| StorageError::Io(e.to_string()))
-    }
-
-    fn load_delivery_map(path: &Path) -> Result<HashMap<ChannelKey, VecDeque<Vec<u8>>>, StorageError> {
-        if !path.exists() {
-            return Ok(HashMap::new());
-        }
-        let bytes = fs::read(path).map_err(|e| StorageError::Io(e.to_string()))?;
-        if bytes.is_empty() {
-            return Ok(HashMap::new());
-        }
-        // Try v2 format (channel-aware). Fallback to legacy v1 for upgrade.
-        if let Ok(map) = bincode::deserialize::<QueueMapV2>(&bytes) {
-            return Ok(map.map);
-        }
-        let legacy: QueueMapV1 = bincode::deserialize(&bytes).map_err(|_| StorageError::Serde)?;
-        let mut upgraded = HashMap::new();
-        for (recipient_key, queue) in legacy.map.into_iter() {
-            upgraded.insert(
-                ChannelKey {
-                    channel_id: Vec::new(),
-                    recipient_key,
-                },
-                queue,
-            );
-        }
-        Ok(upgraded)
-    }
-
-    fn flush_delivery_map(
-        &self,
-        path: &Path,
-        map: &HashMap<ChannelKey, VecDeque<Vec<u8>>>,
-    ) -> Result<(), StorageError> {
-        let payload = QueueMapV2 { map: map.clone() };
-        let bytes = bincode::serialize(&payload).map_err(|_| StorageError::Serde)?;
-        if let Some(parent) = path.parent() {
-            fs::create_dir_all(parent).map_err(|e| StorageError::Io(e.to_string()))?;
-        }
-        fs::write(path, bytes).map_err(|e| StorageError::Io(e.to_string()))
-    }
-
-    fn load_hybrid_keys(path: &Path) -> Result<HashMap<Vec<u8>, Vec<u8>>, StorageError> {
-        if !path.exists() {
-            return Ok(HashMap::new());
-        }
-        let bytes = fs::read(path).map_err(|e| StorageError::Io(e.to_string()))?;
-        if bytes.is_empty() {
-            return Ok(HashMap::new());
-        }
-        bincode::deserialize(&bytes).map_err(|_| StorageError::Serde)
-    }
-
-    fn flush_hybrid_keys(
-        &self,
-        path: &Path,
-        map: &HashMap<Vec<u8>, Vec<u8>>,
-    ) -> Result<(), StorageError> {
-        let bytes = bincode::serialize(map).map_err(|_| StorageError::Serde)?;
-        if let Some(parent) = path.parent() {
-            fs::create_dir_all(parent).map_err(|e| StorageError::Io(e.to_string()))?;
-        }
-        fs::write(path, bytes).map_err(|e| StorageError::Io(e.to_string()))
-    }
-
-    fn load_users(path: &Path) -> Result<HashMap<String, Vec<u8>>, StorageError> {
-        if !path.exists() {
-            return Ok(HashMap::new());
-        }
-        let bytes = fs::read(path).map_err(|e| StorageError::Io(e.to_string()))?;
-        if bytes.is_empty() {
-            return Ok(HashMap::new());
-        }
-        bincode::deserialize(&bytes).map_err(|_| StorageError::Serde)
-    }
-
-    fn flush_users(
-        &self,
-        path: &Path,
-        map: &HashMap<String, Vec<u8>>,
-    ) -> Result<(), StorageError> {
-        let bytes = bincode::serialize(map).map_err(|_| StorageError::Serde)?;
-        if let Some(parent) = path.parent() {
-            fs::create_dir_all(parent).map_err(|e| StorageError::Io(e.to_string()))?;
-        }
-        fs::write(path, bytes).map_err(|e| StorageError::Io(e.to_string()))
-    }
-
-    fn load_map_string_bytes(path: &Path) -> Result<HashMap<String, Vec<u8>>, StorageError> {
-        Self::load_users(path)
-    }
-
-    fn flush_map_string_bytes(
-        &self,
-        path: &Path,
-        map: &HashMap<String, Vec<u8>>,
-    ) -> Result<(), StorageError> {
-        self.flush_users(path, map)
-    }
-}
-
-impl Store for FileBackedStore {
-    fn upload_key_package(
-        &self,
-        identity_key: &[u8],
-        package: Vec<u8>,
-    ) -> Result<(), StorageError> {
-        let mut map = self.key_packages.lock().unwrap();
-        map.entry(identity_key.to_vec())
-            .or_default()
-            .push_back(package);
-        self.flush_kp_map(&self.kp_path, &*map)
-    }
-
-    fn fetch_key_package(&self, identity_key: &[u8]) -> Result<Option<Vec<u8>>, StorageError> {
-        let mut map = self.key_packages.lock().unwrap();
-        let package = map.get_mut(identity_key).and_then(|q| q.pop_front());
-        self.flush_kp_map(&self.kp_path, &*map)?;
-        Ok(package)
-    }
-
-    fn enqueue(
-        &self,
-        recipient_key: &[u8],
-        channel_id: &[u8],
-        payload: Vec<u8>,
-    ) -> Result<(), StorageError> {
-        let mut map = self.deliveries.lock().unwrap();
-        let key = ChannelKey {
-            channel_id: channel_id.to_vec(),
-            recipient_key: recipient_key.to_vec(),
-        };
-        map.entry(key)
-            .or_default()
-            .push_back(payload);
-        self.flush_delivery_map(&self.ds_path, &*map)
-    }
-
-    fn fetch(
-        &self,
-        recipient_key: &[u8],
-        channel_id: &[u8],
-    ) -> Result<Vec<Vec<u8>>, StorageError> {
-        let mut map = self.deliveries.lock().unwrap();
-        let key = ChannelKey {
-            channel_id: channel_id.to_vec(),
-            recipient_key: recipient_key.to_vec(),
-        };
-        let messages = map
-            .get_mut(&key)
-            .map(|q| q.drain(..).collect())
-            .unwrap_or_default();
-        self.flush_delivery_map(&self.ds_path, &*map)?;
-        Ok(messages)
-    }
-
-    fn fetch_limited(
-        &self,
-        recipient_key: &[u8],
-        channel_id: &[u8],
-        limit: usize,
-    ) -> Result<Vec<Vec<u8>>, StorageError> {
-        let mut map = self.deliveries.lock().unwrap();
-        let key = ChannelKey {
-            channel_id: channel_id.to_vec(),
-            recipient_key: recipient_key.to_vec(),
-        };
-        let messages = map
-            .get_mut(&key)
-            .map(|q| {
-                let count = limit.min(q.len());
-                q.drain(..count).collect()
-            })
-            .unwrap_or_default();
-        self.flush_delivery_map(&self.ds_path, &*map)?;
-        Ok(messages)
-    }
-
-    fn queue_depth(
-        &self,
-        recipient_key: &[u8],
-        channel_id: &[u8],
-    ) -> Result<usize, StorageError> {
-        let map = self.deliveries.lock().unwrap();
-        let key = ChannelKey {
-            channel_id: channel_id.to_vec(),
-            recipient_key: recipient_key.to_vec(),
-        };
-        Ok(map.get(&key).map(|q| q.len()).unwrap_or(0))
-    }
-
-    fn gc_expired_messages(&self, _max_age_secs: u64) -> Result<usize, StorageError> {
-        // FileBackedStore does not track timestamps per message — no-op.
-        Ok(0)
-    }
-
-    fn upload_hybrid_key(
-        &self,
-        identity_key: &[u8],
-        hybrid_pk: Vec<u8>,
-    ) -> Result<(), StorageError> {
-        let mut map = self.hybrid_keys.lock().unwrap();
-        map.insert(identity_key.to_vec(), hybrid_pk);
-        self.flush_hybrid_keys(&self.hk_path, &*map)
-    }
-
-    fn fetch_hybrid_key(&self, identity_key: &[u8]) -> Result<Option<Vec<u8>>, StorageError> {
-        let map = self.hybrid_keys.lock().unwrap();
-        Ok(map.get(identity_key).cloned())
-    }
-
-    fn store_server_setup(&self, setup: Vec<u8>) -> Result<(), StorageError> {
-        if let Some(parent) = self.setup_path.parent() {
-            fs::create_dir_all(parent).map_err(|e| StorageError::Io(e.to_string()))?;
-        }
-        fs::write(&self.setup_path, setup).map_err(|e| StorageError::Io(e.to_string()))
-    }
-
-    fn get_server_setup(&self) -> Result<Option<Vec<u8>>, StorageError> {
-        if !self.setup_path.exists() {
-            return Ok(None);
-        }
-        let bytes = fs::read(&self.setup_path).map_err(|e| StorageError::Io(e.to_string()))?;
-        if bytes.is_empty() {
-            return Ok(None);
-        }
-        Ok(Some(bytes))
-    }
-
-    fn store_user_record(&self, username: &str, record: Vec<u8>) -> Result<(), StorageError> {
-        let mut map = self.users.lock().unwrap();
-        map.insert(username.to_string(), record);
-        self.flush_users(&self.users_path, &*map)
-    }
-
-    fn get_user_record(&self, username: &str) -> Result<Option<Vec<u8>>, StorageError> {
-        let map = self.users.lock().unwrap();
-        Ok(map.get(username).cloned())
-    }
-
-    fn has_user_record(&self, username: &str) -> Result<bool, StorageError> {
-        let map = self.users.lock().unwrap();
-        Ok(map.contains_key(username))
-    }
-
-    fn store_user_identity_key(
-        &self,
-        username: &str,
-        identity_key: Vec<u8>,
-    ) -> Result<(), StorageError> {
-        let mut map = self.identity_keys.lock().unwrap();
-        map.insert(username.to_string(), identity_key);
-        self.flush_map_string_bytes(&self.identity_keys_path, &*map)
-    }
-
-    fn get_user_identity_key(&self, username: &str) -> Result<Option<Vec<u8>>, StorageError> {
-        let map = self.identity_keys.lock().unwrap();
-        Ok(map.get(username).cloned())
-    }
-
-    fn publish_endpoint(
-        &self,
-        identity_key: &[u8],
-        node_addr: Vec<u8>,
-    ) -> Result<(), StorageError> {
-        let mut map = self.endpoints.lock().unwrap();
-        map.insert(identity_key.to_vec(), node_addr);
-        Ok(())
-    }
-
-    fn resolve_endpoint(&self, identity_key: &[u8]) -> Result<Option<Vec<u8>>, StorageError> {
-        let map = self.endpoints.lock().unwrap();
-        Ok(map.get(identity_key).cloned())
-    }
-}

crates/quicproquo-bot/Cargo.toml

@@ -0,0 +1,22 @@
+[package]
+name        = "quicproquo-bot"
+version     = "0.1.0"
+edition     = "2021"
+description = "Bot SDK for quicproquo — build automated agents on E2E encrypted messaging."
+license     = "MIT"
+
+[lints]
+workspace = true
+
+[dependencies]
+quicproquo-core   = { path = "../quicproquo-core" }
+quicproquo-proto  = { path = "../quicproquo-proto" }
+quicproquo-client = { path = "../quicproquo-client" }
+
+openmls_rust_crypto = { workspace = true }
+tokio       = { workspace = true }
+anyhow      = { workspace = true }
+tracing     = { workspace = true }
+serde       = { workspace = true }
+serde_json  = { workspace = true }
+hex         = { workspace = true }

crates/quicproquo-bot/src/lib.rs

@@ -0,0 +1,353 @@
+//! # quicproquo-bot — Bot SDK for E2E encrypted messaging
+//!
+//! Build automated agents that run on the quicproquo network with full MLS
+//! end-to-end encryption. The bot SDK wraps the client library into a simple
+//! polling-based API: connect, authenticate, send, receive.
+//!
+//! ## Quick start
+//!
+//! ```rust,no_run
+//! use quicproquo_bot::{Bot, BotConfig};
+//!
+//! #[tokio::main]
+//! async fn main() -> anyhow::Result<()> {
+//!     let config = BotConfig::new("127.0.0.1:7000", "bot-user", "bot-password")
+//!         .ca_cert("server-cert.der")
+//!         .state_path("bot-state.bin");
+//!
+//!     let bot = Bot::connect(config).await?;
+//!
+//!     // Send a DM
+//!     bot.send_dm("alice", "Hello from bot!").await?;
+//!
+//!     // Poll for messages
+//!     loop {
+//!         for msg in bot.receive(5000).await? {
+//!             println!("{}: {}", msg.sender, msg.text);
+//!             if msg.text.starts_with("!echo ") {
+//!                 bot.send_dm(&msg.sender, &msg.text[6..]).await?;
+//!             }
+//!         }
+//!     }
+//! }
+//! ```
+//!
+//! ## Pipe mode (stdin/stdout JSON lines)
+//!
+//! The bot SDK also supports non-interactive pipe mode for shell integration:
+//!
+//! ```bash
+//! # Send via pipe
+//! echo '{"to":"alice","text":"hello"}' | qpq pipe --state bot.bin
+//!
+//! # Receive via pipe (JSON lines to stdout)
+//! qpq pipe --recv --state bot.bin
+//! ```
+
+use std::path::PathBuf;
+use std::sync::Arc;
+
+use anyhow::Context;
+use tokio::task::LocalSet;
+
+use quicproquo_client::{connect_node, init_auth, opaque_login, resolve_user, ClientAuth};
+use quicproquo_core::IdentityKeypair;
+
+/// Configuration for connecting a bot to a quicproquo server.
+#[derive(Clone, Debug)]
+pub struct BotConfig {
+    /// Server address (host:port).
+    pub server: String,
+    /// Path to the server's CA certificate (DER format).
+    pub ca_cert: PathBuf,
+    /// TLS server name (defaults to "localhost").
+    pub server_name: String,
+    /// Bot's username for OPAQUE authentication.
+    pub username: String,
+    /// Bot's password for OPAQUE authentication.
+    pub password: String,
+    /// Path to the bot's encrypted state file.
+    pub state_path: PathBuf,
+    /// Password for the encrypted state file (None = unencrypted).
+    pub state_password: Option<String>,
+    /// Device ID reported to the server.
+    pub device_id: Option<String>,
+}
+
+impl BotConfig {
+    /// Create a new bot configuration with required fields.
+    pub fn new(server: &str, username: &str, password: &str) -> Self {
+        Self {
+            server: server.to_string(),
+            ca_cert: PathBuf::from("server-cert.der"),
+            server_name: "localhost".to_string(),
+            username: username.to_string(),
+            password: password.to_string(),
+            state_path: PathBuf::from("bot-state.bin"),
+            state_password: None,
+            device_id: None,
+        }
+    }
+
+    /// Set the CA certificate path.
+    pub fn ca_cert(mut self, path: &str) -> Self {
+        self.ca_cert = PathBuf::from(path);
+        self
+    }
+
+    /// Set the TLS server name for certificate validation.
+    pub fn server_name(mut self, name: &str) -> Self {
+        self.server_name = name.to_string();
+        self
+    }
+
+    /// Set the state file path.
+    pub fn state_path(mut self, path: &str) -> Self {
+        self.state_path = PathBuf::from(path);
+        self
+    }
+
+    /// Set the state file encryption password.
+    pub fn state_password(mut self, pwd: &str) -> Self {
+        self.state_password = Some(pwd.to_string());
+        self
+    }
+
+    /// Set the device ID.
+    pub fn device_id(mut self, id: &str) -> Self {
+        self.device_id = Some(id.to_string());
+        self
+    }
+}
+
+/// A received message from the quicproquo network.
+#[derive(Clone, Debug, serde::Serialize)]
+pub struct Message {
+    /// The sender's username (or "unknown" if resolution failed).
+    pub sender: String,
+    /// The decrypted plaintext message content.
+    pub text: String,
+    /// Server-assigned sequence number.
+    pub seq: u64,
+}
+
+/// A bot connected to a quicproquo server.
+///
+/// The bot maintains its identity and MLS group state. Each call to
+/// `send_dm` or `receive` opens a fresh QUIC connection (stateless
+/// reconnect pattern — same as the CLI client).
+pub struct Bot {
+    config: BotConfig,
+    identity: Arc<IdentityKeypair>,
+}
+
+impl Bot {
+    /// Connect to a quicproquo server and authenticate.
+    ///
+    /// Loads or creates an identity from the state file, connects via QUIC/TLS,
+    /// and performs OPAQUE password authentication.
+    pub async fn connect(config: BotConfig) -> anyhow::Result<Self> {
+        let state = quicproquo_client::client::state::load_or_init_state(
+            &config.state_path,
+            config.state_password.as_deref(),
+        )
+        .context("load or init bot state")?;
+
+        let identity = Arc::new(IdentityKeypair::from_seed(state.identity_seed));
+
+        // Authenticate on the first connection.
+        let local = LocalSet::new();
+        let cfg = config.clone();
+        let id = Arc::clone(&identity);
+
+        local
+            .run_until(async {
+                let client =
+                    connect_node(&cfg.server, &cfg.ca_cert, &cfg.server_name).await?;
+
+                let pk = id.public_key_bytes();
+                let token = opaque_login(
+                    &client,
+                    &cfg.username,
+                    &cfg.password,
+                    &pk,
+                )
+                .await
+                .context("OPAQUE login")?;
+
+                init_auth(ClientAuth::from_raw(token, cfg.device_id.clone()));
+
+                tracing::info!(username = %cfg.username, server = %cfg.server, "bot authenticated");
+                Ok::<(), anyhow::Error>(())
+            })
+            .await?;
+
+        Ok(Self { config, identity })
+    }
+
+    /// Send a plaintext message to a peer by username.
+    ///
+    /// Resolves the username to an identity key, then encrypts via MLS
+    /// and delivers through the server.
+    pub async fn send_dm(&self, peer_username: &str, text: &str) -> anyhow::Result<()> {
+        // Resolve username → identity key hex so we send to the specific peer.
+        let peer_key = self
+            .resolve_user(peer_username)
+            .await
+            .context("resolve peer username")?;
+        let peer_key_hex = hex::encode(&peer_key);
+
+        quicproquo_client::cmd_send(
+            &self.config.state_path,
+            &self.config.server,
+            &self.config.ca_cert,
+            &self.config.server_name,
+            Some(&peer_key_hex),
+            false,
+            text,
+            self.config.state_password.as_deref(),
+        )
+        .await
+        .context("send message")?;
+
+        Ok(())
+    }
+
+    /// Receive pending messages, waiting up to `timeout_ms` milliseconds.
+    ///
+    /// Returns decrypted application messages. MLS control messages (commits,
+    /// welcomes) are processed internally but not returned.
+    pub async fn receive(&self, timeout_ms: u64) -> anyhow::Result<Vec<Message>> {
+        let plaintexts = quicproquo_client::receive_pending_plaintexts(
+            &self.config.state_path,
+            &self.config.server,
+            &self.config.ca_cert,
+            &self.config.server_name,
+            timeout_ms,
+            self.config.state_password.as_deref(),
+        )
+        .await?;
+
+        let messages: Vec<Message> = plaintexts
+            .into_iter()
+            .enumerate()
+            .map(|(i, plaintext)| Message {
+                sender: "peer".to_string(), // TODO: resolve from MLS group roster
+                text: String::from_utf8_lossy(&plaintext).to_string(),
+                seq: i as u64,
+            })
+            .collect();
+
+        Ok(messages)
+    }
+
+    /// Receive raw plaintext bytes (for binary protocols or non-UTF-8 content).
+    pub async fn receive_raw(&self, timeout_ms: u64) -> anyhow::Result<Vec<Vec<u8>>> {
+        quicproquo_client::receive_pending_plaintexts(
+            &self.config.state_path,
+            &self.config.server,
+            &self.config.ca_cert,
+            &self.config.server_name,
+            timeout_ms,
+            self.config.state_password.as_deref(),
+        )
+        .await
+    }
+
+    /// Resolve a username to a 32-byte identity key.
+    pub async fn resolve_user(&self, username: &str) -> anyhow::Result<Vec<u8>> {
+        let local = LocalSet::new();
+        let cfg = self.config.clone();
+        let username = username.to_string();
+
+        local
+            .run_until(async {
+                let client = connect_node(&cfg.server, &cfg.ca_cert, &cfg.server_name).await?;
+                let key = resolve_user(&client, &username)
+                    .await?
+                    .ok_or_else(|| anyhow::anyhow!("user not found: {username}"))?;
+                Ok(key)
+            })
+            .await
+    }
+
+    /// Get the bot's own username.
+    pub fn username(&self) -> &str {
+        &self.config.username
+    }
+
+    /// Get the bot's identity public key (32 bytes, Ed25519).
+    pub fn identity_key(&self) -> [u8; 32] {
+        self.identity.public_key_bytes()
+    }
+
+    /// Get the bot's identity key as a hex string.
+    pub fn identity_key_hex(&self) -> String {
+        hex::encode(self.identity.public_key_bytes())
+    }
+}
+
+/// Read JSON commands from stdin and process them.
+///
+/// Each line should be a JSON object with:
+/// - `{"action": "send", "to": "username", "text": "message"}`
+/// - `{"action": "recv", "timeout_ms": 5000}`
+/// - `{"action": "resolve", "username": "alice"}`
+///
+/// Results are written to stdout as JSON lines.
+pub async fn run_pipe_mode(bot: &Bot) -> anyhow::Result<()> {
+    use tokio::io::{AsyncBufReadExt, BufReader};
+
+    let stdin = BufReader::new(tokio::io::stdin());
+    let mut lines = stdin.lines();
+
+    while let Ok(Some(line)) = lines.next_line().await {
+        let line = line.trim().to_string();
+        if line.is_empty() {
+            continue;
+        }
+
+        let cmd: serde_json::Value = match serde_json::from_str(&line) {
+            Ok(v) => v,
+            Err(e) => {
+                let err = serde_json::json!({"error": format!("invalid JSON: {e}")});
+                println!("{err}");
+                continue;
+            }
+        };
+
+        let action = cmd["action"].as_str().unwrap_or("");
+        let result = match action {
+            "send" => {
+                let to = cmd["to"].as_str().unwrap_or("");
+                let text = cmd["text"].as_str().unwrap_or("");
+                match bot.send_dm(to, text).await {
+                    Ok(()) => serde_json::json!({"status": "ok", "action": "send"}),
+                    Err(e) => serde_json::json!({"error": format!("{e:#}")}),
+                }
+            }
+            "recv" => {
+                let timeout = cmd["timeout_ms"].as_u64().unwrap_or(5000);
+                match bot.receive(timeout).await {
+                    Ok(msgs) => serde_json::json!({"status": "ok", "messages": msgs}),
+                    Err(e) => serde_json::json!({"error": format!("{e:#}")}),
+                }
+            }
+            "resolve" => {
+                let username = cmd["username"].as_str().unwrap_or("");
+                match bot.resolve_user(username).await {
+                    Ok(key) => serde_json::json!({
+                        "status": "ok",
+                        "identity_key": hex::encode(&key),
+                    }),
+                    Err(e) => serde_json::json!({"error": format!("{e:#}")}),
+                }
+            }
+            _ => serde_json::json!({"error": format!("unknown action: {action}")}),
+        };
+
+        println!("{result}");
+    }
+
+    Ok(())
+}

crates/quicproquo-client/Cargo.toml

@@ -0,0 +1,102 @@
+[package]
+name        = "quicproquo-client"
+version     = "0.1.0"
+edition     = "2021"
+description = "CLI client for quicproquo."
+license     = "MIT"
+
+[[bin]]
+name = "qpq"
+path = "src/main.rs"
+
+[dependencies]
+quicproquo-core  = { path = "../quicproquo-core" }
+quicproquo-proto = { path = "../quicproquo-proto" }
+quicproquo-kt    = { path = "../quicproquo-kt" }
+openmls_rust_crypto = { workspace = true }
+
+# Serialisation + RPC
+capnp         = { workspace = true }
+capnp-rpc     = { workspace = true }
+
+# Async
+tokio         = { workspace = true }
+tokio-util    = { workspace = true }
+futures       = { workspace = true }
+serde         = { workspace = true }
+serde_json    = { workspace = true }
+bincode       = { workspace = true }
+
+# Crypto — OPAQUE PAKE
+opaque-ke     = { workspace = true }
+rand          = { workspace = true }
+
+# Error handling
+anyhow        = { workspace = true }
+thiserror     = { workspace = true }
+
+# Crypto — for fingerprint verification in fetch-key subcommand
+sha2          = { workspace = true }
+argon2        = { workspace = true }
+chacha20poly1305 = { workspace = true }
+ciborium      = { workspace = true }
+zeroize       = { workspace = true }
+quinn         = { workspace = true }
+quinn-proto   = { workspace = true }
+rustls        = { workspace = true }
+
+# Logging
+tracing       = { workspace = true }
+tracing-subscriber = { workspace = true }
+
+# CLI
+clap          = { workspace = true }
+
+# Local message/conversation storage
+rusqlite      = { workspace = true }
+
+# Hex encoding/decoding
+hex           = { workspace = true }
+
+# Secure password prompting (no echo)
+rpassword     = "5"
+
+# mDNS discovery for mesh mode (Freifunk). Only compiled with --features mesh.
+mdns-sd = { version = "0.12", optional = true }
+
+# Optional P2P transport for direct node-to-node messaging.
+quicproquo-p2p = { path = "../quicproquo-p2p", optional = true }
+
+# Optional TUI dependencies (Ratatui full-screen interface).
+ratatui = { version = "0.29", optional = true, default-features = false, features = ["crossterm"] }
+crossterm = { version = "0.28", optional = true }
+
+# YAML playbook parsing (only compiled with --features playbook).
+serde_yaml = { version = "0.9", optional = true }
+
+# v2 SDK-based CLI (thin shell over quicproquo-sdk).
+quicproquo-sdk = { path = "../quicproquo-sdk", optional = true }
+quicproquo-rpc = { path = "../quicproquo-rpc", optional = true }
+rustyline      = { workspace = true, optional = true }
+
+[lints]
+workspace = true
+
+[features]
+# Enable mesh-mode features: mDNS local peer discovery + P2P transport.
+# Build: cargo build -p quicproquo-client --features mesh
+mesh = ["dep:mdns-sd", "dep:quicproquo-p2p"]
+# Enable full-screen Ratatui TUI: cargo build -p quicproquo-client --features tui
+tui = ["dep:ratatui", "dep:crossterm"]
+# Enable playbook (scripted command execution): YAML parser + serde derives.
+# Build: cargo build -p quicproquo-client --features playbook
+playbook = ["dep:serde_yaml"]
+# v2 CLI over SDK: cargo build -p quicproquo-client --features v2
+v2 = ["dep:quicproquo-sdk", "dep:quicproquo-rpc", "dep:rustyline"]
+
+[dev-dependencies]
+dashmap       = { workspace = true }
+assert_cmd    = "2"
+tempfile      = "3"
+portpicker    = "0.1"
+rand          = "0.8"

crates/quicproquo-client/src/client/command_engine.rs

@@ -0,0 +1,508 @@
+//! Command engine: typed command enum, registry, and execution bridge.
+//!
+//! Maps every REPL slash command and lifecycle operation into a single `Command`
+//! enum with typed parameters. `CommandRegistry` parses raw input and delegates
+//! execution to the existing `cmd_*` handlers in `repl.rs`.
+
+use std::collections::HashMap;
+
+use quicproquo_proto::node_capnp::node_service;
+
+use super::repl::{Input, SlashCommand, parse_input};
+use super::session::SessionState;
+
+// ── Comparison operator for assert conditions ────────────────────────────────
+
+/// Comparison operator used in playbook assertions.
+#[derive(Debug, Clone, PartialEq, Eq)]
+#[cfg_attr(feature = "playbook", derive(serde::Serialize, serde::Deserialize))]
+pub enum CmpOp {
+    Eq,
+    Ne,
+    Gt,
+    Lt,
+    Gte,
+    Lte,
+}
+
+impl CmpOp {
+    /// Evaluate this comparison: `lhs <op> rhs`.
+    pub fn eval(&self, lhs: usize, rhs: usize) -> bool {
+        match self {
+            CmpOp::Eq => lhs == rhs,
+            CmpOp::Ne => lhs != rhs,
+            CmpOp::Gt => lhs > rhs,
+            CmpOp::Lt => lhs < rhs,
+            CmpOp::Gte => lhs >= rhs,
+            CmpOp::Lte => lhs <= rhs,
+        }
+    }
+}
+
+// ── Assert conditions for playbook testing ───────────────────────────────────
+
+/// Conditions that can be asserted in a playbook step.
+#[derive(Debug, Clone)]
+#[cfg_attr(feature = "playbook", derive(serde::Serialize, serde::Deserialize))]
+pub enum AssertCondition {
+    Connected,
+    LoggedIn,
+    InConversation { name: String },
+    MessageCount { op: CmpOp, count: usize },
+    MemberCount { op: CmpOp, count: usize },
+    Custom { expression: String },
+}
+
+// ── Command enum ─────────────────────────────────────────────────────────────
+
+/// Every operation the client can perform, with typed parameters.
+///
+/// This is a superset of `SlashCommand` — it adds lifecycle operations
+/// (`Connect`, `Login`, `Register`, `SendMessage`, `Wait`, `Assert`, `SetVar`)
+/// that are needed for non-interactive / playbook execution.
+#[derive(Debug, Clone)]
+#[cfg_attr(feature = "playbook", derive(serde::Serialize, serde::Deserialize))]
+pub enum Command {
+    // ── Lifecycle (not in SlashCommand) ──────────────────────────────────
+    Connect {
+        server: String,
+        ca_cert: Option<String>,
+        insecure: bool,
+    },
+    Login {
+        username: String,
+        password: String,
+    },
+    Register {
+        username: String,
+        password: String,
+    },
+    SendMessage {
+        text: String,
+    },
+    Wait {
+        duration_ms: u64,
+    },
+    Assert {
+        condition: AssertCondition,
+    },
+    SetVar {
+        name: String,
+        value: String,
+    },
+
+    // ── SlashCommand mirror ─────────────────────────────────────────────
+    Help,
+    Quit,
+    Whoami,
+    List,
+    Switch { target: String },
+    Dm { username: String },
+    CreateGroup { name: String },
+    Invite { target: String },
+    Remove { target: String },
+    Leave,
+    Join,
+    Members,
+    GroupInfo,
+    Rename { name: String },
+    History { count: usize },
+
+    // Mesh
+    MeshPeers,
+    MeshServer { addr: String },
+    MeshSend { peer_id: String, message: String },
+    MeshBroadcast { topic: String, message: String },
+    MeshSubscribe { topic: String },
+    MeshRoute,
+    MeshIdentity,
+    MeshStore,
+
+    // Security / crypto
+    Verify { username: String },
+    UpdateKey,
+    Typing,
+    TypingNotify { enabled: bool },
+    React { emoji: String, index: Option<usize> },
+    Edit { index: usize, new_text: String },
+    Delete { index: usize },
+    SendFile { path: String },
+    Download { index: usize },
+    DeleteAccount,
+    Disappear { arg: Option<String> },
+    Privacy { arg: Option<String> },
+    VerifyFs,
+    RotateAllKeys,
+    Devices,
+    RegisterDevice { name: String },
+    RevokeDevice { id_prefix: String },
+}
+
+impl Command {
+    /// Convert a `Command` to a `SlashCommand` when possible.
+    ///
+    /// Returns `None` for lifecycle commands that have no `SlashCommand`
+    /// equivalent (`Connect`, `Login`, `Register`, `SendMessage`, `Wait`,
+    /// `Assert`, `SetVar`).
+    pub(crate) fn to_slash(&self) -> Option<SlashCommand> {
+        match self.clone() {
+            // Lifecycle — no SlashCommand equivalent
+            Command::Connect { .. }
+            | Command::Login { .. }
+            | Command::Register { .. }
+            | Command::SendMessage { .. }
+            | Command::Wait { .. }
+            | Command::Assert { .. }
+            | Command::SetVar { .. } => None,
+
+            // 1:1 mirror
+            Command::Help => Some(SlashCommand::Help),
+            Command::Quit => Some(SlashCommand::Quit),
+            Command::Whoami => Some(SlashCommand::Whoami),
+            Command::List => Some(SlashCommand::List),
+            Command::Switch { target } => Some(SlashCommand::Switch { target }),
+            Command::Dm { username } => Some(SlashCommand::Dm { username }),
+            Command::CreateGroup { name } => Some(SlashCommand::CreateGroup { name }),
+            Command::Invite { target } => Some(SlashCommand::Invite { target }),
+            Command::Remove { target } => Some(SlashCommand::Remove { target }),
+            Command::Leave => Some(SlashCommand::Leave),
+            Command::Join => Some(SlashCommand::Join),
+            Command::Members => Some(SlashCommand::Members),
+            Command::GroupInfo => Some(SlashCommand::GroupInfo),
+            Command::Rename { name } => Some(SlashCommand::Rename { name }),
+            Command::History { count } => Some(SlashCommand::History { count }),
+            Command::MeshPeers => Some(SlashCommand::MeshPeers),
+            Command::MeshServer { addr } => Some(SlashCommand::MeshServer { addr }),
+            Command::MeshSend { peer_id, message } => {
+                Some(SlashCommand::MeshSend { peer_id, message })
+            }
+            Command::MeshBroadcast { topic, message } => {
+                Some(SlashCommand::MeshBroadcast { topic, message })
+            }
+            Command::MeshSubscribe { topic } => Some(SlashCommand::MeshSubscribe { topic }),
+            Command::MeshRoute => Some(SlashCommand::MeshRoute),
+            Command::MeshIdentity => Some(SlashCommand::MeshIdentity),
+            Command::MeshStore => Some(SlashCommand::MeshStore),
+            Command::Verify { username } => Some(SlashCommand::Verify { username }),
+            Command::UpdateKey => Some(SlashCommand::UpdateKey),
+            Command::Typing => Some(SlashCommand::Typing),
+            Command::TypingNotify { enabled } => Some(SlashCommand::TypingNotify { enabled }),
+            Command::React { emoji, index } => Some(SlashCommand::React { emoji, index }),
+            Command::Edit { index, new_text } => Some(SlashCommand::Edit { index, new_text }),
+            Command::Delete { index } => Some(SlashCommand::Delete { index }),
+            Command::SendFile { path } => Some(SlashCommand::SendFile { path }),
+            Command::Download { index } => Some(SlashCommand::Download { index }),
+            Command::DeleteAccount => Some(SlashCommand::DeleteAccount),
+            Command::Disappear { arg } => Some(SlashCommand::Disappear { arg }),
+            Command::Privacy { arg } => Some(SlashCommand::Privacy { arg }),
+            Command::VerifyFs => Some(SlashCommand::VerifyFs),
+            Command::RotateAllKeys => Some(SlashCommand::RotateAllKeys),
+            Command::Devices => Some(SlashCommand::Devices),
+            Command::RegisterDevice { name } => Some(SlashCommand::RegisterDevice { name }),
+            Command::RevokeDevice { id_prefix } => {
+                Some(SlashCommand::RevokeDevice { id_prefix })
+            }
+        }
+    }
+}
+
+// ── CommandResult ────────────────────────────────────────────────────────────
+
+/// Outcome of executing a single `Command`.
+#[derive(Debug, Clone)]
+#[cfg_attr(feature = "playbook", derive(serde::Serialize, serde::Deserialize))]
+pub struct CommandResult {
+    pub success: bool,
+    pub output: Option<String>,
+    pub error: Option<String>,
+    /// Structured key-value outputs for variable capture in playbooks.
+    pub data: HashMap<String, String>,
+}
+
+impl CommandResult {
+    fn ok() -> Self {
+        Self {
+            success: true,
+            output: None,
+            error: None,
+            data: HashMap::new(),
+        }
+    }
+
+    fn err(msg: String) -> Self {
+        Self {
+            success: false,
+            output: None,
+            error: Some(msg),
+            data: HashMap::new(),
+        }
+    }
+}
+
+// ── CommandRegistry ──────────────────────────────────────────────────────────
+
+/// Parses raw input into `Command` and delegates execution to the existing
+/// REPL handlers.
+pub struct CommandRegistry;
+
+impl CommandRegistry {
+    /// Parse a raw input line into a `Command`.
+    ///
+    /// Returns `None` for empty input. Returns `Some(Command::SendMessage)`
+    /// for plain chat text. Slash commands are parsed via the existing
+    /// `parse_input` function.
+    pub fn parse(line: &str) -> Option<Command> {
+        match parse_input(line) {
+            Input::Empty => None,
+            Input::ChatMessage(text) => Some(Command::SendMessage { text }),
+            Input::Slash(sc) => Some(slash_to_command(sc)),
+        }
+    }
+
+    /// Execute a `Command`, delegating slash commands to the existing
+    /// `handle_slash` dispatch and handling lifecycle commands directly.
+    ///
+    /// Currently, output from `cmd_*` handlers goes to stdout (unchanged).
+    /// `CommandResult` captures success/failure status; stdout capture can
+    /// be added later.
+    pub async fn execute(
+        cmd: &Command,
+        session: &mut SessionState,
+        client: &node_service::Client,
+    ) -> CommandResult {
+        match cmd {
+            Command::Wait { duration_ms } => {
+                tokio::time::sleep(std::time::Duration::from_millis(*duration_ms)).await;
+                CommandResult::ok()
+            }
+            Command::SetVar { name, value } => {
+                let mut result = CommandResult::ok();
+                result.data.insert(name.clone(), value.clone());
+                result
+            }
+            Command::Assert { condition } => execute_assert(condition, session),
+            Command::Connect { .. } | Command::Login { .. } | Command::Register { .. } => {
+                // These lifecycle commands require external context (endpoint,
+                // OPAQUE state) that lives outside SessionState. The playbook
+                // executor will handle them directly; calling execute() for
+                // them is an error.
+                CommandResult::err(
+                    "lifecycle commands (connect/login/register) must be handled by the playbook executor".into(),
+                )
+            }
+            Command::SendMessage { text } => {
+                match super::repl::do_send(session, client, text).await {
+                    Ok(()) => CommandResult::ok(),
+                    Err(e) => CommandResult::err(format!("{e:#}")),
+                }
+            }
+            Command::Quit => CommandResult::ok(),
+            other => {
+                // All remaining variants have a SlashCommand equivalent.
+                if let Some(sc) = other.to_slash() {
+                    match execute_slash(session, client, sc).await {
+                        Ok(()) => CommandResult::ok(),
+                        Err(e) => CommandResult::err(format!("{e:#}")),
+                    }
+                } else {
+                    CommandResult::err("command has no slash equivalent".into())
+                }
+            }
+        }
+    }
+}
+
+// ── Conversion helpers ──────────────────────────────────────────────────────
+
+/// Convert a `SlashCommand` into the corresponding `Command`.
+fn slash_to_command(sc: SlashCommand) -> Command {
+    match sc {
+        SlashCommand::Help => Command::Help,
+        SlashCommand::Quit => Command::Quit,
+        SlashCommand::Whoami => Command::Whoami,
+        SlashCommand::List => Command::List,
+        SlashCommand::Switch { target } => Command::Switch { target },
+        SlashCommand::Dm { username } => Command::Dm { username },
+        SlashCommand::CreateGroup { name } => Command::CreateGroup { name },
+        SlashCommand::Invite { target } => Command::Invite { target },
+        SlashCommand::Remove { target } => Command::Remove { target },
+        SlashCommand::Leave => Command::Leave,
+        SlashCommand::Join => Command::Join,
+        SlashCommand::Members => Command::Members,
+        SlashCommand::GroupInfo => Command::GroupInfo,
+        SlashCommand::Rename { name } => Command::Rename { name },
+        SlashCommand::History { count } => Command::History { count },
+        SlashCommand::MeshPeers => Command::MeshPeers,
+        SlashCommand::MeshServer { addr } => Command::MeshServer { addr },
+        SlashCommand::MeshSend { peer_id, message } => Command::MeshSend { peer_id, message },
+        SlashCommand::MeshBroadcast { topic, message } => {
+            Command::MeshBroadcast { topic, message }
+        }
+        SlashCommand::MeshSubscribe { topic } => Command::MeshSubscribe { topic },
+        SlashCommand::MeshRoute => Command::MeshRoute,
+        SlashCommand::MeshIdentity => Command::MeshIdentity,
+        SlashCommand::MeshStore => Command::MeshStore,
+        SlashCommand::Verify { username } => Command::Verify { username },
+        SlashCommand::UpdateKey => Command::UpdateKey,
+        SlashCommand::Typing => Command::Typing,
+        SlashCommand::TypingNotify { enabled } => Command::TypingNotify { enabled },
+        SlashCommand::React { emoji, index } => Command::React { emoji, index },
+        SlashCommand::Edit { index, new_text } => Command::Edit { index, new_text },
+        SlashCommand::Delete { index } => Command::Delete { index },
+        SlashCommand::SendFile { path } => Command::SendFile { path },
+        SlashCommand::Download { index } => Command::Download { index },
+        SlashCommand::DeleteAccount => Command::DeleteAccount,
+        SlashCommand::Disappear { arg } => Command::Disappear { arg },
+        SlashCommand::Privacy { arg } => Command::Privacy { arg },
+        SlashCommand::VerifyFs => Command::VerifyFs,
+        SlashCommand::RotateAllKeys => Command::RotateAllKeys,
+        SlashCommand::Devices => Command::Devices,
+        SlashCommand::RegisterDevice { name } => Command::RegisterDevice { name },
+        SlashCommand::RevokeDevice { id_prefix } => Command::RevokeDevice { id_prefix },
+    }
+}
+
+// ── Execution helpers ───────────────────────────────────────────────────────
+
+/// Execute a `SlashCommand` using the existing `cmd_*` handlers from `repl.rs`.
+///
+/// This duplicates the dispatch table from `handle_slash` but returns
+/// `anyhow::Result<()>` instead of printing errors inline — the caller
+/// decides how to surface errors.
+async fn execute_slash(
+    session: &mut SessionState,
+    client: &node_service::Client,
+    cmd: SlashCommand,
+) -> anyhow::Result<()> {
+    use super::repl::*;
+    match cmd {
+        SlashCommand::Help => {
+            print_help();
+            Ok(())
+        }
+        SlashCommand::Quit => Ok(()),
+        SlashCommand::Whoami => cmd_whoami(session),
+        SlashCommand::List => cmd_list(session),
+        SlashCommand::Switch { target } => cmd_switch(session, &target),
+        SlashCommand::Dm { username } => cmd_dm(session, client, &username).await,
+        SlashCommand::CreateGroup { name } => cmd_create_group(session, &name),
+        SlashCommand::Invite { target } => cmd_invite(session, client, &target).await,
+        SlashCommand::Remove { target } => cmd_remove(session, client, &target).await,
+        SlashCommand::Leave => cmd_leave(session, client).await,
+        SlashCommand::Join => cmd_join(session, client).await,
+        SlashCommand::Members => cmd_members(session, client).await,
+        SlashCommand::GroupInfo => cmd_group_info(session, client).await,
+        SlashCommand::Rename { name } => cmd_rename(session, &name),
+        SlashCommand::History { count } => cmd_history(session, count),
+        SlashCommand::MeshPeers => cmd_mesh_peers(),
+        SlashCommand::MeshServer { addr } => {
+            super::display::print_status(&format!(
+                "mesh server hint: reconnect with --server {addr} to use this node"
+            ));
+            Ok(())
+        }
+        SlashCommand::MeshSend { peer_id, message } => cmd_mesh_send(&peer_id, &message),
+        SlashCommand::MeshBroadcast { topic, message } => cmd_mesh_broadcast(&topic, &message),
+        SlashCommand::MeshSubscribe { topic } => cmd_mesh_subscribe(&topic),
+        SlashCommand::MeshRoute => cmd_mesh_route(session),
+        SlashCommand::MeshIdentity => cmd_mesh_identity(session),
+        SlashCommand::MeshStore => cmd_mesh_store(session),
+        SlashCommand::Verify { username } => cmd_verify(session, client, &username).await,
+        SlashCommand::UpdateKey => cmd_update_key(session, client).await,
+        SlashCommand::Typing => cmd_typing(session, client).await,
+        SlashCommand::TypingNotify { enabled } => {
+            session.typing_notify_enabled = enabled;
+            super::display::print_status(&format!(
+                "typing notifications {}",
+                if enabled { "enabled" } else { "disabled" }
+            ));
+            Ok(())
+        }
+        SlashCommand::React { emoji, index } => cmd_react(session, client, &emoji, index).await,
+        SlashCommand::Edit { index, new_text } => {
+            cmd_edit(session, client, index, &new_text).await
+        }
+        SlashCommand::Delete { index } => cmd_delete(session, client, index).await,
+        SlashCommand::SendFile { path } => cmd_send_file(session, client, &path).await,
+        SlashCommand::Download { index } => cmd_download(session, client, index).await,
+        SlashCommand::DeleteAccount => cmd_delete_account(session, client).await,
+        SlashCommand::Disappear { arg } => cmd_disappear(session, arg.as_deref()),
+        SlashCommand::Privacy { arg } => cmd_privacy(session, arg.as_deref()),
+        SlashCommand::VerifyFs => cmd_verify_fs(session),
+        SlashCommand::RotateAllKeys => cmd_rotate_all_keys(session, client).await,
+        SlashCommand::Devices => cmd_devices(client).await,
+        SlashCommand::RegisterDevice { name } => cmd_register_device(client, &name).await,
+        SlashCommand::RevokeDevice { id_prefix } => cmd_revoke_device(client, &id_prefix).await,
+    }
+}
+
+/// Assert a condition against the current session state.
+fn execute_assert(condition: &AssertCondition, session: &SessionState) -> CommandResult {
+    match condition {
+        AssertCondition::Connected => {
+            // We have a session => we got past connect. Always true when
+            // execute() is called with a valid client reference.
+            CommandResult::ok()
+        }
+        AssertCondition::LoggedIn => {
+            let guard = crate::AUTH_CONTEXT
+                .read()
+                .expect("AUTH_CONTEXT poisoned");
+            if guard.is_some() {
+                CommandResult::ok()
+            } else {
+                CommandResult::err("not logged in".into())
+            }
+        }
+        AssertCondition::InConversation { name } => {
+            if let Some(display) = session.active_display_name() {
+                if display.contains(name.as_str()) {
+                    CommandResult::ok()
+                } else {
+                    CommandResult::err(format!(
+                        "active conversation is '{display}', expected '{name}'"
+                    ))
+                }
+            } else {
+                CommandResult::err("no active conversation".into())
+            }
+        }
+        AssertCondition::MessageCount { op, count } => {
+            let actual = session
+                .active_conversation
+                .as_ref()
+                .and_then(|id| session.conv_store.load_all_messages(id).ok())
+                .map(|msgs| msgs.len())
+                .unwrap_or(0);
+            if op.eval(actual, *count) {
+                CommandResult::ok()
+            } else {
+                CommandResult::err(format!(
+                    "message count assertion failed: {actual} {op:?} {count}"
+                ))
+            }
+        }
+        AssertCondition::MemberCount { op, count } => {
+            let actual = session
+                .active_conversation
+                .as_ref()
+                .and_then(|id| session.members.get(id))
+                .map(|m| m.member_identities().len())
+                .unwrap_or(0);
+            if op.eval(actual, *count) {
+                CommandResult::ok()
+            } else {
+                CommandResult::err(format!(
+                    "member count assertion failed: {actual} {op:?} {count}"
+                ))
+            }
+        }
+        AssertCondition::Custom { expression } => {
+            // Custom expressions are not evaluated yet; always pass.
+            let mut result = CommandResult::ok();
+            result.data.insert("expression".into(), expression.clone());
+            result
+        }
+    }
+}
+

crates/quicproquo-client/src/client/conversation.rs

@@ -0,0 +1,798 @@
+//! Multi-conversation state backed by SQLite (SQLCipher-encrypted when a
+//! password is provided).
+//!
+//! Each conversation (DM or group) has its own MLS group blob, keystore blob,
+//! member list, and message history.
+
+use std::path::{Path, PathBuf};
+use std::time::{SystemTime, UNIX_EPOCH};
+
+use anyhow::Context;
+use argon2::{Algorithm, Argon2, Params, Version};
+use rand::RngCore;
+use rusqlite::{params, Connection, OptionalExtension};
+use zeroize::Zeroizing;
+
+// ── Types ────────────────────────────────────────────────────────────────────
+
+/// 16-byte conversation identifier.
+///   - DMs: the channel_id returned by `createChannel` (server-assigned UUID).
+///   - Groups: SHA-256(group_name)[..16].
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct ConversationId(pub [u8; 16]);
+
+impl ConversationId {
+    pub fn from_slice(s: &[u8]) -> Option<Self> {
+        if s.len() == 16 {
+            let mut buf = [0u8; 16];
+            buf.copy_from_slice(s);
+            Some(Self(buf))
+        } else {
+            None
+        }
+    }
+
+    /// Derive a conversation ID from a group name via SHA-256 truncation.
+    pub fn from_group_name(name: &str) -> Self {
+        use sha2::{Sha256, Digest};
+        let hash = Sha256::digest(name.as_bytes());
+        let mut buf = [0u8; 16];
+        buf.copy_from_slice(&hash[..16]);
+        Self(buf)
+    }
+
+    pub fn hex(&self) -> String {
+        hex::encode(self.0)
+    }
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum ConversationKind {
+    /// 1:1 DM channel with a specific peer.
+    Dm {
+        peer_key: Vec<u8>,
+        peer_username: Option<String>,
+    },
+    /// Named group with N members.
+    Group { name: String },
+}
+
+#[derive(Clone, Debug)]
+pub struct Conversation {
+    pub id: ConversationId,
+    pub kind: ConversationKind,
+    pub display_name: String,
+    /// Serialized MLS group (bincode).
+    pub mls_group_blob: Option<Vec<u8>>,
+    /// Serialized keystore (bincode HashMap).
+    pub keystore_blob: Option<Vec<u8>>,
+    /// Member identity keys (bincode Vec<Vec<u8>>).
+    pub member_keys: Vec<Vec<u8>>,
+    pub unread_count: u32,
+    pub last_activity_ms: u64,
+    pub created_at_ms: u64,
+    /// Whether this conversation uses hybrid (X25519 + ML-KEM-768) MLS keys.
+    pub is_hybrid: bool,
+    /// Highest server-side delivery sequence number seen.
+    pub last_seen_seq: u64,
+}
+
+#[derive(Clone, Debug)]
+pub struct StoredMessage {
+    pub conversation_id: ConversationId,
+    pub message_id: Option<[u8; 16]>,
+    pub sender_key: Vec<u8>,
+    pub sender_name: Option<String>,
+    pub body: String,
+    pub msg_type: String,
+    pub ref_msg_id: Option<[u8; 16]>,
+    pub timestamp_ms: u64,
+    pub is_outgoing: bool,
+}
+
+// ── Key derivation (Argon2id, matching state.rs parameters) ─────────────────
+
+const ARGON2_M_COST: u32 = 19 * 1024;
+const ARGON2_T_COST: u32 = 2;
+const ARGON2_P_COST: u32 = 1;
+const SALT_LEN: usize = 16;
+
+/// Derive a 32-byte SQLCipher key from the user password and a random salt.
+fn derive_convdb_key(password: &str, salt: &[u8]) -> anyhow::Result<Zeroizing<[u8; 32]>> {
+    let params = Params::new(ARGON2_M_COST, ARGON2_T_COST, ARGON2_P_COST, Some(32))
+        .map_err(|e| anyhow::anyhow!("argon2 params: {e}"))?;
+    let argon2 = Argon2::new(Algorithm::Argon2id, Version::default(), params);
+    let mut key = Zeroizing::new([0u8; 32]);
+    argon2
+        .hash_password_into(password.as_bytes(), salt, &mut *key)
+        .map_err(|e| anyhow::anyhow!("convdb key derivation: {e}"))?;
+    Ok(key)
+}
+
+/// Read or create a 16-byte random salt at `salt_path` (mode 0o600).
+fn get_or_create_salt(salt_path: &Path) -> anyhow::Result<Vec<u8>> {
+    if salt_path.exists() {
+        let bytes = std::fs::read(salt_path).context("read convdb salt")?;
+        anyhow::ensure!(bytes.len() == SALT_LEN, "invalid convdb salt length");
+        return Ok(bytes);
+    }
+    let mut salt = vec![0u8; SALT_LEN];
+    rand::rngs::OsRng.fill_bytes(&mut salt);
+    std::fs::write(salt_path, &salt).context("write convdb salt")?;
+    #[cfg(unix)]
+    {
+        use std::os::unix::fs::PermissionsExt;
+        std::fs::set_permissions(salt_path, std::fs::Permissions::from_mode(0o600)).ok();
+    }
+    Ok(salt)
+}
+
+// ── ConversationStore ────────────────────────────────────────────────────────
+
+pub struct ConversationStore {
+    conn: Connection,
+}
+
+impl ConversationStore {
+    /// Open or create the conversation database at `db_path`.
+    /// If `password` is `Some`, the database is encrypted with SQLCipher using
+    /// an Argon2id-derived key. Existing unencrypted databases are migrated
+    /// transparently.
+    pub fn open(db_path: &Path, password: Option<&str>) -> anyhow::Result<Self> {
+        if let Some(parent) = db_path.parent() {
+            std::fs::create_dir_all(parent).ok();
+        }
+
+        match password {
+            Some(pw) => Self::open_encrypted(db_path, pw),
+            None => Self::open_plain(db_path),
+        }
+    }
+
+    fn open_plain(db_path: &Path) -> anyhow::Result<Self> {
+        let conn = Connection::open(db_path).context("open conversation db")?;
+        conn.execute_batch("PRAGMA journal_mode=WAL; PRAGMA foreign_keys=ON;")
+            .context("set pragmas")?;
+        Self::migrate(&conn)?;
+        Ok(Self { conn })
+    }
+
+    fn open_encrypted(db_path: &Path, password: &str) -> anyhow::Result<Self> {
+        let salt_path = PathBuf::from(format!("{}-salt", db_path.display()));
+        let already_encrypted = salt_path.exists();
+
+        // Migrate an existing unencrypted database before opening with encryption.
+        if db_path.exists() && !already_encrypted {
+            Self::migrate_plain_to_encrypted(db_path, &salt_path, password)?;
+            // After migration, salt file exists and DB is encrypted — fall through.
+        }
+
+        let salt = get_or_create_salt(&salt_path)?;
+        let key = derive_convdb_key(password, &salt)?;
+        #[allow(clippy::needless_borrows_for_generic_args)]
+        let hex_key = Zeroizing::new(hex::encode(&*key));
+
+        let conn = Connection::open(db_path).context("open conversation db")?;
+        conn.pragma_update(None, "key", format!("x'{}'", &*hex_key))
+            .context("set SQLCipher key")?;
+        conn.execute_batch("PRAGMA journal_mode=WAL; PRAGMA foreign_keys=ON;")
+            .context("set pragmas")?;
+        Self::migrate(&conn)?;
+        Ok(Self { conn })
+    }
+
+    /// Migrate an unencrypted `.convdb` to an encrypted one in-place.
+    fn migrate_plain_to_encrypted(
+        db_path: &Path,
+        salt_path: &Path,
+        password: &str,
+    ) -> anyhow::Result<()> {
+        let salt = get_or_create_salt(salt_path)?;
+        let key = derive_convdb_key(password, &salt)?;
+        #[allow(clippy::needless_borrows_for_generic_args)]
+        let hex_key = Zeroizing::new(hex::encode(&*key));
+
+        let enc_path = db_path.with_extension("convdb-enc");
+
+        // Open the existing plaintext database.
+        let plain = Connection::open(db_path).context("open plain convdb for migration")?;
+        plain.execute_batch("PRAGMA journal_mode=WAL; PRAGMA foreign_keys=ON;").ok();
+
+        // Attach a new encrypted database and export into it.
+        // Sanitize the path to prevent SQL injection (ATTACH does not support parameterized paths).
+        let enc_path_str = enc_path.display().to_string();
+        anyhow::ensure!(
+            !enc_path_str.contains('\''),
+            "database path must not contain single quotes: {enc_path_str}"
+        );
+        plain
+            .execute_batch(&format!(
+                "ATTACH DATABASE '{enc_path_str}' AS encrypted KEY \"x'{}'\";",
+                &*hex_key
+            ))
+            .context("attach encrypted db for migration")?;
+        plain
+            .execute_batch("SELECT sqlcipher_export('encrypted');")
+            .context("sqlcipher_export to encrypted db")?;
+        plain
+            .execute_batch("DETACH DATABASE encrypted;")
+            .context("detach encrypted db")?;
+
+        drop(plain);
+
+        // Swap files: encrypted → original.
+        std::fs::rename(&enc_path, db_path).context("replace convdb with encrypted version")?;
+        // Clean up WAL/SHM left from the plaintext open.
+        let wal = PathBuf::from(format!("{}-wal", db_path.display()));
+        let shm = PathBuf::from(format!("{}-shm", db_path.display()));
+        std::fs::remove_file(&wal).ok();
+        std::fs::remove_file(&shm).ok();
+
+        tracing::info!("migrated conversation database to encrypted storage");
+        Ok(())
+    }
+
+    fn migrate(conn: &Connection) -> anyhow::Result<()> {
+        conn.execute_batch(
+            "CREATE TABLE IF NOT EXISTS conversations (
+                id              BLOB PRIMARY KEY,
+                kind            TEXT NOT NULL,
+                display_name    TEXT NOT NULL,
+                peer_key        BLOB,
+                peer_username   TEXT,
+                group_name      TEXT,
+                mls_group_blob  BLOB,
+                keystore_blob   BLOB,
+                member_keys     BLOB,
+                unread_count    INTEGER NOT NULL DEFAULT 0,
+                last_activity_ms INTEGER NOT NULL DEFAULT 0,
+                created_at_ms   INTEGER NOT NULL DEFAULT 0
+            );
+
+            CREATE TABLE IF NOT EXISTS messages (
+                id              INTEGER PRIMARY KEY AUTOINCREMENT,
+                conversation_id BLOB NOT NULL REFERENCES conversations(id),
+                message_id      BLOB,
+                sender_key      BLOB NOT NULL,
+                sender_name     TEXT,
+                body            TEXT NOT NULL,
+                msg_type        TEXT NOT NULL,
+                ref_msg_id      BLOB,
+                timestamp_ms    INTEGER NOT NULL,
+                is_outgoing     INTEGER NOT NULL DEFAULT 0
+            );
+
+            CREATE INDEX IF NOT EXISTS idx_messages_conv
+                ON messages(conversation_id, timestamp_ms);
+
+            CREATE TABLE IF NOT EXISTS outbox (
+                id              INTEGER PRIMARY KEY AUTOINCREMENT,
+                conversation_id BLOB NOT NULL,
+                recipient_key   BLOB NOT NULL,
+                payload         BLOB NOT NULL,
+                created_at_ms   INTEGER NOT NULL,
+                retry_count     INTEGER NOT NULL DEFAULT 0,
+                status          TEXT NOT NULL DEFAULT 'pending'
+            );
+            CREATE INDEX IF NOT EXISTS idx_outbox_status
+                ON outbox(status, created_at_ms);",
+        )
+        .context("migrate conversation db")?;
+
+        // Additive migrations for new columns (safe to re-run; errors ignored if column already exists).
+        conn.execute_batch("ALTER TABLE conversations ADD COLUMN is_hybrid INTEGER NOT NULL DEFAULT 0;").ok();
+        conn.execute_batch("ALTER TABLE conversations ADD COLUMN last_seen_seq INTEGER NOT NULL DEFAULT 0;").ok();
+
+        Ok(())
+    }
+
+    // ── Conversation CRUD ────────────────────────────────────────────────
+
+    pub fn save_conversation(&self, conv: &Conversation) -> anyhow::Result<()> {
+        let (kind_str, peer_key, peer_username, group_name) = match &conv.kind {
+            ConversationKind::Dm {
+                peer_key,
+                peer_username,
+            } => ("dm", Some(peer_key.as_slice()), peer_username.as_deref(), None),
+            ConversationKind::Group { name } => ("group", None, None, Some(name.as_str())),
+        };
+        let member_keys_blob = bincode::serialize(&conv.member_keys)
+            .context("serialize member_keys")?;
+
+        self.conn.execute(
+            "INSERT INTO conversations
+                (id, kind, display_name, peer_key, peer_username, group_name,
+                 mls_group_blob, keystore_blob, member_keys, unread_count,
+                 last_activity_ms, created_at_ms, is_hybrid, last_seen_seq)
+             VALUES (?1, ?2, ?3, ?4, ?5, ?6, ?7, ?8, ?9, ?10, ?11, ?12, ?13, ?14)
+             ON CONFLICT(id) DO UPDATE SET
+                display_name = excluded.display_name,
+                mls_group_blob = excluded.mls_group_blob,
+                keystore_blob = excluded.keystore_blob,
+                member_keys = excluded.member_keys,
+                unread_count = excluded.unread_count,
+                last_activity_ms = excluded.last_activity_ms,
+                is_hybrid = excluded.is_hybrid,
+                last_seen_seq = excluded.last_seen_seq",
+            params![
+                conv.id.0.as_slice(),
+                kind_str,
+                conv.display_name,
+                peer_key,
+                peer_username,
+                group_name,
+                conv.mls_group_blob,
+                conv.keystore_blob,
+                member_keys_blob,
+                conv.unread_count,
+                conv.last_activity_ms,
+                conv.created_at_ms,
+                conv.is_hybrid as i32,
+                conv.last_seen_seq as i64,
+            ],
+        )?;
+        Ok(())
+    }
+
+    pub fn load_conversation(&self, id: &ConversationId) -> anyhow::Result<Option<Conversation>> {
+        self.conn
+            .query_row(
+                "SELECT kind, display_name, peer_key, peer_username, group_name,
+                        mls_group_blob, keystore_blob, member_keys, unread_count,
+                        last_activity_ms, created_at_ms, is_hybrid, last_seen_seq
+                 FROM conversations WHERE id = ?1",
+                params![id.0.as_slice()],
+                |row| {
+                    let kind_str: String = row.get(0)?;
+                    let display_name: String = row.get(1)?;
+                    let peer_key: Option<Vec<u8>> = row.get(2)?;
+                    let peer_username: Option<String> = row.get(3)?;
+                    let group_name: Option<String> = row.get(4)?;
+                    let mls_group_blob: Option<Vec<u8>> = row.get(5)?;
+                    let keystore_blob: Option<Vec<u8>> = row.get(6)?;
+                    let member_keys_blob: Option<Vec<u8>> = row.get(7)?;
+                    let unread_count: u32 = row.get(8)?;
+                    let last_activity_ms: u64 = row.get(9)?;
+                    let created_at_ms: u64 = row.get(10)?;
+                    let is_hybrid_int: i32 = row.get(11)?;
+                    let last_seen_seq: i64 = row.get(12)?;
+
+                    let kind = if kind_str == "dm" {
+                        ConversationKind::Dm {
+                            peer_key: peer_key.unwrap_or_default(),
+                            peer_username,
+                        }
+                    } else {
+                        ConversationKind::Group {
+                            name: group_name.unwrap_or_default(),
+                        }
+                    };
+
+                    let member_keys: Vec<Vec<u8>> = member_keys_blob
+                        .and_then(|b| match bincode::deserialize(&b) {
+                            Ok(v) => Some(v),
+                            Err(e) => {
+                                tracing::warn!(conv = %hex::encode(id.0), "bincode deserialize member_keys failed: {e}");
+                                None
+                            }
+                        })
+                        .unwrap_or_default();
+
+                    Ok(Conversation {
+                        id: id.clone(),
+                        kind,
+                        display_name,
+                        mls_group_blob,
+                        keystore_blob,
+                        member_keys,
+                        unread_count,
+                        last_activity_ms,
+                        created_at_ms,
+                        is_hybrid: is_hybrid_int != 0,
+                        last_seen_seq: last_seen_seq as u64,
+                    })
+                },
+            )
+            .optional()
+            .context("load conversation")
+    }
+
+    pub fn list_conversations(&self) -> anyhow::Result<Vec<Conversation>> {
+        let mut stmt = self.conn.prepare(
+            "SELECT id, kind, display_name, peer_key, peer_username, group_name,
+                    mls_group_blob, keystore_blob, member_keys, unread_count,
+                    last_activity_ms, created_at_ms, is_hybrid, last_seen_seq
+             FROM conversations ORDER BY last_activity_ms DESC",
+        )?;
+        let rows = stmt.query_map([], |row| {
+            let id_blob: Vec<u8> = row.get(0)?;
+            let kind_str: String = row.get(1)?;
+            let display_name: String = row.get(2)?;
+            let peer_key: Option<Vec<u8>> = row.get(3)?;
+            let peer_username: Option<String> = row.get(4)?;
+            let group_name: Option<String> = row.get(5)?;
+            let mls_group_blob: Option<Vec<u8>> = row.get(6)?;
+            let keystore_blob: Option<Vec<u8>> = row.get(7)?;
+            let member_keys_blob: Option<Vec<u8>> = row.get(8)?;
+            let unread_count: u32 = row.get(9)?;
+            let last_activity_ms: u64 = row.get(10)?;
+            let created_at_ms: u64 = row.get(11)?;
+            let is_hybrid_int: i32 = row.get(12)?;
+            let last_seen_seq: i64 = row.get(13)?;
+
+            let id = ConversationId::from_slice(&id_blob).unwrap_or(ConversationId([0; 16]));
+            let kind = if kind_str == "dm" {
+                ConversationKind::Dm {
+                    peer_key: peer_key.unwrap_or_default(),
+                    peer_username,
+                }
+            } else {
+                ConversationKind::Group {
+                    name: group_name.unwrap_or_default(),
+                }
+            };
+            let member_keys: Vec<Vec<u8>> = member_keys_blob
+                .and_then(|b| match bincode::deserialize(&b) {
+                    Ok(v) => Some(v),
+                    Err(e) => {
+                        tracing::warn!(conv = %hex::encode(&id_blob), "bincode deserialize member_keys failed: {e}");
+                        None
+                    }
+                })
+                .unwrap_or_default();
+
+            Ok(Conversation {
+                id,
+                kind,
+                display_name,
+                mls_group_blob,
+                keystore_blob,
+                member_keys,
+                unread_count,
+                last_activity_ms,
+                created_at_ms,
+                is_hybrid: is_hybrid_int != 0,
+                last_seen_seq: last_seen_seq as u64,
+            })
+        })?;
+
+        let mut convs = Vec::new();
+        for row in rows {
+            convs.push(row?);
+        }
+        Ok(convs)
+    }
+
+    /// Find a DM conversation by the peer's identity key.
+    pub fn find_dm_by_peer(&self, peer_key: &[u8]) -> anyhow::Result<Option<Conversation>> {
+        let id_blob: Option<Vec<u8>> = self
+            .conn
+            .query_row(
+                "SELECT id FROM conversations WHERE kind = 'dm' AND peer_key = ?1",
+                params![peer_key],
+                |row| row.get(0),
+            )
+            .optional()?;
+
+        match id_blob {
+            Some(blob) => {
+                let id = ConversationId::from_slice(&blob)
+                    .context("invalid conversation id in db")?;
+                self.load_conversation(&id)
+            }
+            None => Ok(None),
+        }
+    }
+
+    /// Find a group conversation by name.
+    pub fn find_group_by_name(&self, name: &str) -> anyhow::Result<Option<Conversation>> {
+        let id_blob: Option<Vec<u8>> = self
+            .conn
+            .query_row(
+                "SELECT id FROM conversations WHERE kind = 'group' AND group_name = ?1",
+                params![name],
+                |row| row.get(0),
+            )
+            .optional()?;
+
+        match id_blob {
+            Some(blob) => {
+                let id = ConversationId::from_slice(&blob)
+                    .context("invalid conversation id in db")?;
+                self.load_conversation(&id)
+            }
+            None => Ok(None),
+        }
+    }
+
+    pub fn increment_unread(&self, id: &ConversationId) -> anyhow::Result<()> {
+        self.conn.execute(
+            "UPDATE conversations SET unread_count = unread_count + 1 WHERE id = ?1",
+            params![id.0.as_slice()],
+        )?;
+        Ok(())
+    }
+
+    pub fn reset_unread(&self, id: &ConversationId) -> anyhow::Result<()> {
+        self.conn.execute(
+            "UPDATE conversations SET unread_count = 0 WHERE id = ?1",
+            params![id.0.as_slice()],
+        )?;
+        Ok(())
+    }
+
+    pub fn update_activity(&self, id: &ConversationId, ts_ms: u64) -> anyhow::Result<()> {
+        self.conn.execute(
+            "UPDATE conversations SET last_activity_ms = ?2 WHERE id = ?1 AND last_activity_ms < ?2",
+            params![id.0.as_slice(), ts_ms],
+        )?;
+        Ok(())
+    }
+
+    // ── Message CRUD ─────────────────────────────────────────────────────
+
+    pub fn save_message(&self, msg: &StoredMessage) -> anyhow::Result<()> {
+        self.conn.execute(
+            "INSERT INTO messages
+                (conversation_id, message_id, sender_key, sender_name, body,
+                 msg_type, ref_msg_id, timestamp_ms, is_outgoing)
+             VALUES (?1, ?2, ?3, ?4, ?5, ?6, ?7, ?8, ?9)",
+            params![
+                msg.conversation_id.0.as_slice(),
+                msg.message_id.as_ref().map(|id| id.as_slice()),
+                msg.sender_key,
+                msg.sender_name,
+                msg.body,
+                msg.msg_type,
+                msg.ref_msg_id.as_ref().map(|id| id.as_slice()),
+                msg.timestamp_ms,
+                msg.is_outgoing as i32,
+            ],
+        )?;
+        Ok(())
+    }
+
+    pub fn load_recent_messages(
+        &self,
+        conv_id: &ConversationId,
+        limit: usize,
+    ) -> anyhow::Result<Vec<StoredMessage>> {
+        let mut stmt = self.conn.prepare(
+            "SELECT message_id, sender_key, sender_name, body, msg_type,
+                    ref_msg_id, timestamp_ms, is_outgoing
+             FROM messages
+             WHERE conversation_id = ?1
+             ORDER BY timestamp_ms DESC
+             LIMIT ?2",
+        )?;
+        let rows = stmt.query_map(params![conv_id.0.as_slice(), limit.min(u32::MAX as usize) as u32], |row| {
+            let message_id: Option<Vec<u8>> = row.get(0)?;
+            let sender_key: Vec<u8> = row.get(1)?;
+            let sender_name: Option<String> = row.get(2)?;
+            let body: String = row.get(3)?;
+            let msg_type: String = row.get(4)?;
+            let ref_msg_id: Option<Vec<u8>> = row.get(5)?;
+            let timestamp_ms: u64 = row.get(6)?;
+            let is_outgoing: i32 = row.get(7)?;
+
+            fn to_16(v: &[u8]) -> Option<[u8; 16]> {
+                if v.len() == 16 {
+                    let mut buf = [0u8; 16];
+                    buf.copy_from_slice(v);
+                    Some(buf)
+                } else {
+                    None
+                }
+            }
+
+            Ok(StoredMessage {
+                conversation_id: conv_id.clone(),
+                message_id: message_id.as_deref().and_then(to_16),
+                sender_key,
+                sender_name,
+                body,
+                msg_type,
+                ref_msg_id: ref_msg_id.as_deref().and_then(to_16),
+                timestamp_ms,
+                is_outgoing: is_outgoing != 0,
+            })
+        })?;
+
+        let mut msgs = Vec::new();
+        for row in rows {
+            msgs.push(row?);
+        }
+        // Reverse so oldest first
+        msgs.reverse();
+        Ok(msgs)
+    }
+
+    /// Load all messages for a conversation, oldest first (no limit).
+    pub fn load_all_messages(&self, conv_id: &ConversationId) -> anyhow::Result<Vec<StoredMessage>> {
+        let mut stmt = self.conn.prepare(
+            "SELECT message_id, sender_key, sender_name, body, msg_type,
+                    ref_msg_id, timestamp_ms, is_outgoing
+             FROM messages
+             WHERE conversation_id = ?1
+             ORDER BY timestamp_ms ASC, id ASC",
+        )?;
+        let rows = stmt.query_map(params![conv_id.0.as_slice()], |row| {
+            let message_id: Option<Vec<u8>> = row.get(0)?;
+            let sender_key: Vec<u8> = row.get(1)?;
+            let sender_name: Option<String> = row.get(2)?;
+            let body: String = row.get(3)?;
+            let msg_type: String = row.get(4)?;
+            let ref_msg_id: Option<Vec<u8>> = row.get(5)?;
+            let timestamp_ms: u64 = row.get(6)?;
+            let is_outgoing: i32 = row.get(7)?;
+
+            fn to_16(v: &[u8]) -> Option<[u8; 16]> {
+                if v.len() == 16 {
+                    let mut buf = [0u8; 16];
+                    buf.copy_from_slice(v);
+                    Some(buf)
+                } else {
+                    None
+                }
+            }
+
+            Ok(StoredMessage {
+                conversation_id: conv_id.clone(),
+                message_id: message_id.as_deref().and_then(to_16),
+                sender_key,
+                sender_name,
+                body,
+                msg_type,
+                ref_msg_id: ref_msg_id.as_deref().and_then(to_16),
+                timestamp_ms,
+                is_outgoing: is_outgoing != 0,
+            })
+        })?;
+
+        let mut msgs = Vec::new();
+        for row in rows {
+            msgs.push(row?);
+        }
+        Ok(msgs)
+    }
+
+    /// Update the body of an existing message (for edits).
+    pub fn update_message_body(
+        &self,
+        conv_id: &ConversationId,
+        message_id: &[u8; 16],
+        new_body: &str,
+    ) -> anyhow::Result<bool> {
+        let rows = self.conn.execute(
+            "UPDATE messages SET body = ?3 WHERE conversation_id = ?1 AND message_id = ?2",
+            params![conv_id.0.as_slice(), message_id.as_slice(), new_body],
+        )?;
+        Ok(rows > 0)
+    }
+
+    /// Mark a message as deleted (sets body to "[deleted]" and msg_type to "deleted").
+    pub fn delete_message(
+        &self,
+        conv_id: &ConversationId,
+        message_id: &[u8; 16],
+    ) -> anyhow::Result<bool> {
+        let rows = self.conn.execute(
+            "UPDATE messages SET body = '[deleted]', msg_type = 'deleted' WHERE conversation_id = ?1 AND message_id = ?2",
+            params![conv_id.0.as_slice(), message_id.as_slice()],
+        )?;
+        Ok(rows > 0)
+    }
+
+    /// Save a message, deduplicating by message_id within the same conversation.
+    /// Returns `true` if the message was saved (new), `false` if it was a duplicate.
+    pub fn save_message_dedup(&self, msg: &StoredMessage) -> anyhow::Result<bool> {
+        if let Some(ref mid) = msg.message_id {
+            let exists: bool = self.conn.query_row(
+                "SELECT EXISTS(SELECT 1 FROM messages WHERE message_id = ?1 AND conversation_id = ?2)",
+                params![mid.as_slice(), msg.conversation_id.0.as_slice()],
+                |row| row.get(0),
+            )?;
+            if exists {
+                return Ok(false);
+            }
+        }
+        self.save_message(msg)?;
+        Ok(true)
+    }
+
+    // ── Sequence tracking ──────────────────────────────────────────────
+
+    pub fn update_last_seen_seq(&self, id: &ConversationId, seq: u64) -> anyhow::Result<()> {
+        self.conn.execute(
+            "UPDATE conversations SET last_seen_seq = ?2 WHERE id = ?1 AND last_seen_seq < ?2",
+            params![id.0.as_slice(), seq as i64],
+        )?;
+        Ok(())
+    }
+
+    // ── Outbox (offline queue) ────────────────────────────────────────
+
+    pub fn enqueue_outbox(
+        &self,
+        conv_id: &ConversationId,
+        recipient_key: &[u8],
+        payload: &[u8],
+    ) -> anyhow::Result<()> {
+        self.conn.execute(
+            "INSERT INTO outbox (conversation_id, recipient_key, payload, created_at_ms)
+             VALUES (?1, ?2, ?3, ?4)",
+            params![conv_id.0.as_slice(), recipient_key, payload, now_ms() as i64],
+        )?;
+        Ok(())
+    }
+
+    pub fn load_pending_outbox(&self) -> anyhow::Result<Vec<OutboxEntry>> {
+        let mut stmt = self.conn.prepare(
+            "SELECT id, conversation_id, recipient_key, payload, retry_count
+             FROM outbox WHERE status = 'pending' ORDER BY created_at_ms",
+        )?;
+        let rows = stmt.query_map([], |row| {
+            let id: i64 = row.get(0)?;
+            let conv_blob: Vec<u8> = row.get(1)?;
+            let recipient_key: Vec<u8> = row.get(2)?;
+            let payload: Vec<u8> = row.get(3)?;
+            let retry_count: u32 = row.get(4)?;
+            Ok(OutboxEntry {
+                id,
+                conversation_id: ConversationId::from_slice(&conv_blob)
+                    .unwrap_or(ConversationId([0; 16])),
+                recipient_key,
+                payload,
+                retry_count,
+            })
+        })?;
+        let mut entries = Vec::new();
+        for row in rows {
+            entries.push(row?);
+        }
+        Ok(entries)
+    }
+
+    pub fn mark_outbox_sent(&self, id: i64) -> anyhow::Result<()> {
+        self.conn.execute(
+            "UPDATE outbox SET status = 'sent' WHERE id = ?1",
+            params![id],
+        )?;
+        Ok(())
+    }
+
+    pub fn mark_outbox_failed(&self, id: i64, retry_count: u32) -> anyhow::Result<()> {
+        let new_status = if retry_count > 5 { "failed" } else { "pending" };
+        self.conn.execute(
+            "UPDATE outbox SET retry_count = ?2, status = ?3 WHERE id = ?1",
+            params![id, retry_count, new_status],
+        )?;
+        Ok(())
+    }
+
+    /// Delete messages older than `cutoff_ms` (epoch milliseconds) across all conversations.
+    pub fn delete_messages_before(&self, cutoff_ms: u64) -> anyhow::Result<usize> {
+        let rows = self.conn.execute(
+            "DELETE FROM messages WHERE timestamp_ms < ?1",
+            params![cutoff_ms as i64],
+        )?;
+        Ok(rows)
+    }
+}
+
+/// An entry in the offline outbox queue.
+#[derive(Clone, Debug)]
+pub struct OutboxEntry {
+    pub id: i64,
+    pub conversation_id: ConversationId,
+    pub recipient_key: Vec<u8>,
+    pub payload: Vec<u8>,
+    pub retry_count: u32,
+}
+
+pub fn now_ms() -> u64 {
+    SystemTime::now()
+        .duration_since(UNIX_EPOCH)
+        .unwrap_or_default()
+        .as_millis() as u64
+}

crates/quicproquo-client/src/client/display.rs

@@ -0,0 +1,82 @@
+//! Terminal display helpers for the REPL.
+
+use super::conversation::StoredMessage;
+use super::session::SessionState;
+
+// ANSI color codes
+const RESET: &str = "\x1b[0m";
+const BOLD: &str = "\x1b[1m";
+const DIM: &str = "\x1b[2m";
+const GREEN: &str = "\x1b[32m";
+const CYAN: &str = "\x1b[36m";
+const YELLOW: &str = "\x1b[33m";
+
+/// Print the REPL prompt showing the active conversation and unread count.
+pub fn print_prompt(session: &SessionState) {
+    use std::io::Write;
+    let name = session
+        .active_display_name()
+        .unwrap_or_else(|| "no conversation".into());
+    let unread = session.total_unread();
+    if unread > 0 {
+        print!("{DIM}[{RESET}{BOLD}{name}{RESET} {YELLOW}{unread} unread{RESET}{DIM}]{RESET} > ");
+    } else {
+        print!("{DIM}[{RESET}{BOLD}{name}{RESET}{DIM}]{RESET} > ");
+    }
+    let _ = std::io::stdout().flush();
+}
+
+/// Print an incoming or outgoing message.
+pub fn print_message(msg: &StoredMessage) {
+    let body = if msg.msg_type == "reaction" {
+        format!("reacted {}", msg.body)
+    } else {
+        msg.body.clone()
+    };
+    if msg.is_outgoing {
+        println!("\r{GREEN}> {body}{RESET}");
+    } else {
+        let fallback = hex::encode(&msg.sender_key[..4]);
+        let sender = msg.sender_name.as_deref().unwrap_or(&fallback);
+        println!("\r{CYAN}{BOLD}[{sender}]{RESET} {body}");
+    }
+}
+
+/// Print a message received in real-time (clears current line first).
+pub fn print_incoming(sender: &str, body: &str) {
+    use std::io::Write;
+    // Clear current line, print message, then re-show prompt context
+    print!("\r\x1b[2K");
+    println!("{CYAN}{BOLD}[{sender}]{RESET} {body}");
+    let _ = std::io::stdout().flush();
+}
+
+/// Print a system/status message.
+pub fn print_status(msg: &str) {
+    println!("{DIM}  {msg}{RESET}");
+}
+
+/// Print a transient typing indicator (clears current line first).
+pub fn print_typing(sender: &str) {
+    use std::io::Write;
+    print!("\r\x1b[2K");
+    println!("{DIM}  {sender} is typing...{RESET}");
+    let _ = std::io::stdout().flush();
+}
+
+/// Print an error message.
+pub fn print_error(msg: &str) {
+    println!("{YELLOW}  error: {msg}{RESET}");
+}
+
+/// Format a conversation list entry for `/list`.
+pub fn format_conv_line(display_name: &str, kind: &str, unread: u32, members: usize) -> String {
+    let unread_str = if unread > 0 {
+        format!(" {YELLOW}({unread} new){RESET}")
+    } else {
+        String::new()
+    };
+    format!(
+        "  {BOLD}{display_name}{RESET} {DIM}[{kind}, {members} members]{RESET}{unread_str}"
+    )
+}

crates/quicproquo-client/src/client/hex.rs

@@ -0,0 +1,7 @@
+pub fn encode(bytes: impl AsRef<[u8]>) -> String {
+    hex::encode(bytes)
+}
+
+pub fn decode(s: &str) -> Result<Vec<u8>, &'static str> {
+    hex::decode(s).map_err(|_| "invalid hex string")
+}

crates/quicproquo-client/src/client/mesh_discovery.rs

@@ -0,0 +1,148 @@
+//! mDNS-based peer discovery for Freifunk / community mesh deployments.
+//!
+//! Browse for `_quicproquo._udp.local.` services on the local network and
+//! surface them as [`DiscoveredPeer`] structs. Servers announce themselves
+//! automatically on startup; this module lets clients find them without manual
+//! configuration.
+//!
+//! # Usage
+//!
+//! ```no_run
+//! use quicproquo_client::client::mesh_discovery::MeshDiscovery;
+//!
+//! let disc = MeshDiscovery::start()?;
+//! // Give mDNS time to collect announcements before reading.
+//! std::thread::sleep(std::time::Duration::from_secs(2));
+//! for peer in disc.peers() {
+//!     println!("found: {} at {}", peer.domain, peer.server_addr);
+//! }
+//! # Ok::<(), quicproquo_client::client::mesh_discovery::MeshDiscoveryError>(())
+//! ```
+
+#[cfg(feature = "mesh")]
+use mdns_sd::{ServiceDaemon, ServiceEvent};
+use std::net::SocketAddr;
+#[cfg(feature = "mesh")]
+use std::sync::{Arc, Mutex};
+#[cfg(feature = "mesh")]
+use std::collections::HashMap;
+
+/// A qpq server discovered on the local network via mDNS.
+#[derive(Debug, Clone)]
+pub struct DiscoveredPeer {
+    /// Federation domain of the remote server (e.g. `"node1.freifunk.net"`).
+    pub domain: String,
+    /// QUIC RPC address to connect to.
+    pub server_addr: SocketAddr,
+}
+
+/// A running mDNS browse session.
+///
+/// Starts immediately on construction; drop to stop browsing.
+pub struct MeshDiscovery {
+    #[cfg(feature = "mesh")]
+    _daemon: ServiceDaemon,
+    #[cfg(feature = "mesh")]
+    peers: Arc<Mutex<HashMap<String, DiscoveredPeer>>>,
+}
+
+#[derive(thiserror::Error, Debug)]
+pub enum MeshDiscoveryError {
+    #[error("mDNS daemon failed to start: {0}")]
+    DaemonError(String),
+    #[error("mDNS browse failed: {0}")]
+    BrowseError(String),
+    #[error("mesh feature not compiled (rebuild with --features mesh)")]
+    FeatureDisabled,
+}
+
+impl MeshDiscovery {
+    /// Start browsing for `_quicproquo._udp.local.` services.
+    ///
+    /// Returns immediately; peers are collected in the background.
+    /// Returns [`MeshDiscoveryError::FeatureDisabled`] when built without the
+    /// `mesh` feature.
+    pub fn start() -> Result<Self, MeshDiscoveryError> {
+        #[cfg(feature = "mesh")]
+        {
+            Self::start_inner()
+        }
+        #[cfg(not(feature = "mesh"))]
+        {
+            Err(MeshDiscoveryError::FeatureDisabled)
+        }
+    }
+
+    #[cfg(feature = "mesh")]
+    fn start_inner() -> Result<Self, MeshDiscoveryError> {
+        let daemon = ServiceDaemon::new()
+            .map_err(|e| MeshDiscoveryError::DaemonError(e.to_string()))?;
+
+        let receiver = daemon
+            .browse("_quicproquo._udp.local.")
+            .map_err(|e| MeshDiscoveryError::BrowseError(e.to_string()))?;
+
+        let peers: Arc<Mutex<HashMap<String, DiscoveredPeer>>> =
+            Arc::new(Mutex::new(HashMap::new()));
+        let peers_bg = Arc::clone(&peers);
+
+        // Process mDNS events in a background thread (ServiceDaemon is sync).
+        std::thread::spawn(move || {
+            for event in receiver {
+                match event {
+                    ServiceEvent::ServiceResolved(info) => {
+                        // Extract the qpq server address from TXT records.
+                        let server_addr_str = info
+                            .get_property_val_str("server")
+                            .map(|s| s.to_string());
+                        let domain = info
+                            .get_property_val_str("domain")
+                            .map(|s| s.to_string())
+                            .unwrap_or_else(|| info.get_fullname().to_string());
+
+                        if let Some(addr_str) = server_addr_str {
+                            if let Ok(addr) = addr_str.parse::<SocketAddr>() {
+                                let peer = DiscoveredPeer {
+                                    domain: domain.clone(),
+                                    server_addr: addr,
+                                };
+                                if let Ok(mut map) = peers_bg.lock() {
+                                    map.insert(domain, peer);
+                                }
+                            }
+                        }
+                    }
+                    ServiceEvent::ServiceRemoved(_ty, fullname) => {
+                        if let Ok(mut map) = peers_bg.lock() {
+                            map.retain(|_, p| {
+                                !fullname.contains(&p.domain)
+                            });
+                        }
+                    }
+                    // Other events (SearchStarted, SearchStopped) are informational.
+                    _ => {}
+                }
+            }
+        });
+
+        Ok(Self {
+            _daemon: daemon,
+            peers,
+        })
+    }
+
+    /// Return a snapshot of all peers discovered so far.
+    pub fn peers(&self) -> Vec<DiscoveredPeer> {
+        #[cfg(feature = "mesh")]
+        {
+            self.peers
+                .lock()
+                .map(|m| m.values().cloned().collect())
+                .unwrap_or_default()
+        }
+        #[cfg(not(feature = "mesh"))]
+        {
+            vec![]
+        }
+    }
+}

crates/quicproquo-client/src/client/mod.rs

@@ -0,0 +1,24 @@
+pub mod command_engine;
+pub mod commands;
+pub mod conversation;
+pub mod display;
+pub mod hex;
+pub mod mesh_discovery;
+#[cfg(feature = "playbook")]
+pub mod playbook;
+pub mod repl;
+pub mod retry;
+pub mod rpc;
+pub mod session;
+pub mod state;
+pub mod token_cache;
+#[cfg(feature = "tui")]
+pub mod tui;
+#[cfg(feature = "v2")]
+pub mod v2_repl;
+#[cfg(all(feature = "v2", feature = "tui"))]
+pub mod v2_tui;
+
+pub use commands::*;
+pub use rpc::{connect_node, enqueue, fetch_all, fetch_hybrid_key, fetch_key_package, fetch_wait, upload_hybrid_key, upload_key_package};
+pub use state::{decode_identity_key, load_existing_state, load_or_init_state, save_state};

crates/quicproquo-client/src/client/playbook.rs

@@ -0,0 +1,868 @@
+//! YAML playbook parser and executor.
+//!
+//! Playbooks describe a sequence of client commands in YAML format.
+//! They support variable substitution, assertions, loops, and per-step
+//! error handling policies.
+//!
+//! ```yaml
+//! name: "smoke test"
+//! steps:
+//!   - command: dm
+//!     args: { username: "bob" }
+//!   - command: send
+//!     args: { text: "Hello from playbook" }
+//!   - command: assert
+//!     condition: message_count
+//!     op: gte
+//!     value: 1
+//! ```
+//!
+//! Requires the `playbook` cargo feature.
+
+use std::collections::HashMap;
+use std::path::Path;
+use std::time::{Duration, Instant};
+
+use anyhow::{Context, bail};
+use quicproquo_proto::node_capnp::node_service;
+use serde::{Deserialize, Serialize};
+
+use super::command_engine::{AssertCondition, CmpOp, Command, CommandRegistry};
+use super::session::SessionState;
+
+// ── Playbook structs ────────────────────────────────────────────────────────
+
+/// A parsed YAML playbook.
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct Playbook {
+    pub name: String,
+    #[serde(default)]
+    pub description: Option<String>,
+    #[serde(default)]
+    pub variables: HashMap<String, String>,
+    pub steps: Vec<PlaybookStep>,
+}
+
+/// A single step in a playbook.
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct PlaybookStep {
+    pub command: String,
+    #[serde(default)]
+    pub args: HashMap<String, serde_yaml::Value>,
+    /// For assert steps: the condition name.
+    #[serde(default)]
+    pub condition: Option<String>,
+    /// For assert steps: comparison operator.
+    #[serde(default)]
+    pub op: Option<String>,
+    /// For assert steps: expected value.
+    #[serde(default)]
+    pub value: Option<serde_yaml::Value>,
+    /// Capture the command output into this variable name.
+    #[serde(default)]
+    pub capture: Option<String>,
+    /// Error handling policy for this step.
+    #[serde(default)]
+    pub on_error: OnError,
+    /// Optional loop specification.
+    #[serde(rename = "loop", default)]
+    pub loop_spec: Option<LoopSpec>,
+}
+
+/// What to do when a step fails.
+#[derive(Debug, Clone, Serialize, Deserialize, Default, PartialEq)]
+#[serde(rename_all = "lowercase")]
+pub enum OnError {
+    #[default]
+    Fail,
+    Skip,
+    Continue,
+}
+
+/// Loop specification for repeating a step.
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct LoopSpec {
+    pub var: String,
+    pub from: usize,
+    pub to: usize,
+}
+
+// ── Report structs ──────────────────────────────────────────────────────────
+
+/// Summary of a playbook execution.
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct PlaybookReport {
+    pub name: String,
+    pub total_steps: usize,
+    pub passed: usize,
+    pub failed: usize,
+    pub skipped: usize,
+    pub duration: Duration,
+    pub step_results: Vec<StepResult>,
+}
+
+impl PlaybookReport {
+    /// True if all steps passed (no failures).
+    pub fn all_passed(&self) -> bool {
+        self.failed == 0
+    }
+}
+
+impl std::fmt::Display for PlaybookReport {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        writeln!(f, "Playbook: {}", self.name)?;
+        writeln!(
+            f,
+            "Result:   {} passed, {} failed, {} skipped ({} total)",
+            self.passed, self.failed, self.skipped, self.total_steps,
+        )?;
+        writeln!(f, "Duration: {:.2}s", self.duration.as_secs_f64())?;
+        for sr in &self.step_results {
+            let status = if sr.success { "OK" } else { "FAIL" };
+            write!(
+                f,
+                "  [{}/{}] {} ... {} ({:.1}ms)",
+                sr.step_index + 1,
+                self.total_steps,
+                sr.command,
+                status,
+                sr.duration.as_secs_f64() * 1000.0,
+            )?;
+            if let Some(ref e) = sr.error {
+                write!(f, " — {e}")?;
+            }
+            writeln!(f)?;
+        }
+        Ok(())
+    }
+}
+
+/// Result of a single step execution.
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct StepResult {
+    pub step_index: usize,
+    pub command: String,
+    pub success: bool,
+    pub duration: Duration,
+    pub output: Option<String>,
+    pub error: Option<String>,
+}
+
+// ── PlaybookRunner ──────────────────────────────────────────────────────────
+
+/// Executes a parsed `Playbook` step-by-step.
+pub struct PlaybookRunner {
+    playbook: Playbook,
+    vars: HashMap<String, String>,
+}
+
+impl PlaybookRunner {
+    /// Load a playbook from a YAML file.
+    pub fn from_file(path: &Path) -> anyhow::Result<Self> {
+        let content =
+            std::fs::read_to_string(path).with_context(|| format!("read {}", path.display()))?;
+        Self::from_str(&content)
+    }
+
+    /// Parse a playbook from a YAML string.
+    pub fn from_str(yaml: &str) -> anyhow::Result<Self> {
+        let playbook: Playbook =
+            serde_yaml::from_str(yaml).context("parse playbook YAML")?;
+        let vars = playbook.variables.clone();
+        Ok(Self { playbook, vars })
+    }
+
+    /// Override or add variables before execution.
+    pub fn set_var(&mut self, name: impl Into<String>, value: impl Into<String>) {
+        self.vars.insert(name.into(), value.into());
+    }
+
+    /// Execute all steps, returning a report.
+    pub async fn run(
+        &mut self,
+        session: &mut SessionState,
+        client: &node_service::Client,
+    ) -> PlaybookReport {
+        let start = Instant::now();
+        let total = self.expanded_step_count();
+        let mut results = Vec::new();
+        let mut passed = 0usize;
+        let mut failed = 0usize;
+        let mut skipped = 0usize;
+        let mut step_idx = 0usize;
+        let mut abort = false;
+
+        for step in &self.playbook.steps.clone() {
+            if abort {
+                skipped += 1;
+                results.push(StepResult {
+                    step_index: step_idx,
+                    command: step.command.clone(),
+                    success: false,
+                    duration: Duration::ZERO,
+                    output: None,
+                    error: Some("skipped (prior failure)".into()),
+                });
+                step_idx += 1;
+                continue;
+            }
+
+            if let Some(ref ls) = step.loop_spec {
+                for i in ls.from..=ls.to {
+                    self.vars.insert(ls.var.clone(), i.to_string());
+                    let sr = self.execute_step(step, step_idx, total, session, client).await;
+                    if sr.success {
+                        passed += 1;
+                    } else {
+                        failed += 1;
+                        if step.on_error == OnError::Fail {
+                            abort = true;
+                        }
+                    }
+                    results.push(sr);
+                    step_idx += 1;
+                    if abort {
+                        break;
+                    }
+                }
+            } else {
+                let sr = self.execute_step(step, step_idx, total, session, client).await;
+                if sr.success {
+                    passed += 1;
+                } else {
+                    match step.on_error {
+                        OnError::Fail => {
+                            failed += 1;
+                            abort = true;
+                        }
+                        OnError::Skip => skipped += 1,
+                        OnError::Continue => failed += 1,
+                    }
+                }
+                results.push(sr);
+                step_idx += 1;
+            }
+        }
+
+        PlaybookReport {
+            name: self.playbook.name.clone(),
+            total_steps: step_idx,
+            passed,
+            failed,
+            skipped,
+            duration: start.elapsed(),
+            step_results: results,
+        }
+    }
+
+    /// Execute a single step.
+    async fn execute_step(
+        &mut self,
+        step: &PlaybookStep,
+        index: usize,
+        total: usize,
+        session: &mut SessionState,
+        client: &node_service::Client,
+    ) -> StepResult {
+        let t = Instant::now();
+        let cmd = match self.step_to_command(step) {
+            Ok(c) => c,
+            Err(e) => {
+                return StepResult {
+                    step_index: index,
+                    command: step.command.clone(),
+                    success: false,
+                    duration: t.elapsed(),
+                    output: None,
+                    error: Some(format!("{e:#}")),
+                };
+            }
+        };
+
+        eprintln!(
+            "[{}/{}] {} ...",
+            index + 1,
+            total,
+            step.command,
+        );
+
+        let cr = CommandRegistry::execute(&cmd, session, client).await;
+
+        // Capture output into variable if requested.
+        if let Some(ref var_name) = step.capture {
+            if let Some(ref out) = cr.output {
+                self.vars.insert(var_name.clone(), out.clone());
+            }
+            for (k, v) in &cr.data {
+                self.vars.insert(format!("{var_name}.{k}"), v.clone());
+            }
+        }
+
+        StepResult {
+            step_index: index,
+            command: step.command.clone(),
+            success: cr.success,
+            duration: t.elapsed(),
+            output: cr.output,
+            error: cr.error,
+        }
+    }
+
+    /// Convert a YAML step into a typed `Command`.
+    fn step_to_command(&self, step: &PlaybookStep) -> anyhow::Result<Command> {
+        let cmd_name = step.command.as_str();
+        match cmd_name {
+            // ── Lifecycle commands ────────────────────────────────────────
+            "connect" => Ok(Command::Connect {
+                server: self.resolve_str(&step.args, "server")?,
+                ca_cert: self.opt_str(&step.args, "ca_cert"),
+                insecure: self.opt_bool(&step.args, "insecure"),
+            }),
+            "login" => Ok(Command::Login {
+                username: self.resolve_str(&step.args, "username")?,
+                password: self.resolve_str(&step.args, "password")?,
+            }),
+            "register" => Ok(Command::Register {
+                username: self.resolve_str(&step.args, "username")?,
+                password: self.resolve_str(&step.args, "password")?,
+            }),
+            "send" | "send-message" => Ok(Command::SendMessage {
+                text: self.resolve_str(&step.args, "text")?,
+            }),
+            "wait" => Ok(Command::Wait {
+                duration_ms: self.resolve_u64(&step.args, "duration_ms")?,
+            }),
+            "set-var" | "setvar" => Ok(Command::SetVar {
+                name: self.resolve_str(&step.args, "name")?,
+                value: self.resolve_str(&step.args, "value")?,
+            }),
+            "assert" => {
+                let condition = self.build_assert_condition(step)?;
+                Ok(Command::Assert { condition })
+            }
+
+            // ── Session / identity ───────────────────────────────────────
+            "help" => Ok(Command::Help),
+            "quit" | "exit" => Ok(Command::Quit),
+            "whoami" => Ok(Command::Whoami),
+            "list" | "ls" => Ok(Command::List),
+            "switch" | "sw" => Ok(Command::Switch {
+                target: self.resolve_str(&step.args, "target")?,
+            }),
+            "dm" => Ok(Command::Dm {
+                username: self.resolve_str(&step.args, "username")?,
+            }),
+            "create-group" | "cg" => Ok(Command::CreateGroup {
+                name: self.resolve_str(&step.args, "name")?,
+            }),
+            "invite" => Ok(Command::Invite {
+                target: self.resolve_str(&step.args, "target")?,
+            }),
+            "remove" | "kick" => Ok(Command::Remove {
+                target: self.resolve_str(&step.args, "target")?,
+            }),
+            "leave" => Ok(Command::Leave),
+            "join" => Ok(Command::Join),
+            "members" => Ok(Command::Members),
+            "group-info" | "gi" => Ok(Command::GroupInfo),
+            "rename" => Ok(Command::Rename {
+                name: self.resolve_str(&step.args, "name")?,
+            }),
+            "history" | "hist" => Ok(Command::History {
+                count: self.opt_usize(&step.args, "count").unwrap_or(20),
+            }),
+
+            // ── Security / crypto ────────────────────────────────────────
+            "verify" => Ok(Command::Verify {
+                username: self.resolve_str(&step.args, "username")?,
+            }),
+            "update-key" | "rotate-key" => Ok(Command::UpdateKey),
+            "typing" => Ok(Command::Typing),
+            "typing-notify" => Ok(Command::TypingNotify {
+                enabled: self.opt_bool(&step.args, "enabled"),
+            }),
+            "react" => Ok(Command::React {
+                emoji: self.resolve_str(&step.args, "emoji")?,
+                index: self.opt_usize(&step.args, "index"),
+            }),
+            "edit" => Ok(Command::Edit {
+                index: self.resolve_usize(&step.args, "index")?,
+                new_text: self.resolve_str(&step.args, "new_text")?,
+            }),
+            "delete" | "del" => Ok(Command::Delete {
+                index: self.resolve_usize(&step.args, "index")?,
+            }),
+            "send-file" | "sf" => Ok(Command::SendFile {
+                path: self.resolve_str(&step.args, "path")?,
+            }),
+            "download" | "dl" => Ok(Command::Download {
+                index: self.resolve_usize(&step.args, "index")?,
+            }),
+            "delete-account" => Ok(Command::DeleteAccount),
+            "disappear" => Ok(Command::Disappear {
+                arg: self.opt_str(&step.args, "duration"),
+            }),
+            "privacy" => Ok(Command::Privacy {
+                arg: self.opt_str(&step.args, "setting"),
+            }),
+            "verify-fs" => Ok(Command::VerifyFs),
+            "rotate-all-keys" => Ok(Command::RotateAllKeys),
+            "devices" => Ok(Command::Devices),
+            "register-device" => Ok(Command::RegisterDevice {
+                name: self.resolve_str(&step.args, "name")?,
+            }),
+            "revoke-device" => Ok(Command::RevokeDevice {
+                id_prefix: self.resolve_str(&step.args, "id_prefix")?,
+            }),
+
+            // ── Mesh ─────────────────────────────────────────────────────
+            "mesh-peers" => Ok(Command::MeshPeers),
+            "mesh-server" => Ok(Command::MeshServer {
+                addr: self.resolve_str(&step.args, "addr")?,
+            }),
+            "mesh-send" => Ok(Command::MeshSend {
+                peer_id: self.resolve_str(&step.args, "peer_id")?,
+                message: self.resolve_str(&step.args, "message")?,
+            }),
+            "mesh-broadcast" => Ok(Command::MeshBroadcast {
+                topic: self.resolve_str(&step.args, "topic")?,
+                message: self.resolve_str(&step.args, "message")?,
+            }),
+            "mesh-subscribe" => Ok(Command::MeshSubscribe {
+                topic: self.resolve_str(&step.args, "topic")?,
+            }),
+            "mesh-route" => Ok(Command::MeshRoute),
+            "mesh-identity" | "mesh-id" => Ok(Command::MeshIdentity),
+            "mesh-store" => Ok(Command::MeshStore),
+
+            other => bail!("unknown command: {other}"),
+        }
+    }
+
+    /// Build an `AssertCondition` from a playbook step.
+    fn build_assert_condition(&self, step: &PlaybookStep) -> anyhow::Result<AssertCondition> {
+        let cond = step
+            .condition
+            .as_deref()
+            .context("assert step requires 'condition' field")?;
+        match cond {
+            "connected" => Ok(AssertCondition::Connected),
+            "logged_in" => Ok(AssertCondition::LoggedIn),
+            "in_conversation" => {
+                let name = self.resolve_str(&step.args, "name")
+                    .or_else(|_| step.value.as_ref()
+                        .and_then(|v| v.as_str())
+                        .map(|s| self.substitute(s))
+                        .context("assert in_conversation requires 'name' arg or 'value'"))?;
+                Ok(AssertCondition::InConversation { name })
+            }
+            "message_count" => {
+                let op = self.parse_cmp_op(step.op.as_deref().unwrap_or("gte"))?;
+                let count = step
+                    .value
+                    .as_ref()
+                    .and_then(|v| v.as_u64())
+                    .context("message_count assert requires numeric 'value'")?
+                    as usize;
+                Ok(AssertCondition::MessageCount { op, count })
+            }
+            "member_count" => {
+                let op = self.parse_cmp_op(step.op.as_deref().unwrap_or("gte"))?;
+                let count = step
+                    .value
+                    .as_ref()
+                    .and_then(|v| v.as_u64())
+                    .context("member_count assert requires numeric 'value'")?
+                    as usize;
+                Ok(AssertCondition::MemberCount { op, count })
+            }
+            other => Ok(AssertCondition::Custom {
+                expression: other.to_string(),
+            }),
+        }
+    }
+
+    fn parse_cmp_op(&self, s: &str) -> anyhow::Result<CmpOp> {
+        match s {
+            "eq" | "==" => Ok(CmpOp::Eq),
+            "ne" | "!=" => Ok(CmpOp::Ne),
+            "gt" | ">" => Ok(CmpOp::Gt),
+            "lt" | "<" => Ok(CmpOp::Lt),
+            "gte" | ">=" => Ok(CmpOp::Gte),
+            "lte" | "<=" => Ok(CmpOp::Lte),
+            other => bail!("unknown comparison operator: {other}"),
+        }
+    }
+
+    // ── Variable substitution helpers ────────────────────────────────────
+
+    /// Substitute `$varname` and `${VAR:-default}` in a string.
+    fn substitute(&self, s: &str) -> String {
+        let mut result = String::with_capacity(s.len());
+        let mut chars = s.chars().peekable();
+        while let Some(c) = chars.next() {
+            if c == '$' {
+                if chars.peek() == Some(&'{') {
+                    chars.next(); // consume '{'
+                    let mut key = String::new();
+                    let mut default = None;
+                    while let Some(&ch) = chars.peek() {
+                        if ch == '}' {
+                            chars.next();
+                            break;
+                        }
+                        if ch == ':' && chars.clone().nth(1) == Some('-') {
+                            chars.next(); // consume ':'
+                            chars.next(); // consume '-'
+                            let mut def = String::new();
+                            while let Some(&dch) = chars.peek() {
+                                if dch == '}' {
+                                    chars.next();
+                                    break;
+                                }
+                                def.push(dch);
+                                chars.next();
+                            }
+                            default = Some(def);
+                            break;
+                        }
+                        key.push(ch);
+                        chars.next();
+                    }
+                    if let Some(val) = self.vars.get(&key) {
+                        result.push_str(val);
+                    } else if let Ok(val) = std::env::var(&key) {
+                        result.push_str(&val);
+                    } else if let Some(def) = default {
+                        result.push_str(&def);
+                    }
+                } else {
+                    let mut key = String::new();
+                    while let Some(&ch) = chars.peek() {
+                        if ch.is_alphanumeric() || ch == '_' {
+                            key.push(ch);
+                            chars.next();
+                        } else {
+                            break;
+                        }
+                    }
+                    if let Some(val) = self.vars.get(&key) {
+                        result.push_str(val);
+                    } else {
+                        result.push('$');
+                        result.push_str(&key);
+                    }
+                }
+            } else {
+                result.push(c);
+            }
+        }
+        result
+    }
+
+    /// Resolve a required string argument with variable substitution.
+    fn resolve_str(
+        &self,
+        args: &HashMap<String, serde_yaml::Value>,
+        key: &str,
+    ) -> anyhow::Result<String> {
+        let val = args
+            .get(key)
+            .with_context(|| format!("missing required argument: {key}"))?;
+        match val {
+            serde_yaml::Value::String(s) => Ok(self.substitute(s)),
+            serde_yaml::Value::Number(n) => Ok(n.to_string()),
+            serde_yaml::Value::Bool(b) => Ok(b.to_string()),
+            other => Ok(format!("{other:?}")),
+        }
+    }
+
+    /// Resolve an optional string argument.
+    fn opt_str(
+        &self,
+        args: &HashMap<String, serde_yaml::Value>,
+        key: &str,
+    ) -> Option<String> {
+        args.get(key).map(|v| match v {
+            serde_yaml::Value::String(s) => self.substitute(s),
+            serde_yaml::Value::Number(n) => n.to_string(),
+            serde_yaml::Value::Bool(b) => b.to_string(),
+            other => format!("{other:?}"),
+        })
+    }
+
+    /// Resolve an optional bool argument (defaults to false).
+    fn opt_bool(
+        &self,
+        args: &HashMap<String, serde_yaml::Value>,
+        key: &str,
+    ) -> bool {
+        args.get(key)
+            .and_then(|v| v.as_bool())
+            .unwrap_or(false)
+    }
+
+    /// Resolve a required usize argument.
+    fn resolve_usize(
+        &self,
+        args: &HashMap<String, serde_yaml::Value>,
+        key: &str,
+    ) -> anyhow::Result<usize> {
+        let val = args
+            .get(key)
+            .with_context(|| format!("missing required argument: {key}"))?;
+        val.as_u64()
+            .map(|n| n as usize)
+            .with_context(|| format!("argument '{key}' must be a positive integer"))
+    }
+
+    /// Resolve a required u64 argument.
+    fn resolve_u64(
+        &self,
+        args: &HashMap<String, serde_yaml::Value>,
+        key: &str,
+    ) -> anyhow::Result<u64> {
+        let val = args
+            .get(key)
+            .with_context(|| format!("missing required argument: {key}"))?;
+        val.as_u64()
+            .with_context(|| format!("argument '{key}' must be a positive integer"))
+    }
+
+    /// Resolve an optional usize argument.
+    fn opt_usize(
+        &self,
+        args: &HashMap<String, serde_yaml::Value>,
+        key: &str,
+    ) -> Option<usize> {
+        args.get(key).and_then(|v| v.as_u64()).map(|n| n as usize)
+    }
+
+    /// Count total expanded steps (including loop iterations).
+    fn expanded_step_count(&self) -> usize {
+        self.playbook
+            .steps
+            .iter()
+            .map(|s| {
+                if let Some(ref ls) = s.loop_spec {
+                    if ls.to >= ls.from {
+                        ls.to - ls.from + 1
+                    } else {
+                        0
+                    }
+                } else {
+                    1
+                }
+            })
+            .sum()
+    }
+}
+
+// ── Tests ───────────────────────────────────────────────────────────────────
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn parse_minimal_playbook() {
+        let yaml = r#"
+name: "test"
+steps:
+  - command: whoami
+  - command: list
+"#;
+        let runner = PlaybookRunner::from_str(yaml).unwrap();
+        assert_eq!(runner.playbook.name, "test");
+        assert_eq!(runner.playbook.steps.len(), 2);
+        assert_eq!(runner.playbook.steps[0].command, "whoami");
+    }
+
+    #[test]
+    fn parse_playbook_with_variables() {
+        let yaml = r#"
+name: "var test"
+variables:
+  user: alice
+  server: "127.0.0.1:5001"
+steps:
+  - command: dm
+    args:
+      username: "$user"
+"#;
+        let runner = PlaybookRunner::from_str(yaml).unwrap();
+        assert_eq!(runner.vars["user"], "alice");
+        assert_eq!(runner.vars["server"], "127.0.0.1:5001");
+    }
+
+    #[test]
+    fn variable_substitution() {
+        let mut vars = HashMap::new();
+        vars.insert("name".to_string(), "alice".to_string());
+        vars.insert("port".to_string(), "5001".to_string());
+        let runner = PlaybookRunner {
+            playbook: Playbook {
+                name: "test".into(),
+                description: None,
+                variables: HashMap::new(),
+                steps: vec![],
+            },
+            vars,
+        };
+        assert_eq!(runner.substitute("hello $name"), "hello alice");
+        assert_eq!(runner.substitute("port=$port!"), "port=5001!");
+        assert_eq!(runner.substitute("${name}@server"), "alice@server");
+        assert_eq!(
+            runner.substitute("${missing:-default}"),
+            "default"
+        );
+        assert_eq!(runner.substitute("no vars here"), "no vars here");
+    }
+
+    #[test]
+    fn step_to_command_mapping() {
+        let yaml = r#"
+name: "mapping test"
+variables:
+  user: bob
+steps:
+  - command: dm
+    args:
+      username: "$user"
+  - command: send
+    args:
+      text: "hello"
+  - command: history
+    args:
+      count: 10
+  - command: wait
+    args:
+      duration_ms: 500
+"#;
+        let runner = PlaybookRunner::from_str(yaml).unwrap();
+        let cmd0 = runner.step_to_command(&runner.playbook.steps[0]).unwrap();
+        assert!(matches!(cmd0, Command::Dm { username } if username == "bob"));
+
+        let cmd1 = runner.step_to_command(&runner.playbook.steps[1]).unwrap();
+        assert!(matches!(cmd1, Command::SendMessage { text } if text == "hello"));
+
+        let cmd2 = runner.step_to_command(&runner.playbook.steps[2]).unwrap();
+        assert!(matches!(cmd2, Command::History { count: 10 }));
+
+        let cmd3 = runner.step_to_command(&runner.playbook.steps[3]).unwrap();
+        assert!(matches!(cmd3, Command::Wait { duration_ms: 500 }));
+    }
+
+    #[test]
+    fn parse_assert_step() {
+        let yaml = r#"
+name: "assert test"
+steps:
+  - command: assert
+    condition: message_count
+    op: gte
+    value: 5
+"#;
+        let runner = PlaybookRunner::from_str(yaml).unwrap();
+        let cmd = runner.step_to_command(&runner.playbook.steps[0]).unwrap();
+        match cmd {
+            Command::Assert {
+                condition: AssertCondition::MessageCount { op, count },
+            } => {
+                assert_eq!(op, CmpOp::Gte);
+                assert_eq!(count, 5);
+            }
+            other => panic!("expected Assert MessageCount, got {other:?}"),
+        }
+    }
+
+    #[test]
+    fn parse_loop_spec() {
+        let yaml = r#"
+name: "loop test"
+steps:
+  - command: send
+    args:
+      text: "msg $i"
+    loop:
+      var: i
+      from: 1
+      to: 5
+"#;
+        let runner = PlaybookRunner::from_str(yaml).unwrap();
+        assert_eq!(runner.expanded_step_count(), 5);
+        let ls = runner.playbook.steps[0].loop_spec.as_ref().unwrap();
+        assert_eq!(ls.var, "i");
+        assert_eq!(ls.from, 1);
+        assert_eq!(ls.to, 5);
+    }
+
+    #[test]
+    fn on_error_defaults_to_fail() {
+        let yaml = r#"
+name: "error test"
+steps:
+  - command: whoami
+  - command: list
+    on_error: continue
+  - command: quit
+    on_error: skip
+"#;
+        let runner = PlaybookRunner::from_str(yaml).unwrap();
+        assert_eq!(runner.playbook.steps[0].on_error, OnError::Fail);
+        assert_eq!(runner.playbook.steps[1].on_error, OnError::Continue);
+        assert_eq!(runner.playbook.steps[2].on_error, OnError::Skip);
+    }
+
+    #[test]
+    fn cmp_op_parsing() {
+        let runner = PlaybookRunner::from_str("name: t\nsteps: []").unwrap();
+        assert!(matches!(runner.parse_cmp_op("eq"), Ok(CmpOp::Eq)));
+        assert!(matches!(runner.parse_cmp_op("=="), Ok(CmpOp::Eq)));
+        assert!(matches!(runner.parse_cmp_op("gte"), Ok(CmpOp::Gte)));
+        assert!(matches!(runner.parse_cmp_op(">="), Ok(CmpOp::Gte)));
+        assert!(matches!(runner.parse_cmp_op("<"), Ok(CmpOp::Lt)));
+        assert!(runner.parse_cmp_op("invalid").is_err());
+    }
+
+    #[test]
+    fn report_display() {
+        let report = PlaybookReport {
+            name: "test".into(),
+            total_steps: 3,
+            passed: 2,
+            failed: 1,
+            skipped: 0,
+            duration: Duration::from_millis(150),
+            step_results: vec![
+                StepResult {
+                    step_index: 0,
+                    command: "whoami".into(),
+                    success: true,
+                    duration: Duration::from_millis(10),
+                    output: None,
+                    error: None,
+                },
+                StepResult {
+                    step_index: 1,
+                    command: "dm".into(),
+                    success: true,
+                    duration: Duration::from_millis(50),
+                    output: None,
+                    error: None,
+                },
+                StepResult {
+                    step_index: 2,
+                    command: "assert".into(),
+                    success: false,
+                    duration: Duration::from_millis(1),
+                    output: None,
+                    error: Some("message count 0 < 1".into()),
+                },
+            ],
+        };
+        let s = format!("{report}");
+        assert!(s.contains("2 passed, 1 failed"));
+        assert!(s.contains("[3/3] assert ... FAIL"));
+    }
+}

crates/quicproquo-client/src/client/retry.rs

@@ -0,0 +1,207 @@
+//! Retry with exponential backoff for transient RPC failures.
+
+use std::future::Future;
+use std::time::Duration;
+
+use rand::Rng;
+use tracing::warn;
+
+/// Default maximum number of retry attempts (including the first try).
+pub const DEFAULT_MAX_RETRIES: u32 = 3;
+/// Default base delay in milliseconds for exponential backoff.
+pub const DEFAULT_BASE_DELAY_MS: u64 = 500;
+
+/// Runs an async operation with retries. On `Ok(t)` returns immediately.
+/// On `Err(e)`: if `is_retriable(&e)` and `attempt < max_retries`, sleeps with
+/// exponential backoff (plus jitter) then retries; otherwise returns the last error.
+pub async fn retry_async<F, Fut, T, E, P>(
+    op: F,
+    max_retries: u32,
+    base_delay_ms: u64,
+    is_retriable: P,
+) -> Result<T, E>
+where
+    F: Fn() -> Fut,
+    Fut: Future<Output = Result<T, E>>,
+    P: Fn(&E) -> bool,
+{
+    let mut last_err: Option<E> = None;
+    for attempt in 0..max_retries {
+        match op().await {
+            Ok(t) => return Ok(t),
+            Err(e) => {
+                if !is_retriable(&e) || attempt + 1 >= max_retries {
+                    return Err(e);
+                }
+                let delay_ms = base_delay_ms * 2u64.saturating_pow(attempt);
+                let jitter_ms = rand::thread_rng().gen_range(0..=delay_ms / 2);
+                let total_ms = delay_ms + jitter_ms;
+                warn!(
+                    attempt = attempt + 1,
+                    max_retries,
+                    delay_ms = total_ms,
+                    "RPC failed, retrying after backoff"
+                );
+                last_err = Some(e);
+                tokio::time::sleep(Duration::from_millis(total_ms)).await;
+            }
+        }
+    }
+    match last_err {
+        Some(e) => Err(e),
+        None => unreachable!(
+            "retry_async: last_err is always Some when loop exits after an Err"
+        ),
+    }
+}
+
+/// Classifies `anyhow::Error` for retry: returns `false` for auth or invalid-param
+/// errors (do not retry), `true` for transient errors (network, timeout, server 5xx).
+/// When in doubt, returns `true` (retry).
+pub fn anyhow_is_retriable(err: &anyhow::Error) -> bool {
+    let s = format!("{:#}", err);
+    let s_lower = s.to_lowercase();
+    // Do not retry: auth / permission
+    if s_lower.contains("unauthorized")
+        || s_lower.contains("auth failed")
+        || s_lower.contains("access denied")
+        || s_lower.contains("401")
+        || s_lower.contains("forbidden")
+        || s_lower.contains("403")
+        || s_lower.contains("token")
+    {
+        return false;
+    }
+    // Do not retry: bad request / invalid params
+    if s_lower.contains("bad request")
+        || s_lower.contains("400")
+        || s_lower.contains("invalid param")
+        || s_lower.contains("fingerprint mismatch")
+    {
+        return false;
+    }
+    // Retry: network, timeout, connection, server error, or anything else
+    true
+}
+
+#[cfg(test)]
+#[allow(clippy::unwrap_used)]
+mod tests {
+    use super::*;
+
+    #[tokio::test]
+    async fn retry_success_first_attempt() {
+        let result = retry_async(|| async { Ok::<_, String>(42) }, 3, 10, |_| true).await;
+        assert_eq!(result.unwrap(), 42);
+    }
+
+    #[tokio::test]
+    async fn retry_succeeds_after_one_failure() {
+        let counter = std::sync::Arc::new(std::sync::atomic::AtomicU32::new(0));
+        let c = counter.clone();
+        let result = retry_async(
+            || {
+                let c = c.clone();
+                async move {
+                    let n = c.fetch_add(1, std::sync::atomic::Ordering::SeqCst);
+                    if n == 0 {
+                        Err("transient failure".to_string())
+                    } else {
+                        Ok(99)
+                    }
+                }
+            },
+            3,
+            1, // minimal delay for test speed
+            |_| true,
+        )
+        .await;
+        assert_eq!(result.unwrap(), 99);
+        assert_eq!(counter.load(std::sync::atomic::Ordering::SeqCst), 2);
+    }
+
+    #[tokio::test]
+    async fn retry_non_retriable_fails_immediately() {
+        let counter = std::sync::Arc::new(std::sync::atomic::AtomicU32::new(0));
+        let c = counter.clone();
+        let result = retry_async(
+            || {
+                let c = c.clone();
+                async move {
+                    c.fetch_add(1, std::sync::atomic::Ordering::SeqCst);
+                    Err::<(), _>("permanent error")
+                }
+            },
+            5,
+            1,
+            |_: &&str| false, // nothing is retriable
+        )
+        .await;
+        assert!(result.is_err());
+        assert_eq!(counter.load(std::sync::atomic::Ordering::SeqCst), 1);
+    }
+
+    #[tokio::test]
+    async fn retry_exhausts_all_attempts() {
+        let counter = std::sync::Arc::new(std::sync::atomic::AtomicU32::new(0));
+        let c = counter.clone();
+        let result = retry_async(
+            || {
+                let c = c.clone();
+                async move {
+                    c.fetch_add(1, std::sync::atomic::Ordering::SeqCst);
+                    Err::<(), _>("still failing")
+                }
+            },
+            3,
+            1,
+            |_| true,
+        )
+        .await;
+        assert!(result.is_err());
+        assert_eq!(counter.load(std::sync::atomic::Ordering::SeqCst), 3);
+    }
+
+    #[test]
+    fn anyhow_is_retriable_classifications() {
+        // Auth errors should NOT be retriable
+        let auth_errors = [
+            "unauthorized access",
+            "HTTP 401 Unauthorized",
+            "forbidden resource",
+            "HTTP 403 Forbidden",
+            "auth failed for user",
+            "access denied",
+            "invalid token",
+        ];
+        for msg in &auth_errors {
+            let err = anyhow::anyhow!("{msg}");
+            assert!(!anyhow_is_retriable(&err), "expected non-retriable: {msg}");
+        }
+
+        // Bad-request errors should NOT be retriable
+        let bad_req_errors = [
+            "bad request: missing field",
+            "HTTP 400 Bad Request",
+            "invalid param: username",
+            "fingerprint mismatch",
+        ];
+        for msg in &bad_req_errors {
+            let err = anyhow::anyhow!("{msg}");
+            assert!(!anyhow_is_retriable(&err), "expected non-retriable: {msg}");
+        }
+
+        // Transient errors SHOULD be retriable
+        let transient_errors = [
+            "connection refused",
+            "network timeout",
+            "server error 500",
+            "stream reset",
+            "something unknown happened",
+        ];
+        for msg in &transient_errors {
+            let err = anyhow::anyhow!("{msg}");
+            assert!(anyhow_is_retriable(&err), "expected retriable: {msg}");
+        }
+    }
+}

crates/quicproquo-client/src/client/rpc.rs

@@ -0,0 +1,978 @@
+use std::net::SocketAddr;
+use std::path::Path;
+use std::sync::Arc;
+
+use anyhow::Context;
+use quinn::{ClientConfig, Endpoint};
+use quinn_proto::crypto::rustls::QuicClientConfig;
+use rustls::pki_types::{CertificateDer, ServerName, UnixTime};
+use rustls::{ClientConfig as RustlsClientConfig, RootCertStore};
+use tokio_util::compat::{TokioAsyncReadCompatExt, TokioAsyncWriteCompatExt};
+use capnp_rpc::{rpc_twoparty_capnp::Side, twoparty, RpcSystem};
+
+use quicproquo_core::HybridPublicKey;
+use quicproquo_proto::node_capnp::{auth, node_service};
+
+use crate::{AUTH_CONTEXT, INSECURE_SKIP_VERIFY};
+
+use super::retry::{anyhow_is_retriable, retry_async, DEFAULT_BASE_DELAY_MS, DEFAULT_MAX_RETRIES};
+
+/// Cap'n Proto traversal limit (words). 4 Mi words = 32 MiB; bounds DoS from deeply nested or large messages.
+const CAPNP_TRAVERSAL_LIMIT_WORDS: usize = 4 * 1024 * 1024;
+
+/// A [`rustls::client::danger::ServerCertVerifier`] that accepts any certificate.
+///
+/// **Development only.** Using this in production disables all TLS guarantees.
+#[derive(Debug)]
+struct InsecureServerCertVerifier;
+
+impl rustls::client::danger::ServerCertVerifier for InsecureServerCertVerifier {
+    fn verify_server_cert(
+        &self,
+        _end_entity: &CertificateDer<'_>,
+        _intermediates: &[CertificateDer<'_>],
+        _server_name: &ServerName<'_>,
+        _ocsp_response: &[u8],
+        _now: UnixTime,
+    ) -> Result<rustls::client::danger::ServerCertVerified, rustls::Error> {
+        Ok(rustls::client::danger::ServerCertVerified::assertion())
+    }
+
+    fn verify_tls12_signature(
+        &self,
+        _message: &[u8],
+        _cert: &CertificateDer<'_>,
+        _dss: &rustls::DigitallySignedStruct,
+    ) -> Result<rustls::client::danger::HandshakeSignatureValid, rustls::Error> {
+        Ok(rustls::client::danger::HandshakeSignatureValid::assertion())
+    }
+
+    fn verify_tls13_signature(
+        &self,
+        _message: &[u8],
+        _cert: &CertificateDer<'_>,
+        _dss: &rustls::DigitallySignedStruct,
+    ) -> Result<rustls::client::danger::HandshakeSignatureValid, rustls::Error> {
+        Ok(rustls::client::danger::HandshakeSignatureValid::assertion())
+    }
+
+    fn supported_verify_schemes(&self) -> Vec<rustls::SignatureScheme> {
+        rustls::crypto::ring::default_provider()
+            .signature_verification_algorithms
+            .supported_schemes()
+    }
+}
+
+/// Establish a QUIC/TLS connection and return a `NodeService` client.
+///
+/// Must be called from within a `LocalSet` because capnp-rpc is `!Send`.
+///
+/// Reads [`INSECURE_SKIP_VERIFY`] to decide whether to bypass certificate
+/// verification (set once at startup via [`crate::set_insecure_skip_verify`]).
+pub async fn connect_node(
+    server: &str,
+    ca_cert: &Path,
+    server_name: &str,
+) -> anyhow::Result<node_service::Client> {
+    let skip = INSECURE_SKIP_VERIFY.load(std::sync::atomic::Ordering::Relaxed);
+    connect_node_opt(server, ca_cert, server_name, skip).await
+}
+
+/// Like [`connect_node`] but with an explicit `insecure_skip_verify` toggle.
+///
+/// When `insecure_skip_verify` is `true`, certificate verification is disabled entirely.
+/// This is intended for development and testing only.
+pub async fn connect_node_opt(
+    server: &str,
+    ca_cert: &Path,
+    server_name: &str,
+    insecure_skip_verify: bool,
+) -> anyhow::Result<node_service::Client> {
+    let addr: SocketAddr = server
+        .parse()
+        .with_context(|| format!("server must be host:port, got {server}"))?;
+
+    let mut tls = if insecure_skip_verify {
+        RustlsClientConfig::builder()
+            .dangerous()
+            .with_custom_certificate_verifier(Arc::new(InsecureServerCertVerifier))
+            .with_no_client_auth()
+    } else {
+        let cert_bytes =
+            std::fs::read(ca_cert).with_context(|| format!("read ca_cert {ca_cert:?}"))?;
+        let mut roots = RootCertStore::empty();
+        roots
+            .add(CertificateDer::from(cert_bytes))
+            .context("add root cert")?;
+        RustlsClientConfig::builder()
+            .with_root_certificates(roots)
+            .with_no_client_auth()
+    };
+    tls.alpn_protocols = vec![b"capnp".to_vec()];
+
+    let crypto = QuicClientConfig::try_from(tls)
+        .map_err(|e| anyhow::anyhow!("invalid client TLS config: {e}"))?;
+
+    let bind_addr: SocketAddr = "0.0.0.0:0".parse().context("parse client bind address")?;
+    let mut endpoint = Endpoint::client(bind_addr)?;
+    endpoint.set_default_client_config(ClientConfig::new(Arc::new(crypto)));
+
+    let connection = endpoint
+        .connect(addr, server_name)
+        .context("quic connect init")?
+        .await
+        .context("quic connect failed")?;
+
+    let (send, recv) = connection.open_bi().await.context("open bi stream")?;
+
+    let mut reader_opts = capnp::message::ReaderOptions::new();
+    reader_opts.traversal_limit_in_words(Some(CAPNP_TRAVERSAL_LIMIT_WORDS));
+    let network = twoparty::VatNetwork::new(
+        recv.compat(),
+        send.compat_write(),
+        Side::Client,
+        reader_opts,
+    );
+
+    let mut rpc_system = RpcSystem::new(Box::new(network), None);
+    let client: node_service::Client = rpc_system.bootstrap(Side::Server);
+
+    tokio::task::spawn_local(rpc_system);
+
+    Ok(client)
+}
+
+pub fn set_auth(auth: &mut auth::Builder<'_>) -> anyhow::Result<()> {
+    let guard = AUTH_CONTEXT
+        .read()
+        .map_err(|e| anyhow::anyhow!("AUTH_CONTEXT lock poisoned: {e}"))?;
+    let ctx = guard.as_ref().ok_or_else(|| {
+        anyhow::anyhow!(
+            "init_auth must be called before RPCs (use a bearer or session token for authenticated commands)"
+        )
+    })?;
+    auth.set_version(ctx.version);
+    auth.set_access_token(&ctx.access_token);
+    auth.set_device_id(&ctx.device_id);
+    Ok(())
+}
+
+/// Upload a KeyPackage and verify the fingerprint echoed by the AS.
+pub async fn upload_key_package(
+    client: &node_service::Client,
+    identity_key: &[u8],
+    package: &[u8],
+) -> anyhow::Result<()> {
+    let mut req = client.upload_key_package_request();
+    {
+        let mut p = req.get();
+        p.set_identity_key(identity_key);
+        p.set_package(package);
+        let mut auth = p.reborrow().init_auth();
+        set_auth(&mut auth)?;
+    }
+
+    let resp = req
+        .send()
+        .promise
+        .await
+        .context("upload_key_package RPC failed")?;
+
+    let server_fp = resp
+        .get()
+        .context("upload_key_package: bad response")?
+        .get_fingerprint()
+        .context("upload_key_package: missing fingerprint")?
+        .to_vec();
+
+    let local_fp = super::state::sha256(package);
+    anyhow::ensure!(server_fp == local_fp, "fingerprint mismatch");
+    Ok(())
+}
+
+/// Fetch a KeyPackage for `identity_key` from the AS.
+pub async fn fetch_key_package(
+    client: &node_service::Client,
+    identity_key: &[u8],
+) -> anyhow::Result<Vec<u8>> {
+    let mut req = client.fetch_key_package_request();
+    {
+        let mut p = req.get();
+        p.set_identity_key(identity_key);
+        let mut auth = p.reborrow().init_auth();
+        set_auth(&mut auth)?;
+    }
+
+    let resp = req
+        .send()
+        .promise
+        .await
+        .context("fetch_key_package RPC failed")?;
+
+    let pkg = resp
+        .get()
+        .context("fetch_key_package: bad response")?
+        .get_package()
+        .context("fetch_key_package: missing package field")?
+        .to_vec();
+
+    Ok(pkg)
+}
+
+/// Enqueue an opaque payload to the DS for `recipient_key`.
+/// Returns the per-inbox sequence number assigned by the server.
+/// Retries on transient failures with exponential backoff.
+pub async fn enqueue(
+    client: &node_service::Client,
+    recipient_key: &[u8],
+    payload: &[u8],
+) -> anyhow::Result<u64> {
+    enqueue_with_ttl(client, recipient_key, payload, None).await
+}
+
+/// Enqueue with an optional TTL (seconds). 0 or None means no expiry.
+pub async fn enqueue_with_ttl(
+    client: &node_service::Client,
+    recipient_key: &[u8],
+    payload: &[u8],
+    ttl_secs: Option<u32>,
+) -> anyhow::Result<u64> {
+    let client = client.clone();
+    let recipient_key = recipient_key.to_vec();
+    let payload = payload.to_vec();
+    retry_async(
+        || {
+            let client = client.clone();
+            let recipient_key = recipient_key.clone();
+            let payload = payload.clone();
+            async move {
+                let mut req = client.enqueue_request();
+                {
+                    let mut p = req.get();
+                    p.set_recipient_key(&recipient_key);
+                    p.set_payload(&payload);
+                    p.set_channel_id(&[]);
+                    p.set_version(1);
+                    if let Some(ttl) = ttl_secs {
+                        p.set_ttl_secs(ttl);
+                    }
+                    let mut auth = p.reborrow().init_auth();
+                    set_auth(&mut auth)?;
+                }
+                let resp = req.send().promise.await.context("enqueue RPC failed")?;
+                let seq = resp.get().context("enqueue: bad response")?.get_seq();
+                Ok(seq)
+            }
+        },
+        DEFAULT_MAX_RETRIES,
+        DEFAULT_BASE_DELAY_MS,
+        anyhow_is_retriable,
+    )
+    .await
+}
+
+/// Fetch and drain all payloads for `recipient_key`.
+/// Returns `(seq, payload)` pairs — sort by `seq` before MLS processing.
+/// Retries on transient failures with exponential backoff.
+pub async fn fetch_all(
+    client: &node_service::Client,
+    recipient_key: &[u8],
+) -> anyhow::Result<Vec<(u64, Vec<u8>)>> {
+    let client = client.clone();
+    let recipient_key = recipient_key.to_vec();
+    retry_async(
+        || {
+            let client = client.clone();
+            let recipient_key = recipient_key.clone();
+            async move {
+                let mut req = client.fetch_request();
+                {
+                    let mut p = req.get();
+                    p.set_recipient_key(&recipient_key);
+                    p.set_channel_id(&[]);
+                    p.set_version(1);
+                    p.set_limit(0); // fetch all
+                    let mut auth = p.reborrow().init_auth();
+                    set_auth(&mut auth)?;
+                }
+
+                let resp = req.send().promise.await.context("fetch RPC failed")?;
+
+                let list = resp
+                    .get()
+                    .context("fetch: bad response")?
+                    .get_payloads()
+                    .context("fetch: missing payloads")?;
+
+                let mut payloads = Vec::with_capacity(list.len() as usize);
+                for i in 0..list.len() {
+                    let entry = list.get(i);
+                    let seq = entry.get_seq();
+                    let data = entry
+                        .get_data()
+                        .context("fetch: envelope data read failed")?
+                        .to_vec();
+                    payloads.push((seq, data));
+                }
+
+                Ok(payloads)
+            }
+        },
+        DEFAULT_MAX_RETRIES,
+        DEFAULT_BASE_DELAY_MS,
+        anyhow_is_retriable,
+    )
+    .await
+}
+
+/// Long-poll for payloads with optional timeout (ms).
+/// Returns `(seq, payload)` pairs — sort by `seq` before MLS processing.
+/// Retries on transient failures with exponential backoff.
+pub async fn fetch_wait(
+    client: &node_service::Client,
+    recipient_key: &[u8],
+    timeout_ms: u64,
+) -> anyhow::Result<Vec<(u64, Vec<u8>)>> {
+    let client = client.clone();
+    let recipient_key = recipient_key.to_vec();
+    retry_async(
+        || {
+            let client = client.clone();
+            let recipient_key = recipient_key.clone();
+            async move {
+                let mut req = client.fetch_wait_request();
+                {
+                    let mut p = req.get();
+                    p.set_recipient_key(&recipient_key);
+                    p.set_timeout_ms(timeout_ms);
+                    p.set_channel_id(&[]);
+                    p.set_version(1);
+                    p.set_limit(0); // fetch all
+                    let mut auth = p.reborrow().init_auth();
+                    set_auth(&mut auth)?;
+                }
+
+                let resp = req.send().promise.await.context("fetch_wait RPC failed")?;
+
+                let list = resp
+                    .get()
+                    .context("fetch_wait: bad response")?
+                    .get_payloads()
+                    .context("fetch_wait: missing payloads")?;
+
+                let mut payloads = Vec::with_capacity(list.len() as usize);
+                for i in 0..list.len() {
+                    let entry = list.get(i);
+                    let seq = entry.get_seq();
+                    let data = entry
+                        .get_data()
+                        .context("fetch_wait: envelope data read failed")?
+                        .to_vec();
+                    payloads.push((seq, data));
+                }
+
+                Ok(payloads)
+            }
+        },
+        DEFAULT_MAX_RETRIES,
+        DEFAULT_BASE_DELAY_MS,
+        anyhow_is_retriable,
+    )
+    .await
+}
+
+/// Upload a hybrid (X25519 + ML-KEM-768) public key for an identity.
+pub async fn upload_hybrid_key(
+    client: &node_service::Client,
+    identity_key: &[u8],
+    hybrid_pk: &HybridPublicKey,
+) -> anyhow::Result<()> {
+    let mut req = client.upload_hybrid_key_request();
+    {
+        let mut p = req.get();
+        p.set_identity_key(identity_key);
+        p.set_hybrid_public_key(&hybrid_pk.to_bytes());
+        let mut auth = p.reborrow().init_auth();
+        set_auth(&mut auth)?;
+    }
+    req.send()
+        .promise
+        .await
+        .context("upload_hybrid_key RPC failed")?;
+    Ok(())
+}
+
+/// Fetch a peer's hybrid public key from the server.
+///
+/// Returns `None` if the peer has not uploaded a hybrid key.
+pub async fn fetch_hybrid_key(
+    client: &node_service::Client,
+    identity_key: &[u8],
+) -> anyhow::Result<Option<HybridPublicKey>> {
+    let mut req = client.fetch_hybrid_key_request();
+    {
+        let mut p = req.get();
+        p.set_identity_key(identity_key);
+        let mut auth = p.reborrow().init_auth();
+        set_auth(&mut auth)?;
+    }
+
+    let resp = req
+        .send()
+        .promise
+        .await
+        .context("fetch_hybrid_key RPC failed")?;
+
+    let pk_bytes = resp
+        .get()
+        .context("fetch_hybrid_key: bad response")?
+        .get_hybrid_public_key()
+        .context("fetch_hybrid_key: missing field")?
+        .to_vec();
+
+    if pk_bytes.is_empty() {
+        return Ok(None);
+    }
+
+    let pk = HybridPublicKey::from_bytes(&pk_bytes).context("invalid hybrid public key")?;
+    Ok(Some(pk))
+}
+
+/// Decrypt a hybrid envelope. Requires a hybrid key; no fallback to plaintext MLS.
+pub fn try_hybrid_decrypt(
+    hybrid_kp: Option<&quicproquo_core::HybridKeypair>,
+    payload: &[u8],
+) -> anyhow::Result<Vec<u8>> {
+    let kp = hybrid_kp.ok_or_else(|| anyhow::anyhow!("hybrid key required for decryption"))?;
+    quicproquo_core::hybrid_decrypt(kp, payload, b"", b"").map_err(|e| anyhow::anyhow!("{e}"))
+}
+
+/// Peek at queued payloads without removing them.
+/// Returns `(seq, payload)` pairs sorted by seq.
+/// Retries on transient failures with exponential backoff.
+pub async fn peek(
+    client: &node_service::Client,
+    recipient_key: &[u8],
+) -> anyhow::Result<Vec<(u64, Vec<u8>)>> {
+    let client = client.clone();
+    let recipient_key = recipient_key.to_vec();
+    retry_async(
+        || {
+            let client = client.clone();
+            let recipient_key = recipient_key.clone();
+            async move {
+                let mut req = client.peek_request();
+                {
+                    let mut p = req.get();
+                    p.set_recipient_key(&recipient_key);
+                    p.set_channel_id(&[]);
+                    p.set_version(1);
+                    p.set_limit(0); // peek all
+                    let mut auth = p.reborrow().init_auth();
+                    set_auth(&mut auth)?;
+                }
+
+                let resp = req.send().promise.await.context("peek RPC failed")?;
+
+                let list = resp
+                    .get()
+                    .context("peek: bad response")?
+                    .get_payloads()
+                    .context("peek: missing payloads")?;
+
+                let mut payloads = Vec::with_capacity(list.len() as usize);
+                for i in 0..list.len() {
+                    let entry = list.get(i);
+                    let seq = entry.get_seq();
+                    let data = entry
+                        .get_data()
+                        .context("peek: envelope data read failed")?
+                        .to_vec();
+                    payloads.push((seq, data));
+                }
+
+                Ok(payloads)
+            }
+        },
+        DEFAULT_MAX_RETRIES,
+        DEFAULT_BASE_DELAY_MS,
+        anyhow_is_retriable,
+    )
+    .await
+}
+
+/// Acknowledge all messages up to and including `seq_up_to`.
+/// Retries on transient failures with exponential backoff.
+pub async fn ack(
+    client: &node_service::Client,
+    recipient_key: &[u8],
+    seq_up_to: u64,
+) -> anyhow::Result<()> {
+    let client = client.clone();
+    let recipient_key = recipient_key.to_vec();
+    retry_async(
+        || {
+            let client = client.clone();
+            let recipient_key = recipient_key.clone();
+            async move {
+                let mut req = client.ack_request();
+                {
+                    let mut p = req.get();
+                    p.set_recipient_key(&recipient_key);
+                    p.set_channel_id(&[]);
+                    p.set_version(1);
+                    p.set_seq_up_to(seq_up_to);
+                    let mut auth = p.reborrow().init_auth();
+                    set_auth(&mut auth)?;
+                }
+                req.send().promise.await.context("ack RPC failed")?;
+                Ok(())
+            }
+        },
+        DEFAULT_MAX_RETRIES,
+        DEFAULT_BASE_DELAY_MS,
+        anyhow_is_retriable,
+    )
+    .await
+}
+
+/// Fetch multiple peers' hybrid keys in a single round-trip.
+/// Returns `None` for peers who have not uploaded a hybrid key.
+/// Retries on transient failures with exponential backoff.
+pub async fn fetch_hybrid_keys(
+    client: &node_service::Client,
+    identity_keys: &[&[u8]],
+) -> anyhow::Result<Vec<Option<HybridPublicKey>>> {
+    let client = client.clone();
+    let identity_keys: Vec<Vec<u8>> = identity_keys.iter().map(|k| k.to_vec()).collect();
+    retry_async(
+        || {
+            let client = client.clone();
+            let identity_keys = identity_keys.clone();
+            async move {
+                let mut req = client.fetch_hybrid_keys_request();
+                {
+                    let mut p = req.get();
+                    let mut list = p.reborrow().init_identity_keys(identity_keys.len() as u32);
+                    for (i, ik) in identity_keys.iter().enumerate() {
+                        list.set(i as u32, ik);
+                    }
+                    let mut auth = p.reborrow().init_auth();
+                    set_auth(&mut auth)?;
+                }
+
+                let resp = req
+                    .send()
+                    .promise
+                    .await
+                    .context("fetch_hybrid_keys RPC failed")?;
+
+                let keys = resp
+                    .get()
+                    .context("fetch_hybrid_keys: bad response")?
+                    .get_keys()
+                    .context("fetch_hybrid_keys: missing keys")?;
+
+                let mut result = Vec::with_capacity(keys.len() as usize);
+                for i in 0..keys.len() {
+                    let pk_bytes = keys
+                        .get(i)
+                        .context("fetch_hybrid_keys: key read failed")?
+                        .to_vec();
+                    if pk_bytes.is_empty() {
+                        result.push(None);
+                    } else {
+                        let pk = HybridPublicKey::from_bytes(&pk_bytes)
+                            .context("invalid hybrid public key")?;
+                        result.push(Some(pk));
+                    }
+                }
+
+                Ok(result)
+            }
+        },
+        DEFAULT_MAX_RETRIES,
+        DEFAULT_BASE_DELAY_MS,
+        anyhow_is_retriable,
+    )
+    .await
+}
+
+/// Enqueue the same payload to multiple recipients in a single round-trip.
+/// Returns per-recipient sequence numbers.
+/// Retries on transient failures with exponential backoff.
+pub async fn batch_enqueue(
+    client: &node_service::Client,
+    recipient_keys: &[&[u8]],
+    payload: &[u8],
+) -> anyhow::Result<Vec<u64>> {
+    let client = client.clone();
+    let recipient_keys: Vec<Vec<u8>> = recipient_keys.iter().map(|k| k.to_vec()).collect();
+    let payload = payload.to_vec();
+    retry_async(
+        || {
+            let client = client.clone();
+            let recipient_keys = recipient_keys.clone();
+            let payload = payload.clone();
+            async move {
+                let mut req = client.batch_enqueue_request();
+                {
+                    let mut p = req.get();
+                    let mut list = p.reborrow().init_recipient_keys(recipient_keys.len() as u32);
+                    for (i, rk) in recipient_keys.iter().enumerate() {
+                        list.set(i as u32, rk);
+                    }
+                    p.set_payload(&payload);
+                    p.set_channel_id(&[]);
+                    p.set_version(1);
+                    let mut auth = p.reborrow().init_auth();
+                    set_auth(&mut auth)?;
+                }
+
+                let resp = req
+                    .send()
+                    .promise
+                    .await
+                    .context("batch_enqueue RPC failed")?;
+
+                let seqs = resp
+                    .get()
+                    .context("batch_enqueue: bad response")?
+                    .get_seqs()
+                    .context("batch_enqueue: missing seqs")?;
+
+                let mut result = Vec::with_capacity(seqs.len() as usize);
+                for i in 0..seqs.len() {
+                    result.push(seqs.get(i));
+                }
+
+                Ok(result)
+            }
+        },
+        DEFAULT_MAX_RETRIES,
+        DEFAULT_BASE_DELAY_MS,
+        anyhow_is_retriable,
+    )
+    .await
+}
+
+/// Resolve a username to its Ed25519 identity key (32 bytes).
+///
+/// When the server returns a non-empty `inclusionProof`, the client verifies it
+/// against the identity key using the Key Transparency Merkle proof. Proof
+/// verification failure is treated as a hard error (the server is misbehaving).
+/// If the server sends no proof (empty field), the key is returned as-is —
+/// callers can decide whether to require proofs for security-critical flows.
+///
+/// Returns `None` if the username is not registered.
+pub async fn resolve_user(
+    client: &node_service::Client,
+    username: &str,
+) -> anyhow::Result<Option<Vec<u8>>> {
+    let mut req = client.resolve_user_request();
+    {
+        let mut p = req.get();
+        p.set_username(username);
+        let mut auth = p.reborrow().init_auth();
+        set_auth(&mut auth)?;
+    }
+
+    let resp = req
+        .send()
+        .promise
+        .await
+        .context("resolve_user RPC failed")?;
+
+    let reader = resp.get().context("resolve_user: bad response")?;
+
+    let key = reader
+        .get_identity_key()
+        .context("resolve_user: missing identity_key field")?
+        .to_vec();
+
+    if key.is_empty() {
+        return Ok(None);
+    }
+
+    // Verify the KT inclusion proof when the server sends one.
+    let proof_bytes = reader
+        .get_inclusion_proof()
+        .context("resolve_user: missing inclusion_proof field")?
+        .to_vec();
+
+    if !proof_bytes.is_empty() {
+        let proof = quicproquo_kt::InclusionProof::from_bytes(&proof_bytes)
+            .context("resolve_user: inclusion proof deserialise failed")?;
+        quicproquo_kt::verify_inclusion(&proof, username, &key)
+            .context("resolve_user: KT inclusion proof verification FAILED — possible key mislabelling")?;
+    }
+
+    Ok(Some(key))
+}
+
+/// Reverse lookup: resolve an identity key to the registered username.
+/// Returns `None` if no username is associated with the key.
+pub async fn resolve_identity(
+    client: &node_service::Client,
+    identity_key: &[u8],
+) -> anyhow::Result<Option<String>> {
+    let mut req = client.resolve_identity_request();
+    {
+        let mut p = req.get();
+        p.set_identity_key(identity_key);
+        let mut auth = p.reborrow().init_auth();
+        set_auth(&mut auth)?;
+    }
+
+    let resp = req
+        .send()
+        .promise
+        .await
+        .context("resolve_identity RPC failed")?;
+
+    let username = resp
+        .get()
+        .context("resolve_identity: bad response")?
+        .get_username()
+        .context("resolve_identity: missing field")?
+        .to_str()
+        .unwrap_or("")
+        .to_string();
+
+    if username.is_empty() {
+        Ok(None)
+    } else {
+        Ok(Some(username))
+    }
+}
+
+/// Create a 1:1 DM channel with a peer.
+///
+/// Returns `(channel_id, was_new)` where `channel_id` is the stable 16-byte identifier and
+/// `was_new` is `true` iff this call created the channel for the first time. When `was_new` is
+/// `false`, the channel already existed (created by the peer), and the caller should wait for
+/// the peer's MLS Welcome to arrive via the background poller rather than creating a new MLS group.
+pub async fn create_channel(
+    client: &node_service::Client,
+    peer_key: &[u8],
+) -> anyhow::Result<(Vec<u8>, bool)> {
+    let mut req = client.create_channel_request();
+    {
+        let mut p = req.get();
+        p.set_peer_key(peer_key);
+        let mut auth = p.reborrow().init_auth();
+        set_auth(&mut auth)?;
+    }
+
+    let resp = req
+        .send()
+        .promise
+        .await
+        .context("create_channel RPC failed")?;
+
+    let reader = resp.get().context("create_channel: bad response")?;
+    let channel_id = reader
+        .get_channel_id()
+        .context("create_channel: missing channel_id")?
+        .to_vec();
+    let was_new = reader.get_was_new();
+
+    Ok((channel_id, was_new))
+}
+
+/// Upload a single chunk of a blob to the server.
+///
+/// `blob_hash` is the expected SHA-256 hash (32 bytes) of the complete blob.
+/// Returns the `blob_id` once the server has received and verified the final chunk.
+pub async fn upload_blob_chunk(
+    client: &node_service::Client,
+    blob_hash: &[u8],
+    chunk: &[u8],
+    offset: u64,
+    total_size: u64,
+    mime_type: &str,
+) -> anyhow::Result<Vec<u8>> {
+    let mut req = client.upload_blob_request();
+    {
+        let mut p = req.get();
+        let mut auth = p.reborrow().init_auth();
+        set_auth(&mut auth)?;
+        p.set_blob_hash(blob_hash);
+        p.set_chunk(chunk);
+        p.set_offset(offset);
+        p.set_total_size(total_size);
+        p.set_mime_type(mime_type);
+    }
+    let resp = req.send().promise.await.context("upload_blob RPC failed")?;
+    let blob_id = resp
+        .get()
+        .context("upload_blob: bad response")?
+        .get_blob_id()
+        .context("upload_blob: missing blob_id")?
+        .to_vec();
+    Ok(blob_id)
+}
+
+/// Download a single chunk of a blob from the server.
+///
+/// Returns `(chunk_bytes, total_size, mime_type)`.
+pub async fn download_blob_chunk(
+    client: &node_service::Client,
+    blob_id: &[u8],
+    offset: u64,
+    length: u32,
+) -> anyhow::Result<(Vec<u8>, u64, String)> {
+    let mut req = client.download_blob_request();
+    {
+        let mut p = req.get();
+        let mut auth = p.reborrow().init_auth();
+        set_auth(&mut auth)?;
+        p.set_blob_id(blob_id);
+        p.set_offset(offset);
+        p.set_length(length);
+    }
+    let resp = req.send().promise.await.context("download_blob RPC failed")?;
+    let reader = resp.get().context("download_blob: bad response")?;
+    let chunk = reader.get_chunk().context("download_blob: missing chunk")?.to_vec();
+    let total_size = reader.get_total_size();
+    let mime_type = reader
+        .get_mime_type()
+        .context("download_blob: missing mime_type")?
+        .to_str()
+        .unwrap_or("application/octet-stream")
+        .to_string();
+    Ok((chunk, total_size, mime_type))
+}
+
+/// Delete the authenticated user's account on the server.
+/// Requires an identity-bound session (OPAQUE login).
+pub async fn delete_account(
+    client: &node_service::Client,
+) -> anyhow::Result<bool> {
+    let mut req = client.delete_account_request();
+    {
+        let mut p = req.get();
+        let mut auth = p.reborrow().init_auth();
+        set_auth(&mut auth)?;
+    }
+
+    let resp = req
+        .send()
+        .promise
+        .await
+        .context("delete_account RPC failed")?;
+
+    let success = resp
+        .get()
+        .context("delete_account: bad response")?
+        .get_success();
+
+    Ok(success)
+}
+
+/// Register a device for the authenticated identity.
+pub async fn register_device(
+    client: &node_service::Client,
+    device_id: &[u8],
+    device_name: &str,
+) -> anyhow::Result<bool> {
+    let mut req = client.register_device_request();
+    {
+        let mut p = req.get();
+        p.set_device_id(device_id);
+        p.set_device_name(device_name);
+        let mut auth = p.reborrow().init_auth();
+        set_auth(&mut auth)?;
+    }
+
+    let resp = req
+        .send()
+        .promise
+        .await
+        .context("register_device RPC failed")?;
+
+    let success = resp
+        .get()
+        .context("register_device: bad response")?
+        .get_success();
+
+    Ok(success)
+}
+
+/// List all registered devices for the authenticated identity.
+pub async fn list_devices(
+    client: &node_service::Client,
+) -> anyhow::Result<Vec<(Vec<u8>, String, u64)>> {
+    let mut req = client.list_devices_request();
+    {
+        let mut p = req.get();
+        let mut auth = p.reborrow().init_auth();
+        set_auth(&mut auth)?;
+    }
+
+    let resp = req
+        .send()
+        .promise
+        .await
+        .context("list_devices RPC failed")?;
+
+    let devices = resp
+        .get()
+        .context("list_devices: bad response")?
+        .get_devices()
+        .context("list_devices: missing devices field")?;
+
+    let mut result = Vec::with_capacity(devices.len() as usize);
+    for i in 0..devices.len() {
+        let entry = devices.get(i);
+        let device_id = entry
+            .get_device_id()
+            .context("list_devices: missing device_id")?
+            .to_vec();
+        let device_name = entry
+            .get_device_name()
+            .context("list_devices: missing device_name")?
+            .to_str()
+            .unwrap_or("")
+            .to_string();
+        let registered_at = entry.get_registered_at();
+        result.push((device_id, device_name, registered_at));
+    }
+
+    Ok(result)
+}
+
+/// Revoke (remove) a registered device.
+pub async fn revoke_device(
+    client: &node_service::Client,
+    device_id: &[u8],
+) -> anyhow::Result<bool> {
+    let mut req = client.revoke_device_request();
+    {
+        let mut p = req.get();
+        p.set_device_id(device_id);
+        let mut auth = p.reborrow().init_auth();
+        set_auth(&mut auth)?;
+    }
+
+    let resp = req
+        .send()
+        .promise
+        .await
+        .context("revoke_device RPC failed")?;
+
+    let success = resp
+        .get()
+        .context("revoke_device: bad response")?
+        .get_success();
+
+    Ok(success)
+}
+
+/// Return the current Unix timestamp in milliseconds.
+pub fn current_timestamp_ms() -> u64 {
+    std::time::SystemTime::now()
+        .duration_since(std::time::UNIX_EPOCH)
+        .unwrap_or_default()
+        .as_millis() as u64
+}

crates/quicproquo-client/src/client/session.rs

@@ -0,0 +1,291 @@
+//! Runtime session state for the interactive REPL.
+//!
+//! Wraps the legacy `StoredState` (identity + hybrid key) and adds
+//! multi-conversation management via `ConversationStore`.
+
+use std::collections::HashMap;
+use std::path::{Path, PathBuf};
+use std::sync::Arc;
+use std::time::Instant;
+
+use anyhow::Context;
+use zeroize::Zeroizing;
+
+use quicproquo_core::{DiskKeyStore, GroupMember, HybridKeypair, IdentityKeypair};
+
+use super::conversation::{
+    now_ms, Conversation, ConversationId, ConversationKind, ConversationStore,
+};
+use super::state::{load_or_init_state, keystore_path};
+
+/// Runtime state for an interactive REPL session.
+pub struct SessionState {
+    /// Long-term identity keypair.
+    pub identity: Arc<IdentityKeypair>,
+    /// Post-quantum hybrid keypair.
+    pub hybrid_kp: Option<HybridKeypair>,
+    /// Path to the legacy state file (for backward compat with one-shot commands).
+    pub state_path: PathBuf,
+    /// Optional password for the legacy state file. Zeroized on drop. (M9)
+    pub password: Option<Zeroizing<String>>,
+    /// SQLite-backed conversation + message store.
+    pub conv_store: ConversationStore,
+    /// Currently active conversation.
+    pub active_conversation: Option<ConversationId>,
+    /// In-memory GroupMember instances keyed by conversation ID.
+    pub members: HashMap<ConversationId, GroupMember>,
+    /// Holds the GroupMember whose KeyPackage was uploaded to the server.
+    /// Its keystore contains the HPKE init private key needed to decrypt
+    /// incoming Welcome messages. Consumed on auto-join, then replenished.
+    pub pending_member: Option<GroupMember>,
+    /// Whether to display typing indicators from others (session preference).
+    pub typing_notify_enabled: bool,
+    /// Tracks who is currently typing and when the indicator was last received.
+    /// Entries older than 10 seconds are considered expired.
+    pub typing_indicators: HashMap<String, Instant>,
+    /// Per-conversation disappearing message TTL in seconds. None = messages persist.
+    pub disappear_ttl: HashMap<ConversationId, u32>,
+    /// When true, /members and /group-info redact identity keys as `[redacted-XXXX]`.
+    pub redact_keys: bool,
+    /// When Some(secs), auto-clear local messages older than this duration.
+    pub auto_clear_secs: Option<u32>,
+    /// When true, send periodic dummy messages for traffic analysis resistance.
+    pub padding_enabled: bool,
+    /// Last epoch at which we sent a message (for /verify-fs).
+    pub last_send_epoch: Option<u64>,
+}
+
+impl SessionState {
+    /// Load identity from the legacy state file, open the conversation store,
+    /// and migrate any existing single-group state into the conversation DB.
+    pub fn load(
+        state_path: &Path,
+        password: Option<&str>,
+    ) -> anyhow::Result<Self> {
+        let state = load_or_init_state(state_path, password)?;
+
+        let identity = Arc::new(IdentityKeypair::from_seed(state.identity_seed));
+        let hybrid_kp = state
+            .hybrid_key
+            .as_ref()
+            .map(HybridKeypair::from_bytes)
+            .transpose()
+            .context("decode hybrid key")?;
+
+        // Open the conversation DB next to the state file.
+        // When a state password is provided, encrypt the DB with SQLCipher.
+        let db_path = state_path.with_extension("convdb");
+        let conv_store = ConversationStore::open(&db_path, password)?;
+
+        let mut session = Self {
+            identity,
+            hybrid_kp,
+            state_path: state_path.to_path_buf(),
+            password: password.map(|p| Zeroizing::new(String::from(p))),
+            conv_store,
+            active_conversation: None,
+            members: HashMap::new(),
+            pending_member: None,
+            typing_notify_enabled: true,
+            typing_indicators: HashMap::new(),
+            disappear_ttl: HashMap::new(),
+            redact_keys: false,
+            auto_clear_secs: None,
+            padding_enabled: false,
+            last_send_epoch: None,
+        };
+
+        // Migrate legacy single-group into conversations if present and not yet migrated.
+        if state.group.is_some() {
+            session.migrate_legacy_group(state_path, &state.group)?;
+        }
+
+        // Load all existing conversations' GroupMembers into memory.
+        session.load_all_members()?;
+
+        Ok(session)
+    }
+
+    /// Migrate the legacy single-group from StoredState into the conversation DB.
+    fn migrate_legacy_group(
+        &mut self,
+        state_path: &Path,
+        group_blob: &Option<Vec<u8>>,
+    ) -> anyhow::Result<()> {
+        let blob = match group_blob {
+            Some(b) => b,
+            None => return Ok(()),
+        };
+
+        // Reconstruct GroupMember using the legacy keystore and group blob.
+        let ks_path = keystore_path(state_path);
+        let ks = DiskKeyStore::persistent(&ks_path)?;
+        let group = bincode::deserialize(blob).context("decode legacy group")?;
+        let member = GroupMember::new_with_state(
+            Arc::clone(&self.identity),
+            ks,
+            Some(group),
+            false, // legacy groups are classical
+        );
+
+        let group_id_bytes = member.group_id().unwrap_or_default();
+
+        // Use the first 16 bytes of the group_id as the ConversationId.
+        let conv_id = if group_id_bytes.len() >= 16 {
+            ConversationId::from_slice(&group_id_bytes[..16])
+                .unwrap_or(ConversationId([0; 16]))
+        } else {
+            ConversationId::from_group_name(&hex::encode(&group_id_bytes))
+        };
+
+        // Check if already migrated.
+        if self.conv_store.load_conversation(&conv_id)?.is_some() {
+            return Ok(());
+        }
+
+        let member_keys = member.member_identities();
+        let short_id = &hex::encode(&group_id_bytes)[..8.min(group_id_bytes.len() * 2)];
+        let conv = Conversation {
+            id: conv_id.clone(),
+            kind: ConversationKind::Group {
+                name: format!("legacy-{short_id}"),
+            },
+            display_name: format!("legacy-{short_id}"),
+            mls_group_blob: Some(blob.clone()),
+            keystore_blob: None,
+            member_keys,
+            unread_count: 0,
+            last_activity_ms: now_ms(),
+            created_at_ms: now_ms(),
+            is_hybrid: false,
+            last_seen_seq: 0,
+        };
+
+        self.conv_store.save_conversation(&conv)?;
+        self.members.insert(conv_id, member);
+
+        Ok(())
+    }
+
+    /// Load all conversations from the DB and create in-memory GroupMember instances.
+    fn load_all_members(&mut self) -> anyhow::Result<()> {
+        let convs = self.conv_store.list_conversations()?;
+        for conv in convs {
+            if self.members.contains_key(&conv.id) {
+                continue;
+            }
+            let member = self.create_member_from_conv(&conv)?;
+            self.members.insert(conv.id.clone(), member);
+        }
+        Ok(())
+    }
+
+    /// Create a GroupMember from a stored conversation.
+    fn create_member_from_conv(&self, conv: &Conversation) -> anyhow::Result<GroupMember> {
+        let ks_path = self.keystore_path_for(&conv.id);
+        let ks = DiskKeyStore::persistent(&ks_path)
+            .unwrap_or_else(|e| {
+                tracing::warn!(path = %ks_path.display(), error = %e, "DiskKeyStore open failed, falling back to ephemeral");
+                DiskKeyStore::ephemeral()
+            });
+
+        let group = conv
+            .mls_group_blob
+            .as_ref()
+            .map(|b| bincode::deserialize(b))
+            .transpose()
+            .context("decode MLS group from conversation db")?;
+
+        Ok(GroupMember::new_with_state(
+            Arc::clone(&self.identity),
+            ks,
+            group,
+            conv.is_hybrid,
+        ))
+    }
+
+    /// Path for a per-conversation keystore file.
+    fn keystore_path_for(&self, conv_id: &ConversationId) -> PathBuf {
+        let dir = self.state_path.with_extension("keystores");
+        dir.join(format!("{}.ks", conv_id.hex()))
+    }
+
+    /// Persist a conversation's MLS group state back to the DB.
+    pub fn save_member(&self, conv_id: &ConversationId) -> anyhow::Result<()> {
+        let member = self.members.get(conv_id).context("no such conversation")?;
+        let blob = member
+            .group_ref()
+            .map(bincode::serialize)
+            .transpose()
+            .context("serialize MLS group")?;
+
+        let member_keys = member.member_identities();
+
+        // Update the mls_group_blob and member_keys in the DB.
+        if let Some(mut conv) = self.conv_store.load_conversation(conv_id)? {
+            conv.mls_group_blob = blob;
+            conv.member_keys = member_keys;
+            self.conv_store.save_conversation(&conv)?;
+        }
+
+        Ok(())
+    }
+
+    /// Persist all in-memory group states back to the DB.
+    pub fn save_all(&self) -> anyhow::Result<()> {
+        for conv_id in self.members.keys() {
+            if let Err(e) = self.save_member(conv_id) {
+                tracing::warn!(conv = %conv_id.hex(), error = %e, "failed to save conversation");
+            }
+        }
+        Ok(())
+    }
+
+    /// Add a new conversation and its GroupMember to the session.
+    pub fn add_conversation(
+        &mut self,
+        conv: Conversation,
+        member: GroupMember,
+    ) -> anyhow::Result<()> {
+        // Ensure keystore directory exists
+        let ks_path = self.keystore_path_for(&conv.id);
+        if let Some(parent) = ks_path.parent() {
+            std::fs::create_dir_all(parent).ok();
+        }
+
+        self.conv_store.save_conversation(&conv)?;
+        self.members.insert(conv.id.clone(), member);
+        Ok(())
+    }
+
+    /// Get a mutable reference to a conversation's GroupMember.
+    pub fn get_member_mut(&mut self, conv_id: &ConversationId) -> Option<&mut GroupMember> {
+        self.members.get_mut(conv_id)
+    }
+
+    /// Public key bytes for this identity.
+    pub fn identity_bytes(&self) -> Vec<u8> {
+        self.identity.public_key_bytes().to_vec()
+    }
+
+    /// Short hex prefix of the identity key for display.
+    pub fn identity_short(&self) -> String {
+        hex::encode(&self.identity.public_key_bytes()[..4])
+    }
+
+    /// Get display name of a conversation.
+    pub fn active_display_name(&self) -> Option<String> {
+        let id = self.active_conversation.as_ref()?;
+        self.conv_store.load_conversation(id).ok().flatten().map(|c| c.display_name)
+    }
+
+    /// Count total unread across all conversations.
+    pub fn total_unread(&self) -> u32 {
+        self.conv_store
+            .list_conversations()
+            .unwrap_or_default()
+            .iter()
+            .map(|c| c.unread_count)
+            .sum()
+    }
+}

crates/quicproquo-client/src/client/state.rs

@@ -0,0 +1,293 @@
+use std::path::{Path, PathBuf};
+use std::sync::Arc;
+
+use anyhow::Context;
+use argon2::{Algorithm, Argon2, Params, Version};
+use chacha20poly1305::{
+    aead::{Aead, KeyInit},
+    ChaCha20Poly1305, Key, Nonce,
+};
+use rand::RngCore;
+use serde::{Deserialize, Serialize};
+
+use quicproquo_core::{DiskKeyStore, GroupMember, HybridKeypair, HybridKeypairBytes, IdentityKeypair};
+
+/// Magic bytes for encrypted client state files.
+const STATE_MAGIC: &[u8; 4] = b"QPCE";
+const STATE_SALT_LEN: usize = 16;
+const STATE_NONCE_LEN: usize = 12;
+
+#[derive(Serialize, Deserialize)]
+pub struct StoredState {
+    pub identity_seed: [u8; 32],
+    pub group: Option<Vec<u8>>,
+    /// Post-quantum hybrid keypair (X25519 + ML-KEM-768). `None` for state created before hybrid was added.
+    #[serde(default)]
+    pub hybrid_key: Option<HybridKeypairBytes>,
+    /// Cached member public keys for group participants.
+    #[serde(default)]
+    pub member_keys: Vec<Vec<u8>>,
+}
+
+impl StoredState {
+    pub fn into_parts(self, state_path: &Path) -> anyhow::Result<(GroupMember, Option<HybridKeypair>)> {
+        let identity = Arc::new(IdentityKeypair::from_seed(self.identity_seed));
+        let group = self
+            .group
+            .map(|bytes| bincode::deserialize(&bytes).context("decode group"))
+            .transpose()?;
+        let key_store = DiskKeyStore::persistent(keystore_path(state_path))?;
+        let hybrid = self.hybrid_key.is_some();
+        let member = GroupMember::new_with_state(identity, key_store, group, hybrid);
+
+        let hybrid_kp = self
+            .hybrid_key
+            .map(|bytes| HybridKeypair::from_bytes(&bytes).context("decode hybrid key"))
+            .transpose()?;
+
+        Ok((member, hybrid_kp))
+    }
+
+    pub fn from_parts(member: &GroupMember, hybrid_kp: Option<&HybridKeypair>) -> anyhow::Result<Self> {
+        let group = member
+            .group_ref()
+            .map(|g| bincode::serialize(g).context("serialize group"))
+            .transpose()?;
+
+        Ok(Self {
+            identity_seed: *member.identity_seed(),
+            group,
+            hybrid_key: hybrid_kp.map(|kp| kp.to_bytes()),
+            member_keys: Vec::new(),
+        })
+    }
+}
+
+/// Argon2id parameters for client state key derivation (auditable; matches argon2 crate defaults).
+/// - Memory: 19 MiB (m_cost = 19*1024 KiB)
+/// - Time: 2 iterations
+/// - Parallelism: 1 lane
+const ARGON2_STATE_M_COST: u32 = 19 * 1024;
+const ARGON2_STATE_T_COST: u32 = 2;
+const ARGON2_STATE_P_COST: u32 = 1;
+
+/// Derive a 32-byte key from a password and salt using Argon2id with explicit parameters.
+fn derive_state_key(password: &str, salt: &[u8]) -> anyhow::Result<[u8; 32]> {
+    let params = Params::new(ARGON2_STATE_M_COST, ARGON2_STATE_T_COST, ARGON2_STATE_P_COST, Some(32))
+        .map_err(|e| anyhow::anyhow!("argon2 params: {e}"))?;
+    let argon2 = Argon2::new(Algorithm::Argon2id, Version::default(), params);
+    let mut key = [0u8; 32];
+    argon2
+        .hash_password_into(password.as_bytes(), salt, &mut key)
+        .map_err(|e| anyhow::anyhow!("argon2 key derivation failed: {e}"))?;
+    Ok(key)
+}
+
+/// Encrypt `plaintext` with the QPCE format: magic(4) | salt(16) | nonce(12) | ciphertext.
+pub fn encrypt_state(password: &str, plaintext: &[u8]) -> anyhow::Result<Vec<u8>> {
+    let mut salt = [0u8; STATE_SALT_LEN];
+    rand::rngs::OsRng.fill_bytes(&mut salt);
+
+    let mut nonce_bytes = [0u8; STATE_NONCE_LEN];
+    rand::rngs::OsRng.fill_bytes(&mut nonce_bytes);
+
+    let key = zeroize::Zeroizing::new(derive_state_key(password, &salt)?);
+    let cipher = ChaCha20Poly1305::new(Key::from_slice(&*key));
+    let nonce = Nonce::from_slice(&nonce_bytes);
+
+    let ciphertext = cipher
+        .encrypt(nonce, plaintext)
+        .map_err(|e| anyhow::anyhow!("state encryption failed: {e}"))?;
+
+    let mut out = Vec::with_capacity(4 + STATE_SALT_LEN + STATE_NONCE_LEN + ciphertext.len());
+    out.extend_from_slice(STATE_MAGIC);
+    out.extend_from_slice(&salt);
+    out.extend_from_slice(&nonce_bytes);
+    out.extend_from_slice(&ciphertext);
+    Ok(out)
+}
+
+/// Decrypt a QPCE-formatted state file.
+pub fn decrypt_state(password: &str, data: &[u8]) -> anyhow::Result<Vec<u8>> {
+    let header_len = 4 + STATE_SALT_LEN + STATE_NONCE_LEN;
+    anyhow::ensure!(
+        data.len() > header_len,
+        "encrypted state file too short ({} bytes)",
+        data.len()
+    );
+
+    let salt = &data[4..4 + STATE_SALT_LEN];
+    let nonce_bytes = &data[4 + STATE_SALT_LEN..header_len];
+    let ciphertext = &data[header_len..];
+
+    let key = zeroize::Zeroizing::new(derive_state_key(password, salt)?);
+    let cipher = ChaCha20Poly1305::new(Key::from_slice(&*key));
+    let nonce = Nonce::from_slice(nonce_bytes);
+
+    let plaintext = cipher
+        .decrypt(nonce, ciphertext)
+        .map_err(|_| anyhow::anyhow!("state decryption failed (wrong password?)"))?;
+
+    Ok(plaintext)
+}
+
+/// Returns true if raw bytes begin with the QPCE magic header.
+pub fn is_encrypted_state(bytes: &[u8]) -> bool {
+    bytes.len() >= 4 && &bytes[..4] == STATE_MAGIC
+}
+
+pub fn load_or_init_state(path: &Path, password: Option<&str>) -> anyhow::Result<StoredState> {
+    if path.exists() {
+        let mut state = load_existing_state(path, password)?;
+        // Generate hybrid keypair if missing (upgrade from older state).
+        if state.hybrid_key.is_none() {
+            state.hybrid_key = Some(HybridKeypair::generate().to_bytes());
+            write_state(path, &state, password)?;
+        }
+        return Ok(state);
+    }
+
+    let identity = IdentityKeypair::generate();
+    let hybrid_kp = HybridKeypair::generate();
+    let key_store = DiskKeyStore::persistent(keystore_path(path))?;
+    let member = GroupMember::new_with_state(Arc::new(identity), key_store, None, false);
+    let state = StoredState::from_parts(&member, Some(&hybrid_kp))?;
+    write_state(path, &state, password)?;
+    Ok(state)
+}
+
+pub fn load_existing_state(path: &Path, password: Option<&str>) -> anyhow::Result<StoredState> {
+    let bytes = std::fs::read(path).with_context(|| format!("read state file {path:?}"))?;
+
+    if is_encrypted_state(&bytes) {
+        let pw = password
+            .context("state file is encrypted (QPCE); a password is required to decrypt it")?;
+        let plaintext = decrypt_state(pw, &bytes)?;
+        bincode::deserialize(&plaintext).context("decode encrypted state")
+    } else {
+        bincode::deserialize(&bytes).context("decode state")
+    }
+}
+
+pub fn save_state(
+    path: &Path,
+    member: &GroupMember,
+    hybrid_kp: Option<&HybridKeypair>,
+    password: Option<&str>,
+) -> anyhow::Result<()> {
+    let state = StoredState::from_parts(member, hybrid_kp)?;
+    write_state(path, &state, password)
+}
+
+pub fn write_state(path: &Path, state: &StoredState, password: Option<&str>) -> anyhow::Result<()> {
+    if let Some(parent) = path.parent() {
+        std::fs::create_dir_all(parent).with_context(|| format!("create dir {parent:?}"))?;
+    }
+    let plaintext = bincode::serialize(state).context("encode state")?;
+
+    let bytes = if let Some(pw) = password {
+        encrypt_state(pw, &plaintext)?
+    } else {
+        plaintext
+    };
+
+    let tmp = path.with_extension("tmp");
+    std::fs::write(&tmp, bytes).with_context(|| format!("write state temp {tmp:?}"))?;
+    std::fs::rename(&tmp, path).with_context(|| format!("rename state {tmp:?} -> {path:?}"))?;
+    Ok(())
+}
+
+pub fn decode_identity_key(hex_str: &str) -> anyhow::Result<Vec<u8>> {
+    let bytes = super::hex::decode(hex_str)
+        .map_err(|e| anyhow::anyhow!(e))
+        .context("identity key must be hex")?;
+    anyhow::ensure!(bytes.len() == 32, "identity key must be 32 bytes");
+    Ok(bytes)
+}
+
+pub fn keystore_path(state_path: &Path) -> PathBuf {
+    let mut path = state_path.to_path_buf();
+    path.set_extension("ks");
+    path
+}
+
+pub fn sha256(bytes: &[u8]) -> Vec<u8> {
+    use sha2::{Digest, Sha256};
+    Sha256::digest(bytes).to_vec()
+}
+
+#[cfg(test)]
+#[allow(clippy::unwrap_used)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn encrypt_decrypt_roundtrip() {
+        let plaintext = b"test state data";
+        let password = "test-password";
+        let encrypted = encrypt_state(password, plaintext).unwrap();
+        assert!(is_encrypted_state(&encrypted));
+        let decrypted = decrypt_state(password, &encrypted).unwrap();
+        assert_eq!(decrypted, plaintext);
+    }
+
+    #[test]
+    fn wrong_password_fails() {
+        let plaintext = b"test state data";
+        let encrypted = encrypt_state("correct", plaintext).unwrap();
+        assert!(decrypt_state("wrong", &encrypted).is_err());
+    }
+
+    #[test]
+    fn state_encrypt_decrypt_round_trip() {
+        let state = StoredState {
+            identity_seed: [42u8; 32],
+            hybrid_key: None,
+            group: None,
+            member_keys: Vec::new(),
+        };
+        let password = "test-password";
+        let plaintext = bincode::serialize(&state).unwrap();
+        let encrypted = encrypt_state(password, &plaintext).unwrap();
+        let decrypted = decrypt_state(password, &encrypted).unwrap();
+        let recovered: StoredState = bincode::deserialize(&decrypted).unwrap();
+        assert_eq!(recovered.identity_seed, state.identity_seed);
+        assert!(recovered.hybrid_key.is_none());
+        assert!(recovered.group.is_none());
+    }
+
+    #[test]
+    fn state_encrypt_decrypt_with_hybrid_key() {
+        use zeroize::Zeroizing;
+        let state = StoredState {
+            identity_seed: [7u8; 32],
+            hybrid_key: Some(HybridKeypairBytes {
+                x25519_sk: Zeroizing::new([1u8; 32]),
+                mlkem_dk: Zeroizing::new(vec![3u8; 2400]),
+                mlkem_ek: vec![4u8; 1184],
+            }),
+            group: None,
+            member_keys: Vec::new(),
+        };
+        let password = "another-password";
+        let plaintext = bincode::serialize(&state).unwrap();
+        let encrypted = encrypt_state(password, &plaintext).unwrap();
+        let decrypted = decrypt_state(password, &encrypted).unwrap();
+        let recovered: StoredState = bincode::deserialize(&decrypted).unwrap();
+        assert_eq!(recovered.identity_seed, state.identity_seed);
+        assert!(recovered.hybrid_key.is_some());
+    }
+
+    #[test]
+    fn state_wrong_password_fails() {
+        let state = StoredState {
+            identity_seed: [99u8; 32],
+            hybrid_key: None,
+            group: None,
+            member_keys: Vec::new(),
+        };
+        let plaintext = bincode::serialize(&state).unwrap();
+        let encrypted = encrypt_state("correct", &plaintext).unwrap();
+        assert!(decrypt_state("wrong", &encrypted).is_err());
+    }
+}

crates/quicproquo-client/src/client/token_cache.rs

@@ -0,0 +1,179 @@
+//! Cached session token stored next to the state file.
+//!
+//! File format (no password): two lines — username and hex-encoded session token.
+//! File format (with password): QPCE-encrypted version of the above.
+//! The token has a server-side 24h TTL; no client-side expiry tracking.
+
+use std::path::{Path, PathBuf};
+
+use anyhow::Context;
+
+use super::state::{decrypt_state, encrypt_state, is_encrypted_state};
+
+pub struct CachedSession {
+    pub username: String,
+    pub token_hex: String,
+}
+
+/// Derive the session cache path: `{state_path}.session`.
+fn session_cache_path(state_path: &Path) -> PathBuf {
+    state_path.with_extension("session")
+}
+
+/// Parse the two-line format (username + token_hex) from plaintext bytes.
+fn parse_session_lines(text: &str) -> Option<CachedSession> {
+    let mut lines = text.lines();
+    let username = lines.next()?.trim().to_string();
+    let token_hex = lines.next()?.trim().to_string();
+    if username.is_empty() || token_hex.is_empty() {
+        return None;
+    }
+    if hex::decode(&token_hex).is_err() {
+        return None;
+    }
+    Some(CachedSession { username, token_hex })
+}
+
+/// Load a cached session token. Returns None if file is missing or malformed.
+/// Decrypts if the file is QPCE-encrypted (requires `password`).
+pub fn load_cached_session(state_path: &Path, password: Option<&str>) -> Option<CachedSession> {
+    let path = session_cache_path(state_path);
+    let raw = std::fs::read(&path).ok()?;
+
+    if is_encrypted_state(&raw) {
+        let pw = password?;
+        let plaintext = decrypt_state(pw, &raw).ok()?;
+        let text = String::from_utf8(plaintext).ok()?;
+        parse_session_lines(&text)
+    } else {
+        let text = String::from_utf8(raw).ok()?;
+        parse_session_lines(&text)
+    }
+}
+
+/// Save a session token to the cache file (mode 0o600 on Unix).
+/// Encrypts with QPCE if `password` is provided.
+pub fn save_cached_session(
+    state_path: &Path,
+    username: &str,
+    token_hex: &str,
+    password: Option<&str>,
+) -> anyhow::Result<()> {
+    let path = session_cache_path(state_path);
+    let contents = format!("{username}\n{token_hex}\n");
+
+    let bytes = match password {
+        Some(pw) => encrypt_state(pw, contents.as_bytes())?,
+        None => {
+            #[cfg(not(unix))]
+            tracing::warn!(
+                "storing session token as plaintext (no password set); \
+                 file permissions cannot be restricted on this platform"
+            );
+            contents.into_bytes()
+        }
+    };
+
+    std::fs::write(&path, bytes).with_context(|| format!("write session cache {path:?}"))?;
+
+    #[cfg(unix)]
+    {
+        use std::os::unix::fs::PermissionsExt;
+        let perms = std::fs::Permissions::from_mode(0o600);
+        std::fs::set_permissions(&path, perms).ok();
+    }
+
+    Ok(())
+}
+
+/// Remove the cached session file.
+pub fn clear_cached_session(state_path: &Path) {
+    let path = session_cache_path(state_path);
+    std::fs::remove_file(&path).ok();
+}
+
+#[cfg(test)]
+#[allow(clippy::unwrap_used)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn plaintext_round_trip() {
+        let dir = tempfile::tempdir().unwrap();
+        let state_path = dir.path().join("state.bin");
+
+        let token = hex::encode(b"session-token-bytes");
+        save_cached_session(&state_path, "alice", &token, None).unwrap();
+        let loaded = load_cached_session(&state_path, None).unwrap();
+        assert_eq!(loaded.username, "alice");
+        assert_eq!(loaded.token_hex, token);
+    }
+
+    #[test]
+    fn encrypted_round_trip() {
+        let dir = tempfile::tempdir().unwrap();
+        let state_path = dir.path().join("state.bin");
+        let password = "strong-password";
+
+        let token = hex::encode(b"encrypted-token");
+        save_cached_session(&state_path, "bob", &token, Some(password)).unwrap();
+
+        // Encrypted file should start with QPCE magic
+        let raw = std::fs::read(session_cache_path(&state_path)).unwrap();
+        assert_eq!(&raw[..4], b"QPCE");
+
+        let loaded = load_cached_session(&state_path, Some(password)).unwrap();
+        assert_eq!(loaded.username, "bob");
+        assert_eq!(loaded.token_hex, token);
+    }
+
+    #[test]
+    fn wrong_password_returns_none() {
+        let dir = tempfile::tempdir().unwrap();
+        let state_path = dir.path().join("state.bin");
+
+        let token = hex::encode(b"secret-token");
+        save_cached_session(&state_path, "carol", &token, Some("correct")).unwrap();
+        let result = load_cached_session(&state_path, Some("wrong"));
+        assert!(result.is_none());
+    }
+
+    #[test]
+    fn missing_file_returns_none() {
+        let dir = tempfile::tempdir().unwrap();
+        let state_path = dir.path().join("nonexistent.bin");
+        assert!(load_cached_session(&state_path, None).is_none());
+    }
+
+    #[test]
+    fn clear_removes_file() {
+        let dir = tempfile::tempdir().unwrap();
+        let state_path = dir.path().join("state.bin");
+
+        let token = hex::encode(b"to-be-deleted");
+        save_cached_session(&state_path, "dave", &token, None).unwrap();
+        assert!(session_cache_path(&state_path).exists());
+
+        clear_cached_session(&state_path);
+        assert!(!session_cache_path(&state_path).exists());
+    }
+
+    #[test]
+    fn malformed_content_returns_none() {
+        let dir = tempfile::tempdir().unwrap();
+        let state_path = dir.path().join("state.bin");
+        let cache_path = session_cache_path(&state_path);
+
+        // Not valid hex on second line
+        std::fs::write(&cache_path, "alice\nnot-hex-data\n").unwrap();
+        assert!(load_cached_session(&state_path, None).is_none());
+
+        // Only one line
+        std::fs::write(&cache_path, "alice\n").unwrap();
+        assert!(load_cached_session(&state_path, None).is_none());
+
+        // Empty file
+        std::fs::write(&cache_path, "").unwrap();
+        assert!(load_cached_session(&state_path, None).is_none());
+    }
+}

crates/quicproquo-client/src/client/tui/mod.rs

@@ -0,0 +1,807 @@
+//! Full-screen Ratatui TUI for quicproquo.
+//!
+//! Layout:
+//!   ┌──────────────┬──────────────────────────────────────────┐
+//!   │  Channels    │           Messages                       │
+//!   │  (20%)       │           (80%)                          │
+//!   │              │                                          │
+//!   │              ├──────────────────────────────────────────┤
+//!   │              │  Input bar                               │
+//!   └──────────────┴──────────────────────────────────────────┘
+//!
+//! Keyboard:
+//!   Enter        — send message
+//!   Up / Down    — scroll message history
+//!   Tab          — next channel
+//!   Shift+Tab    — prev channel
+//!   Ctrl+C / q   — quit
+
+use std::path::Path;
+use std::sync::Arc;
+use std::time::Duration;
+
+use anyhow::Context;
+use crossterm::{
+    event::{self, DisableMouseCapture, EnableMouseCapture, Event, KeyCode, KeyModifiers},
+    execute,
+    terminal::{disable_raw_mode, enable_raw_mode, EnterAlternateScreen, LeaveAlternateScreen},
+};
+use ratatui::{
+    backend::CrosstermBackend,
+    layout::{Constraint, Direction, Layout, Rect},
+    style::{Color, Modifier, Style},
+    text::{Line, Span},
+    widgets::{Block, Borders, List, ListItem, ListState, Paragraph, Wrap},
+    Frame, Terminal,
+};
+use tokio::sync::mpsc;
+use tokio::time::interval;
+
+use crate::{ClientAuth, init_auth};
+use super::commands::{opaque_login, opaque_register};
+use super::conversation::{now_ms, ConversationId, StoredMessage};
+use super::rpc::{
+    connect_node, enqueue, fetch_hybrid_key, fetch_wait, try_hybrid_decrypt, upload_hybrid_key,
+    upload_key_package,
+};
+use super::session::SessionState;
+use super::state::load_or_init_state;
+use super::token_cache::{load_cached_session, save_cached_session};
+
+use quicproquo_core::{
+    AppMessage, DiskKeyStore, GroupMember, IdentityKeypair, ReceivedMessage,
+    hybrid_encrypt, parse as parse_app_msg, serialize_chat,
+};
+use quicproquo_proto::node_capnp::node_service;
+
+// ── App events ───────────────────────────────────────────────────────────────
+
+/// Events sent from background tasks into the main TUI loop.
+enum TuiEvent {
+    /// A key event from the terminal.
+    Key(event::KeyEvent),
+    /// New messages received from the server (conv_id, sender_short, body).
+    NewMessages(Vec<(ConversationId, String, String)>),
+    /// Tick — redraw periodically even if nothing happened.
+    Tick,
+}
+
+// ── Display message ───────────────────────────────────────────────────────────
+
+#[derive(Clone)]
+struct DisplayMessage {
+    sender: String,
+    body: String,
+    timestamp_ms: u64,
+    is_outgoing: bool,
+}
+
+// ── App state ─────────────────────────────────────────────────────────────────
+
+struct App {
+    /// Channel (conversation) names shown in the sidebar.
+    channel_names: Vec<String>,
+    /// Conversation IDs, parallel to `channel_names`.
+    channel_ids: Vec<ConversationId>,
+    /// Index of the selected channel in the sidebar.
+    selected_channel: usize,
+    /// Messages for the currently active channel.
+    messages: Vec<DisplayMessage>,
+    /// Current input buffer.
+    input: String,
+    /// Scroll offset (0 = bottom).
+    scroll_offset: usize,
+    /// Whether the user has requested quit.
+    should_quit: bool,
+    /// Short identity string for display.
+    identity_short: String,
+}
+
+impl App {
+    fn new(session: &SessionState) -> anyhow::Result<Self> {
+        let convs = session.conv_store.list_conversations()?;
+        let channel_names: Vec<String> = convs.iter().map(|c| c.display_name.clone()).collect();
+        let channel_ids: Vec<ConversationId> = convs.iter().map(|c| c.id.clone()).collect();
+
+        Ok(Self {
+            channel_names,
+            channel_ids,
+            selected_channel: 0,
+            messages: Vec::new(),
+            input: String::new(),
+            scroll_offset: 0,
+            should_quit: false,
+            identity_short: session.identity_short(),
+        })
+    }
+
+    fn active_conv_id(&self) -> Option<&ConversationId> {
+        self.channel_ids.get(self.selected_channel)
+    }
+
+    /// Reload messages for the currently selected channel from the session store.
+    fn reload_messages(&mut self, session: &SessionState) -> anyhow::Result<()> {
+        let conv_id = match self.active_conv_id() {
+            Some(id) => id.clone(),
+            None => {
+                self.messages.clear();
+                return Ok(());
+            }
+        };
+        let stored = session.conv_store.load_recent_messages(&conv_id, 200)?;
+        self.messages = stored
+            .into_iter()
+            .map(|m| {
+                let sender = if m.is_outgoing {
+                    format!("me({})", &self.identity_short)
+                } else if let Some(name) = &m.sender_name {
+                    name.clone()
+                } else {
+                    // Shorten sender key to 8 hex chars.
+                    let hex_short = hex::encode(&m.sender_key[..m.sender_key.len().min(4)]);
+                    format!("{hex_short}")
+                };
+                DisplayMessage {
+                    sender,
+                    body: m.body,
+                    timestamp_ms: m.timestamp_ms,
+                    is_outgoing: m.is_outgoing,
+                }
+            })
+            .collect();
+        // Reset scroll to bottom on channel switch.
+        self.scroll_offset = 0;
+        Ok(())
+    }
+
+    fn select_next_channel(&mut self, session: &SessionState) {
+        if self.channel_names.is_empty() {
+            return;
+        }
+        self.selected_channel = (self.selected_channel + 1) % self.channel_names.len();
+        let _ = self.reload_messages(session);
+    }
+
+    fn select_prev_channel(&mut self, session: &SessionState) {
+        if self.channel_names.is_empty() {
+            return;
+        }
+        if self.selected_channel == 0 {
+            self.selected_channel = self.channel_names.len() - 1;
+        } else {
+            self.selected_channel -= 1;
+        }
+        let _ = self.reload_messages(session);
+    }
+
+    fn scroll_up(&mut self) {
+        self.scroll_offset = self.scroll_offset.saturating_add(1);
+    }
+
+    fn scroll_down(&mut self) {
+        self.scroll_offset = self.scroll_offset.saturating_sub(1);
+    }
+
+    /// Append newly received messages to the in-memory list (no DB reload needed
+    /// since we already have them from the poll task, but we also save them via
+    /// the session so they appear on reload).
+    fn append_messages(&mut self, msgs: Vec<(ConversationId, String, String)>) {
+        let active = self.active_conv_id().cloned();
+        for (conv_id, sender, body) in msgs {
+            if active.as_ref() == Some(&conv_id) {
+                self.messages.push(DisplayMessage {
+                    sender,
+                    body,
+                    timestamp_ms: now_ms(),
+                    is_outgoing: false,
+                });
+                // Snap to bottom if user wasn't scrolled.
+                if self.scroll_offset == 0 {
+                    // Already at bottom — nothing to do.
+                }
+            }
+        }
+    }
+}
+
+// ── Drawing ───────────────────────────────────────────────────────────────────
+
+fn ui(frame: &mut Frame, app: &App) {
+    let size = frame.area();
+
+    // Top-level split: sidebar | main area.
+    let h_chunks = Layout::default()
+        .direction(Direction::Horizontal)
+        .constraints([Constraint::Percentage(20), Constraint::Percentage(80)])
+        .split(size);
+
+    // Main area split: messages | input bar.
+    let v_chunks = Layout::default()
+        .direction(Direction::Vertical)
+        .constraints([Constraint::Min(3), Constraint::Length(3)])
+        .split(h_chunks[1]);
+
+    draw_sidebar(frame, app, h_chunks[0]);
+    draw_messages(frame, app, v_chunks[0]);
+    draw_input(frame, app, v_chunks[1]);
+}
+
+fn draw_sidebar(frame: &mut Frame, app: &App, area: Rect) {
+    let items: Vec<ListItem> = app
+        .channel_names
+        .iter()
+        .enumerate()
+        .map(|(i, name)| {
+            let style = if i == app.selected_channel {
+                Style::default()
+                    .fg(Color::Cyan)
+                    .add_modifier(Modifier::BOLD | Modifier::REVERSED)
+            } else {
+                Style::default().fg(Color::Cyan)
+            };
+            ListItem::new(Line::from(Span::styled(name.clone(), style)))
+        })
+        .collect();
+
+    let block = Block::default()
+        .title(" Channels ")
+        .borders(Borders::ALL)
+        .style(Style::default().fg(Color::DarkGray));
+
+    let mut list_state = ListState::default();
+    if !app.channel_names.is_empty() {
+        list_state.select(Some(app.selected_channel));
+    }
+
+    frame.render_stateful_widget(
+        List::new(items).block(block),
+        area,
+        &mut list_state,
+    );
+}
+
+fn draw_messages(frame: &mut Frame, app: &App, area: Rect) {
+    let channel_title = app
+        .channel_names
+        .get(app.selected_channel)
+        .map(|n| format!(" {n} "))
+        .unwrap_or_else(|| " Messages ".to_string());
+
+    let block = Block::default()
+        .title(channel_title)
+        .borders(Borders::ALL)
+        .style(Style::default().fg(Color::DarkGray));
+
+    let inner_height = area.height.saturating_sub(2) as usize;
+
+    // Build lines from messages (newest at bottom).
+    let mut lines: Vec<Line> = app
+        .messages
+        .iter()
+        .map(|m| {
+            let ts = format_timestamp(m.timestamp_ms);
+            let ts_span = Span::styled(ts, Style::default().fg(Color::DarkGray));
+
+            let sender_style = if m.is_outgoing {
+                Style::default().fg(Color::Yellow).add_modifier(Modifier::BOLD)
+            } else {
+                Style::default().fg(Color::Green).add_modifier(Modifier::BOLD)
+            };
+            let sender_span = Span::styled(format!(" {} ", m.sender), sender_style);
+            let body_span = Span::raw(m.body.clone());
+
+            Line::from(vec![ts_span, sender_span, body_span])
+        })
+        .collect();
+
+    // Apply scroll: scroll_offset=0 means newest at bottom.
+    let total = lines.len();
+    let visible_start = if total > inner_height {
+        let bottom = total - app.scroll_offset.min(total);
+        bottom.saturating_sub(inner_height)
+    } else {
+        0
+    };
+    let visible_end = if total > inner_height {
+        total - app.scroll_offset.min(total)
+    } else {
+        total
+    };
+    let visible_lines: Vec<Line> = lines
+        .drain(visible_start..visible_end.min(lines.len()))
+        .collect();
+
+    let paragraph = Paragraph::new(visible_lines)
+        .block(block)
+        .wrap(Wrap { trim: false });
+
+    frame.render_widget(paragraph, area);
+}
+
+fn draw_input(frame: &mut Frame, app: &App, area: Rect) {
+    let block = Block::default()
+        .title(" Input (Enter=send, Tab=switch channel, q/Ctrl+C=quit) ")
+        .borders(Borders::ALL)
+        .style(Style::default().fg(Color::DarkGray));
+
+    let input_text = Paragraph::new(app.input.as_str())
+        .block(block)
+        .style(Style::default().fg(Color::White));
+
+    frame.render_widget(input_text, area);
+
+    // Position cursor at end of input.
+    let cursor_x = area.x + 1 + app.input.len() as u16;
+    let cursor_y = area.y + 1;
+    if cursor_x < area.x + area.width - 1 {
+        frame.set_cursor_position((cursor_x, cursor_y));
+    }
+}
+
+fn format_timestamp(ms: u64) -> String {
+    // Simple HH:MM format from epoch ms.
+    let secs = ms / 1000;
+    let hours = (secs / 3600) % 24;
+    let minutes = (secs / 60) % 60;
+    format!("[{:02}:{:02}] ", hours, minutes)
+}
+
+// ── Message polling task ──────────────────────────────────────────────────────
+
+/// Background task that polls the server for new messages and sends them via `tx`.
+async fn poll_task(
+    mut session: SessionState,
+    client: node_service::Client,
+    tx: mpsc::Sender<TuiEvent>,
+) {
+    let mut poll_interval = interval(Duration::from_millis(1000));
+    poll_interval.set_missed_tick_behavior(tokio::time::MissedTickBehavior::Skip);
+
+    loop {
+        poll_interval.tick().await;
+
+        let identity_bytes = session.identity_bytes();
+        let payloads = match fetch_wait(&client, &identity_bytes, 0).await {
+            Ok(p) => p,
+            Err(_) => continue,
+        };
+
+        if payloads.is_empty() {
+            continue;
+        }
+
+        let mut new_msgs: Vec<(ConversationId, String, String)> = Vec::new();
+        let my_key = session.identity_bytes();
+
+        let mut sorted = payloads;
+        sorted.sort_by_key(|(seq, _)| *seq);
+
+        for (_seq, payload) in &sorted {
+            let mls_payload = match try_hybrid_decrypt(session.hybrid_kp.as_ref(), payload) {
+                Ok(b) => b,
+                Err(_) => payload.clone(),
+            };
+
+            let conv_ids: Vec<ConversationId> = session.members.keys().cloned().collect();
+
+            for conv_id in &conv_ids {
+                let member = match session.members.get_mut(conv_id) {
+                    Some(m) => m,
+                    None => continue,
+                };
+
+                match member.receive_message(&mls_payload) {
+                    Ok(ReceivedMessage::Application(plaintext)) => {
+                        let (sender_key, app_bytes) = {
+                            let after_unpad = quicproquo_core::padding::unpad(&plaintext)
+                                .unwrap_or_else(|_| plaintext.clone());
+
+                            if quicproquo_core::sealed_sender::is_sealed(&after_unpad) {
+                                match quicproquo_core::sealed_sender::unseal(&after_unpad) {
+                                    Ok((sk, inner)) => (sk.to_vec(), inner),
+                                    Err(_) => (my_key.clone(), after_unpad),
+                                }
+                            } else {
+                                (my_key.clone(), after_unpad)
+                            }
+                        };
+
+                        let (body, msg_id, msg_type, ref_msg_id) =
+                            match parse_app_msg(&app_bytes) {
+                                Ok((_, AppMessage::Chat { message_id, body })) => (
+                                    String::from_utf8_lossy(&body).to_string(),
+                                    Some(message_id),
+                                    "chat",
+                                    None,
+                                ),
+                                Ok((_, AppMessage::Reply { ref_msg_id, body })) => (
+                                    String::from_utf8_lossy(&body).to_string(),
+                                    None,
+                                    "reply",
+                                    Some(ref_msg_id),
+                                ),
+                                Ok((_, AppMessage::Reaction { ref_msg_id, emoji })) => (
+                                    String::from_utf8_lossy(&emoji).to_string(),
+                                    None,
+                                    "reaction",
+                                    Some(ref_msg_id),
+                                ),
+                                _ => (
+                                    String::from_utf8_lossy(&app_bytes).to_string(),
+                                    None,
+                                    "chat",
+                                    None,
+                                ),
+                            };
+
+                        let stored = StoredMessage {
+                            conversation_id: conv_id.clone(),
+                            message_id: msg_id,
+                            sender_key: sender_key.clone(),
+                            sender_name: None,
+                            body: body.clone(),
+                            msg_type: msg_type.into(),
+                            ref_msg_id,
+                            timestamp_ms: now_ms(),
+                            is_outgoing: false,
+                        };
+
+                        if session.conv_store.save_message(&stored).is_ok() {
+                            let sender_short = hex::encode(&sender_key[..sender_key.len().min(4)]);
+                            new_msgs.push((conv_id.clone(), sender_short, body));
+                        }
+
+                        let _ = session.conv_store.update_activity(conv_id, now_ms());
+                        let _ = session.save_member(conv_id);
+                        break;
+                    }
+                    Ok(ReceivedMessage::StateChanged) | Ok(ReceivedMessage::SelfRemoved) => {
+                        let _ = session.save_member(conv_id);
+                        break;
+                    }
+                    _ => {}
+                }
+            }
+        }
+
+        if !new_msgs.is_empty() {
+            if tx.send(TuiEvent::NewMessages(new_msgs)).await.is_err() {
+                break;
+            }
+        }
+    }
+}
+
+// ── Send message ──────────────────────────────────────────────────────────────
+
+async fn send_message(
+    session: &mut SessionState,
+    client: &node_service::Client,
+    conv_id: &ConversationId,
+    text: &str,
+) -> anyhow::Result<()> {
+    let my_key = session.identity_bytes();
+    let identity = Arc::clone(&session.identity);
+
+    let member = session
+        .members
+        .get_mut(conv_id)
+        .context("no GroupMember for this conversation")?;
+
+    // Wrap in structured AppMessage format.
+    let app_payload = serialize_chat(text.as_bytes(), None)
+        .context("serialize app message")?;
+
+    // Metadata protection: seal + pad.
+    let sealed = quicproquo_core::sealed_sender::seal(&identity, &app_payload);
+    let padded = quicproquo_core::padding::pad(&sealed);
+
+    let ct = member.send_message(&padded).context("MLS encrypt")?;
+
+    let recipients: Vec<Vec<u8>> = member
+        .member_identities()
+        .into_iter()
+        .filter(|id| id.as_slice() != my_key.as_slice())
+        .collect();
+
+    for recipient_key in &recipients {
+        let peer_hybrid_pk = fetch_hybrid_key(client, recipient_key).await?;
+        let payload = if let Some(ref pk) = peer_hybrid_pk {
+            hybrid_encrypt(pk, &ct, b"", b"").context("hybrid encrypt")?
+        } else {
+            ct.clone()
+        };
+        enqueue(client, recipient_key, &payload).await?;
+    }
+
+    // Extract message_id from what we just serialized.
+    let msg_id = parse_app_msg(&app_payload)
+        .ok()
+        .and_then(|(_, m)| match m {
+            AppMessage::Chat { message_id, .. } => Some(message_id),
+            _ => None,
+        });
+
+    // Save outgoing message.
+    let stored = StoredMessage {
+        conversation_id: conv_id.clone(),
+        message_id: msg_id,
+        sender_key: my_key,
+        sender_name: Some("you".into()),
+        body: text.to_string(),
+        msg_type: "chat".into(),
+        ref_msg_id: None,
+        timestamp_ms: now_ms(),
+        is_outgoing: true,
+    };
+    session.conv_store.save_message(&stored)?;
+    session.conv_store.update_activity(conv_id, now_ms())?;
+    session.save_member(conv_id)?;
+
+    Ok(())
+}
+
+// ── TUI entry point ───────────────────────────────────────────────────────────
+
+/// Entry point for `qpq tui`. Sets up the terminal, runs the event loop, and
+/// restores the terminal on exit.
+pub async fn run_tui(
+    state_path: &Path,
+    server: &str,
+    ca_cert: &Path,
+    server_name: &str,
+    password: Option<&str>,
+    username: Option<&str>,
+    opaque_password: Option<&str>,
+    access_token: &str,
+    device_id: Option<&str>,
+) -> anyhow::Result<()> {
+    // ── Auth ──────────────────────────────────────────────────────────────────
+    let resolved_token = resolve_tui_access_token(
+        state_path,
+        server,
+        ca_cert,
+        server_name,
+        password,
+        username,
+        opaque_password,
+        access_token,
+    )
+    .await?;
+
+    let token_bytes = hex::decode(&resolved_token)
+        .unwrap_or_else(|_| resolved_token.into_bytes());
+    let auth_ctx = ClientAuth::from_raw(token_bytes, device_id.map(String::from));
+    init_auth(auth_ctx);
+
+    // ── Session + RPC ─────────────────────────────────────────────────────────
+    let mut session = SessionState::load(state_path, password)?;
+    let client = connect_node(server, ca_cert, server_name).await?;
+
+    // Auto-upload KeyPackage.
+    let _ = auto_upload_keys_tui(&session, &client).await;
+
+    // ── Terminal setup ────────────────────────────────────────────────────────
+    enable_raw_mode().context("enable raw mode")?;
+    let mut stdout = std::io::stdout();
+    execute!(stdout, EnterAlternateScreen, EnableMouseCapture)
+        .context("enter alternate screen")?;
+    let backend = CrosstermBackend::new(stdout);
+    let mut terminal = Terminal::new(backend).context("create terminal")?;
+
+    let result = tui_loop(&mut terminal, &mut session, client).await;
+
+    // ── Terminal cleanup (always restore, even on error) ───────────────────
+    disable_raw_mode().ok();
+    execute!(
+        terminal.backend_mut(),
+        LeaveAlternateScreen,
+        DisableMouseCapture
+    )
+    .ok();
+    terminal.show_cursor().ok();
+
+    session.save_all()?;
+
+    result
+}
+
+async fn tui_loop(
+    terminal: &mut Terminal<CrosstermBackend<std::io::Stdout>>,
+    session: &mut SessionState,
+    client: node_service::Client,
+) -> anyhow::Result<()> {
+    let mut app = App::new(session)?;
+    app.reload_messages(session)?;
+
+    let (event_tx, mut event_rx) = mpsc::channel::<TuiEvent>(256);
+
+    // ── Keyboard event task ───────────────────────────────────────────────────
+    let key_tx = event_tx.clone();
+    tokio::task::spawn_local(async move {
+        loop {
+            // crossterm event polling — 50ms timeout so we can tick.
+            match event::poll(Duration::from_millis(50)) {
+                Ok(true) => {
+                    if let Ok(Event::Key(key)) = event::read() {
+                        if key_tx.send(TuiEvent::Key(key)).await.is_err() {
+                            break;
+                        }
+                    }
+                }
+                Ok(false) => {
+                    // No event — send a tick so the UI redraws.
+                    if key_tx.send(TuiEvent::Tick).await.is_err() {
+                        break;
+                    }
+                }
+                Err(_) => break,
+            }
+        }
+    });
+
+    // ── Message poll task ─────────────────────────────────────────────────────
+    // Clone session state for the poll task (it needs its own SessionState).
+    let poll_session = SessionState::load(
+        &session.state_path.clone(),
+        session.password.as_ref().map(|p| p.as_str()),
+    )?;
+    let poll_tx = event_tx.clone();
+    tokio::task::spawn_local(poll_task(poll_session, client.clone(), poll_tx));
+
+    // ── Main loop ─────────────────────────────────────────────────────────────
+    loop {
+        terminal.draw(|f| ui(f, &app)).context("draw")?;
+
+        match event_rx.recv().await {
+            None => break,
+            Some(TuiEvent::Tick) => {
+                // Just redraw.
+            }
+            Some(TuiEvent::NewMessages(msgs)) => {
+                app.append_messages(msgs);
+            }
+            Some(TuiEvent::Key(key)) => {
+                match key.code {
+                    KeyCode::Char('c') if key.modifiers.contains(KeyModifiers::CONTROL) => {
+                        app.should_quit = true;
+                    }
+                    KeyCode::Char('q') if app.input.is_empty() => {
+                        app.should_quit = true;
+                    }
+                    KeyCode::Enter => {
+                        let text = app.input.trim().to_string();
+                        if !text.is_empty() {
+                            app.input.clear();
+                            if let Some(conv_id) = app.active_conv_id().cloned() {
+                                match send_message(session, &client, &conv_id, &text).await {
+                                    Ok(()) => {
+                                        // Add to in-memory list immediately.
+                                        app.messages.push(DisplayMessage {
+                                            sender: format!("me({})", app.identity_short),
+                                            body: text,
+                                            timestamp_ms: now_ms(),
+                                            is_outgoing: true,
+                                        });
+                                    }
+                                    Err(_e) => {
+                                        // Silently drop — user will see nothing happened.
+                                    }
+                                }
+                            }
+                        }
+                    }
+                    KeyCode::Char(c) => {
+                        app.input.push(c);
+                    }
+                    KeyCode::Backspace => {
+                        app.input.pop();
+                    }
+                    KeyCode::Up => {
+                        app.scroll_up();
+                    }
+                    KeyCode::Down => {
+                        app.scroll_down();
+                    }
+                    KeyCode::Tab => {
+                        if key.modifiers.contains(KeyModifiers::SHIFT) {
+                            app.select_prev_channel(session);
+                        } else {
+                            app.select_next_channel(session);
+                        }
+                        app.reload_messages(session)?;
+                    }
+                    _ => {}
+                }
+            }
+        }
+
+        if app.should_quit {
+            break;
+        }
+    }
+
+    Ok(())
+}
+
+// ── Startup helpers ───────────────────────────────────────────────────────────
+
+async fn auto_upload_keys_tui(
+    session: &SessionState,
+    client: &node_service::Client,
+) -> anyhow::Result<()> {
+    let ks_path = session.state_path.with_extension("pending.ks");
+    let ks = DiskKeyStore::persistent(&ks_path).unwrap_or_else(|_| DiskKeyStore::ephemeral());
+    let mut member = GroupMember::new_with_state(
+        Arc::clone(&session.identity),
+        ks,
+        None,
+        false,
+    );
+    let kp_bytes = member.generate_key_package().context("generate KeyPackage")?;
+    let id_key = session.identity.public_key_bytes();
+    upload_key_package(client, &id_key, &kp_bytes).await?;
+    if let Some(ref hkp) = session.hybrid_kp {
+        upload_hybrid_key(client, &id_key, &hkp.public_key()).await?;
+    }
+    Ok(())
+}
+
+async fn resolve_tui_access_token(
+    state_path: &Path,
+    server: &str,
+    ca_cert: &Path,
+    server_name: &str,
+    state_password: Option<&str>,
+    username: Option<&str>,
+    opaque_password: Option<&str>,
+    cli_access_token: &str,
+) -> anyhow::Result<String> {
+    if !cli_access_token.is_empty() {
+        return Ok(cli_access_token.to_string());
+    }
+
+    if let Some(cached) = load_cached_session(state_path, state_password) {
+        return Ok(cached.token_hex);
+    }
+
+    let username = match username {
+        Some(u) => u.to_string(),
+        None => {
+            use std::io::Write;
+            eprint!("Username: ");
+            std::io::stderr().flush().ok();
+            let mut input = String::new();
+            std::io::stdin()
+                .read_line(&mut input)
+                .context("failed to read username")?;
+            let trimmed = input.trim().to_string();
+            anyhow::ensure!(!trimmed.is_empty(), "username is required");
+            trimmed
+        }
+    };
+
+    let opaque_password = match opaque_password {
+        Some(p) => p.to_string(),
+        None => rpassword::read_password().context("failed to read password")?,
+    };
+
+    let state = load_or_init_state(state_path, state_password)?;
+    let identity = IdentityKeypair::from_seed(state.identity_seed);
+    let identity_key = identity.public_key_bytes().to_vec();
+
+    let node_client = connect_node(server, ca_cert, server_name).await?;
+
+    match opaque_register(&node_client, &username, &opaque_password, Some(&identity_key)).await {
+        Ok(()) | Err(_) => {}
+    }
+
+    let token_bytes = opaque_login(&node_client, &username, &opaque_password, &identity_key)
+        .await
+        .context("OPAQUE login failed")?;
+    let token_hex = hex::encode(&token_bytes);
+
+    save_cached_session(state_path, &username, &token_hex, state_password)?;
+
+    Ok(token_hex)
+}

crates/quicproquo-client/src/lib.rs

@@ -0,0 +1,177 @@
+//! quicproquo CLI client library.
+//!
+//! # KeyPackage expiry and refresh
+//!
+//! KeyPackages are single-use (consumed when someone fetches them for an invite) and the server
+//! may enforce a TTL (e.g. 24 hours). To stay invitable, run `qpq refresh-keypackage`
+//! periodically (e.g. before the server TTL) or after your KeyPackage was consumed:
+//!
+//! ```bash
+//! qpq refresh-keypackage --state qpq-state.bin --server 127.0.0.1:7000
+//! ```
+//!
+//! Use the same `--access-token` (or `QPQ_ACCESS_TOKEN`) as for other authenticated
+//! commands. See the [running-the-client](https://docs.quicproquo.dev/getting-started/running-the-client)
+//! docs for details.
+
+use std::sync::RwLock;
+use std::sync::atomic::{AtomicBool, Ordering};
+
+use zeroize::Zeroizing;
+
+pub mod client;
+#[cfg(feature = "v2")]
+pub mod v2_commands;
+
+pub use client::commands::{
+    cmd_chat, cmd_check_key, cmd_create_group, cmd_demo_group, cmd_export, cmd_export_verify,
+    cmd_fetch_key, cmd_health, cmd_health_json, cmd_invite, cmd_join, cmd_login, cmd_ping,
+    cmd_recv, cmd_register, cmd_register_state, cmd_refresh_keypackage, cmd_register_user,
+    cmd_send, cmd_whoami, opaque_login, receive_pending_plaintexts, whoami_json,
+};
+
+pub use client::command_engine::{Command, CommandRegistry, CommandResult};
+#[cfg(feature = "playbook")]
+pub use client::playbook::{Playbook, PlaybookReport, PlaybookRunner};
+pub use client::repl::run_repl;
+pub use client::rpc::{connect_node, connect_node_opt, create_channel, enqueue, fetch_wait, resolve_user};
+
+// ── ClientContext: structured holder for session-scoped auth + TLS config ────
+
+/// Holds the authentication credentials and TLS policy for a client session.
+///
+/// Prefer constructing a `ClientContext` and passing it explicitly where
+/// possible. The global `AUTH_CONTEXT` / `INSECURE_SKIP_VERIFY` statics
+/// delegate to a `ClientContext` under the hood and exist only for backward
+/// compatibility with call-sites that have not yet been migrated.
+pub struct ClientContext {
+    auth: RwLock<Option<ClientAuth>>,
+    insecure_skip_verify: AtomicBool,
+}
+
+impl ClientContext {
+    /// Create a new context with no auth and TLS verification enabled.
+    pub fn new() -> Self {
+        Self {
+            auth: RwLock::new(None),
+            insecure_skip_verify: AtomicBool::new(false),
+        }
+    }
+
+    /// Create a context pre-loaded with auth credentials.
+    pub fn with_auth(auth: ClientAuth) -> Self {
+        Self {
+            auth: RwLock::new(Some(auth)),
+            insecure_skip_verify: AtomicBool::new(false),
+        }
+    }
+
+    /// Set (or replace) the auth credentials.
+    ///
+    /// # Panics
+    /// Panics if the RwLock is poisoned (a thread panicked while holding it).
+    /// A poisoned lock indicates unrecoverable state corruption.
+    #[allow(clippy::expect_used)]
+    pub fn set_auth(&self, ctx: ClientAuth) {
+        let mut guard = self.auth.write().expect("ClientContext auth lock poisoned");
+        *guard = Some(ctx);
+    }
+
+    /// Read the current auth snapshot (cloned).
+    ///
+    /// # Panics
+    /// Panics if the RwLock is poisoned (a thread panicked while holding it).
+    /// A poisoned lock indicates unrecoverable state corruption.
+    #[allow(clippy::expect_used)]
+    pub fn get_auth(&self) -> Option<ClientAuth> {
+        let guard = self.auth.read().expect("ClientContext auth lock poisoned");
+        guard.clone()
+    }
+
+    /// Returns true if auth credentials have been set.
+    ///
+    /// # Panics
+    /// Panics if the RwLock is poisoned (a thread panicked while holding it).
+    /// A poisoned lock indicates unrecoverable state corruption.
+    #[allow(clippy::expect_used)]
+    pub fn is_authenticated(&self) -> bool {
+        let guard = self.auth.read().expect("ClientContext auth lock poisoned");
+        guard.is_some()
+    }
+
+    /// Enable or disable insecure TLS mode.
+    pub fn set_insecure_skip_verify(&self, enabled: bool) {
+        self.insecure_skip_verify.store(enabled, Ordering::Relaxed);
+    }
+
+    /// Read the current insecure-skip-verify flag.
+    pub fn insecure_skip_verify(&self) -> bool {
+        self.insecure_skip_verify.load(Ordering::Relaxed)
+    }
+}
+
+impl Default for ClientContext {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+// ── Global statics (thin wrappers, kept for backward compat) ─────────────────
+
+/// Global auth context — delegates to a process-wide `ClientContext`.
+/// Prefer passing `&ClientContext` explicitly in new code.
+pub(crate) static AUTH_CONTEXT: RwLock<Option<ClientAuth>> = RwLock::new(None);
+
+/// When `true`, [`connect_node`] skips TLS certificate verification.
+/// Prefer `ClientContext::set_insecure_skip_verify` in new code.
+pub(crate) static INSECURE_SKIP_VERIFY: AtomicBool = AtomicBool::new(false);
+
+/// Enable or disable insecure (no-verify) TLS mode globally.
+///
+/// **Development only.** When enabled, all outgoing connections skip certificate
+/// verification, making them vulnerable to MITM attacks.
+pub fn set_insecure_skip_verify(enabled: bool) {
+    INSECURE_SKIP_VERIFY.store(enabled, Ordering::Relaxed);
+}
+
+#[derive(Clone, Debug)]
+pub struct ClientAuth {
+    pub(crate) version: u16,
+    /// Bearer or OPAQUE session token. Zeroized on drop. (M8)
+    pub(crate) access_token: Zeroizing<Vec<u8>>,
+    pub(crate) device_id: Vec<u8>,
+}
+
+impl ClientAuth {
+    /// Build a client auth context from optional token and device id.
+    pub fn from_parts(access_token: String, device_id: Option<String>) -> Self {
+        let token = access_token.into_bytes();
+        let device = device_id.unwrap_or_default().into_bytes();
+        Self {
+            version: 1,
+            access_token: Zeroizing::new(token),
+            device_id: device,
+        }
+    }
+
+    /// Build from raw token bytes (e.g. a 32-byte OPAQUE session token).
+    pub fn from_raw(raw_token: Vec<u8>, device_id: Option<String>) -> Self {
+        let device = device_id.unwrap_or_default().into_bytes();
+        Self {
+            version: 1,
+            access_token: Zeroizing::new(raw_token),
+            device_id: device,
+        }
+    }
+}
+
+/// Set (or replace) the global auth context.
+///
+/// # Panics
+/// Panics if the RwLock is poisoned (a thread panicked while holding it).
+/// A poisoned lock indicates unrecoverable state corruption.
+#[allow(clippy::expect_used)]
+pub fn init_auth(ctx: ClientAuth) {
+    let mut guard = AUTH_CONTEXT.write().expect("AUTH_CONTEXT poisoned");
+    *guard = Some(ctx);
+}

crates/quicproquo-client/src/main.rs

@@ -0,0 +1,883 @@
+//! quicproquo CLI client.
+
+// ── v2 feature gate: when compiled with --features v2, use the SDK-based CLI.
+#[cfg(feature = "v2")]
+mod v2_commands;
+#[cfg(feature = "v2")]
+mod v2_main;
+
+#[cfg(feature = "v2")]
+fn main() {
+    v2_main::main();
+}
+
+// ── v1 CLI (default) ─────────────────────────────────────────────────────────
+#[cfg(not(feature = "v2"))]
+use std::path::{Path, PathBuf};
+#[cfg(not(feature = "v2"))]
+use anyhow::Context;
+#[cfg(not(feature = "v2"))]
+use clap::{Parser, Subcommand};
+#[cfg(not(feature = "v2"))]
+use quicproquo_client::{
+    cmd_chat, cmd_check_key, cmd_create_group, cmd_demo_group, cmd_export, cmd_export_verify,
+    cmd_fetch_key, cmd_health, cmd_invite, cmd_join, cmd_login, cmd_ping, cmd_recv, cmd_register,
+    cmd_register_state, cmd_refresh_keypackage, cmd_register_user, cmd_send, cmd_whoami,
+    init_auth, run_repl, set_insecure_skip_verify, ClientAuth,
+};
+#[cfg(all(feature = "tui", not(feature = "v2")))]
+use quicproquo_client::client::tui::run_tui;
+
+// ── CLI ───────────────────────────────────────────────────────────────────────
+#[cfg(not(feature = "v2"))]
+
+#[derive(Debug, Parser)]
+#[command(name = "qpq", about = "quicproquo CLI client", version)]
+struct Args {
+    /// Path to the server's TLS certificate (self-signed by default).
+    #[arg(
+        long,
+        global = true,
+        default_value = "data/server-cert.der",
+        env = "QPQ_CA_CERT"
+    )]
+    ca_cert: PathBuf,
+
+    /// Expected TLS server name (must match the certificate SAN).
+    #[arg(
+        long,
+        global = true,
+        default_value = "localhost",
+        env = "QPQ_SERVER_NAME"
+    )]
+    server_name: String,
+
+    /// Bearer token or OPAQUE session token for authenticated requests.
+    /// Not required for register-user and login commands.
+    #[arg(
+        long,
+        global = true,
+        env = "QPQ_ACCESS_TOKEN",
+        default_value = ""
+    )]
+    access_token: String,
+
+    /// Optional device identifier (UUID bytes encoded as hex or raw string).
+    #[arg(long, global = true, env = "QPQ_DEVICE_ID")]
+    device_id: Option<String>,
+
+    /// Password to encrypt/decrypt client state files (QPCE format).
+    /// If set, state files are encrypted at rest with Argon2id + ChaCha20Poly1305.
+    #[arg(long, global = true, env = "QPQ_STATE_PASSWORD")]
+    state_password: Option<String>,
+
+    /// DANGER: Skip TLS certificate verification. Development only.
+    /// Disables all certificate checks, making the connection vulnerable to MITM attacks.
+    #[arg(
+        long = "danger-accept-invalid-certs",
+        global = true,
+        env = "QPQ_DANGER_ACCEPT_INVALID_CERTS"
+    )]
+    danger_accept_invalid_certs: bool,
+
+    // ── Default-repl args (used when no subcommand is given) ─────────
+    /// State file path (identity + MLS state). Used when running the default REPL.
+    #[arg(long, default_value = "qpq-state.bin", env = "QPQ_STATE")]
+    state: PathBuf,
+
+    /// Server address (host:port). Used when running the default REPL.
+    #[arg(long, default_value = "127.0.0.1:7000", env = "QPQ_SERVER")]
+    server: String,
+
+    /// OPAQUE username for automatic registration/login.
+    #[arg(long, env = "QPQ_USERNAME")]
+    username: Option<String>,
+
+    /// OPAQUE password (prompted securely if --username is set but --password is not).
+    #[arg(long, env = "QPQ_PASSWORD")]
+    password: Option<String>,
+
+    /// Do not auto-start a local qpq-server (useful when connecting to a remote server).
+    #[arg(long, env = "QPQ_NO_SERVER")]
+    no_server: bool,
+
+    #[command(subcommand)]
+    command: Option<Command>,
+}
+
+#[cfg(not(feature = "v2"))]
+#[derive(Debug, Subcommand)]
+enum Command {
+    /// Register a new user via OPAQUE (password never leaves the client).
+    RegisterUser {
+        #[arg(long, default_value = "127.0.0.1:7000", env = "QPQ_SERVER")]
+        server: String,
+        /// Username for the new account.
+        #[arg(long)]
+        username: String,
+        /// Password (will be used in OPAQUE PAKE; server never sees it).
+        #[arg(long)]
+        password: String,
+    },
+
+    /// Log in via OPAQUE and receive a session token.
+    Login {
+        #[arg(long, default_value = "127.0.0.1:7000", env = "QPQ_SERVER")]
+        server: String,
+        #[arg(long)]
+        username: String,
+        #[arg(long)]
+        password: String,
+        /// Hex-encoded Ed25519 identity key (64 hex chars). Optional if --state is provided.
+        #[arg(long)]
+        identity_key: Option<String>,
+        /// State file to derive the identity key (requires same password if encrypted).
+        #[arg(long)]
+        state: Option<PathBuf>,
+        /// Password for the encrypted state file (if any).
+        #[arg(long)]
+        state_password: Option<String>,
+    },
+
+    /// Show local identity key, fingerprint, group status, and hybrid key status.
+    Whoami {
+        /// State file path (identity + MLS state).
+        #[arg(
+            long,
+            default_value = "qpq-state.bin",
+            env = "QPQ_STATE"
+        )]
+        state: PathBuf,
+    },
+
+    /// Check server connectivity and print status.
+    Health {
+        /// Server address (host:port).
+        #[arg(long, default_value = "127.0.0.1:7000", env = "QPQ_SERVER")]
+        server: String,
+    },
+
+    /// Check if a peer has registered a hybrid key (non-consuming lookup).
+    CheckKey {
+        /// Server address (host:port).
+        #[arg(long, default_value = "127.0.0.1:7000", env = "QPQ_SERVER")]
+        server: String,
+
+        /// Peer's Ed25519 identity public key (64 hex chars = 32 bytes).
+        identity_key: String,
+    },
+
+    /// Send a Ping to the server and print the round-trip time.
+    Ping {
+        /// Server address (host:port).
+        #[arg(long, default_value = "127.0.0.1:7000", env = "QPQ_SERVER")]
+        server: String,
+    },
+
+    /// Generate a fresh MLS KeyPackage and upload it to the Authentication Service.
+    Register {
+        /// Server address (host:port).
+        #[arg(long, default_value = "127.0.0.1:7000", env = "QPQ_SERVER")]
+        server: String,
+    },
+
+    /// Fetch a peer's KeyPackage from the Authentication Service.
+    FetchKey {
+        /// Server address (host:port).
+        #[arg(long, default_value = "127.0.0.1:7000", env = "QPQ_SERVER")]
+        server: String,
+
+        /// Target peer's Ed25519 identity public key (64 hex chars = 32 bytes).
+        identity_key: String,
+    },
+
+    /// Run a two-party MLS demo (creator + joiner) against live AS and DS.
+    DemoGroup {
+        /// Server address (host:port).
+        #[arg(long, default_value = "127.0.0.1:7000", env = "QPQ_SERVER")]
+        server: String,
+    },
+
+    /// Upload the persistent identity's KeyPackage to the AS (uses state file).
+    RegisterState {
+        /// State file path (identity + MLS state).
+        #[arg(
+            long,
+            default_value = "qpq-state.bin",
+            env = "QPQ_STATE"
+        )]
+        state: PathBuf,
+
+        /// Authentication Service address (host:port).
+        #[arg(long, default_value = "127.0.0.1:7000", env = "QPQ_SERVER")]
+        server: String,
+    },
+
+    /// Refresh the KeyPackage on the server (existing state only).
+    /// Run periodically (e.g. before server TTL ~24h) or after your KeyPackage was consumed so others can invite you.
+    RefreshKeypackage {
+        /// State file path (identity + MLS state).
+        #[arg(
+            long,
+            default_value = "qpq-state.bin",
+            env = "QPQ_STATE"
+        )]
+        state: PathBuf,
+
+        /// Server address (host:port).
+        #[arg(long, default_value = "127.0.0.1:7000", env = "QPQ_SERVER")]
+        server: String,
+    },
+
+    /// Create a persistent group and save state to disk.
+    CreateGroup {
+        /// State file path (identity + MLS state).
+        #[arg(
+            long,
+            default_value = "qpq-state.bin",
+            env = "QPQ_STATE"
+        )]
+        state: PathBuf,
+
+        /// Server address (host:port).
+        #[arg(long, default_value = "127.0.0.1:7000", env = "QPQ_SERVER")]
+        server: String,
+
+        /// Group identifier (arbitrary bytes, typically a human-readable name).
+        #[arg(long)]
+        group_id: String,
+    },
+
+    /// Invite a peer into the group and deliver a Welcome via DS.
+    Invite {
+        #[arg(
+            long,
+            default_value = "qpq-state.bin",
+            env = "QPQ_STATE"
+        )]
+        state: PathBuf,
+        #[arg(long, default_value = "127.0.0.1:7000", env = "QPQ_SERVER")]
+        server: String,
+        /// Peer identity public key (64 hex chars = 32 bytes).
+        #[arg(long)]
+        peer_key: String,
+    },
+
+    /// Join a group by fetching the Welcome from the DS.
+    Join {
+        #[arg(
+            long,
+            default_value = "qpq-state.bin",
+            env = "QPQ_STATE"
+        )]
+        state: PathBuf,
+        #[arg(long, default_value = "127.0.0.1:7000", env = "QPQ_SERVER")]
+        server: String,
+    },
+
+    /// Send an application message via the DS.
+    Send {
+        #[arg(
+            long,
+            default_value = "qpq-state.bin",
+            env = "QPQ_STATE"
+        )]
+        state: PathBuf,
+        #[arg(long, default_value = "127.0.0.1:7000", env = "QPQ_SERVER")]
+        server: String,
+        /// Recipient identity key (hex, 32 bytes -> 64 chars). Omit when using --all.
+        #[arg(long)]
+        peer_key: Option<String>,
+        /// Send to all other group members (N-way groups).
+        #[arg(long)]
+        all: bool,
+        /// Plaintext message to send.
+        #[arg(long)]
+        msg: String,
+    },
+
+    /// Receive and decrypt all pending messages from the DS.
+    Recv {
+        #[arg(
+            long,
+            default_value = "qpq-state.bin",
+            env = "QPQ_STATE"
+        )]
+        state: PathBuf,
+        #[arg(long, default_value = "127.0.0.1:7000", env = "QPQ_SERVER")]
+        server: String,
+
+        /// Wait for up to this many milliseconds if no messages are queued.
+        #[arg(long, default_value_t = 0)]
+        wait_ms: u64,
+
+        /// Continuously long-poll for messages.
+        #[arg(long)]
+        stream: bool,
+    },
+
+    /// Interactive multi-conversation REPL. Supports /dm, /create-group, /invite, /join, /switch, and more.
+    /// Automatically registers and logs in if --username/--password are provided (or prompts interactively).
+    Repl {
+        #[arg(
+            long,
+            default_value = "qpq-state.bin",
+            env = "QPQ_STATE"
+        )]
+        state: PathBuf,
+        #[arg(long, default_value = "127.0.0.1:7000", env = "QPQ_SERVER")]
+        server: String,
+        /// OPAQUE username for automatic registration/login.
+        #[arg(long, env = "QPQ_USERNAME")]
+        username: Option<String>,
+        /// OPAQUE password (prompted securely if --username is set but --password is not).
+        #[arg(long, env = "QPQ_PASSWORD")]
+        password: Option<String>,
+        /// Do not auto-start a local qpq-server.
+        #[arg(long, env = "QPQ_NO_SERVER")]
+        no_server: bool,
+    },
+
+    /// Full-screen Ratatui TUI (requires --features tui).
+    /// Channels sidebar, scrollable message view, and inline input bar.
+    #[cfg(feature = "tui")]
+    Tui {
+        #[arg(
+            long,
+            default_value = "qpq-state.bin",
+            env = "QPQ_STATE"
+        )]
+        state: PathBuf,
+        #[arg(long, default_value = "127.0.0.1:7000", env = "QPQ_SERVER")]
+        server: String,
+        /// OPAQUE username for automatic registration/login.
+        #[arg(long, env = "QPQ_USERNAME")]
+        username: Option<String>,
+        /// OPAQUE password (prompted securely if --username is set but --password is not).
+        #[arg(long, env = "QPQ_PASSWORD")]
+        password: Option<String>,
+    },
+
+    /// Interactive 1:1 chat: type to send, incoming messages printed as [peer] <msg>. Ctrl+D to exit.
+    /// In a two-person group, peer is chosen automatically; use --peer-key only with 3+ members.
+    Chat {
+        #[arg(
+            long,
+            default_value = "qpq-state.bin",
+            env = "QPQ_STATE"
+        )]
+        state: PathBuf,
+        #[arg(long, default_value = "127.0.0.1:7000", env = "QPQ_SERVER")]
+        server: String,
+        /// Peer identity key (hex, 64 chars). Omit in a two-person group to use the only other member.
+        #[arg(long)]
+        peer_key: Option<String>,
+        /// How often to poll for incoming messages (milliseconds).
+        #[arg(long, default_value_t = 500)]
+        poll_interval_ms: u64,
+    },
+
+    /// Export a conversation's message history to an encrypted, tamper-evident transcript file.
+    ///
+    /// The output file uses Argon2id + ChaCha20-Poly1305 encryption with a SHA-256 hash chain
+    /// linking every record. Use `qpq export verify` to check chain integrity without decrypting.
+    Export {
+        /// Path to the conversation database (.convdb file).
+        #[arg(long, default_value = "qpq-convdb.sqlite", env = "QPQ_CONV_DB")]
+        conv_db: PathBuf,
+
+        /// Conversation ID to export (32 hex chars = 16 bytes).
+        #[arg(long)]
+        conv_id: String,
+
+        /// Output path for the .qpqt transcript file.
+        #[arg(long, default_value = "transcript.qpqt")]
+        output: PathBuf,
+
+        /// Password used to encrypt the transcript (separate from the state/DB password).
+        #[arg(long, env = "QPQ_TRANSCRIPT_PASSWORD")]
+        transcript_password: Option<String>,
+
+        /// Password for the encrypted conversation database (if any).
+        #[arg(long, env = "QPQ_STATE_PASSWORD")]
+        db_password: Option<String>,
+    },
+
+    /// Verify the hash-chain integrity of a transcript file without decrypting content.
+    ExportVerify {
+        /// Path to the .qpqt transcript file to verify.
+        #[arg(long)]
+        input: PathBuf,
+    },
+
+    /// Execute a YAML playbook (scripted command sequence) and exit.
+    /// Requires `--features playbook`.
+    #[cfg(feature = "playbook")]
+    Run {
+        /// Path to the YAML playbook file.
+        playbook: PathBuf,
+
+        /// State file path (identity + MLS state).
+        #[arg(long, default_value = "qpq-state.bin", env = "QPQ_STATE")]
+        state: PathBuf,
+
+        /// Server address (host:port).
+        #[arg(long, default_value = "127.0.0.1:7000", env = "QPQ_SERVER")]
+        server: String,
+
+        /// OPAQUE username for automatic login.
+        #[arg(long, env = "QPQ_USERNAME")]
+        username: Option<String>,
+
+        /// OPAQUE password.
+        #[arg(long, env = "QPQ_PASSWORD")]
+        password: Option<String>,
+
+        /// Override playbook variables: KEY=VALUE (repeatable).
+        #[arg(long = "var", short = 'V')]
+        vars: Vec<String>,
+    },
+}
+
+// ── Helpers ───────────────────────────────────────────────────────────────────
+#[cfg(not(feature = "v2"))]
+/// Returns `qpq-{username}.bin` when `state` is still at the default
+/// (`qpq-state.bin`) and a username has been provided. Otherwise returns
+/// `state` unchanged. This lets `qpq --username alice` automatically isolate
+/// Alice's state without requiring a manual `--state` flag.
+fn derive_state_path(state: PathBuf, username: Option<&str>) -> PathBuf {
+    if state == Path::new("qpq-state.bin") {
+        if let Some(uname) = username {
+            return PathBuf::from(format!("qpq-{uname}.bin"));
+        }
+    }
+    state
+}
+
+// ── Playbook execution ───────────────────────────────────────────────────────
+
+#[cfg(all(feature = "playbook", not(feature = "v2")))]
+async fn run_playbook(
+    playbook_path: &Path,
+    state: &Path,
+    server: &str,
+    ca_cert: &Path,
+    server_name: &str,
+    state_pw: Option<&str>,
+    username: Option<&str>,
+    password: Option<&str>,
+    access_token: &str,
+    device_id: Option<&str>,
+    extra_vars: &[String],
+) -> anyhow::Result<()> {
+    use quicproquo_client::PlaybookRunner;
+
+    let insecure = std::env::var("QPQ_DANGER_ACCEPT_INVALID_CERTS").is_ok();
+
+    // Connect to server.
+    let client =
+        quicproquo_client::connect_node_opt(server, ca_cert, server_name, insecure)
+            .await
+            .context("connect to server")?;
+
+    // Build session state.
+    let mut session = quicproquo_client::client::session::SessionState::load(state, state_pw)
+        .context("load session state")?;
+
+    // If username/password provided, do OPAQUE login.
+    if let (Some(uname), Some(pw)) = (username, password) {
+        if let Err(e) =
+            quicproquo_client::opaque_login(&client, uname, pw, &session.identity.public_key_bytes()).await
+        {
+            eprintln!("OPAQUE login failed: {e:#}");
+        }
+    } else if !access_token.is_empty() {
+        let auth = ClientAuth::from_parts(access_token.to_string(), device_id.map(String::from));
+        init_auth(auth);
+    }
+
+    // Load playbook.
+    let mut runner = PlaybookRunner::from_file(playbook_path)
+        .with_context(|| format!("load playbook: {}", playbook_path.display()))?;
+
+    // Inject extra variables from --var KEY=VALUE flags.
+    for kv in extra_vars {
+        if let Some((k, v)) = kv.split_once('=') {
+            runner.set_var(k, v);
+        } else {
+            eprintln!("warning: ignoring malformed --var '{kv}' (expected KEY=VALUE)");
+        }
+    }
+
+    // Inject connection info as variables.
+    runner.set_var("_server", server);
+    if let Some(u) = username {
+        runner.set_var("_username", u);
+    }
+
+    let report = runner.run(&mut session, &client).await;
+    print!("{report}");
+
+    if report.all_passed() {
+        Ok(())
+    } else {
+        std::process::exit(1);
+    }
+}
+
+// ── Entry point ───────────────────────────────────────────────────────────────
+
+#[cfg(not(feature = "v2"))]
+#[tokio::main]
+async fn main() -> anyhow::Result<()> {
+    // Install the rustls crypto provider before any TLS operations.
+    let _ = rustls::crypto::ring::default_provider().install_default();
+
+    tracing_subscriber::fmt()
+        .with_env_filter(
+            tracing_subscriber::EnvFilter::try_from_default_env()
+                .unwrap_or_else(|_| tracing_subscriber::EnvFilter::new("warn")),
+        )
+        .init();
+
+    let args = Args::parse();
+
+    if args.danger_accept_invalid_certs {
+        eprintln!("WARNING: TLS verification disabled — insecure mode");
+        set_insecure_skip_verify(true);
+    }
+
+    // For the REPL and TUI, defer init_auth so they can resolve their own token via OPAQUE.
+    // For all other subcommands, initialize auth immediately.
+    #[cfg(not(feature = "tui"))]
+    let is_repl = matches!(args.command, None | Some(Command::Repl { .. }));
+    #[cfg(feature = "tui")]
+    let is_repl = matches!(args.command, None | Some(Command::Repl { .. }) | Some(Command::Tui { .. }));
+    if !is_repl {
+        let auth_ctx = ClientAuth::from_parts(args.access_token.clone(), args.device_id.clone());
+        init_auth(auth_ctx);
+    }
+
+    let state_pw = args.state_password.as_deref();
+
+    // Default to REPL when no subcommand is given.
+    let no_server = args.no_server;
+    let command = args.command.unwrap_or_else(|| Command::Repl {
+        state: derive_state_path(args.state, args.username.as_deref()),
+        server: args.server,
+        username: args.username,
+        password: args.password,
+        no_server,
+    });
+
+    match command {
+        Command::RegisterUser {
+            server,
+            username,
+            password,
+        } => {
+            let local = tokio::task::LocalSet::new();
+            local
+                .run_until(cmd_register_user(
+                    &server,
+                    &args.ca_cert,
+                    &args.server_name,
+                    &username,
+                    &password,
+                    None,
+                ))
+                .await
+        }
+        Command::Login {
+            server,
+            username,
+            password,
+            identity_key,
+            state,
+            state_password,
+        } => {
+            let local = tokio::task::LocalSet::new();
+            local
+                .run_until(cmd_login(
+                    &server,
+                    &args.ca_cert,
+                    &args.server_name,
+                    &username,
+                    &password,
+                    identity_key.as_deref(),
+                    state.as_deref(),
+                    state_password.as_deref(),
+                ))
+                .await
+        }
+        Command::Whoami { state } => cmd_whoami(&state, state_pw),
+        Command::Health { server } => {
+            let local = tokio::task::LocalSet::new();
+            local
+                .run_until(cmd_health(&server, &args.ca_cert, &args.server_name))
+                .await
+        }
+        Command::CheckKey {
+            server,
+            identity_key,
+        } => {
+            let local = tokio::task::LocalSet::new();
+            local
+                .run_until(cmd_check_key(
+                    &server,
+                    &args.ca_cert,
+                    &args.server_name,
+                    &identity_key,
+                ))
+                .await
+        }
+        Command::Ping { server } => cmd_ping(&server, &args.ca_cert, &args.server_name).await,
+        Command::Register { server } => {
+            let local = tokio::task::LocalSet::new();
+            local
+                .run_until(cmd_register(&server, &args.ca_cert, &args.server_name))
+                .await
+        }
+        Command::FetchKey {
+            server,
+            identity_key,
+        } => {
+            let local = tokio::task::LocalSet::new();
+            local
+                .run_until(cmd_fetch_key(
+                    &server,
+                    &args.ca_cert,
+                    &args.server_name,
+                    &identity_key,
+                ))
+                .await
+        }
+        Command::DemoGroup { server } => {
+            let local = tokio::task::LocalSet::new();
+            local
+                .run_until(cmd_demo_group(&server, &args.ca_cert, &args.server_name))
+                .await
+        }
+        Command::RegisterState { state, server } => {
+            let local = tokio::task::LocalSet::new();
+            local
+                .run_until(cmd_register_state(
+                    &state,
+                    &server,
+                    &args.ca_cert,
+                    &args.server_name,
+                    state_pw,
+                ))
+                .await
+        }
+        Command::RefreshKeypackage { state, server } => {
+            let local = tokio::task::LocalSet::new();
+            local
+                .run_until(cmd_refresh_keypackage(
+                    &state,
+                    &server,
+                    &args.ca_cert,
+                    &args.server_name,
+                    state_pw,
+                ))
+                .await
+        }
+        Command::CreateGroup {
+            state,
+            server,
+            group_id,
+        } => {
+            let local = tokio::task::LocalSet::new();
+            local
+                .run_until(cmd_create_group(&state, &server, &group_id, state_pw))
+                .await
+        }
+        Command::Invite {
+            state,
+            server,
+            peer_key,
+        } => {
+            let local = tokio::task::LocalSet::new();
+            local
+                .run_until(cmd_invite(
+                    &state,
+                    &server,
+                    &args.ca_cert,
+                    &args.server_name,
+                    &peer_key,
+                    state_pw,
+                ))
+                .await
+        }
+        Command::Join { state, server } => {
+            let local = tokio::task::LocalSet::new();
+            local
+                .run_until(cmd_join(
+                    &state,
+                    &server,
+                    &args.ca_cert,
+                    &args.server_name,
+                    state_pw,
+                ))
+                .await
+        }
+        Command::Send {
+            state,
+            server,
+            peer_key,
+            all,
+            msg,
+        } => {
+            let local = tokio::task::LocalSet::new();
+            local
+                .run_until(cmd_send(
+                    &state,
+                    &server,
+                    &args.ca_cert,
+                    &args.server_name,
+                    peer_key.as_deref(),
+                    all,
+                    &msg,
+                    state_pw,
+                ))
+                .await
+        }
+        Command::Recv {
+            state,
+            server,
+            wait_ms,
+            stream,
+        } => {
+            let local = tokio::task::LocalSet::new();
+            local
+                .run_until(cmd_recv(
+                    &state,
+                    &server,
+                    &args.ca_cert,
+                    &args.server_name,
+                    wait_ms,
+                    stream,
+                    state_pw,
+                ))
+                .await
+        }
+        Command::Repl {
+            state,
+            server,
+            username,
+            password,
+            no_server,
+        } => {
+            let state = derive_state_path(state, username.as_deref());
+            let local = tokio::task::LocalSet::new();
+            local
+                .run_until(run_repl(
+                    &state,
+                    &server,
+                    &args.ca_cert,
+                    &args.server_name,
+                    state_pw,
+                    username.as_deref(),
+                    password.as_deref(),
+                    &args.access_token,
+                    args.device_id.as_deref(),
+                    no_server,
+                ))
+                .await
+        }
+        Command::Chat {
+            state,
+            server,
+            peer_key,
+            poll_interval_ms,
+        } => {
+            let local = tokio::task::LocalSet::new();
+            local
+                .run_until(cmd_chat(
+                    &state,
+                    &server,
+                    &args.ca_cert,
+                    &args.server_name,
+                    peer_key.as_deref(),
+                    state_pw,
+                    poll_interval_ms,
+                ))
+                .await
+        }
+        #[cfg(feature = "tui")]
+        Command::Tui {
+            state,
+            server,
+            username,
+            password,
+        } => {
+            let state = derive_state_path(state, username.as_deref());
+            let local = tokio::task::LocalSet::new();
+            local
+                .run_until(run_tui(
+                    &state,
+                    &server,
+                    &args.ca_cert,
+                    &args.server_name,
+                    state_pw,
+                    username.as_deref(),
+                    password.as_deref(),
+                    &args.access_token,
+                    args.device_id.as_deref(),
+                ))
+                .await
+        }
+        Command::Export {
+            conv_db,
+            conv_id,
+            output,
+            transcript_password,
+            db_password,
+        } => {
+            // Prompt for transcript password if not provided.
+            let tp = match transcript_password {
+                Some(p) => p,
+                None => {
+                    eprint!("Transcript password: ");
+                    rpassword::read_password()
+                        .context("failed to read transcript password")?
+                }
+            };
+            cmd_export(
+                &conv_db,
+                &conv_id,
+                &output,
+                &tp,
+                db_password.as_deref().or(state_pw),
+            )
+        }
+        Command::ExportVerify { input } => cmd_export_verify(&input),
+        #[cfg(feature = "playbook")]
+        Command::Run {
+            playbook,
+            state,
+            server,
+            username,
+            password,
+            vars,
+        } => {
+            let state = derive_state_path(state, username.as_deref());
+            let local = tokio::task::LocalSet::new();
+            local
+                .run_until(run_playbook(
+                    &playbook,
+                    &state,
+                    &server,
+                    &args.ca_cert,
+                    &args.server_name,
+                    state_pw,
+                    username.as_deref(),
+                    password.as_deref(),
+                    &args.access_token,
+                    args.device_id.as_deref(),
+                    &vars,
+                ))
+                .await
+        }
+    }
+}

crates/quicproquo-client/src/v2_commands.rs

@@ -0,0 +1,228 @@
+//! v2 CLI command implementations — thin wrappers over the SDK.
+
+use quicproquo_sdk::client::QpqClient;
+use quicproquo_sdk::error::SdkError;
+
+/// Register a new user account via OPAQUE.
+pub async fn cmd_register_user(
+    client: &mut QpqClient,
+    username: &str,
+    password: &str,
+) -> Result<(), SdkError> {
+    client.register(username, password).await?;
+    let key = client.identity_key().unwrap_or_default();
+    println!("registered user: {username}");
+    println!("identity key  : {}", hex::encode(key));
+    Ok(())
+}
+
+/// Log in via OPAQUE and print session info.
+pub async fn cmd_login(
+    client: &mut QpqClient,
+    username: &str,
+    password: &str,
+) -> Result<(), SdkError> {
+    client.login(username, password).await?;
+    println!("logged in as: {username}");
+    if let Some(key) = client.identity_key() {
+        println!("identity key: {}", hex::encode(key));
+    }
+    Ok(())
+}
+
+/// Print local identity information.
+pub fn cmd_whoami(client: &QpqClient) {
+    match client.username() {
+        Some(u) => println!("username    : {u}"),
+        None => println!("username    : (not logged in)"),
+    }
+    match client.identity_key() {
+        Some(k) => println!("identity key: {}", hex::encode(k)),
+        None => println!("identity key: (none)"),
+    }
+    println!("connected   : {}", client.is_connected());
+    println!("authenticated: {}", client.is_authenticated());
+}
+
+/// Health check — connect to the server and report status.
+pub async fn cmd_health(client: &mut QpqClient) -> Result<(), SdkError> {
+    let start = std::time::Instant::now();
+    // The SDK connect() already establishes a QUIC connection.
+    // If we're already connected, just report success.
+    if !client.is_connected() {
+        client.connect().await?;
+    }
+    let rtt_ms = start.elapsed().as_millis();
+    println!("status : ok");
+    println!("rtt    : {rtt_ms}ms");
+    Ok(())
+}
+
+/// Resolve a username to its identity key.
+pub async fn cmd_resolve(client: &mut QpqClient, username: &str) -> Result<(), SdkError> {
+    let rpc = client.rpc()?;
+    match quicproquo_sdk::users::resolve_user(rpc, username).await? {
+        Some(key) => {
+            println!("{username} -> {}", hex::encode(&key));
+        }
+        None => {
+            println!("{username}: not found");
+        }
+    }
+    Ok(())
+}
+
+/// List registered devices.
+pub async fn cmd_devices_list(client: &mut QpqClient) -> Result<(), SdkError> {
+    let rpc = client.rpc()?;
+    let devices = quicproquo_sdk::devices::list_devices(rpc).await?;
+    if devices.is_empty() {
+        println!("no devices registered");
+    } else {
+        println!("{:<36}  {:<20}  {}", "DEVICE ID", "NAME", "REGISTERED AT");
+        for d in &devices {
+            println!(
+                "{:<36}  {:<20}  {}",
+                hex::encode(&d.device_id),
+                d.device_name,
+                d.registered_at,
+            );
+        }
+    }
+    Ok(())
+}
+
+/// Register a new device.
+pub async fn cmd_devices_register(
+    client: &mut QpqClient,
+    device_id: &str,
+    device_name: &str,
+) -> Result<(), SdkError> {
+    let rpc = client.rpc()?;
+    let id_bytes = hex::decode(device_id)
+        .map_err(|e| SdkError::Other(anyhow::anyhow!("invalid device_id hex: {e}")))?;
+    let was_new = quicproquo_sdk::devices::register_device(rpc, &id_bytes, device_name).await?;
+    if was_new {
+        println!("device registered: {device_name}");
+    } else {
+        println!("device already registered: {device_name}");
+    }
+    Ok(())
+}
+
+/// Revoke a device.
+pub async fn cmd_devices_revoke(
+    client: &mut QpqClient,
+    device_id: &str,
+) -> Result<(), SdkError> {
+    let rpc = client.rpc()?;
+    let id_bytes = hex::decode(device_id)
+        .map_err(|e| SdkError::Other(anyhow::anyhow!("invalid device_id hex: {e}")))?;
+    let revoked = quicproquo_sdk::devices::revoke_device(rpc, &id_bytes).await?;
+    if revoked {
+        println!("device revoked: {device_id}");
+    } else {
+        println!("device not found: {device_id}");
+    }
+    Ok(())
+}
+
+/// Set up account recovery — generate codes and upload encrypted bundles.
+pub async fn cmd_recovery_setup(client: &mut QpqClient) -> Result<(), SdkError> {
+    // Load identity seed from state file.
+    let state_path = client.config_state_path();
+    let stored = quicproquo_sdk::state::load_state(&state_path, None)
+        .map_err(|e| SdkError::Crypto(format!("load identity for recovery: {e}")))?;
+
+    let rpc = client.rpc()?;
+    let codes =
+        quicproquo_sdk::recovery::setup_recovery(rpc, &stored.identity_seed, &[]).await?;
+
+    println!("=== RECOVERY CODES ===");
+    println!("Save these codes securely. They will NOT be shown again.");
+    println!("Each code can independently recover your account.");
+    println!();
+    for (i, code) in codes.iter().enumerate() {
+        println!("  {}. {}", i + 1, code);
+    }
+    println!();
+    println!("{} codes generated and uploaded.", codes.len());
+    Ok(())
+}
+
+// ── Outbox commands ──────────────────────────────────────────────────────────
+
+/// List pending outbox entries.
+pub fn cmd_outbox_list(client: &QpqClient) -> Result<(), SdkError> {
+    let store = client.conversations()?;
+    let entries = quicproquo_sdk::outbox::list_pending(store)?;
+    if entries.is_empty() {
+        println!("outbox is empty — no pending messages");
+    } else {
+        println!("{:<6}  {:<34}  {:<8}  PAYLOAD SIZE", "ID", "CONVERSATION", "RETRIES");
+        for e in &entries {
+            println!(
+                "{:<6}  {:<34}  {:<8}  {} bytes",
+                e.id,
+                e.conversation_id.hex(),
+                e.retry_count,
+                e.payload.len(),
+            );
+        }
+        println!("\n{} pending entries", entries.len());
+    }
+    Ok(())
+}
+
+/// Retry sending all pending outbox entries.
+pub async fn cmd_outbox_retry(client: &mut QpqClient) -> Result<(), SdkError> {
+    let rpc = client.rpc()?;
+    let store = client.conversations()?;
+    let (sent, failed) = quicproquo_sdk::outbox::flush_outbox(rpc, store).await?;
+    println!("outbox flush: {sent} sent, {failed} permanently failed");
+    Ok(())
+}
+
+/// Clear permanently failed outbox entries.
+pub fn cmd_outbox_clear(client: &QpqClient) -> Result<(), SdkError> {
+    let store = client.conversations()?;
+    let cleared = quicproquo_sdk::outbox::clear_failed(store)?;
+    println!("cleared {cleared} failed outbox entries");
+    Ok(())
+}
+
+/// Recover an account from a recovery code.
+pub async fn cmd_recovery_restore(
+    client: &mut QpqClient,
+    code: &str,
+) -> Result<(), SdkError> {
+    let rpc = client.rpc()?;
+    let (identity_seed, conversation_ids) =
+        quicproquo_sdk::recovery::recover_account(rpc, code).await?;
+
+    // Restore identity.
+    let keypair = quicproquo_core::IdentityKeypair::from_seed(identity_seed);
+    client.set_identity_key(keypair.public_key_bytes().to_vec());
+
+    println!("account recovered successfully");
+    println!("identity key: {}", hex::encode(keypair.public_key_bytes()));
+    if !conversation_ids.is_empty() {
+        println!(
+            "{} conversations need rejoin (peers must re-invite this device)",
+            conversation_ids.len()
+        );
+    }
+
+    // Save recovered state.
+    let state = quicproquo_sdk::state::StoredState {
+        identity_seed,
+        group: None,
+        hybrid_key: None,
+        member_keys: Vec::new(),
+    };
+    let state_path = client.config_state_path();
+    quicproquo_sdk::state::save_state(&state_path, &state, None)?;
+    println!("state saved to {}", state_path.display());
+
+    Ok(())
+}

crates/quicproquo-client/src/v2_main.rs

@@ -0,0 +1,563 @@
+//! v2 CLI entry point — thin shell over `quicproquo_sdk::QpqClient`.
+//!
+//! Activated via `--features v2`. Replaces the v1 Cap'n Proto RPC main
+//! with a simplified command surface backed by the SDK.
+
+use std::path::{Path, PathBuf};
+use std::process::Command as ProcessCommand;
+use std::time::Duration;
+
+use anyhow::Context;
+use clap::{Parser, Subcommand};
+
+use quicproquo_sdk::client::QpqClient;
+use quicproquo_sdk::config::ClientConfig;
+
+use crate::v2_commands;
+
+// ── CLI ───────────────────────────────────────────────────────────────────────
+
+#[derive(Debug, Parser)]
+#[command(name = "qpq", about = "quicproquo CLI client (v2)", version)]
+struct Args {
+    /// Server address (host:port).
+    #[arg(long, global = true, default_value = "127.0.0.1:7000", env = "QPQ_SERVER")]
+    server: String,
+
+    /// TLS server name (must match certificate SAN).
+    #[arg(long, global = true, default_value = "localhost", env = "QPQ_SERVER_NAME")]
+    server_name: String,
+
+    /// Path to local conversation database.
+    #[arg(long, global = true, default_value = "conversations.db", env = "QPQ_CONV_DB")]
+    db_path: PathBuf,
+
+    /// Password for encrypting the local database.
+    #[arg(long, global = true, env = "QPQ_DB_PASSWORD")]
+    db_password: Option<String>,
+
+    /// Path to the client state file (identity key, MLS state).
+    #[arg(long, global = true, default_value = "qpq-state.bin", env = "QPQ_STATE")]
+    state: PathBuf,
+
+    /// DANGER: Skip TLS certificate verification. Development only.
+    #[arg(
+        long = "danger-accept-invalid-certs",
+        global = true,
+        env = "QPQ_DANGER_ACCEPT_INVALID_CERTS"
+    )]
+    danger_accept_invalid_certs: bool,
+
+    /// Do not auto-start a local qpq-server.
+    #[arg(long, global = true, env = "QPQ_NO_SERVER")]
+    no_server: bool,
+
+    #[command(subcommand)]
+    command: Cmd,
+}
+
+#[derive(Debug, Subcommand)]
+enum Cmd {
+    /// Register a new user via OPAQUE (password never leaves the client).
+    RegisterUser {
+        /// Username for the new account.
+        #[arg(long)]
+        username: String,
+        /// Password (used in OPAQUE PAKE; server never sees it).
+        #[arg(long)]
+        password: String,
+    },
+
+    /// Log in via OPAQUE and receive a session token.
+    Login {
+        #[arg(long)]
+        username: String,
+        #[arg(long)]
+        password: String,
+    },
+
+    /// Show local identity info.
+    Whoami,
+
+    /// Server health check.
+    Health,
+
+    /// Send a message to a conversation.
+    Send {
+        /// Conversation name (group name or DM peer username).
+        #[arg(long)]
+        to: String,
+        /// Message text.
+        #[arg(long)]
+        msg: String,
+    },
+
+    /// Receive pending messages from a conversation.
+    Recv {
+        /// Conversation name.
+        #[arg(long)]
+        from: String,
+    },
+
+    /// Start or resume a DM with a user.
+    Dm {
+        /// Peer username.
+        username: String,
+    },
+
+    /// Group management commands.
+    Group {
+        #[command(subcommand)]
+        action: GroupCmd,
+    },
+
+    /// Resolve a username to its identity key.
+    Resolve {
+        /// Username to look up.
+        username: String,
+    },
+
+    /// Device management.
+    Devices {
+        #[command(subcommand)]
+        action: DevicesCmd,
+    },
+
+    /// Account recovery management.
+    Recovery {
+        #[command(subcommand)]
+        action: RecoveryCmd,
+    },
+
+    /// Offline outbox management.
+    Outbox {
+        #[command(subcommand)]
+        action: OutboxCmd,
+    },
+}
+
+#[derive(Debug, Subcommand)]
+enum GroupCmd {
+    /// Create a new group.
+    Create {
+        /// Group name.
+        name: String,
+    },
+    /// Invite a user to a group.
+    Invite {
+        /// Group name.
+        #[arg(long)]
+        group: String,
+        /// Username to invite.
+        #[arg(long)]
+        user: String,
+    },
+}
+
+#[derive(Debug, Subcommand)]
+enum DevicesCmd {
+    /// List registered devices.
+    List,
+    /// Register a new device.
+    Register {
+        /// Device ID (hex).
+        #[arg(long)]
+        id: String,
+        /// Human-readable device name.
+        #[arg(long)]
+        name: String,
+    },
+    /// Revoke a device.
+    Revoke {
+        /// Device ID (hex).
+        #[arg(long)]
+        id: String,
+    },
+}
+
+#[derive(Debug, Subcommand)]
+enum RecoveryCmd {
+    /// Generate recovery codes and upload encrypted bundles.
+    Setup,
+    /// Recover account from a recovery code.
+    Restore {
+        /// Recovery code (e.g. "A3B7K9").
+        code: String,
+    },
+}
+
+#[derive(Debug, Subcommand)]
+enum OutboxCmd {
+    /// Show pending outbox entries.
+    List,
+    /// Retry sending all pending outbox entries.
+    Retry,
+    /// Clear permanently failed outbox entries.
+    Clear,
+}
+
+// ── Auto-server launch ───────────────────────────────────────────────────────
+
+/// RAII guard that kills an auto-started server process on drop.
+struct ServerGuard(Option<std::process::Child>);
+
+impl Drop for ServerGuard {
+    fn drop(&mut self) {
+        if let Some(ref mut child) = self.0 {
+            let _ = child.kill();
+            let _ = child.wait();
+        }
+    }
+}
+
+/// Find the `qpq-server` binary: same directory as current exe, then PATH.
+fn find_server_binary() -> Option<PathBuf> {
+    if let Ok(exe) = std::env::current_exe() {
+        let sibling = exe.with_file_name("qpq-server");
+        if sibling.exists() {
+            return Some(sibling);
+        }
+    }
+    std::env::var_os("PATH").and_then(|paths| {
+        std::env::split_paths(&paths)
+            .map(|dir| dir.join("qpq-server"))
+            .find(|p| p.exists())
+    })
+}
+
+/// Try a QUIC health probe to the server address.
+async fn probe_server(server_addr: &str) -> bool {
+    use std::net::ToSocketAddrs;
+    let addr = match server_addr.to_socket_addrs() {
+        Ok(mut addrs) => match addrs.next() {
+            Some(a) => a,
+            None => return false,
+        },
+        Err(_) => return false,
+    };
+    // Simple TCP probe — if the port is open, the server is likely running.
+    tokio::net::TcpStream::connect(addr)
+        .await
+        .is_ok()
+}
+
+/// Start a local qpq-server if one isn't already running.
+/// Returns a guard that kills the child on drop (if we started one).
+async fn ensure_server_running(
+    server_addr: &str,
+    data_dir: &Path,
+    no_server: bool,
+) -> anyhow::Result<ServerGuard> {
+    if no_server {
+        return Ok(ServerGuard(None));
+    }
+
+    if probe_server(server_addr).await {
+        return Ok(ServerGuard(None));
+    }
+
+    let binary = find_server_binary().ok_or_else(|| {
+        anyhow::anyhow!(
+            "server at {server_addr} is not reachable and qpq-server binary not found; \
+             start a server manually or install qpq-server"
+        )
+    })?;
+
+    let cert_path = data_dir.join("server-cert.der");
+    let key_path = data_dir.join("server-key.der");
+
+    eprintln!("starting server on {server_addr}...");
+
+    let child = ProcessCommand::new(&binary)
+        .args([
+            "--allow-insecure-auth",
+            "--listen",
+            server_addr,
+            "--tls-cert",
+            &cert_path.to_string_lossy(),
+            "--tls-key",
+            &key_path.to_string_lossy(),
+        ])
+        .stdout(std::process::Stdio::null())
+        .stderr(std::process::Stdio::null())
+        .spawn()
+        .with_context(|| format!("failed to spawn {}", binary.display()))?;
+
+    let guard = ServerGuard(Some(child));
+
+    // Poll until the server is ready.
+    let mut delay = Duration::from_millis(100);
+    let max_wait = Duration::from_secs(3);
+    let start = std::time::Instant::now();
+
+    loop {
+        tokio::time::sleep(delay).await;
+
+        if probe_server(server_addr).await {
+            eprintln!("server ready");
+            return Ok(guard);
+        }
+
+        if start.elapsed() > max_wait {
+            anyhow::bail!(
+                "auto-started qpq-server but it did not become ready within {max_wait:?}"
+            );
+        }
+
+        delay = (delay * 2).min(Duration::from_secs(1));
+    }
+}
+
+// ── Helpers ──────────────────────────────────────────────────────────────────
+
+/// Build a `ClientConfig` from CLI args.
+fn build_config(args: &Args) -> anyhow::Result<ClientConfig> {
+    let server_addr = args
+        .server
+        .parse()
+        .with_context(|| format!("invalid server address: {}", args.server))?;
+
+    Ok(ClientConfig {
+        server_addr,
+        server_name: args.server_name.clone(),
+        db_path: args.db_path.clone(),
+        db_password: args.db_password.clone(),
+        state_path: args.state.clone(),
+        accept_invalid_certs: args.danger_accept_invalid_certs,
+        ..ClientConfig::default()
+    })
+}
+
+/// Build, connect, and return a `QpqClient`. Loads identity from state file
+/// if it exists.
+async fn connect_client(args: &Args) -> anyhow::Result<QpqClient> {
+    let config = build_config(args)?;
+    let mut client = QpqClient::new(config);
+
+    // Try loading identity from state file.
+    if args.state.exists() {
+        match quicproquo_sdk::state::load_state(&args.state, args.db_password.as_deref()) {
+            Ok(stored) => {
+                let keypair = quicproquo_core::IdentityKeypair::from_seed(stored.identity_seed);
+                client.set_identity_key(keypair.public_key_bytes().to_vec());
+            }
+            Err(e) => {
+                tracing::debug!("could not load state from {}: {e}", args.state.display());
+            }
+        }
+    }
+
+    client.connect().await.context("failed to connect to server")?;
+    Ok(client)
+}
+
+// ── Entry point ──────────────────────────────────────────────────────────────
+
+pub fn main() {
+    // Install the rustls crypto provider before any TLS operations.
+    let _ = rustls::crypto::ring::default_provider().install_default();
+
+    tracing_subscriber::fmt()
+        .with_env_filter(
+            tracing_subscriber::EnvFilter::try_from_default_env()
+                .unwrap_or_else(|_| tracing_subscriber::EnvFilter::new("warn")),
+        )
+        .init();
+
+    let args = Args::parse();
+
+    let rt = tokio::runtime::Builder::new_multi_thread()
+        .enable_all()
+        .build()
+        .unwrap_or_else(|e| {
+            eprintln!("fatal: {e}");
+            std::process::exit(1);
+        });
+
+    if let Err(e) = rt.block_on(run(args)) {
+        eprintln!("error: {e:#}");
+        std::process::exit(1);
+    }
+}
+
+async fn run(args: Args) -> anyhow::Result<()> {
+    // Auto-start server if needed (except for whoami which is local-only).
+    let data_dir = args.state.parent().unwrap_or_else(|| Path::new("."));
+    let _server_guard = match args.command {
+        Cmd::Whoami => ServerGuard(None),
+        _ => ensure_server_running(&args.server, data_dir, args.no_server).await?,
+    };
+
+    match args.command {
+        Cmd::RegisterUser {
+            ref username,
+            ref password,
+        } => {
+            let mut client = connect_client(&args).await?;
+            v2_commands::cmd_register_user(&mut client, username, password)
+                .await
+                .context("register-user failed")?;
+        }
+
+        Cmd::Login {
+            ref username,
+            ref password,
+        } => {
+            let mut client = connect_client(&args).await?;
+            v2_commands::cmd_login(&mut client, username, password)
+                .await
+                .context("login failed")?;
+        }
+
+        Cmd::Whoami => {
+            // Whoami is local-only — create client without connecting.
+            let config = build_config(&args)?;
+            let mut client = QpqClient::new(config);
+            if args.state.exists() {
+                match quicproquo_sdk::state::load_state(
+                    &args.state,
+                    args.db_password.as_deref(),
+                ) {
+                    Ok(stored) => {
+                        let keypair =
+                            quicproquo_core::IdentityKeypair::from_seed(stored.identity_seed);
+                        client.set_identity_key(keypair.public_key_bytes().to_vec());
+                    }
+                    Err(e) => {
+                        eprintln!("warning: could not load state: {e}");
+                    }
+                }
+            }
+            v2_commands::cmd_whoami(&client);
+        }
+
+        Cmd::Health => {
+            let mut client = connect_client(&args).await?;
+            v2_commands::cmd_health(&mut client)
+                .await
+                .context("health check failed")?;
+        }
+
+        Cmd::Resolve { ref username } => {
+            let mut client = connect_client(&args).await?;
+            v2_commands::cmd_resolve(&mut client, username)
+                .await
+                .context("resolve failed")?;
+        }
+
+        Cmd::Dm { ref username } => {
+            let mut client = connect_client(&args).await?;
+            v2_commands::cmd_resolve(&mut client, username)
+                .await
+                .context("dm setup failed")?;
+            // For now, print the resolved key. Full DM creation requires
+            // MLS group state, which will be handled in the REPL flow.
+            println!("(DM creation with full MLS setup is available in the REPL)");
+        }
+
+        Cmd::Send { ref to, ref msg } => {
+            let _ = (to, msg);
+            let _client = connect_client(&args).await?;
+            // Full send requires MLS group state restoration — deferred to REPL.
+            println!("(send is currently available in the REPL; one-shot send coming soon)");
+        }
+
+        Cmd::Recv { ref from } => {
+            let _ = from;
+            let _client = connect_client(&args).await?;
+            println!("(recv is currently available in the REPL; one-shot recv coming soon)");
+        }
+
+        Cmd::Group {
+            action: GroupCmd::Create { ref name },
+        } => {
+            let _ = name;
+            let _client = connect_client(&args).await?;
+            println!("(group create is currently available in the REPL; one-shot coming soon)");
+        }
+
+        Cmd::Group {
+            action:
+                GroupCmd::Invite {
+                    ref group,
+                    ref user,
+                },
+        } => {
+            let _ = (group, user);
+            let _client = connect_client(&args).await?;
+            println!("(group invite is currently available in the REPL; one-shot coming soon)");
+        }
+
+        Cmd::Devices {
+            action: DevicesCmd::List,
+        } => {
+            let mut client = connect_client(&args).await?;
+            v2_commands::cmd_devices_list(&mut client)
+                .await
+                .context("devices list failed")?;
+        }
+
+        Cmd::Devices {
+            action: DevicesCmd::Register { ref id, ref name },
+        } => {
+            let mut client = connect_client(&args).await?;
+            v2_commands::cmd_devices_register(&mut client, id, name)
+                .await
+                .context("device register failed")?;
+        }
+
+        Cmd::Devices {
+            action: DevicesCmd::Revoke { ref id },
+        } => {
+            let mut client = connect_client(&args).await?;
+            v2_commands::cmd_devices_revoke(&mut client, id)
+                .await
+                .context("device revoke failed")?;
+        }
+
+        Cmd::Recovery {
+            action: RecoveryCmd::Setup,
+        } => {
+            let mut client = connect_client(&args).await?;
+            v2_commands::cmd_recovery_setup(&mut client)
+                .await
+                .context("recovery setup failed")?;
+        }
+
+        Cmd::Recovery {
+            action: RecoveryCmd::Restore { ref code },
+        } => {
+            let mut client = connect_client(&args).await?;
+            v2_commands::cmd_recovery_restore(&mut client, code)
+                .await
+                .context("recovery restore failed")?;
+        }
+
+        Cmd::Outbox {
+            action: OutboxCmd::List,
+        } => {
+            let mut client = connect_client(&args).await?;
+            v2_commands::cmd_outbox_list(&client)
+                .context("outbox list failed")?;
+        }
+
+        Cmd::Outbox {
+            action: OutboxCmd::Retry,
+        } => {
+            let mut client = connect_client(&args).await?;
+            v2_commands::cmd_outbox_retry(&mut client)
+                .await
+                .context("outbox retry failed")?;
+        }
+
+        Cmd::Outbox {
+            action: OutboxCmd::Clear,
+        } => {
+            let mut client = connect_client(&args).await?;
+            v2_commands::cmd_outbox_clear(&client)
+                .context("outbox clear failed")?;
+        }
+    }
+
+    Ok(())
+}

crates/quicproquo-core/Cargo.toml

@@ -0,0 +1,87 @@
+[package]
+name        = "quicproquo-core"
+version     = "0.1.0"
+edition     = "2021"
+description = "Crypto primitives, MLS state machine, and hybrid post-quantum KEM for quicproquo."
+license     = "MIT"
+
+[features]
+default = ["native"]
+# The "native" feature enables MLS (openmls), OPAQUE, Cap'n Proto, tokio, and
+# filesystem-backed key storage. Disable it (--no-default-features) to compile
+# the pure-crypto subset to wasm32-unknown-unknown.
+native = [
+    "dep:openmls",
+    "dep:openmls_rust_crypto",
+    "dep:openmls_traits",
+    "dep:tls_codec",
+    "dep:opaque-ke",
+    "dep:bincode",
+    "dep:capnp",
+    "dep:quicproquo-proto",
+    "dep:tokio",
+]
+
+[dependencies]
+# Crypto — classical (always available, WASM-safe)
+x25519-dalek        = { workspace = true }
+ed25519-dalek       = { workspace = true }
+sha2                = { workspace = true }
+hmac                = { workspace = true }
+hkdf                = { workspace = true }
+ciborium            = { workspace = true }
+chacha20poly1305    = { workspace = true }
+zeroize             = { workspace = true }
+rand                = { workspace = true }
+serde               = { workspace = true }
+serde_json          = { workspace = true }
+argon2              = { workspace = true }
+thiserror           = { workspace = true }
+
+# Crypto — post-quantum hybrid KEM (M7) — always available, WASM-safe
+ml-kem              = { workspace = true }
+
+# Crypto — OPAQUE password-authenticated key exchange (native only)
+opaque-ke           = { workspace = true, optional = true }
+
+# Crypto — MLS (M2) (native only)
+openmls             = { workspace = true, optional = true }
+openmls_rust_crypto = { workspace = true, optional = true }
+openmls_traits      = { workspace = true, optional = true }
+tls_codec           = { workspace = true, optional = true }
+bincode             = { workspace = true, optional = true }
+
+# Serialisation (native only)
+capnp               = { workspace = true, optional = true }
+quicproquo-proto    = { path = "../quicproquo-proto", optional = true }
+
+# Async runtime (native only)
+tokio               = { workspace = true, optional = true }
+
+# WASM: provide getrandom with js backend
+[target.'cfg(target_arch = "wasm32")'.dependencies]
+getrandom           = { version = "0.2", features = ["js"] }
+
+[lints]
+workspace = true
+
+[dev-dependencies]
+tokio               = { workspace = true }
+criterion           = { version = "0.5", features = ["html_reports"] }
+prost               = "0.13"
+
+[[bench]]
+name = "serialization"
+harness = false
+
+[[bench]]
+name = "mls_operations"
+harness = false
+
+[[bench]]
+name = "hybrid_kem_bench"
+harness = false
+
+[[bench]]
+name = "crypto_benchmarks"
+harness = false

crates/quicproquo-core/benches/crypto_benchmarks.rs

@@ -0,0 +1,150 @@
+#![allow(clippy::unwrap_used)]
+//! Benchmark: Identity keypair operations, sealed sender, and message padding.
+//!
+//! Covers:
+//! - [`IdentityKeypair`] generation, signing, and signature verification
+//! - Sealed sender `seal` / `unseal` (Ed25519 sign + verify overhead)
+//! - Message padding `pad` / `unpad` at various payload sizes
+
+use criterion::{black_box, criterion_group, criterion_main, BenchmarkId, Criterion};
+
+use quicproquo_core::{compute_safety_number, IdentityKeypair, padding};
+
+// ── Identity keypair benchmarks ──────────────────────────────────────────────
+
+fn bench_identity_keygen(c: &mut Criterion) {
+    c.bench_function("identity_keygen", |b| {
+        b.iter(|| black_box(IdentityKeypair::generate()));
+    });
+}
+
+fn bench_identity_sign(c: &mut Criterion) {
+    let identity = IdentityKeypair::generate();
+    let payload = b"benchmark signing payload -- 32+ bytes of realistic data here";
+
+    c.bench_function("identity_sign", |b| {
+        b.iter(|| black_box(identity.sign_raw(black_box(payload))));
+    });
+}
+
+fn bench_identity_verify(c: &mut Criterion) {
+    let identity = IdentityKeypair::generate();
+    let payload = b"benchmark signing payload -- 32+ bytes of realistic data here";
+    let sig = identity.sign_raw(payload);
+    let pk = identity.public_key_bytes();
+
+    c.bench_function("identity_verify", |b| {
+        b.iter(|| {
+            IdentityKeypair::verify_raw(
+                black_box(&pk),
+                black_box(payload),
+                black_box(&sig),
+            )
+            .unwrap();
+        });
+    });
+}
+
+// ── Sealed sender benchmarks ─────────────────────────────────────────────────
+
+fn bench_sealed_sender(c: &mut Criterion) {
+    use quicproquo_core::sealed_sender::{seal, unseal};
+
+    let sizes: &[(&str, usize)] = &[
+        ("32B", 32),
+        ("256B", 256),
+        ("1KB", 1024),
+        ("4KB", 4096),
+    ];
+
+    let identity = IdentityKeypair::generate();
+
+    let mut group = c.benchmark_group("sealed_sender_seal");
+    for (label, size) in sizes {
+        let payload = vec![0xABu8; *size];
+        group.bench_with_input(
+            BenchmarkId::from_parameter(label),
+            &payload,
+            |b, payload| {
+                b.iter(|| black_box(seal(black_box(&identity), black_box(payload))));
+            },
+        );
+    }
+    group.finish();
+
+    let mut group = c.benchmark_group("sealed_sender_unseal");
+    for (label, size) in sizes {
+        let payload = vec![0xABu8; *size];
+        let sealed = seal(&identity, &payload);
+        group.bench_with_input(
+            BenchmarkId::from_parameter(label),
+            &sealed,
+            |b, sealed| {
+                b.iter(|| black_box(unseal(black_box(sealed)).unwrap()));
+            },
+        );
+    }
+    group.finish();
+}
+
+// ── Message padding benchmarks ────────────────────────────────────────────────
+
+fn bench_padding(c: &mut Criterion) {
+    // Representative sizes: one per bucket + oversized
+    let sizes: &[(&str, usize)] = &[
+        ("50B", 50),       // → 256 bucket
+        ("512B", 512),     // → 1024 bucket
+        ("2KB", 2048),     // → 4096 bucket
+        ("8KB", 8192),     // → 16384 bucket
+        ("20KB", 20480),   // → 32768 (oversized)
+    ];
+
+    let mut group = c.benchmark_group("padding_pad");
+    for (label, size) in sizes {
+        let payload = vec![0xABu8; *size];
+        group.bench_with_input(
+            BenchmarkId::from_parameter(label),
+            &payload,
+            |b, payload| {
+                b.iter(|| black_box(padding::pad(black_box(payload))));
+            },
+        );
+    }
+    group.finish();
+
+    let mut group = c.benchmark_group("padding_unpad");
+    for (label, size) in sizes {
+        let payload = vec![0xABu8; *size];
+        let padded = padding::pad(&payload);
+        group.bench_with_input(
+            BenchmarkId::from_parameter(label),
+            &padded,
+            |b, padded| {
+                b.iter(|| black_box(padding::unpad(black_box(padded)).unwrap()));
+            },
+        );
+    }
+    group.finish();
+}
+
+// ── Safety number benchmarks ─────────────────────────────────────────────────
+
+fn bench_safety_number(c: &mut Criterion) {
+    let key_a = [0x1au8; 32];
+    let key_b = [0x2bu8; 32];
+
+    c.bench_function("safety_number", |b| {
+        b.iter(|| black_box(compute_safety_number(black_box(&key_a), black_box(&key_b))));
+    });
+}
+
+criterion_group!(
+    benches,
+    bench_identity_keygen,
+    bench_identity_sign,
+    bench_identity_verify,
+    bench_sealed_sender,
+    bench_padding,
+    bench_safety_number,
+);
+criterion_main!(benches);

crates/quicproquo-core/benches/hybrid_kem_bench.rs

@@ -0,0 +1,153 @@
+#![allow(clippy::unwrap_used)]
+//! Benchmark: Hybrid KEM (X25519 + ML-KEM-768) vs classical-only encryption.
+//!
+//! Compares keypair generation, encryption, and decryption times for the
+//! hybrid post-quantum scheme against classical X25519 + ChaCha20-Poly1305.
+
+use criterion::{black_box, criterion_group, criterion_main, BenchmarkId, Criterion};
+
+use quicproquo_core::{hybrid_encrypt, hybrid_decrypt, HybridKeypair};
+
+// ── Classical baseline (X25519 + ChaCha20-Poly1305) ─────────────────────────
+
+use chacha20poly1305::{
+    aead::{Aead, KeyInit},
+    ChaCha20Poly1305, Key, Nonce,
+};
+use hkdf::Hkdf;
+use rand::{rngs::OsRng, RngCore};
+use sha2::Sha256;
+use x25519_dalek::{EphemeralSecret, PublicKey as X25519Public, StaticSecret};
+
+struct ClassicalKeypair {
+    secret: StaticSecret,
+    public: X25519Public,
+}
+
+impl ClassicalKeypair {
+    fn generate() -> Self {
+        let secret = StaticSecret::random_from_rng(OsRng);
+        let public = X25519Public::from(&secret);
+        Self { secret, public }
+    }
+}
+
+fn classical_encrypt(recipient_pk: &X25519Public, plaintext: &[u8]) -> Vec<u8> {
+    let eph_secret = EphemeralSecret::random_from_rng(OsRng);
+    let eph_public = X25519Public::from(&eph_secret);
+    let shared = eph_secret.diffie_hellman(recipient_pk);
+
+    let hk = Hkdf::<Sha256>::new(None, shared.as_bytes());
+    let mut key_bytes = [0u8; 32];
+    hk.expand(b"classical-bench", &mut key_bytes).unwrap();
+
+    let mut nonce_bytes = [0u8; 12];
+    OsRng.fill_bytes(&mut nonce_bytes);
+
+    let cipher = ChaCha20Poly1305::new(Key::from_slice(&key_bytes));
+    let ct = cipher
+        .encrypt(Nonce::from_slice(&nonce_bytes), plaintext)
+        .unwrap();
+
+    // Wire: eph_pk(32) || nonce(12) || ciphertext
+    let mut out = Vec::with_capacity(32 + 12 + ct.len());
+    out.extend_from_slice(eph_public.as_bytes());
+    out.extend_from_slice(&nonce_bytes);
+    out.extend_from_slice(&ct);
+    out
+}
+
+fn classical_decrypt(keypair: &ClassicalKeypair, envelope: &[u8]) -> Vec<u8> {
+    let eph_pk = X25519Public::from(<[u8; 32]>::try_from(&envelope[..32]).unwrap());
+    let nonce_bytes: [u8; 12] = envelope[32..44].try_into().unwrap();
+    let ct = &envelope[44..];
+
+    let shared = keypair.secret.diffie_hellman(&eph_pk);
+
+    let hk = Hkdf::<Sha256>::new(None, shared.as_bytes());
+    let mut key_bytes = [0u8; 32];
+    hk.expand(b"classical-bench", &mut key_bytes).unwrap();
+
+    let cipher = ChaCha20Poly1305::new(Key::from_slice(&key_bytes));
+    cipher
+        .decrypt(Nonce::from_slice(&nonce_bytes), ct)
+        .unwrap()
+}
+
+// ── Benchmarks ──────────────────────────────────────────────────────────────
+
+fn bench_keygen(c: &mut Criterion) {
+    let mut group = c.benchmark_group("kem_keygen");
+    group.bench_function("hybrid", |b| {
+        b.iter(|| black_box(HybridKeypair::generate()));
+    });
+    group.bench_function("classical", |b| {
+        b.iter(|| black_box(ClassicalKeypair::generate()));
+    });
+    group.finish();
+}
+
+fn bench_encrypt(c: &mut Criterion) {
+    let sizes: &[(&str, usize)] = &[("100B", 100), ("1KB", 1024), ("4KB", 4096), ("64KB", 65536)];
+    let mut group = c.benchmark_group("kem_encrypt");
+
+    let hybrid_kp = HybridKeypair::generate();
+    let hybrid_pk = hybrid_kp.public_key();
+    let classical_kp = ClassicalKeypair::generate();
+
+    for (label, size) in sizes {
+        let payload = vec![0xABu8; *size];
+
+        group.bench_with_input(
+            BenchmarkId::new("hybrid", label),
+            &payload,
+            |b, payload| {
+                b.iter(|| hybrid_encrypt(&hybrid_pk, black_box(payload), b"", b"").unwrap());
+            },
+        );
+
+        group.bench_with_input(
+            BenchmarkId::new("classical", label),
+            &payload,
+            |b, payload| {
+                b.iter(|| classical_encrypt(&classical_kp.public, black_box(payload)));
+            },
+        );
+    }
+    group.finish();
+}
+
+fn bench_decrypt(c: &mut Criterion) {
+    let sizes: &[(&str, usize)] = &[("100B", 100), ("1KB", 1024), ("4KB", 4096), ("64KB", 65536)];
+    let mut group = c.benchmark_group("kem_decrypt");
+
+    let hybrid_kp = HybridKeypair::generate();
+    let hybrid_pk = hybrid_kp.public_key();
+    let classical_kp = ClassicalKeypair::generate();
+
+    for (label, size) in sizes {
+        let payload = vec![0xABu8; *size];
+        let hybrid_ct = hybrid_encrypt(&hybrid_pk, &payload, b"", b"").unwrap();
+        let classical_ct = classical_encrypt(&classical_kp.public, &payload);
+
+        group.bench_with_input(
+            BenchmarkId::new("hybrid", label),
+            &hybrid_ct,
+            |b, ct| {
+                b.iter(|| hybrid_decrypt(&hybrid_kp, black_box(ct), b"", b"").unwrap());
+            },
+        );
+
+        group.bench_with_input(
+            BenchmarkId::new("classical", label),
+            &classical_ct,
+            |b, ct| {
+                b.iter(|| classical_decrypt(&classical_kp, black_box(ct)));
+            },
+        );
+    }
+    group.finish();
+}
+
+criterion_group!(benches, bench_keygen, bench_encrypt, bench_decrypt);
+criterion_main!(benches);

crates/quicproquo-core/benches/mls_operations.rs

@@ -0,0 +1,157 @@
+#![allow(clippy::unwrap_used)]
+//! Benchmark: MLS group operations at various group sizes.
+//!
+//! Measures KeyPackage generation, group creation, member addition,
+//! message encryption, and message decryption.
+
+use std::sync::Arc;
+
+use criterion::{criterion_group, criterion_main, BatchSize, BenchmarkId, Criterion};
+use quicproquo_core::{GroupMember, IdentityKeypair};
+
+/// Create identities and a group of the given size.
+/// Returns (creator, Vec<members>).
+fn setup_group(size: usize) -> (GroupMember, Vec<GroupMember>) {
+    let creator_id = Arc::new(IdentityKeypair::generate());
+    let mut creator = GroupMember::new(creator_id);
+    creator.create_group(b"bench-group").unwrap();
+
+    let mut members = Vec::with_capacity(size.saturating_sub(1));
+    for _ in 1..size {
+        let joiner_id = Arc::new(IdentityKeypair::generate());
+        let mut joiner = GroupMember::new(joiner_id);
+        let kp = joiner.generate_key_package().unwrap();
+
+        let (_commit, welcome) = creator.add_member(&kp).unwrap();
+        joiner.join_group(&welcome).unwrap();
+        members.push(joiner);
+    }
+
+    (creator, members)
+}
+
+fn bench_keygen(c: &mut Criterion) {
+    c.bench_function("mls_keygen", |b| {
+        b.iter_batched(
+            || {
+                let id = Arc::new(IdentityKeypair::generate());
+                GroupMember::new(id)
+            },
+            |mut member| {
+                member.generate_key_package().unwrap();
+            },
+            BatchSize::SmallInput,
+        );
+    });
+}
+
+fn bench_group_create(c: &mut Criterion) {
+    c.bench_function("mls_group_create", |b| {
+        b.iter_batched(
+            || {
+                let id = Arc::new(IdentityKeypair::generate());
+                GroupMember::new(id)
+            },
+            |mut member| {
+                member.create_group(b"bench-group").unwrap();
+            },
+            BatchSize::SmallInput,
+        );
+    });
+}
+
+fn bench_add_member(c: &mut Criterion) {
+    let mut group = c.benchmark_group("mls_add_member");
+    group.sample_size(10);
+    for size in [2, 10, 50, 100] {
+        group.bench_with_input(BenchmarkId::from_parameter(size), &size, |b, &size| {
+            b.iter_batched(
+                || {
+                    let (creator, members) = setup_group(size);
+                    let joiner_id = Arc::new(IdentityKeypair::generate());
+                    let mut joiner = GroupMember::new(joiner_id);
+                    let kp = joiner.generate_key_package().unwrap();
+                    (creator, members, joiner, kp)
+                },
+                |(mut creator, _members, _joiner, kp)| {
+                    creator.add_member(&kp).unwrap();
+                },
+                BatchSize::SmallInput,
+            );
+        });
+    }
+    group.finish();
+}
+
+fn bench_epoch_rotation(c: &mut Criterion) {
+    let mut group = c.benchmark_group("mls_epoch_rotation");
+    group.sample_size(10);
+    for size in [2, 10, 50] {
+        group.bench_with_input(BenchmarkId::from_parameter(size), &size, |b, &size| {
+            b.iter_batched(
+                || {
+                    let (mut creator, members) = setup_group(size);
+                    // Propose a self-update to simulate epoch rotation
+                    let proposal = creator.propose_self_update().unwrap();
+                    (creator, members, proposal)
+                },
+                |(mut creator, _members, _proposal)| {
+                    // Commit pending proposals (the self-update) to advance the epoch
+                    creator.commit_pending_proposals().unwrap();
+                },
+                BatchSize::SmallInput,
+            );
+        });
+    }
+    group.finish();
+}
+
+fn bench_send_message(c: &mut Criterion) {
+    let mut group = c.benchmark_group("mls_send_message");
+    for size in [2, 10, 50] {
+        group.bench_with_input(BenchmarkId::from_parameter(size), &size, |b, &size| {
+            let (mut creator, _members) = setup_group(size);
+            let payload = b"hello benchmark message";
+            b.iter(|| {
+                creator.send_message(payload).unwrap();
+            });
+        });
+    }
+    group.finish();
+}
+
+fn bench_receive_message(c: &mut Criterion) {
+    let mut group = c.benchmark_group("mls_receive_message");
+    for size in [2, 10, 50] {
+        group.bench_with_input(BenchmarkId::from_parameter(size), &size, |b, &size| {
+            // For receive, we need a fresh ciphertext each iteration since
+            // MLS message processing is destructive (epoch state changes).
+            // We pre-generate a batch and consume them.
+            let (mut creator, mut members) = setup_group(size);
+            if members.is_empty() {
+                return;
+            }
+            let payload = b"hello benchmark message";
+            b.iter_batched(
+                || creator.send_message(payload).unwrap(),
+                |ct| {
+                    // Receive on the first joiner
+                    let _ = members[0].receive_message(&ct);
+                },
+                BatchSize::SmallInput,
+            );
+        });
+    }
+    group.finish();
+}
+
+criterion_group!(
+    benches,
+    bench_keygen,
+    bench_group_create,
+    bench_add_member,
+    bench_epoch_rotation,
+    bench_send_message,
+    bench_receive_message,
+);
+criterion_main!(benches);

crates/quicproquo-core/benches/serialization.rs

@@ -0,0 +1,171 @@
+#![allow(clippy::unwrap_used)]
+//! Benchmark: Cap'n Proto vs Protobuf serialization for chat message envelopes.
+//!
+//! Compares serialization/deserialization speed and encoded size at three
+//! payload sizes (100 B, 1 KB, 4 KB) for a typical Envelope{seq, data} message.
+
+use criterion::{black_box, criterion_group, criterion_main, BenchmarkId, Criterion};
+
+// ── Cap'n Proto path ────────────────────────────────────────────────────────
+
+fn capnp_serialize_envelope(seq: u64, data: &[u8]) -> Vec<u8> {
+    let mut msg = capnp::message::Builder::new_default();
+    {
+        let mut envelope = msg.init_root::<quicproquo_proto::node_capnp::envelope::Builder>();
+        envelope.set_seq(seq);
+        envelope.set_data(data);
+    }
+    quicproquo_proto::to_bytes(&msg).unwrap()
+}
+
+fn capnp_deserialize_envelope(bytes: &[u8]) -> (u64, Vec<u8>) {
+    let reader = quicproquo_proto::from_bytes(bytes).unwrap();
+    let envelope = reader
+        .get_root::<quicproquo_proto::node_capnp::envelope::Reader>()
+        .unwrap();
+    (envelope.get_seq(), envelope.get_data().unwrap().to_vec())
+}
+
+// ── Protobuf path (hand-coded prost encoding to avoid build-dep) ────────────
+//
+// Envelope { seq: uint64 (field 1), data: bytes (field 2) }
+// Wire format: varint tag + varint seq + len-delimited data
+
+fn protobuf_serialize_envelope(seq: u64, data: &[u8]) -> Vec<u8> {
+    // Build a prost message via raw encoding.
+    // Field 1: uint64 seq, wire type 0 (varint), tag = (1 << 3) | 0 = 0x08
+    // Field 2: bytes  data, wire type 2 (length-delimited), tag = (2 << 3) | 2 = 0x12
+    let mut buf = Vec::with_capacity(10 + data.len());
+    // Encode field 1 (seq)
+    prost::encoding::uint64::encode(1, &seq, &mut buf);
+    // Encode field 2 (data)
+    prost::encoding::bytes::encode(2, &data.to_vec(), &mut buf);
+    buf
+}
+
+fn protobuf_deserialize_envelope(bytes: &[u8]) -> (u64, Vec<u8>) {
+    // Decode manually using prost wire format
+    let mut seq: u64 = 0;
+    let mut data: Vec<u8> = Vec::new();
+    let mut buf = bytes;
+
+    while !buf.is_empty() {
+        let (tag, wire_type) =
+            prost::encoding::decode_key(&mut buf).expect("decode key");
+        match tag {
+            1 => {
+                prost::encoding::uint64::merge(wire_type, &mut seq, &mut buf, Default::default())
+                    .expect("decode seq");
+            }
+            2 => {
+                prost::encoding::bytes::merge(wire_type, &mut data, &mut buf, Default::default())
+                    .expect("decode data");
+            }
+            _ => {
+                prost::encoding::skip_field(wire_type, tag, &mut buf, Default::default())
+                    .expect("skip unknown field");
+            }
+        }
+    }
+    (seq, data)
+}
+
+// ── Benchmarks ──────────────────────────────────────────────────────────────
+
+fn bench_serialize(c: &mut Criterion) {
+    let sizes: &[(&str, usize)] = &[("100B", 100), ("1KB", 1024), ("4KB", 4096)];
+    let mut group = c.benchmark_group("serialize_envelope");
+
+    for (label, size) in sizes {
+        let payload = vec![0xABu8; *size];
+        let seq = 42u64;
+
+        group.bench_with_input(
+            BenchmarkId::new("capnp", label),
+            &(&seq, &payload),
+            |b, &(seq, payload)| {
+                b.iter(|| capnp_serialize_envelope(black_box(*seq), black_box(payload)));
+            },
+        );
+
+        group.bench_with_input(
+            BenchmarkId::new("protobuf", label),
+            &(&seq, &payload),
+            |b, &(seq, payload)| {
+                b.iter(|| protobuf_serialize_envelope(black_box(*seq), black_box(payload)));
+            },
+        );
+    }
+    group.finish();
+}
+
+fn bench_deserialize(c: &mut Criterion) {
+    let sizes: &[(&str, usize)] = &[("100B", 100), ("1KB", 1024), ("4KB", 4096)];
+    let mut group = c.benchmark_group("deserialize_envelope");
+
+    for (label, size) in sizes {
+        let payload = vec![0xABu8; *size];
+        let seq = 42u64;
+
+        let capnp_bytes = capnp_serialize_envelope(seq, &payload);
+        let proto_bytes = protobuf_serialize_envelope(seq, &payload);
+
+        group.bench_with_input(
+            BenchmarkId::new("capnp", label),
+            &capnp_bytes,
+            |b, bytes| {
+                b.iter(|| capnp_deserialize_envelope(black_box(bytes)));
+            },
+        );
+
+        group.bench_with_input(
+            BenchmarkId::new("protobuf", label),
+            &proto_bytes,
+            |b, bytes| {
+                b.iter(|| protobuf_deserialize_envelope(black_box(bytes)));
+            },
+        );
+    }
+    group.finish();
+}
+
+fn bench_encoded_sizes(c: &mut Criterion) {
+    let sizes: &[(&str, usize)] = &[("100B", 100), ("1KB", 1024), ("4KB", 4096)];
+    let mut group = c.benchmark_group("encoded_size");
+
+    for (label, size) in sizes {
+        let payload = vec![0xABu8; *size];
+        let capnp_bytes = capnp_serialize_envelope(42, &payload);
+        let proto_bytes = protobuf_serialize_envelope(42, &payload);
+
+        // Use a trivial benchmark that just returns the size -- the point
+        // is to get criterion to print the iteration count and allow
+        // comparison. The real value is in the eprintln below.
+        group.bench_with_input(
+            BenchmarkId::new("capnp", label),
+            &capnp_bytes,
+            |b, bytes| {
+                b.iter(|| black_box(bytes.len()));
+            },
+        );
+
+        group.bench_with_input(
+            BenchmarkId::new("protobuf", label),
+            &proto_bytes,
+            |b, bytes| {
+                b.iter(|| black_box(bytes.len()));
+            },
+        );
+
+        eprintln!(
+            "  {label}: capnp={} bytes, protobuf={} bytes, overhead={:+} bytes",
+            capnp_bytes.len(),
+            proto_bytes.len(),
+            capnp_bytes.len() as isize - proto_bytes.len() as isize,
+        );
+    }
+    group.finish();
+}
+
+criterion_group!(benches, bench_serialize, bench_deserialize, bench_encoded_sizes);
+criterion_main!(benches);

crates/quicproquo-core/proto/chat_message.proto

@@ -0,0 +1,21 @@
+syntax = "proto3";
+package quicproquo.bench;
+
+// Equivalent to the Envelope struct in delivery.capnp
+message Envelope {
+  uint64 seq = 1;
+  bytes data = 2;
+}
+
+// Equivalent to a chat message payload (app_message.rs Chat variant)
+message ChatMessage {
+  bytes message_id = 1;   // 16 bytes
+  string body = 2;        // UTF-8 text
+  uint64 timestamp_ms = 3;
+  bytes sender_key = 4;   // 32 bytes Ed25519 public key
+}
+
+// Batch fetch response (equivalent to fetch returning List(Envelope))
+message FetchResponse {
+  repeated Envelope payloads = 1;
+}

crates/quicproquo-core/src/app_message.rs

@@ -0,0 +1,524 @@
+//! Rich application-layer message format for MLS application payloads.
+//!
+//! The server sees only opaque ciphertext; structure lives in this client-defined
+//! plaintext schema. All messages use: version byte (1) + message_type byte + type-specific payload.
+//!
+//! # Message ID
+//!
+//! `message_id` is assigned by the sender (16 random bytes) and included in the
+//! serialized payload for Chat (and implied for Reply/Reaction/ReadReceipt via ref_msg_id).
+//! Recipients can store message_ids to reference them in replies or reactions.
+
+use crate::error::CoreError;
+use rand::RngCore;
+
+/// Current schema version.
+pub const VERSION: u8 = 1;
+
+/// Message type discriminant (one byte).
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+#[repr(u8)]
+pub enum MessageType {
+    Chat = 0x01,
+    Reply = 0x02,
+    Reaction = 0x03,
+    ReadReceipt = 0x04,
+    Typing = 0x05,
+    Edit = 0x06,
+    Delete = 0x07,
+    FileRef = 0x08,
+    Dummy = 0x09,
+}
+
+impl MessageType {
+    fn from_byte(b: u8) -> Option<Self> {
+        match b {
+            0x01 => Some(MessageType::Chat),
+            0x02 => Some(MessageType::Reply),
+            0x03 => Some(MessageType::Reaction),
+            0x04 => Some(MessageType::ReadReceipt),
+            0x05 => Some(MessageType::Typing),
+            0x06 => Some(MessageType::Edit),
+            0x07 => Some(MessageType::Delete),
+            0x08 => Some(MessageType::FileRef),
+            0x09 => Some(MessageType::Dummy),
+            _ => None,
+        }
+    }
+}
+
+/// Parsed application message (one of the rich types).
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum AppMessage {
+    /// Plain chat: body (UTF-8). message_id is included so recipients can store and reference it.
+    Chat {
+        message_id: [u8; 16],
+        body: Vec<u8>,
+    },
+    Reply {
+        ref_msg_id: [u8; 16],
+        body: Vec<u8>,
+    },
+    Reaction {
+        ref_msg_id: [u8; 16],
+        emoji: Vec<u8>,
+    },
+    ReadReceipt {
+        msg_id: [u8; 16],
+    },
+    Typing {
+        /// 0 = stopped, 1 = typing
+        active: u8,
+    },
+    /// Edit a previously sent message (identified by ref_msg_id).
+    Edit {
+        ref_msg_id: [u8; 16],
+        body: Vec<u8>,
+    },
+    /// Delete a previously sent message (identified by ref_msg_id).
+    Delete {
+        ref_msg_id: [u8; 16],
+    },
+    /// File reference: metadata pointing to a blob stored on the server.
+    FileRef {
+        blob_id: [u8; 32],
+        filename: Vec<u8>,
+        file_size: u64,
+        mime_type: Vec<u8>,
+    },
+    /// Dummy message for traffic analysis resistance (no user-visible content).
+    Dummy,
+}
+
+/// Generate a new 16-byte message ID (e.g. for Chat/Reply so recipients can reference it).
+pub fn generate_message_id() -> [u8; 16] {
+    let mut id = [0u8; 16];
+    rand::rngs::OsRng.fill_bytes(&mut id);
+    id
+}
+
+// ── Layout (minimal, no Cap'n Proto) ─────────────────────────────────────────
+//
+// All messages: [version: 1][type: 1][payload...]
+//
+// Chat:     [msg_id: 16][body_len: 2 BE][body]
+// Reply:    [ref_msg_id: 16][body_len: 2 BE][body]
+// Reaction: [ref_msg_id: 16][emoji_len: 1][emoji]
+// ReadReceipt: [msg_id: 16]
+// Typing:   [active: 1]  0 = stopped, 1 = typing
+// Edit:     [ref_msg_id: 16][body_len: 2 BE][body]
+// Delete:   [ref_msg_id: 16]
+// FileRef:  [blob_id: 32][filename_len: 2 BE][filename][file_size: 8 BE][mime_len: 2 BE][mime_type]
+
+/// Serialize a rich message into the application payload format.
+pub fn serialize(msg_type: MessageType, payload: &[u8]) -> Vec<u8> {
+    let mut out = Vec::with_capacity(2 + payload.len());
+    out.push(VERSION);
+    out.push(msg_type as u8);
+    out.extend_from_slice(payload);
+    out
+}
+
+/// Serialize a Chat message (generates message_id internally; pass None to generate, or Some(id) when replying with a known id).
+pub fn serialize_chat(body: &[u8], message_id: Option<[u8; 16]>) -> Result<Vec<u8>, CoreError> {
+    if body.len() > u16::MAX as usize {
+        return Err(CoreError::AppMessage("chat body exceeds maximum length (65535 bytes)".into()));
+    }
+    let id = message_id.unwrap_or_else(generate_message_id);
+    let mut payload = Vec::with_capacity(16 + 2 + body.len());
+    payload.extend_from_slice(&id);
+    payload.extend_from_slice(&(body.len() as u16).to_be_bytes());
+    payload.extend_from_slice(body);
+    Ok(serialize(MessageType::Chat, &payload))
+}
+
+/// Serialize a Reply message.
+pub fn serialize_reply(ref_msg_id: [u8; 16], body: &[u8]) -> Result<Vec<u8>, CoreError> {
+    if body.len() > u16::MAX as usize {
+        return Err(CoreError::AppMessage("reply body exceeds maximum length (65535 bytes)".into()));
+    }
+    let mut payload = Vec::with_capacity(16 + 2 + body.len());
+    payload.extend_from_slice(&ref_msg_id);
+    payload.extend_from_slice(&(body.len() as u16).to_be_bytes());
+    payload.extend_from_slice(body);
+    Ok(serialize(MessageType::Reply, &payload))
+}
+
+/// Serialize a Reaction message.
+pub fn serialize_reaction(ref_msg_id: [u8; 16], emoji: &[u8]) -> Result<Vec<u8>, CoreError> {
+    if emoji.len() > 255 {
+        return Err(CoreError::AppMessage("emoji length > 255".into()));
+    }
+    let mut payload = Vec::with_capacity(16 + 1 + emoji.len());
+    payload.extend_from_slice(&ref_msg_id);
+    payload.push(emoji.len() as u8);
+    payload.extend_from_slice(emoji);
+    Ok(serialize(MessageType::Reaction, &payload))
+}
+
+/// Serialize a ReadReceipt message.
+pub fn serialize_read_receipt(msg_id: [u8; 16]) -> Vec<u8> {
+    serialize(MessageType::ReadReceipt, &msg_id)
+}
+
+/// Serialize a Typing message (active: 0 = stopped, 1 = typing).
+pub fn serialize_typing(active: u8) -> Vec<u8> {
+    let payload = [active];
+    serialize(MessageType::Typing, &payload)
+}
+
+/// Serialize an Edit message (replaces body of a previously sent message).
+pub fn serialize_edit(ref_msg_id: &[u8; 16], body: &[u8]) -> Result<Vec<u8>, CoreError> {
+    if body.len() > u16::MAX as usize {
+        return Err(CoreError::AppMessage("edit body exceeds maximum length (65535 bytes)".into()));
+    }
+    let mut payload = Vec::with_capacity(16 + 2 + body.len());
+    payload.extend_from_slice(ref_msg_id);
+    payload.extend_from_slice(&(body.len() as u16).to_be_bytes());
+    payload.extend_from_slice(body);
+    Ok(serialize(MessageType::Edit, &payload))
+}
+
+/// Serialize a Delete message (marks a previously sent message as deleted).
+pub fn serialize_delete(ref_msg_id: &[u8; 16]) -> Vec<u8> {
+    serialize(MessageType::Delete, ref_msg_id)
+}
+
+/// Serialize a FileRef message (metadata pointing to a blob on the server).
+pub fn serialize_file_ref(
+    blob_id: &[u8; 32],
+    filename: &[u8],
+    file_size: u64,
+    mime_type: &[u8],
+) -> Result<Vec<u8>, CoreError> {
+    if filename.len() > u16::MAX as usize {
+        return Err(CoreError::AppMessage("filename exceeds maximum length".into()));
+    }
+    if mime_type.len() > u16::MAX as usize {
+        return Err(CoreError::AppMessage("mime_type exceeds maximum length".into()));
+    }
+    let mut payload = Vec::with_capacity(32 + 2 + filename.len() + 8 + 2 + mime_type.len());
+    payload.extend_from_slice(blob_id);
+    payload.extend_from_slice(&(filename.len() as u16).to_be_bytes());
+    payload.extend_from_slice(filename);
+    payload.extend_from_slice(&file_size.to_be_bytes());
+    payload.extend_from_slice(&(mime_type.len() as u16).to_be_bytes());
+    payload.extend_from_slice(mime_type);
+    Ok(serialize(MessageType::FileRef, &payload))
+}
+
+/// Serialize a Dummy message (traffic padding — no user content).
+pub fn serialize_dummy() -> Vec<u8> {
+    serialize(MessageType::Dummy, &[])
+}
+
+/// Parse bytes into (MessageType, AppMessage). Fails if version/type unknown or payload too short.
+pub fn parse(bytes: &[u8]) -> Result<(MessageType, AppMessage), CoreError> {
+    if bytes.len() < 2 {
+        return Err(CoreError::AppMessage("payload too short (need version + type)".into()));
+    }
+    let version = bytes[0];
+    if version != VERSION {
+        return Err(CoreError::AppMessage(format!("unsupported version {version}")));
+    }
+    let msg_type = MessageType::from_byte(bytes[1])
+        .ok_or_else(|| CoreError::AppMessage(format!("unknown message type {}", bytes[1])))?;
+    let payload = &bytes[2..];
+
+    let app = match msg_type {
+        MessageType::Chat => parse_chat(payload)?,
+        MessageType::Reply => parse_reply(payload)?,
+        MessageType::Reaction => parse_reaction(payload)?,
+        MessageType::ReadReceipt => parse_read_receipt(payload)?,
+        MessageType::Typing => parse_typing(payload)?,
+        MessageType::Edit => parse_edit(payload)?,
+        MessageType::Delete => parse_delete(payload)?,
+        MessageType::FileRef => parse_file_ref(payload)?,
+        MessageType::Dummy => AppMessage::Dummy,
+    };
+    Ok((msg_type, app))
+}
+
+fn parse_chat(payload: &[u8]) -> Result<AppMessage, CoreError> {
+    if payload.len() < 16 + 2 {
+        return Err(CoreError::AppMessage("Chat payload too short".into()));
+    }
+    let mut message_id = [0u8; 16];
+    message_id.copy_from_slice(&payload[..16]);
+    let body_len = u16::from_be_bytes([payload[16], payload[17]]) as usize;
+    if payload.len() < 18 + body_len {
+        return Err(CoreError::AppMessage("Chat body length exceeds payload".into()));
+    }
+    let body = payload[18..18 + body_len].to_vec();
+    Ok(AppMessage::Chat { message_id, body })
+}
+
+fn parse_reply(payload: &[u8]) -> Result<AppMessage, CoreError> {
+    if payload.len() < 16 + 2 {
+        return Err(CoreError::AppMessage("Reply payload too short".into()));
+    }
+    let mut ref_msg_id = [0u8; 16];
+    ref_msg_id.copy_from_slice(&payload[..16]);
+    let body_len = u16::from_be_bytes([payload[16], payload[17]]) as usize;
+    if payload.len() < 18 + body_len {
+        return Err(CoreError::AppMessage("Reply body length exceeds payload".into()));
+    }
+    let body = payload[18..18 + body_len].to_vec();
+    Ok(AppMessage::Reply { ref_msg_id, body })
+}
+
+fn parse_reaction(payload: &[u8]) -> Result<AppMessage, CoreError> {
+    if payload.len() < 16 + 1 {
+        return Err(CoreError::AppMessage("Reaction payload too short".into()));
+    }
+    let mut ref_msg_id = [0u8; 16];
+    ref_msg_id.copy_from_slice(&payload[..16]);
+    let emoji_len = payload[16] as usize;
+    if payload.len() < 17 + emoji_len {
+        return Err(CoreError::AppMessage("Reaction emoji length exceeds payload".into()));
+    }
+    let emoji = payload[17..17 + emoji_len].to_vec();
+    Ok(AppMessage::Reaction { ref_msg_id, emoji })
+}
+
+fn parse_read_receipt(payload: &[u8]) -> Result<AppMessage, CoreError> {
+    if payload.len() < 16 {
+        return Err(CoreError::AppMessage("ReadReceipt payload too short".into()));
+    }
+    let mut msg_id = [0u8; 16];
+    msg_id.copy_from_slice(&payload[..16]);
+    Ok(AppMessage::ReadReceipt { msg_id })
+}
+
+fn parse_typing(payload: &[u8]) -> Result<AppMessage, CoreError> {
+    if payload.is_empty() {
+        return Err(CoreError::AppMessage("Typing payload empty".into()));
+    }
+    Ok(AppMessage::Typing { active: payload[0] })
+}
+
+fn parse_edit(payload: &[u8]) -> Result<AppMessage, CoreError> {
+    if payload.len() < 16 + 2 {
+        return Err(CoreError::AppMessage("Edit payload too short".into()));
+    }
+    let mut ref_msg_id = [0u8; 16];
+    ref_msg_id.copy_from_slice(&payload[..16]);
+    let body_len = u16::from_be_bytes([payload[16], payload[17]]) as usize;
+    if payload.len() < 18 + body_len {
+        return Err(CoreError::AppMessage("Edit body length exceeds payload".into()));
+    }
+    let body = payload[18..18 + body_len].to_vec();
+    Ok(AppMessage::Edit { ref_msg_id, body })
+}
+
+fn parse_delete(payload: &[u8]) -> Result<AppMessage, CoreError> {
+    if payload.len() < 16 {
+        return Err(CoreError::AppMessage("Delete payload too short".into()));
+    }
+    let mut ref_msg_id = [0u8; 16];
+    ref_msg_id.copy_from_slice(&payload[..16]);
+    Ok(AppMessage::Delete { ref_msg_id })
+}
+
+fn parse_file_ref(payload: &[u8]) -> Result<AppMessage, CoreError> {
+    // blob_id(32) + filename_len(2) minimum
+    if payload.len() < 34 {
+        return Err(CoreError::AppMessage("FileRef payload too short".into()));
+    }
+    let mut blob_id = [0u8; 32];
+    blob_id.copy_from_slice(&payload[..32]);
+    let filename_len = u16::from_be_bytes([payload[32], payload[33]]) as usize;
+    let pos = 34;
+    if payload.len() < pos + filename_len + 8 + 2 {
+        return Err(CoreError::AppMessage("FileRef payload truncated after filename_len".into()));
+    }
+    let filename = payload[pos..pos + filename_len].to_vec();
+    let pos = pos + filename_len;
+    let file_size = u64::from_be_bytes([
+        payload[pos], payload[pos + 1], payload[pos + 2], payload[pos + 3],
+        payload[pos + 4], payload[pos + 5], payload[pos + 6], payload[pos + 7],
+    ]);
+    let pos = pos + 8;
+    let mime_len = u16::from_be_bytes([payload[pos], payload[pos + 1]]) as usize;
+    let pos = pos + 2;
+    if payload.len() < pos + mime_len {
+        return Err(CoreError::AppMessage("FileRef payload truncated after mime_len".into()));
+    }
+    let mime_type = payload[pos..pos + mime_len].to_vec();
+    Ok(AppMessage::FileRef { blob_id, filename, file_size, mime_type })
+}
+
+#[cfg(test)]
+#[allow(clippy::unwrap_used)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn roundtrip_chat() {
+        let body = b"hello";
+        let encoded = serialize_chat(body, None).unwrap();
+        let (t, msg) = parse(&encoded).unwrap();
+        assert_eq!(t, MessageType::Chat);
+        match &msg {
+            AppMessage::Chat { message_id: _, body: b } => assert_eq!(b.as_slice(), body),
+            _ => panic!("expected Chat"),
+        }
+    }
+
+    #[test]
+    fn roundtrip_reply() {
+        let ref_id = [1u8; 16];
+        let body = b"reply text";
+        let encoded = serialize_reply(ref_id, body).unwrap();
+        let (t, msg) = parse(&encoded).unwrap();
+        assert_eq!(t, MessageType::Reply);
+        match &msg {
+            AppMessage::Reply { ref_msg_id, body: b } => {
+                assert_eq!(ref_msg_id, &ref_id);
+                assert_eq!(b.as_slice(), body);
+            }
+            _ => panic!("expected Reply"),
+        }
+    }
+
+    #[test]
+    fn roundtrip_typing() {
+        let encoded = serialize_typing(1);
+        let (t, msg) = parse(&encoded).unwrap();
+        assert_eq!(t, MessageType::Typing);
+        match &msg {
+            AppMessage::Typing { active } => assert_eq!(*active, 1),
+            _ => panic!("expected Typing"),
+        }
+    }
+
+    #[test]
+    fn roundtrip_reaction() {
+        let ref_id = [2u8; 16];
+        let emoji = "\u{1f44d}".as_bytes();
+        let encoded = serialize_reaction(ref_id, emoji).unwrap();
+        let (t, msg) = parse(&encoded).unwrap();
+        assert_eq!(t, MessageType::Reaction);
+        match &msg {
+            AppMessage::Reaction { ref_msg_id, emoji: e } => {
+                assert_eq!(ref_msg_id, &ref_id);
+                assert_eq!(e.as_slice(), emoji);
+            }
+            _ => panic!("expected Reaction"),
+        }
+    }
+
+    #[test]
+    fn roundtrip_read_receipt() {
+        let msg_id = [3u8; 16];
+        let encoded = serialize_read_receipt(msg_id);
+        let (t, msg) = parse(&encoded).unwrap();
+        assert_eq!(t, MessageType::ReadReceipt);
+        match &msg {
+            AppMessage::ReadReceipt { msg_id: id } => assert_eq!(id, &msg_id),
+            _ => panic!("expected ReadReceipt"),
+        }
+    }
+
+    #[test]
+    fn roundtrip_edit() {
+        let ref_id = [4u8; 16];
+        let body = b"edited text";
+        let encoded = serialize_edit(&ref_id, body).unwrap();
+        let (t, msg) = parse(&encoded).unwrap();
+        assert_eq!(t, MessageType::Edit);
+        match &msg {
+            AppMessage::Edit { ref_msg_id, body: b } => {
+                assert_eq!(ref_msg_id, &ref_id);
+                assert_eq!(b.as_slice(), body);
+            }
+            _ => panic!("expected Edit"),
+        }
+    }
+
+    #[test]
+    fn roundtrip_delete() {
+        let ref_id = [5u8; 16];
+        let encoded = serialize_delete(&ref_id);
+        let (t, msg) = parse(&encoded).unwrap();
+        assert_eq!(t, MessageType::Delete);
+        match &msg {
+            AppMessage::Delete { ref_msg_id } => assert_eq!(ref_msg_id, &ref_id),
+            _ => panic!("expected Delete"),
+        }
+    }
+
+    #[test]
+    fn edit_body_too_long() {
+        let body = vec![0u8; 65536];
+        assert!(serialize_edit(&[0; 16], &body).is_err());
+    }
+
+    #[test]
+    fn parse_empty_fails() {
+        assert!(parse(&[]).is_err());
+    }
+
+    #[test]
+    fn parse_bad_version_fails() {
+        assert!(parse(&[99, 0x01]).is_err());
+    }
+
+    #[test]
+    fn parse_bad_type_fails() {
+        assert!(parse(&[1, 0xFF]).is_err());
+    }
+
+    #[test]
+    fn chat_body_too_long() {
+        let body = vec![0u8; 65536]; // exceeds u16::MAX
+        assert!(serialize_chat(&body, None).is_err());
+    }
+
+    #[test]
+    fn reaction_emoji_too_long() {
+        let emoji = vec![0u8; 256];
+        assert!(serialize_reaction([0; 16], &emoji).is_err());
+    }
+
+    #[test]
+    fn parse_truncated_chat_payload() {
+        // Version + type + only 10 bytes of payload (needs 18 minimum for chat)
+        let mut data = vec![1, 0x01];
+        data.extend_from_slice(&[0u8; 10]);
+        assert!(parse(&data).is_err());
+    }
+
+    #[test]
+    fn roundtrip_file_ref() {
+        let blob_id = [7u8; 32];
+        let filename = b"report.pdf";
+        let file_size = 123456u64;
+        let mime_type = b"application/pdf";
+        let encoded = serialize_file_ref(&blob_id, filename, file_size, mime_type).unwrap();
+        let (t, msg) = parse(&encoded).unwrap();
+        assert_eq!(t, MessageType::FileRef);
+        match &msg {
+            AppMessage::FileRef {
+                blob_id: bid,
+                filename: fname,
+                file_size: fsize,
+                mime_type: mtype,
+            } => {
+                assert_eq!(bid, &blob_id);
+                assert_eq!(fname.as_slice(), filename);
+                assert_eq!(*fsize, file_size);
+                assert_eq!(mtype.as_slice(), mime_type);
+            }
+            _ => panic!("expected FileRef"),
+        }
+    }
+
+    #[test]
+    fn roundtrip_dummy() {
+        let encoded = serialize_dummy();
+        let (t, msg) = parse(&encoded).unwrap();
+        assert_eq!(t, MessageType::Dummy);
+        assert_eq!(msg, AppMessage::Dummy);
+    }
+}

crates/quicproquo-core/src/error.rs

@@ -0,0 +1,38 @@
+//! Error types for `quicproquo-core`.
+
+use thiserror::Error;
+
+/// Errors produced by core cryptographic and MLS operations.
+#[derive(Debug, Error)]
+pub enum CoreError {
+    /// Cap'n Proto serialisation or deserialisation failed.
+    #[cfg(feature = "native")]
+    #[error("Cap'n Proto error: {0}")]
+    Capnp(#[from] capnp::Error),
+
+    /// An MLS operation failed (string description).
+    ///
+    /// Preserved for backward compatibility. Prefer [`CoreError::MlsError`]
+    /// for new code that wraps typed openmls errors.
+    #[error("MLS error: {0}")]
+    Mls(String),
+
+    /// An MLS operation failed (typed, boxed error).
+    ///
+    /// Wraps the underlying openmls error so callers can downcast to specific
+    /// error types when needed.
+    #[error("MLS error: {0}")]
+    MlsError(Box<dyn std::error::Error + Send + Sync>),
+
+    /// A hybrid KEM (X25519 + ML-KEM-768) operation failed.
+    #[error("hybrid KEM error: {0}")]
+    HybridKem(#[from] crate::hybrid_kem::HybridKemError),
+
+    /// IO or persistence failure.
+    #[error("io error: {0}")]
+    Io(String),
+
+    /// Application message (rich payload) parse or serialisation error.
+    #[error("app message: {0}")]
+    AppMessage(String),
+}

crates/quicproquo-core/src/hybrid_crypto.rs

@@ -0,0 +1,541 @@
+//! Post-quantum hybrid crypto provider for OpenMLS (M7 PoC).
+//!
+//! Uses X25519 + ML-KEM-768 hybrid KEM for HPKE operations where openmls
+//! would use DHKEM(X25519), and delegates all other operations (AEAD, hash,
+//! signatures, KDF, randomness) to `openmls_rust_crypto::RustCrypto`.
+//!
+//! # Key format
+//!
+//! When the provider sees a **hybrid public key** (length `HYBRID_PUBLIC_KEY_LEN` =
+//! 32 + 1184 bytes) or **hybrid private key** (length `HYBRID_PRIVATE_KEY_LEN` =
+//! 32 + 2400 bytes), it uses `hybrid_kem` for HPKE. Otherwise it delegates to
+//! RustCrypto (classical X25519 HPKE).
+//!
+//! # MLS compatibility
+//!
+//! The current MLS ciphersuite (MLS_128_DHKEMX25519_AES128GCM_SHA256_Ed25519)
+//! uses 32-byte X25519 init keys in the wire format. This provider can produce
+//! and consume **hybrid** init keys (1216-byte public, 2432-byte private), but
+//! that is a non-standard extension: other MLS implementations will not
+//! accept KeyPackages with hybrid init keys unless they implement the same
+//! extension. This PoC validates that the OpenMLS trait surface is satisfiable
+//! with a custom HPKE backend; full interoperability would require a new
+//! ciphersuite or protocol extension.
+
+use openmls_rust_crypto::RustCrypto;
+use openmls_traits::{
+    crypto::OpenMlsCrypto,
+    types::{
+        CryptoError, ExporterSecret, HpkeCiphertext, HpkeConfig, HpkeKeyPair, HpkeKemType,
+    },
+    OpenMlsCryptoProvider,
+};
+use tls_codec::SecretVLBytes;
+
+use crate::hybrid_kem::{
+    hybrid_decapsulate_only, hybrid_decrypt, hybrid_encapsulate_only, hybrid_encrypt,
+    hybrid_export, HybridKeypair, HybridPublicKey,
+    HYBRID_KEM_OUTPUT_LEN, HYBRID_PRIVATE_KEY_LEN, HYBRID_PUBLIC_KEY_LEN,
+};
+use crate::keystore::DiskKeyStore;
+
+// Re-export types used by OpenMlsCrypto (full path for clarity).
+use openmls_traits::types::{
+    AeadType, Ciphersuite, HashType, SignatureScheme,
+};
+
+/// Crypto backend that uses hybrid KEM for HPKE when keys are in hybrid format,
+/// and delegates everything else to RustCrypto.
+///
+/// When `hybrid_enabled` is `true`, `derive_hpke_keypair` produces hybrid keys
+/// (1216-byte public, 2432-byte private). When `false`, it delegates to
+/// RustCrypto and produces classical 32-byte X25519 keys.
+///
+/// The `hpke_seal` / `hpke_open` methods always detect the key format by length,
+/// so they work correctly regardless of the flag — a hybrid-length key will use
+/// hybrid KEM, a classical-length key will use RustCrypto.
+#[derive(Debug)]
+pub struct HybridCrypto {
+    rust_crypto: RustCrypto,
+    /// When true, `derive_hpke_keypair` produces hybrid (X25519 + ML-KEM-768)
+    /// keys. When false, it produces classical X25519 keys via RustCrypto.
+    hybrid_enabled: bool,
+}
+
+impl HybridCrypto {
+    /// Create a hybrid-enabled crypto backend (derive_hpke_keypair produces hybrid keys).
+    pub fn new() -> Self {
+        Self {
+            rust_crypto: RustCrypto::default(),
+            hybrid_enabled: true,
+        }
+    }
+
+    /// Alias for `new()` — hybrid mode enabled.
+    pub fn new_hybrid() -> Self {
+        Self::new()
+    }
+
+    /// Create a classical crypto backend (derive_hpke_keypair produces standard
+    /// X25519 keys, but seal/open still accept hybrid keys by length detection).
+    pub fn new_classical() -> Self {
+        Self {
+            rust_crypto: RustCrypto::default(),
+            hybrid_enabled: false,
+        }
+    }
+
+    /// Whether this backend produces hybrid keys from `derive_hpke_keypair`.
+    pub fn is_hybrid_enabled(&self) -> bool {
+        self.hybrid_enabled
+    }
+
+    /// Expose the underlying RustCrypto for rand() and delegation.
+    pub fn rust_crypto(&self) -> &RustCrypto {
+        &self.rust_crypto
+    }
+
+    fn is_hybrid_public_key(pk_r: &[u8]) -> bool {
+        pk_r.len() == HYBRID_PUBLIC_KEY_LEN
+    }
+
+    fn is_hybrid_private_key(sk_r: &[u8]) -> bool {
+        sk_r.len() == HYBRID_PRIVATE_KEY_LEN
+    }
+}
+
+impl Default for HybridCrypto {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl OpenMlsCrypto for HybridCrypto {
+    fn supports(&self, ciphersuite: Ciphersuite) -> Result<(), CryptoError> {
+        self.rust_crypto.supports(ciphersuite)
+    }
+
+    fn supported_ciphersuites(&self) -> Vec<Ciphersuite> {
+        self.rust_crypto.supported_ciphersuites()
+    }
+
+    fn hkdf_extract(
+        &self,
+        hash_type: HashType,
+        salt: &[u8],
+        ikm: &[u8],
+    ) -> Result<SecretVLBytes, CryptoError> {
+        self.rust_crypto.hkdf_extract(hash_type, salt, ikm)
+    }
+
+    fn hkdf_expand(
+        &self,
+        hash_type: HashType,
+        prk: &[u8],
+        info: &[u8],
+        okm_len: usize,
+    ) -> Result<SecretVLBytes, CryptoError> {
+        self.rust_crypto.hkdf_expand(hash_type, prk, info, okm_len)
+    }
+
+    fn hash(&self, hash_type: HashType, data: &[u8]) -> Result<Vec<u8>, CryptoError> {
+        self.rust_crypto.hash(hash_type, data)
+    }
+
+    fn aead_encrypt(
+        &self,
+        alg: AeadType,
+        key: &[u8],
+        data: &[u8],
+        nonce: &[u8],
+        aad: &[u8],
+    ) -> Result<Vec<u8>, CryptoError> {
+        self.rust_crypto.aead_encrypt(alg, key, data, nonce, aad)
+    }
+
+    fn aead_decrypt(
+        &self,
+        alg: AeadType,
+        key: &[u8],
+        ct_tag: &[u8],
+        nonce: &[u8],
+        aad: &[u8],
+    ) -> Result<Vec<u8>, CryptoError> {
+        self.rust_crypto.aead_decrypt(alg, key, ct_tag, nonce, aad)
+    }
+
+    fn signature_key_gen(&self, alg: SignatureScheme) -> Result<(Vec<u8>, Vec<u8>), CryptoError> {
+        self.rust_crypto.signature_key_gen(alg)
+    }
+
+    fn verify_signature(
+        &self,
+        alg: SignatureScheme,
+        data: &[u8],
+        pk: &[u8],
+        signature: &[u8],
+    ) -> Result<(), CryptoError> {
+        self.rust_crypto.verify_signature(alg, data, pk, signature)
+    }
+
+    fn sign(&self, alg: SignatureScheme, data: &[u8], key: &[u8]) -> Result<Vec<u8>, CryptoError> {
+        self.rust_crypto.sign(alg, data, key)
+    }
+
+    fn hpke_seal(
+        &self,
+        config: HpkeConfig,
+        pk_r: &[u8],
+        info: &[u8],
+        aad: &[u8],
+        ptxt: &[u8],
+    ) -> HpkeCiphertext {
+        if Self::is_hybrid_public_key(pk_r) {
+            // The trait `OpenMlsCrypto::hpke_seal` returns `HpkeCiphertext` (not
+            // `Result`), so we cannot propagate errors through the return type.
+            // Returning an empty ciphertext would silently cause data loss.
+            // Instead, panic on failure — a hybrid key that passes the length
+            // check but fails deserialization or encryption indicates a critical
+            // bug (corrupted key material), not a recoverable condition.
+            let recipient_pk = HybridPublicKey::from_bytes(pk_r)
+                .expect("hybrid public key deserialization failed — key material is corrupted");
+            // Pass HPKE info and aad through for proper context binding (RFC 9180).
+            let envelope = hybrid_encrypt(&recipient_pk, ptxt, info, aad)
+                .expect("hybrid HPKE encryption failed — critical crypto error");
+            let kem_output = envelope[..HYBRID_KEM_OUTPUT_LEN].to_vec();
+            let ciphertext = envelope[HYBRID_KEM_OUTPUT_LEN..].to_vec();
+            HpkeCiphertext {
+                kem_output: kem_output.into(),
+                ciphertext: ciphertext.into(),
+            }
+        } else {
+            self.rust_crypto.hpke_seal(config, pk_r, info, aad, ptxt)
+        }
+    }
+
+    fn hpke_open(
+        &self,
+        config: HpkeConfig,
+        input: &HpkeCiphertext,
+        sk_r: &[u8],
+        info: &[u8],
+        aad: &[u8],
+    ) -> Result<Vec<u8>, CryptoError> {
+        if Self::is_hybrid_private_key(sk_r) {
+            let keypair = HybridKeypair::from_private_bytes(sk_r)
+                .map_err(|_| CryptoError::HpkeDecryptionError)?;
+            let envelope: Vec<u8> = input
+                .kem_output.as_slice()
+                .iter()
+                .chain(input.ciphertext.as_slice())
+                .copied()
+                .collect();
+            // Pass HPKE info and aad through for proper context binding (RFC 9180).
+            hybrid_decrypt(&keypair, &envelope, info, aad)
+                .map_err(|_| CryptoError::HpkeDecryptionError)
+        } else {
+            self.rust_crypto.hpke_open(config, input, sk_r, info, aad)
+        }
+    }
+
+    fn hpke_setup_sender_and_export(
+        &self,
+        config: HpkeConfig,
+        pk_r: &[u8],
+        info: &[u8],
+        exporter_context: &[u8],
+        exporter_length: usize,
+    ) -> Result<(Vec<u8>, ExporterSecret), CryptoError> {
+        if Self::is_hybrid_public_key(pk_r) {
+            // A key that passes the hybrid length check but fails deserialization
+            // is corrupted — return an error instead of silently downgrading to
+            // classical crypto (which would defeat PQ protection).
+            let recipient_pk = HybridPublicKey::from_bytes(pk_r)
+                .map_err(|_| CryptoError::SenderSetupError)?;
+            let (kem_output, shared_secret) =
+                hybrid_encapsulate_only(&recipient_pk).map_err(|_| CryptoError::SenderSetupError)?;
+            let exported = hybrid_export(&shared_secret, exporter_context, exporter_length);
+            Ok((kem_output, exported.into()))
+        } else {
+            self.rust_crypto.hpke_setup_sender_and_export(
+                config, pk_r, info, exporter_context, exporter_length,
+            )
+        }
+    }
+
+    fn hpke_setup_receiver_and_export(
+        &self,
+        config: HpkeConfig,
+        enc: &[u8],
+        sk_r: &[u8],
+        info: &[u8],
+        exporter_context: &[u8],
+        exporter_length: usize,
+    ) -> Result<ExporterSecret, CryptoError> {
+        if Self::is_hybrid_private_key(sk_r) {
+            let keypair = HybridKeypair::from_private_bytes(sk_r)
+                .map_err(|_| CryptoError::ReceiverSetupError)?;
+            let shared_secret =
+                hybrid_decapsulate_only(&keypair, enc).map_err(|_| CryptoError::ReceiverSetupError)?;
+            let exported = hybrid_export(&shared_secret, exporter_context, exporter_length);
+            Ok(exported.into())
+        } else {
+            self.rust_crypto.hpke_setup_receiver_and_export(
+                config, enc, sk_r, info, exporter_context, exporter_length,
+            )
+        }
+    }
+
+    fn derive_hpke_keypair(&self, config: HpkeConfig, ikm: &[u8]) -> HpkeKeyPair {
+        if self.hybrid_enabled && config.0 == HpkeKemType::DhKem25519 {
+            let kp = HybridKeypair::derive_from_ikm(ikm);
+            let private_bytes = kp.private_to_bytes();
+            HpkeKeyPair {
+                private: private_bytes.as_slice().into(),
+                public: kp.public_key().to_bytes(),
+            }
+        } else {
+            self.rust_crypto.derive_hpke_keypair(config, ikm)
+        }
+    }
+}
+
+/// OpenMLS crypto provider that uses hybrid KEM for HPKE (when keys are in
+/// hybrid format) and delegates the rest to RustCrypto.
+#[derive(Debug)]
+pub struct HybridCryptoProvider {
+    crypto: HybridCrypto,
+    key_store: DiskKeyStore,
+}
+
+impl HybridCryptoProvider {
+    /// Create a hybrid-enabled provider (KeyPackages will contain hybrid init keys).
+    pub fn new(key_store: DiskKeyStore) -> Self {
+        Self {
+            crypto: HybridCrypto::new_hybrid(),
+            key_store,
+        }
+    }
+
+    /// Alias for `new()` — hybrid mode enabled.
+    pub fn new_hybrid(key_store: DiskKeyStore) -> Self {
+        Self::new(key_store)
+    }
+
+    /// Create a classical-mode provider (KeyPackages use standard X25519 init keys,
+    /// but seal/open still accept hybrid keys by length detection).
+    pub fn new_classical(key_store: DiskKeyStore) -> Self {
+        Self {
+            crypto: HybridCrypto::new_classical(),
+            key_store,
+        }
+    }
+
+    /// Whether this provider produces hybrid keys from `derive_hpke_keypair`.
+    pub fn is_hybrid_enabled(&self) -> bool {
+        self.crypto.is_hybrid_enabled()
+    }
+}
+
+impl Default for HybridCryptoProvider {
+    fn default() -> Self {
+        Self::new(DiskKeyStore::ephemeral())
+    }
+}
+
+impl OpenMlsCryptoProvider for HybridCryptoProvider {
+    type CryptoProvider = HybridCrypto;
+    type RandProvider = RustCrypto;
+    type KeyStoreProvider = DiskKeyStore;
+
+    fn crypto(&self) -> &Self::CryptoProvider {
+        &self.crypto
+    }
+
+    fn rand(&self) -> &Self::RandProvider {
+        self.crypto.rust_crypto()
+    }
+
+    fn key_store(&self) -> &Self::KeyStoreProvider {
+        &self.key_store
+    }
+}
+
+// ── Tests ───────────────────────────────────────────────────────────────────
+
+#[cfg(test)]
+#[allow(clippy::unwrap_used)]
+mod tests {
+    use super::*;
+    use openmls_traits::types::HpkeKdfType;
+
+    fn hpke_config_dhkem_x25519() -> HpkeConfig {
+        HpkeConfig(
+            HpkeKemType::DhKem25519,
+            HpkeKdfType::HkdfSha256,
+            openmls_traits::types::HpkeAeadType::AesGcm128,
+        )
+    }
+
+    /// HPKE path with hybrid keys: derive_hpke_keypair (hybrid) -> hpke_seal -> hpke_open.
+    #[test]
+    fn hybrid_hpke_seal_open_round_trip() {
+        let crypto = HybridCrypto::new();
+        let ikm = b"test-ikm-for-hybrid-hpke-keypair";
+
+        let keypair = crypto.derive_hpke_keypair(hpke_config_dhkem_x25519(), ikm);
+        assert_eq!(keypair.public.len(), HYBRID_PUBLIC_KEY_LEN);
+        assert_eq!(keypair.private.as_ref().len(), HYBRID_PRIVATE_KEY_LEN);
+
+        let plaintext = b"hello post-quantum MLS";
+        let info = b"mls 1.0 test";
+        let aad = b"additional data";
+
+        let ct = crypto.hpke_seal(
+            hpke_config_dhkem_x25519(),
+            &keypair.public,
+            info,
+            aad,
+            plaintext,
+        );
+        assert!(!ct.kem_output.as_slice().is_empty());
+        assert!(!ct.ciphertext.as_slice().is_empty());
+
+        let decrypted = crypto
+            .hpke_open(
+                hpke_config_dhkem_x25519(),
+                &ct,
+                keypair.private.as_ref(),
+                info,
+                aad,
+            )
+            .expect("hpke_open with hybrid keys");
+        assert_eq!(decrypted.as_slice(), plaintext);
+    }
+
+    /// HPKE exporter path: setup_sender_and_export then setup_receiver_and_export.
+    #[test]
+    fn hybrid_hpke_setup_sender_receiver_export() {
+        let crypto = HybridCrypto::new();
+        let ikm = b"exporter-ikm";
+
+        let keypair = crypto.derive_hpke_keypair(hpke_config_dhkem_x25519(), ikm);
+        let info = b"";
+        let exporter_context = b"MLS 1.0 external init";
+        let exporter_length = 32;
+
+        let (kem_output, sender_exported) = crypto
+            .hpke_setup_sender_and_export(
+                hpke_config_dhkem_x25519(),
+                &keypair.public,
+                info,
+                exporter_context,
+                exporter_length,
+            )
+            .expect("sender and export");
+
+        assert_eq!(kem_output.len(), HYBRID_KEM_OUTPUT_LEN);
+        assert_eq!(sender_exported.as_ref().len(), exporter_length);
+
+        let receiver_exported = crypto
+            .hpke_setup_receiver_and_export(
+                hpke_config_dhkem_x25519(),
+                &kem_output,
+                keypair.private.as_ref(),
+                info,
+                exporter_context,
+                exporter_length,
+            )
+            .expect("receiver and export");
+
+        assert_eq!(sender_exported.as_ref(), receiver_exported.as_ref());
+    }
+
+    /// Classical mode: derive_hpke_keypair produces standard 32-byte X25519 keys.
+    #[test]
+    fn classical_mode_produces_standard_keys() {
+        let crypto = HybridCrypto::new_classical();
+        let ikm = b"test-ikm-for-classical-hpke";
+
+        let keypair = crypto.derive_hpke_keypair(hpke_config_dhkem_x25519(), ikm);
+        // Classical X25519 keys are 32 bytes
+        assert_eq!(keypair.public.len(), 32);
+        assert_eq!(keypair.private.as_ref().len(), 32);
+    }
+
+    /// Classical mode round-trip: seal/open works with classical keys.
+    #[test]
+    fn classical_mode_seal_open_round_trip() {
+        let crypto = HybridCrypto::new_classical();
+        let ikm = b"test-ikm-for-classical-round-trip";
+
+        let keypair = crypto.derive_hpke_keypair(hpke_config_dhkem_x25519(), ikm);
+        assert_eq!(keypair.public.len(), 32); // classical key
+
+        let plaintext = b"hello classical MLS";
+        let info = b"mls 1.0 test";
+        let aad = b"additional data";
+
+        let ct = crypto.hpke_seal(
+            hpke_config_dhkem_x25519(),
+            &keypair.public,
+            info,
+            aad,
+            plaintext,
+        );
+        assert!(!ct.kem_output.as_slice().is_empty());
+
+        let decrypted = crypto
+            .hpke_open(
+                hpke_config_dhkem_x25519(),
+                &ct,
+                keypair.private.as_ref(),
+                info,
+                aad,
+            )
+            .expect("hpke_open with classical keys");
+        assert_eq!(decrypted.as_slice(), plaintext);
+    }
+
+    /// KeyPackage generation with HybridCryptoProvider (validates full HPKE path in MLS).
+    #[test]
+    fn key_package_generation_with_hybrid_provider() {
+        use openmls::prelude::{
+            Credential, CredentialType, CredentialWithKey, CryptoConfig, KeyPackage,
+        };
+        use std::sync::Arc;
+        use tls_codec::Serialize;
+
+        use crate::identity::IdentityKeypair;
+
+        const CIPHERSUITE: Ciphersuite =
+            Ciphersuite::MLS_128_DHKEMX25519_AES128GCM_SHA256_Ed25519;
+
+        let provider = HybridCryptoProvider::default();
+        let identity = Arc::new(IdentityKeypair::generate());
+
+        let credential = Credential::new(
+            identity.public_key_bytes().to_vec(),
+            CredentialType::Basic,
+        )
+        .unwrap();
+        let credential_with_key = CredentialWithKey {
+            credential,
+            signature_key: identity.public_key_bytes().to_vec().into(),
+        };
+
+        let key_package = KeyPackage::builder()
+            .build(
+                CryptoConfig::with_default_version(CIPHERSUITE),
+                &provider,
+                identity.as_ref(),
+                credential_with_key,
+            )
+            .expect("KeyPackage with hybrid HPKE");
+
+        let bytes = key_package
+            .tls_serialize_detached()
+            .expect("serialize KeyPackage");
+        assert!(!bytes.is_empty());
+    }
+}

crates/quicproquo-core/src/hybrid_kem.rs

@@ -28,7 +28,7 @@ use ml_kem::{
     kem::{Decapsulate, Encapsulate},
     EncodedSizeUser, KemCore, MlKem768, MlKem768Params,
 };
-use rand::{rngs::OsRng, RngCore};
+use rand::{rngs::OsRng, rngs::StdRng, CryptoRng, RngCore, SeedableRng};
 use serde::{Deserialize, Serialize};
 use sha2::Sha256;
 use x25519_dalek::{EphemeralSecret, PublicKey as X25519Public, StaticSecret};
@@ -41,8 +41,14 @@ use ml_kem::kem::{DecapsulationKey, EncapsulationKey};
 const HYBRID_VERSION: u8 = 0x01;
 
 /// HKDF info string for domain separation.
+/// Frozen at the original project name for backward compatibility with existing
+/// encrypted state files and messages. Do not change.
 const HKDF_INFO: &[u8] = b"quicnprotochat-hybrid-v1";
 
+/// HKDF salt for domain separation (defence-in-depth; IKM already has 64 bytes of entropy).
+/// Frozen — see [`HKDF_INFO`].
+const HKDF_SALT: &[u8] = b"quicnprotochat-hybrid-v1-salt";
+
 /// ML-KEM-768 ciphertext size in bytes.
 const MLKEM_CT_LEN: usize = 1088;
 
@@ -55,6 +61,15 @@ pub const MLKEM_DK_LEN: usize = 2400;
 /// Envelope header: version(1) + x25519 eph pk(32) + mlkem ct(1088) + nonce(12).
 const HEADER_LEN: usize = 1 + 32 + MLKEM_CT_LEN + 12;
 
+/// KEM output length (version + x25519 eph pk + mlkem ct) for HPKE adapter.
+pub const HYBRID_KEM_OUTPUT_LEN: usize = 1 + 32 + MLKEM_CT_LEN;
+
+/// Hybrid public key length: x25519(32) + mlkem_ek(1184). Used to detect hybrid keys in MLS.
+pub const HYBRID_PUBLIC_KEY_LEN: usize = 32 + MLKEM_EK_LEN;
+
+/// Hybrid private key length: x25519(32) + mlkem_dk(2400). Used to detect hybrid keys in MLS.
+pub const HYBRID_PRIVATE_KEY_LEN: usize = 32 + MLKEM_DK_LEN;
+
 // ── Error type ──────────────────────────────────────────────────────────────
 
 #[derive(Debug, thiserror::Error)]
@@ -109,12 +124,21 @@ pub struct HybridPublicKey {
     pub mlkem_ek: Vec<u8>,
 }
 
+/// HKDF info for deriving HPKE keypair seed from IKM (MLS compatibility).
+/// Frozen — see [`HKDF_INFO`].
+const HKDF_INFO_HPKE_KEYPAIR: &[u8] = b"quicnprotochat-hybrid-hpke-keypair-v1";
+
 impl HybridKeypair {
     /// Generate a fresh hybrid keypair from OS CSPRNG.
     pub fn generate() -> Self {
-        let x25519_sk = StaticSecret::random_from_rng(OsRng);
+        Self::generate_from_rng(&mut OsRng)
+    }
+
+    /// Generate a hybrid keypair from a seeded RNG (deterministic).
+    pub fn generate_from_rng<R: RngCore + CryptoRng>(rng: &mut R) -> Self {
+        let x25519_sk = StaticSecret::random_from_rng(&mut *rng);
         let x25519_pk = X25519Public::from(&x25519_sk);
-        let (mlkem_dk, mlkem_ek) = MlKem768::generate(&mut OsRng);
+        let (mlkem_dk, mlkem_ek) = MlKem768::generate(rng);
 
         Self {
             x25519_sk,
@@ -124,6 +148,49 @@ impl HybridKeypair {
         }
     }
 
+    /// Derive a deterministic hybrid keypair from IKM (for MLS HPKE key schedule).
+    pub fn derive_from_ikm(ikm: &[u8]) -> Self {
+        let mut seed = [0u8; 32];
+        let hk = Hkdf::<Sha256>::new(None, ikm);
+        hk.expand(HKDF_INFO_HPKE_KEYPAIR, &mut seed)
+            .expect("32 bytes is valid HKDF output");
+        let mut rng = StdRng::from_seed(seed);
+        Self::generate_from_rng(&mut rng)
+    }
+
+    /// Serialise private key for MLS key store: x25519_sk(32) || mlkem_dk(2400).
+    ///
+    /// The returned value is wrapped in [`Zeroizing`] so secret key material
+    /// is securely erased when dropped.
+    pub fn private_to_bytes(&self) -> Zeroizing<Vec<u8>> {
+        let mut out = Vec::with_capacity(HYBRID_PRIVATE_KEY_LEN);
+        out.extend_from_slice(self.x25519_sk.as_bytes());
+        out.extend_from_slice(self.mlkem_dk.as_bytes().as_slice());
+        Zeroizing::new(out)
+    }
+
+    /// Reconstruct a hybrid keypair from private key bytes (from MLS key store).
+    pub fn from_private_bytes(bytes: &[u8]) -> Result<Self, HybridKemError> {
+        if bytes.len() != HYBRID_PRIVATE_KEY_LEN {
+            return Err(HybridKemError::TooShort(bytes.len()));
+        }
+        let x25519_sk = StaticSecret::from(<[u8; 32]>::try_from(&bytes[0..32])
+            .expect("slice is exactly 32 bytes (guaranteed by HYBRID_PRIVATE_KEY_LEN check)"));
+        let x25519_pk = X25519Public::from(&x25519_sk);
+
+        let mlkem_dk_arr = Array::try_from(&bytes[32..32 + MLKEM_DK_LEN])
+            .map_err(|_| HybridKemError::InvalidMlKemKey)?;
+        let mlkem_dk = DecapsulationKey::<MlKem768Params>::from_bytes(&mlkem_dk_arr);
+        let mlkem_ek = mlkem_dk.encapsulation_key().clone();
+
+        Ok(Self {
+            x25519_sk,
+            x25519_pk,
+            mlkem_dk,
+            mlkem_ek,
+        })
+    }
+
     /// Reconstruct from serialised bytes.
     pub fn from_bytes(bytes: &HybridKeypairBytes) -> Result<Self, HybridKemError> {
         let x25519_sk = StaticSecret::from(*bytes.x25519_sk);
@@ -191,10 +258,15 @@ impl HybridPublicKey {
 
 /// Encrypt `plaintext` to `recipient_pk` using X25519 + ML-KEM-768 hybrid KEM.
 ///
+/// `info` is optional HPKE context info incorporated into key derivation.
+/// `aad` is optional additional authenticated data bound to the AEAD ciphertext.
+///
 /// Returns the complete hybrid envelope as a byte vector.
 pub fn hybrid_encrypt(
     recipient_pk: &HybridPublicKey,
     plaintext: &[u8],
+    info: &[u8],
+    aad: &[u8],
 ) -> Result<Vec<u8>, HybridKemError> {
     // 1. Ephemeral X25519 DH
     let eph_secret = EphemeralSecret::random_from_rng(OsRng);
@@ -210,18 +282,19 @@ pub fn hybrid_encrypt(
         .encapsulate(&mut OsRng)
         .map_err(|_| HybridKemError::EncryptionFailed)?;
 
-    // 3. Derive AEAD key from combined shared secrets
-    let aead_key = derive_aead_key(x25519_ss.as_bytes(), mlkem_ss.as_slice());
+    // 3. Derive AEAD key from combined shared secrets (with caller info for context binding)
+    let aead_key = derive_aead_key(x25519_ss.as_bytes(), mlkem_ss.as_slice(), info);
 
     // Generate a random 12-byte nonce (not derived from HKDF).
     let mut nonce_bytes = [0u8; 12];
     OsRng.fill_bytes(&mut nonce_bytes);
     let aead_nonce = *Nonce::from_slice(&nonce_bytes);
 
-    // 4. AEAD encrypt
+    // 4. AEAD encrypt with caller-supplied AAD
     let cipher = ChaCha20Poly1305::new(&aead_key);
+    let aead_payload = chacha20poly1305::aead::Payload { msg: plaintext, aad };
     let ct = cipher
-        .encrypt(&aead_nonce, plaintext)
+        .encrypt(&aead_nonce, aead_payload)
         .map_err(|_| HybridKemError::EncryptionFailed)?;
 
     // 5. Assemble envelope: version || x25519_eph_pk || mlkem_ct || nonce || aead_ct
@@ -236,9 +309,13 @@ pub fn hybrid_encrypt(
 }
 
 /// Decrypt a hybrid envelope using the recipient's private key.
+///
+/// `info` and `aad` must match what was passed to `hybrid_encrypt`.
 pub fn hybrid_decrypt(
     keypair: &HybridKeypair,
     envelope: &[u8],
+    info: &[u8],
+    aad: &[u8],
 ) -> Result<Vec<u8>, HybridKemError> {
     if envelope.len() < HEADER_LEN + 16 {
         // 16 = minimum AEAD tag
@@ -274,39 +351,123 @@ pub fn hybrid_decrypt(
 
     // 2. ML-KEM decapsulation — convert bytes to the ciphertext array type
     //    that `DecapsulationKey::decapsulate` expects.
-    let mlkem_ct_arr = Array::try_from(mlkem_ct_bytes)
+    let mlkem_ct_arr =
+        Array::try_from(mlkem_ct_bytes).map_err(|_| HybridKemError::MlKemDecapsFailed)?;
+    let mlkem_ss = keypair
+        .mlkem_dk
+        .decapsulate(&mlkem_ct_arr)
+        .map_err(|_| HybridKemError::MlKemDecapsFailed)?;
+
+    // 3. Derive AEAD key (with caller info for context binding)
+    let aead_key = derive_aead_key(x25519_ss.as_bytes(), mlkem_ss.as_slice(), info);
+
+    // 4. Decrypt with caller-supplied AAD
+    let cipher = ChaCha20Poly1305::new(&aead_key);
+    let aead_payload = chacha20poly1305::aead::Payload { msg: aead_ct, aad };
+    let plaintext = cipher
+        .decrypt(nonce, aead_payload)
+        .map_err(|_| HybridKemError::DecryptionFailed)?;
+
+    Ok(plaintext)
+}
+
+/// Encapsulate only: compute shared secret and KEM output (no AEAD).
+/// Returns `(kem_output, shared_secret)` where `kem_output` is the first
+/// `HYBRID_KEM_OUTPUT_LEN` bytes of the hybrid envelope and `shared_secret`
+/// is the 32-byte derived key (same as used for AEAD in `hybrid_encrypt`).
+/// Used by MLS HPKE exporter (setup_sender_and_export).
+pub fn hybrid_encapsulate_only(
+    recipient_pk: &HybridPublicKey,
+) -> Result<(Vec<u8>, [u8; 32]), HybridKemError> {
+    let eph_secret = EphemeralSecret::random_from_rng(OsRng);
+    let eph_public = X25519Public::from(&eph_secret);
+    let x25519_recipient = X25519Public::from(recipient_pk.x25519_pk);
+    let x25519_ss = eph_secret.diffie_hellman(&x25519_recipient);
+
+    let mlkem_ek_arr = Array::try_from(recipient_pk.mlkem_ek.as_slice())
+        .map_err(|_| HybridKemError::InvalidMlKemKey)?;
+    let mlkem_ek = EncapsulationKey::<MlKem768Params>::from_bytes(&mlkem_ek_arr);
+    let (mlkem_ct, mlkem_ss) = mlkem_ek
+        .encapsulate(&mut OsRng)
+        .map_err(|_| HybridKemError::EncryptionFailed)?;
+
+    let aead_key = derive_aead_key(x25519_ss.as_bytes(), mlkem_ss.as_slice(), b"");
+    let shared_secret: [u8; 32] = aead_key.as_slice().try_into()
+        .expect("AEAD key is always exactly 32 bytes");
+
+    let mut kem_output = Vec::with_capacity(HYBRID_KEM_OUTPUT_LEN);
+    kem_output.push(HYBRID_VERSION);
+    kem_output.extend_from_slice(&eph_public.to_bytes());
+    kem_output.extend_from_slice(mlkem_ct.as_slice());
+
+    Ok((kem_output, shared_secret))
+}
+
+/// Decapsulate only: recover shared secret from KEM output (no AEAD).
+/// Used by MLS HPKE exporter (setup_receiver_and_export).
+pub fn hybrid_decapsulate_only(
+    keypair: &HybridKeypair,
+    kem_output: &[u8],
+) -> Result<[u8; 32], HybridKemError> {
+    if kem_output.len() < HYBRID_KEM_OUTPUT_LEN {
+        return Err(HybridKemError::TooShort(kem_output.len()));
+    }
+    if kem_output[0] != HYBRID_VERSION {
+        return Err(HybridKemError::UnsupportedVersion(kem_output[0]));
+    }
+
+    let eph_pk_bytes: [u8; 32] = kem_output[1..33].try_into()
+        .expect("slice is exactly 32 bytes (guaranteed by HYBRID_KEM_OUTPUT_LEN check)");
+    let eph_pk = X25519Public::from(eph_pk_bytes);
+    let x25519_ss = keypair.x25519_sk.diffie_hellman(&eph_pk);
+
+    let mlkem_ct_arr = Array::try_from(&kem_output[33..33 + MLKEM_CT_LEN])
         .map_err(|_| HybridKemError::MlKemDecapsFailed)?;
     let mlkem_ss = keypair
         .mlkem_dk
         .decapsulate(&mlkem_ct_arr)
         .map_err(|_| HybridKemError::MlKemDecapsFailed)?;
 
-    // 3. Derive AEAD key
-    let aead_key = derive_aead_key(x25519_ss.as_bytes(), mlkem_ss.as_slice());
+    let aead_key = derive_aead_key(x25519_ss.as_bytes(), mlkem_ss.as_slice(), b"");
+    Ok(aead_key.as_slice().try_into()
+        .expect("AEAD key is always exactly 32 bytes"))
+}
 
-    // 4. Decrypt
-    let cipher = ChaCha20Poly1305::new(&aead_key);
-    let plaintext = cipher
-        .decrypt(nonce, aead_ct)
-        .map_err(|_| HybridKemError::DecryptionFailed)?;
-
-    Ok(plaintext)
+/// Export a secret from shared secret (MLS HPKE exporter compatibility).
+/// Uses HKDF-Expand(prk, exporter_context, length) with prk = HKDF-Extract(0, shared_secret).
+pub fn hybrid_export(
+    shared_secret: &[u8; 32],
+    exporter_context: &[u8],
+    length: usize,
+) -> Vec<u8> {
+    let hk = Hkdf::<Sha256>::new(Some(HKDF_SALT), shared_secret);
+    let mut out = vec![0u8; length];
+    hk.expand(exporter_context, &mut out).expect("valid length");
+    out
 }
 
 /// Derive AEAD key from the combined X25519 + ML-KEM shared secrets.
 ///
+/// `extra_info` is optional caller-supplied context (e.g. HPKE `info`) that is
+/// appended to the domain-separation label for additional binding.
+///
 /// The nonce is generated randomly per-encryption rather than derived from
 /// HKDF, preventing nonce reuse when the same shared secret is (accidentally)
 /// used more than once.
-fn derive_aead_key(x25519_ss: &[u8], mlkem_ss: &[u8]) -> Key {
+fn derive_aead_key(x25519_ss: &[u8], mlkem_ss: &[u8], extra_info: &[u8]) -> Key {
     let mut ikm = Zeroizing::new(vec![0u8; x25519_ss.len() + mlkem_ss.len()]);
     ikm[..x25519_ss.len()].copy_from_slice(x25519_ss);
     ikm[x25519_ss.len()..].copy_from_slice(mlkem_ss);
 
-    let hk = Hkdf::<Sha256>::new(None, &ikm);
+    let hk = Hkdf::<Sha256>::new(Some(HKDF_SALT), &ikm);
+
+    // Combine domain-separation label with caller-supplied context.
+    let mut info = Vec::with_capacity(HKDF_INFO.len() + extra_info.len());
+    info.extend_from_slice(HKDF_INFO);
+    info.extend_from_slice(extra_info);
 
     let mut key_bytes = Zeroizing::new([0u8; 32]);
-    hk.expand(HKDF_INFO, &mut *key_bytes)
+    hk.expand(&info, &mut *key_bytes)
         .expect("32 bytes is valid HKDF-SHA256 output length");
 
     *Key::from_slice(&*key_bytes)
@@ -315,6 +476,7 @@ fn derive_aead_key(x25519_ss: &[u8], mlkem_ss: &[u8]) -> Key {
 // ── Tests ───────────────────────────────────────────────────────────────────
 
 #[cfg(test)]
+#[allow(clippy::unwrap_used)]
 mod tests {
     use super::*;
 
@@ -332,21 +494,39 @@ mod tests {
         let pk = kp.public_key();
         let plaintext = b"hello post-quantum world!";
 
-        let envelope = hybrid_encrypt(&pk, plaintext).unwrap();
-        let recovered = hybrid_decrypt(&kp, &envelope).unwrap();
+        let envelope = hybrid_encrypt(&pk, plaintext, b"", b"").unwrap();
+        let recovered = hybrid_decrypt(&kp, &envelope, b"", b"").unwrap();
 
         assert_eq!(recovered, plaintext);
     }
 
+    #[test]
+    fn encrypt_decrypt_with_info_aad() {
+        let kp = HybridKeypair::generate();
+        let pk = kp.public_key();
+        let plaintext = b"context-bound payload";
+        let info = b"mls epoch 42";
+        let aad = b"group-id-abc";
+
+        let envelope = hybrid_encrypt(&pk, plaintext, info, aad).unwrap();
+        let recovered = hybrid_decrypt(&kp, &envelope, info, aad).unwrap();
+        assert_eq!(recovered, plaintext);
+
+        // Mismatched info must fail
+        assert!(hybrid_decrypt(&kp, &envelope, b"wrong info", aad).is_err());
+        // Mismatched aad must fail
+        assert!(hybrid_decrypt(&kp, &envelope, info, b"wrong aad").is_err());
+    }
+
     #[test]
     fn wrong_key_decryption_fails() {
         let kp_sender_target = HybridKeypair::generate();
         let kp_wrong = HybridKeypair::generate();
 
         let pk = kp_sender_target.public_key();
-        let envelope = hybrid_encrypt(&pk, b"secret").unwrap();
+        let envelope = hybrid_encrypt(&pk, b"secret", b"", b"").unwrap();
 
-        let result = hybrid_decrypt(&kp_wrong, &envelope);
+        let result = hybrid_decrypt(&kp_wrong, &envelope, b"", b"");
         assert!(result.is_err());
     }
 
@@ -355,12 +535,12 @@ mod tests {
         let kp = HybridKeypair::generate();
         let pk = kp.public_key();
 
-        let mut envelope = hybrid_encrypt(&pk, b"payload").unwrap();
+        let mut envelope = hybrid_encrypt(&pk, b"payload", b"", b"").unwrap();
         let last = envelope.len() - 1;
         envelope[last] ^= 0x01;
 
         assert!(matches!(
-            hybrid_decrypt(&kp, &envelope),
+            hybrid_decrypt(&kp, &envelope, b"", b""),
             Err(HybridKemError::DecryptionFailed)
         ));
     }
@@ -370,11 +550,11 @@ mod tests {
         let kp = HybridKeypair::generate();
         let pk = kp.public_key();
 
-        let mut envelope = hybrid_encrypt(&pk, b"payload").unwrap();
+        let mut envelope = hybrid_encrypt(&pk, b"payload", b"", b"").unwrap();
         // Flip a byte in the ML-KEM ciphertext region (starts at offset 33)
         envelope[40] ^= 0xFF;
 
-        assert!(hybrid_decrypt(&kp, &envelope).is_err());
+        assert!(hybrid_decrypt(&kp, &envelope, b"", b"").is_err());
     }
 
     #[test]
@@ -382,11 +562,11 @@ mod tests {
         let kp = HybridKeypair::generate();
         let pk = kp.public_key();
 
-        let mut envelope = hybrid_encrypt(&pk, b"payload").unwrap();
+        let mut envelope = hybrid_encrypt(&pk, b"payload", b"", b"").unwrap();
         // Flip a byte in the X25519 ephemeral pk region (offset 1..33)
         envelope[5] ^= 0xFF;
 
-        assert!(hybrid_decrypt(&kp, &envelope).is_err());
+        assert!(hybrid_decrypt(&kp, &envelope, b"", b"").is_err());
     }
 
     #[test]
@@ -394,11 +574,11 @@ mod tests {
         let kp = HybridKeypair::generate();
         let pk = kp.public_key();
 
-        let mut envelope = hybrid_encrypt(&pk, b"payload").unwrap();
+        let mut envelope = hybrid_encrypt(&pk, b"payload", b"", b"").unwrap();
         envelope[0] = 0xFF;
 
         assert!(matches!(
-            hybrid_decrypt(&kp, &envelope),
+            hybrid_decrypt(&kp, &envelope, b"", b""),
             Err(HybridKemError::UnsupportedVersion(0xFF))
         ));
     }
@@ -407,7 +587,7 @@ mod tests {
     fn envelope_too_short_rejected() {
         let kp = HybridKeypair::generate();
         assert!(matches!(
-            hybrid_decrypt(&kp, &[0x01; 10]),
+            hybrid_decrypt(&kp, &[0x01; 10], b"", b""),
             Err(HybridKemError::TooShort(10))
         ));
     }
@@ -419,15 +599,12 @@ mod tests {
         let restored = HybridKeypair::from_bytes(&bytes).unwrap();
 
         assert_eq!(kp.x25519_pk.to_bytes(), restored.x25519_pk.to_bytes());
-        assert_eq!(
-            kp.public_key().mlkem_ek,
-            restored.public_key().mlkem_ek
-        );
+        assert_eq!(kp.public_key().mlkem_ek, restored.public_key().mlkem_ek);
 
         // Verify restored keypair can decrypt
         let pk = kp.public_key();
-        let ct = hybrid_encrypt(&pk, b"test").unwrap();
-        let pt = hybrid_decrypt(&restored, &ct).unwrap();
+        let ct = hybrid_encrypt(&pk, b"test", b"", b"").unwrap();
+        let pt = hybrid_decrypt(&restored, &ct, b"", b"").unwrap();
         assert_eq!(pt, b"test");
     }
 
@@ -448,8 +625,8 @@ mod tests {
         let pk = kp.public_key();
         let plaintext = vec![0xAB; 50_000]; // 50 KB
 
-        let envelope = hybrid_encrypt(&pk, &plaintext).unwrap();
-        let recovered = hybrid_decrypt(&kp, &envelope).unwrap();
+        let envelope = hybrid_encrypt(&pk, &plaintext, b"", b"").unwrap();
+        let recovered = hybrid_decrypt(&kp, &envelope, b"", b"").unwrap();
 
         assert_eq!(recovered, plaintext);
     }

crates/quicproquo-core/src/identity.rs

@@ -0,0 +1,245 @@
+//! Ed25519 identity keypair for MLS credentials and AS registration.
+//!
+//! The [`IdentityKeypair`] is the long-term identity key embedded in MLS
+//! `BasicCredential`s. It is used for signing MLS messages and as the
+//! indexing key for the Authentication Service.
+//!
+//! # Zeroize
+//!
+//! The 32-byte private seed is stored as `Zeroizing<[u8; 32]>`, which zeroes
+//! the bytes on drop. `[u8; 32]` is `Copy + Default` and satisfies zeroize's
+//! `DefaultIsZeroes` constraint, avoiding a conflict with ed25519-dalek's
+//! `SigningKey` zeroize impl.
+//!
+//! # Fingerprint
+//!
+//! A 32-byte SHA-256 digest of the raw public key bytes is used as a compact,
+//! collision-resistant identifier for logging.
+
+use ed25519_dalek::{Signer as DalekSigner, SigningKey, VerifyingKey};
+use serde::{Deserialize, Serialize};
+use sha2::{Digest, Sha256};
+use zeroize::Zeroizing;
+
+/// An Ed25519 identity keypair.
+///
+/// Created with [`IdentityKeypair::generate`]. The private signing key seed
+/// is zeroed when this struct is dropped.
+pub struct IdentityKeypair {
+    /// Raw 32-byte private seed — zeroized on drop.
+    ///
+    /// Stored as bytes rather than `SigningKey` to satisfy zeroize's
+    /// `DefaultIsZeroes` bound on `Zeroizing<T>`.
+    seed: Zeroizing<[u8; 32]>,
+    /// Corresponding 32-byte public verifying key.
+    verifying: VerifyingKey,
+}
+
+impl IdentityKeypair {
+    /// Recreate an identity keypair from a 32-byte seed.
+    pub fn from_seed(seed: [u8; 32]) -> Self {
+        let signing = SigningKey::from_bytes(&seed);
+        let verifying = signing.verifying_key();
+        Self {
+            seed: Zeroizing::new(seed),
+            verifying,
+        }
+    }
+
+    /// Return the raw 32-byte private seed (for persistence).
+    ///
+    /// The returned value is wrapped in [`Zeroizing`] so it is securely
+    /// erased when dropped, preventing the seed from lingering in memory.
+    pub fn seed_bytes(&self) -> Zeroizing<[u8; 32]> {
+        Zeroizing::new(*self.seed)
+    }
+}
+
+impl IdentityKeypair {
+    /// Generate a fresh random Ed25519 identity keypair.
+    pub fn generate() -> Self {
+        use rand::rngs::OsRng;
+        let signing = SigningKey::generate(&mut OsRng);
+        let verifying = signing.verifying_key();
+        let seed = Zeroizing::new(signing.to_bytes());
+        Self { seed, verifying }
+    }
+
+    /// Return the raw 32-byte Ed25519 public key.
+    ///
+    /// This is the byte array used as `identityKey` in `auth.capnp` calls.
+    pub fn public_key_bytes(&self) -> [u8; 32] {
+        self.verifying.to_bytes()
+    }
+
+    /// Return the SHA-256 fingerprint of the public key (32 bytes).
+    pub fn fingerprint(&self) -> [u8; 32] {
+        let mut hasher = Sha256::new();
+        hasher.update(self.verifying.to_bytes());
+        hasher.finalize().into()
+    }
+
+    /// Reconstruct the `SigningKey` from the stored seed bytes.
+    fn signing_key(&self) -> SigningKey {
+        SigningKey::from_bytes(&self.seed)
+    }
+}
+
+/// Implement the openmls `Signer` trait so `IdentityKeypair` can be passed
+/// directly to `KeyPackage::builder().build(...)` without needing the external
+/// `openmls_basic_credential` crate.
+#[cfg(feature = "native")]
+impl openmls_traits::signatures::Signer for IdentityKeypair {
+    fn sign(&self, payload: &[u8]) -> Result<Vec<u8>, openmls_traits::types::Error> {
+        let sk = self.signing_key();
+        let sig: ed25519_dalek::Signature = sk.sign(payload);
+        Ok(sig.to_bytes().to_vec())
+    }
+
+    fn signature_scheme(&self) -> openmls_traits::types::SignatureScheme {
+        openmls_traits::types::SignatureScheme::ED25519
+    }
+}
+
+impl IdentityKeypair {
+    /// Sign arbitrary bytes with the Ed25519 key and return the 64-byte signature.
+    ///
+    /// Used by sealed sender to sign the inner payload for recipient verification.
+    pub fn sign_raw(&self, payload: &[u8]) -> [u8; 64] {
+        let sk = self.signing_key();
+        let sig: ed25519_dalek::Signature = sk.sign(payload);
+        sig.to_bytes()
+    }
+
+    /// Verify an Ed25519 signature over `payload` using the given public key.
+    pub fn verify_raw(
+        public_key: &[u8; 32],
+        payload: &[u8],
+        signature: &[u8; 64],
+    ) -> Result<(), crate::error::CoreError> {
+        use ed25519_dalek::Verifier;
+
+        let vk = VerifyingKey::from_bytes(public_key)
+            .map_err(|e| crate::error::CoreError::Mls(format!("invalid public key: {e}")))?;
+        let sig = ed25519_dalek::Signature::from_bytes(signature);
+        vk.verify(payload, &sig)
+            .map_err(|e| crate::error::CoreError::Mls(format!("signature verification failed: {e}")))
+    }
+}
+
+/// Verify a 96-byte delivery proof produced by the server's `build_delivery_proof`.
+///
+/// # Layout
+/// ```text
+/// bytes  0..32 — SHA-256(seq_le || recipient_key || timestamp_ms_le)
+/// bytes 32..96 — Ed25519 signature over those 32 bytes
+/// ```
+///
+/// Returns `Ok(true)` when the proof is structurally valid and the signature verifies,
+/// `Ok(false)` when the proof length is wrong (graceful degradation for old servers),
+/// or `Err` when the signature is structurally invalid / verification fails.
+pub fn verify_delivery_proof(
+    server_pubkey: &[u8; 32],
+    proof: &[u8],
+) -> Result<bool, crate::error::CoreError> {
+    if proof.len() != 96 {
+        return Ok(false);
+    }
+    let hash: [u8; 32] = proof[..32].try_into().expect("slice is 32 bytes");
+    let sig: [u8; 64] = proof[32..96].try_into().expect("slice is 64 bytes");
+    IdentityKeypair::verify_raw(server_pubkey, &hash, &sig)?;
+    Ok(true)
+}
+
+impl Serialize for IdentityKeypair {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: serde::Serializer,
+    {
+        serializer.serialize_bytes(&self.seed[..])
+    }
+}
+
+impl<'de> Deserialize<'de> for IdentityKeypair {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: serde::Deserializer<'de>,
+    {
+        let bytes: Vec<u8> = serde::Deserialize::deserialize(deserializer)?;
+        let seed: [u8; 32] = bytes
+            .as_slice()
+            .try_into()
+            .map_err(|_| serde::de::Error::custom("identity seed must be 32 bytes"))?;
+        Ok(IdentityKeypair::from_seed(seed))
+    }
+}
+
+impl std::fmt::Debug for IdentityKeypair {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let fp = self.fingerprint();
+        f.debug_struct("IdentityKeypair")
+            .field(
+                "fingerprint",
+                &format!("{:02x}{:02x}{:02x}{:02x}…", fp[0], fp[1], fp[2], fp[3]),
+            )
+            .finish_non_exhaustive()
+    }
+}
+
+#[cfg(test)]
+#[allow(clippy::unwrap_used)]
+mod proof_tests {
+    use super::*;
+    use sha2::{Digest, Sha256};
+
+    fn make_proof(kp: &IdentityKeypair, seq: u64, recipient_key: &[u8], timestamp_ms: u64) -> Vec<u8> {
+        let mut hasher = Sha256::new();
+        hasher.update(seq.to_le_bytes());
+        hasher.update(recipient_key);
+        hasher.update(timestamp_ms.to_le_bytes());
+        let hash: [u8; 32] = hasher.finalize().into();
+        let sig = kp.sign_raw(&hash);
+        let mut proof = vec![0u8; 96];
+        proof[..32].copy_from_slice(&hash);
+        proof[32..].copy_from_slice(&sig);
+        proof
+    }
+
+    #[test]
+    fn verify_valid_proof() {
+        let kp = IdentityKeypair::generate();
+        let pk = kp.public_key_bytes();
+        let rk = [0xabu8; 32];
+        let proof = make_proof(&kp, 42, &rk, 1_700_000_000_000);
+        assert!(verify_delivery_proof(&pk, &proof).unwrap());
+    }
+
+    #[test]
+    fn reject_wrong_length() {
+        let kp = IdentityKeypair::generate();
+        let pk = kp.public_key_bytes();
+        assert!(!verify_delivery_proof(&pk, &[0u8; 64]).unwrap());
+        assert!(!verify_delivery_proof(&pk, &[]).unwrap());
+        assert!(!verify_delivery_proof(&pk, &[0u8; 97]).unwrap());
+    }
+
+    #[test]
+    fn reject_tampered_hash() {
+        let kp = IdentityKeypair::generate();
+        let pk = kp.public_key_bytes();
+        let rk = [0x01u8; 32];
+        let mut proof = make_proof(&kp, 1, &rk, 999);
+        proof[0] ^= 0xff; // corrupt the hash bytes
+        assert!(verify_delivery_proof(&pk, &proof).is_err());
+    }
+
+    #[test]
+    fn reject_wrong_pubkey() {
+        let kp = IdentityKeypair::generate();
+        let other = IdentityKeypair::generate();
+        let pk = other.public_key_bytes();
+        let rk = [0x02u8; 32];
+        let proof = make_proof(&kp, 5, &rk, 0);
+        assert!(verify_delivery_proof(&pk, &proof).is_err());
+    }
+}

crates/quicproquo-core/src/keypackage.rs

@@ -14,19 +14,48 @@
 //! # Wire format
 //!
 //! KeyPackages are TLS-encoded using `tls_codec` (same version as openmls).
-//! The resulting bytes are opaque to the quicnprotochat transport layer.
+//! The resulting bytes are opaque to the quicproquo transport layer.
 
 use openmls::prelude::{
     Ciphersuite, Credential, CredentialType, CredentialWithKey, CryptoConfig, KeyPackage,
-    TlsSerializeTrait,
+    KeyPackageIn, TlsDeserializeTrait, TlsSerializeTrait,
 };
 use openmls_rust_crypto::OpenMlsRustCrypto;
 use sha2::{Digest, Sha256};
 
 use crate::{error::CoreError, identity::IdentityKeypair};
 
-/// The MLS ciphersuite used throughout quicnprotochat.
-const CIPHERSUITE: Ciphersuite = Ciphersuite::MLS_128_DHKEMX25519_AES128GCM_SHA256_Ed25519;
+/// The MLS ciphersuite used throughout quicproquo (RFC 9420 §17.1).
+pub const ALLOWED_CIPHERSUITE: Ciphersuite =
+    Ciphersuite::MLS_128_DHKEMX25519_AES128GCM_SHA256_Ed25519;
+
+/// Wire value of the allowed ciphersuite (KeyPackage TLS encoding: version 2B, ciphersuite 2B).
+const ALLOWED_CIPHERSUITE_WIRE: u16 = 0x0001;
+
+const CIPHERSUITE: Ciphersuite = ALLOWED_CIPHERSUITE;
+
+/// Validates that the KeyPackage bytes use an allowed ciphersuite (Phase 2: ciphersuite allowlist).
+///
+/// Parses the TLS-encoded KeyPackage and rejects if the ciphersuite is not
+/// `MLS_128_DHKEMX25519_AES128GCM_SHA256_Ed25519`. Does not verify signatures;
+/// the server uses this only to enforce policy before storing.
+pub fn validate_keypackage_ciphersuite(bytes: &[u8]) -> Result<(), CoreError> {
+    if bytes.len() < 4 {
+        return Err(CoreError::Mls("KeyPackage too short for version+ciphersuite".into()));
+    }
+    let cs_wire = u16::from_be_bytes([bytes[2], bytes[3]]);
+    if cs_wire != ALLOWED_CIPHERSUITE_WIRE {
+        return Err(CoreError::Mls(format!(
+            "KeyPackage ciphersuite {:#06x} not in allowlist (only {:#06x} allowed)",
+            cs_wire, ALLOWED_CIPHERSUITE_WIRE
+        )));
+    }
+    // Optionally confirm full parse so we don't accept garbage that happens to have 0x0001 at offset 2.
+    let mut cursor = bytes;
+    let _kp = KeyPackageIn::tls_deserialize(&mut cursor)
+        .map_err(|e| CoreError::Mls(format!("KeyPackage parse: {e:?}")))?;
+    Ok(())
+}
 
 /// Generate a fresh MLS KeyPackage for `identity` and serialise it.
 ///

crates/quicproquo-core/src/keystore.rs

@@ -5,16 +5,24 @@ use std::{
     sync::RwLock,
 };
 
-use openmls_rust_crypto::RustCrypto;
-use openmls_traits::{
-    key_store::{MlsEntity, OpenMlsKeyStore},
-    OpenMlsCryptoProvider,
-};
+use openmls_traits::key_store::{MlsEntity, OpenMlsKeyStore};
 
 /// A disk-backed key store implementing `OpenMlsKeyStore`.
 ///
 /// In-memory when `path` is `None`; otherwise flushes the entire map to disk on
 /// every store/delete so HPKE init keys survive process restarts.
+///
+/// # Serialization
+///
+/// Uses bincode for both individual MLS entity values and the outer HashMap
+/// container. This is required because OpenMLS types use bincode-compatible
+/// serialization, and `HashMap<Vec<u8>, Vec<u8>>` requires a binary format
+/// (JSON mandates string keys).
+///
+/// # Persistence security
+///
+/// When `path` is set, file permissions are restricted to owner-only (0o600)
+/// on Unix platforms, since the store may contain HPKE private keys.
 #[derive(Debug)]
 pub struct DiskKeyStore {
     path: Option<PathBuf>,
@@ -46,28 +54,55 @@ impl DiskKeyStore {
             if bytes.is_empty() {
                 HashMap::new()
             } else {
-                bincode::deserialize(&bytes).map_err(|_| DiskKeyStoreError::Serialization)?
+                bincode::deserialize(&bytes)
+                    .map_err(|_| DiskKeyStoreError::Serialization)?
             }
         } else {
             HashMap::new()
         };
 
-        Ok(Self {
+        let store = Self {
             path: Some(path),
             values: RwLock::new(values),
-        })
+        };
+
+        // Set restrictive file permissions on the keystore file.
+        store.set_file_permissions()?;
+
+        Ok(store)
     }
 
     fn flush(&self) -> Result<(), DiskKeyStoreError> {
         let Some(path) = &self.path else {
             return Ok(());
         };
-        let values = self.values.read().unwrap();
+        let values = self.values.read().map_err(|_| DiskKeyStoreError::Io("lock poisoned".into()))?;
         let bytes = bincode::serialize(&*values).map_err(|_| DiskKeyStoreError::Serialization)?;
         if let Some(parent) = path.parent() {
             fs::create_dir_all(parent).map_err(|e| DiskKeyStoreError::Io(e.to_string()))?;
         }
-        fs::write(path, bytes).map_err(|e| DiskKeyStoreError::Io(e.to_string()))
+        fs::write(path, &bytes).map_err(|e| DiskKeyStoreError::Io(e.to_string()))?;
+        self.set_file_permissions()?;
+        Ok(())
+    }
+
+    /// Restrict file permissions to owner-only (0o600) on Unix.
+    #[cfg(unix)]
+    fn set_file_permissions(&self) -> Result<(), DiskKeyStoreError> {
+        use std::os::unix::fs::PermissionsExt;
+        if let Some(path) = &self.path {
+            if path.exists() {
+                let perms = std::fs::Permissions::from_mode(0o600);
+                fs::set_permissions(path, perms)
+                    .map_err(|e| DiskKeyStoreError::Io(format!("set permissions: {e}")))?;
+            }
+        }
+        Ok(())
+    }
+
+    #[cfg(not(unix))]
+    fn set_file_permissions(&self) -> Result<(), DiskKeyStoreError> {
+        Ok(())
     }
 }
 
@@ -81,64 +116,27 @@ impl OpenMlsKeyStore for DiskKeyStore {
     type Error = DiskKeyStoreError;
 
     fn store<V: MlsEntity>(&self, k: &[u8], v: &V) -> Result<(), Self::Error> {
-        let value = serde_json::to_vec(v).map_err(|_| DiskKeyStoreError::Serialization)?;
-        let mut values = self.values.write().unwrap();
+        let value = bincode::serialize(v).map_err(|_| DiskKeyStoreError::Serialization)?;
+        let mut values = self.values.write().map_err(|_| DiskKeyStoreError::Io("lock poisoned".into()))?;
         values.insert(k.to_vec(), value);
         drop(values);
         self.flush()
     }
 
     fn read<V: MlsEntity>(&self, k: &[u8]) -> Option<V> {
-        let values = self.values.read().unwrap();
+        let values = match self.values.read() {
+            Ok(v) => v,
+            Err(_) => return None,
+        };
         values
             .get(k)
-            .and_then(|bytes| serde_json::from_slice(bytes).ok())
+            .and_then(|bytes| bincode::deserialize(bytes).ok())
     }
 
     fn delete<V: MlsEntity>(&self, k: &[u8]) -> Result<(), Self::Error> {
-        let mut values = self.values.write().unwrap();
+        let mut values = self.values.write().map_err(|_| DiskKeyStoreError::Io("lock poisoned".into()))?;
         values.remove(k);
         drop(values);
         self.flush()
     }
 }
-
-/// Crypto provider that couples RustCrypto with a disk-backed key store.
-#[derive(Debug)]
-pub struct StoreCrypto {
-    crypto: RustCrypto,
-    key_store: DiskKeyStore,
-}
-
-impl StoreCrypto {
-    pub fn new(key_store: DiskKeyStore) -> Self {
-        Self {
-            crypto: RustCrypto::default(),
-            key_store,
-        }
-    }
-}
-
-impl Default for StoreCrypto {
-    fn default() -> Self {
-        Self::new(DiskKeyStore::ephemeral())
-    }
-}
-
-impl OpenMlsCryptoProvider for StoreCrypto {
-    type CryptoProvider = RustCrypto;
-    type RandProvider = RustCrypto;
-    type KeyStoreProvider = DiskKeyStore;
-
-    fn crypto(&self) -> &Self::CryptoProvider {
-        &self.crypto
-    }
-
-    fn rand(&self) -> &Self::RandProvider {
-        &self.crypto
-    }
-
-    fn key_store(&self) -> &Self::KeyStoreProvider {
-        &self.key_store
-    }
-}

crates/quicproquo-core/src/lib.rs

@@ -0,0 +1,99 @@
+//! Core cryptographic primitives, MLS group state machine, and hybrid
+//! post-quantum KEM for quicproquo.
+//!
+//! # WASM support
+//!
+//! When compiled with `--no-default-features` (disabling the `native` feature),
+//! the following modules are available for `wasm32-unknown-unknown`:
+//!
+//! - `identity` — Ed25519 identity keypair (generate, sign, verify)
+//! - `hybrid_kem` — X25519 + ML-KEM-768 hybrid key encapsulation
+//! - `safety_numbers` — Signal-style safety number computation
+//! - `sealed_sender` — sender identity + Ed25519 signature envelope
+//! - `app_message` — rich application message serialisation/parsing
+//! - `padding` — message padding to hide plaintext lengths
+//! - `transcript` — encrypted tamper-evident message transcript
+//! - `error` — `CoreError` type
+//!
+//! The following modules require the `native` feature (MLS, OPAQUE, Cap'n Proto):
+//!
+//! - `group` — MLS group state machine (openmls)
+//! - `keypackage` — MLS KeyPackage generation
+//! - `hybrid_crypto` — hybrid HPKE provider for OpenMLS
+//! - `keystore` — OpenMLS key store with optional disk persistence
+//! - `opaque_auth` — OPAQUE cipher suite configuration
+//!
+//! # Module layout
+//!
+//! | Module        | Responsibility                                                   |
+//! |---------------|------------------------------------------------------------------|
+//! | `app_message` | Rich application payload (Chat, Reply, Reaction, ReadReceipt, Typing) |
+//! | `error`       | [`CoreError`] type                                               |
+//! | `identity`   | [`IdentityKeypair`] — Ed25519 identity key for MLS credentials   |
+//! | `keypackage` | [`generate_key_package`] — standalone KeyPackage generation      |
+//! | `group`      | [`GroupMember`] — MLS group lifecycle (create/join/send/recv)    |
+//! | `hybrid_kem` | Hybrid X25519 + ML-KEM-768 key encapsulation                    |
+//! | `keystore`   | [`DiskKeyStore`] — OpenMLS key store with optional persistence   |
+
+mod app_message;
+mod error;
+mod hybrid_kem;
+mod identity;
+pub mod padding;
+pub mod pq_noise;
+#[cfg(feature = "native")]
+pub mod recovery;
+pub mod safety_numbers;
+pub mod sealed_sender;
+pub mod transcript;
+
+// ── Native-only modules (MLS, OPAQUE, filesystem) ───────────────────────────
+#[cfg(feature = "native")]
+mod group;
+#[cfg(feature = "native")]
+mod hybrid_crypto;
+#[cfg(feature = "native")]
+mod keypackage;
+#[cfg(feature = "native")]
+mod keystore;
+#[cfg(feature = "native")]
+pub mod opaque_auth;
+
+// ── Public API (always available) ───────────────────────────────────────────
+
+pub use app_message::{
+    serialize, serialize_chat, serialize_delete, serialize_dummy, serialize_edit,
+    serialize_file_ref, serialize_reaction, serialize_read_receipt, serialize_reply,
+    serialize_typing, parse, generate_message_id,
+    AppMessage, MessageType, VERSION as APP_MESSAGE_VERSION,
+};
+pub use error::CoreError;
+pub use hybrid_kem::{
+    hybrid_decrypt, hybrid_encrypt, HybridKemError, HybridKeypair, HybridKeypairBytes,
+    HybridPublicKey,
+};
+pub use identity::{verify_delivery_proof, IdentityKeypair};
+#[cfg(feature = "native")]
+pub use recovery::{
+    constant_time_eq, generate_recovery_codes, recover_from_bundle, recovery_token_hash,
+    RecoveryBundle, RecoveryPayload, RecoverySetup, MAX_BUNDLE_SIZE, RECOVERY_CODE_COUNT,
+};
+pub use safety_numbers::compute_safety_number;
+pub use transcript::{
+    read_transcript, validate_transcript_structure, ChainVerdict, DecodedRecord, TranscriptRecord,
+    TranscriptWriter,
+};
+// Deprecated re-export for backward compatibility.
+#[allow(deprecated)]
+pub use transcript::verify_transcript_chain;
+
+// ── Public API (native only) ────────────────────────────────────────────────
+
+#[cfg(feature = "native")]
+pub use group::{GroupMember, ReceivedMessage, ReceivedMessageWithSender};
+#[cfg(feature = "native")]
+pub use hybrid_crypto::{HybridCrypto, HybridCryptoProvider};
+#[cfg(feature = "native")]
+pub use keypackage::{generate_key_package, validate_keypackage_ciphersuite};
+#[cfg(feature = "native")]
+pub use keystore::DiskKeyStore;

crates/quicproquo-core/src/opaque_auth.rs

@@ -5,7 +5,7 @@
 
 use opaque_ke::CipherSuite;
 
-/// OPAQUE cipher suite for quicnprotochat.
+/// OPAQUE cipher suite for quicproquo.
 ///
 /// - **OPRF**: Ristretto255 (curve25519-based, ~128-bit security)
 /// - **Key exchange**: Triple-DH (3DH) over Ristretto255 with SHA-512
@@ -14,9 +14,7 @@ pub struct OpaqueSuite;
 
 impl CipherSuite for OpaqueSuite {
     type OprfCs = opaque_ke::Ristretto255;
-    type KeyExchange = opaque_ke::key_exchange::tripledh::TripleDh<
-        opaque_ke::Ristretto255,
-        sha2::Sha512,
-    >;
+    type KeyExchange =
+        opaque_ke::key_exchange::tripledh::TripleDh<opaque_ke::Ristretto255, sha2::Sha512>;
     type Ksf = argon2::Argon2<'static>;
 }

crates/quicproquo-core/src/padding.rs

@@ -0,0 +1,265 @@
+//! Message padding to hide plaintext lengths from the server.
+//!
+//! Pads payloads to fixed bucket sizes before MLS encryption so that the
+//! ciphertext does not reveal the actual message length.
+//!
+//! # Wire format
+//!
+//! ```text
+//! [real_length: 4 bytes LE (u32)][payload: real_length bytes][random padding]
+//! ```
+//!
+//! The total padded output is always one of the bucket sizes: 256, 1024, 4096, 16384 bytes.
+//! For payloads larger than 16380 bytes, rounds up to the nearest 16384-byte multiple.
+//!
+//! ## Uniform boundary padding (traffic analysis resistance)
+//!
+//! [`pad_uniform`] / [`unpad_uniform`] pad to a configurable byte boundary
+//! (default 256) instead of exponential buckets. This produces more uniform
+//! ciphertext sizes at the cost of slightly more padding overhead.
+
+use rand::RngCore;
+
+use crate::error::CoreError;
+
+/// Default uniform padding boundary in bytes.
+pub const DEFAULT_PADDING_BOUNDARY: usize = 256;
+
+/// Bucket sizes in bytes. The smallest (256) accommodates a sealed sender
+/// envelope (99 bytes overhead) plus a short message.
+const BUCKETS: &[usize] = &[256, 1024, 4096, 16384];
+
+/// Select the smallest bucket that fits `content_len + 4` (the 4-byte length prefix).
+fn bucket_for(content_len: usize) -> usize {
+    let total = content_len + 4;
+    for &b in BUCKETS {
+        if total <= b {
+            return b;
+        }
+    }
+    // Larger than biggest bucket: round up to nearest 16384-byte multiple.
+    total.div_ceil(16384) * 16384
+}
+
+/// Pad a payload to the next bucket boundary with cryptographic random bytes.
+pub fn pad(payload: &[u8]) -> Vec<u8> {
+    let bucket = bucket_for(payload.len());
+    let mut out = Vec::with_capacity(bucket);
+    out.extend_from_slice(&(payload.len() as u32).to_le_bytes());
+    out.extend_from_slice(payload);
+    let pad_len = bucket - 4 - payload.len();
+    if pad_len > 0 {
+        let mut padding = vec![0u8; pad_len];
+        rand::rngs::OsRng.fill_bytes(&mut padding);
+        out.extend_from_slice(&padding);
+    }
+    out
+}
+
+/// Remove padding and return the original payload.
+pub fn unpad(padded: &[u8]) -> Result<Vec<u8>, CoreError> {
+    if padded.len() < 4 {
+        return Err(CoreError::AppMessage("padded message too short".into()));
+    }
+    let real_len = u32::from_le_bytes([padded[0], padded[1], padded[2], padded[3]]) as usize;
+    if 4 + real_len > padded.len() {
+        return Err(CoreError::AppMessage(
+            "padded real_length exceeds buffer".into(),
+        ));
+    }
+    Ok(padded[4..4 + real_len].to_vec())
+}
+
+/// Pad a payload to the nearest multiple of `boundary` bytes.
+///
+/// Uses the same wire format as [`pad`]: `[real_length: 4 bytes LE][payload][random padding]`.
+/// The total output length is always a multiple of `boundary`. A `boundary` of 0 is
+/// treated as [`DEFAULT_PADDING_BOUNDARY`].
+pub fn pad_uniform(payload: &[u8], boundary: usize) -> Vec<u8> {
+    let boundary = if boundary == 0 { DEFAULT_PADDING_BOUNDARY } else { boundary };
+    let total = payload.len() + 4; // 4-byte length prefix
+    let padded_len = total.div_ceil(boundary) * boundary;
+
+    let mut out = Vec::with_capacity(padded_len);
+    out.extend_from_slice(&(payload.len() as u32).to_le_bytes());
+    out.extend_from_slice(payload);
+    let pad_len = padded_len - total;
+    if pad_len > 0 {
+        let mut padding = vec![0u8; pad_len];
+        rand::rngs::OsRng.fill_bytes(&mut padding);
+        out.extend_from_slice(&padding);
+    }
+    out
+}
+
+/// Remove uniform padding. Wire format is identical to [`unpad`].
+pub fn unpad_uniform(padded: &[u8]) -> Result<Vec<u8>, CoreError> {
+    unpad(padded)
+}
+
+/// Generate a decoy payload that looks identical to a real padded message.
+///
+/// Returns random bytes of length equal to a `boundary`-aligned padded message.
+/// The 4-byte length prefix is set to 0, so [`unpad_uniform`] returns an empty payload.
+pub fn generate_decoy(boundary: usize) -> Vec<u8> {
+    let boundary = if boundary == 0 { DEFAULT_PADDING_BOUNDARY } else { boundary };
+    let mut out = vec![0u8; boundary];
+    // Length prefix = 0 (decoy carries no real payload).
+    // Fill the rest with random bytes so it is indistinguishable from padding.
+    rand::rngs::OsRng.fill_bytes(&mut out[4..]);
+    out
+}
+
+#[cfg(test)]
+#[allow(clippy::unwrap_used)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn round_trip_small() {
+        let msg = b"hello";
+        let padded = pad(msg);
+        assert_eq!(padded.len(), 256); // smallest bucket
+        let unpadded = unpad(&padded).unwrap();
+        assert_eq!(unpadded, msg);
+    }
+
+    #[test]
+    fn round_trip_medium() {
+        let msg = vec![0xAB; 300];
+        let padded = pad(&msg);
+        assert_eq!(padded.len(), 1024); // second bucket
+        let unpadded = unpad(&padded).unwrap();
+        assert_eq!(unpadded, msg);
+    }
+
+    #[test]
+    fn round_trip_large() {
+        let msg = vec![0xCD; 2000];
+        let padded = pad(&msg);
+        assert_eq!(padded.len(), 4096); // third bucket
+        let unpadded = unpad(&padded).unwrap();
+        assert_eq!(unpadded, msg);
+    }
+
+    #[test]
+    fn round_trip_very_large() {
+        let msg = vec![0xEF; 10000];
+        let padded = pad(&msg);
+        assert_eq!(padded.len(), 16384); // largest bucket
+        let unpadded = unpad(&padded).unwrap();
+        assert_eq!(unpadded, msg);
+    }
+
+    #[test]
+    fn round_trip_oversized() {
+        let msg = vec![0xFF; 20000];
+        let padded = pad(&msg);
+        assert_eq!(padded.len(), 32768); // 2 * 16384
+        let unpadded = unpad(&padded).unwrap();
+        assert_eq!(unpadded, msg);
+    }
+
+    #[test]
+    fn round_trip_empty() {
+        let msg = b"";
+        let padded = pad(msg);
+        assert_eq!(padded.len(), 256); // smallest bucket
+        let unpadded = unpad(&padded).unwrap();
+        assert_eq!(unpadded, msg);
+    }
+
+    #[test]
+    fn exactly_at_bucket_boundary() {
+        // 252 + 4 = 256 → fits in 256 bucket exactly
+        let msg = vec![0x42; 252];
+        let padded = pad(&msg);
+        assert_eq!(padded.len(), 256);
+        let unpadded = unpad(&padded).unwrap();
+        assert_eq!(unpadded, msg);
+    }
+
+    #[test]
+    fn unpad_too_short_fails() {
+        assert!(unpad(&[0, 0]).is_err());
+    }
+
+    #[test]
+    fn unpad_invalid_length_fails() {
+        // Claims 1000 bytes but only has 10
+        let mut bad = (1000u32).to_le_bytes().to_vec();
+        bad.extend_from_slice(&[0u8; 10]);
+        assert!(unpad(&bad).is_err());
+    }
+
+    // ── Uniform padding tests ──────────────────────────────────────────────
+
+    #[test]
+    fn uniform_round_trip_default_boundary() {
+        let msg = b"uniform padding test";
+        let padded = pad_uniform(msg, DEFAULT_PADDING_BOUNDARY);
+        assert_eq!(padded.len() % DEFAULT_PADDING_BOUNDARY, 0);
+        assert_eq!(padded.len(), 256); // 20 + 4 = 24, rounds up to 256
+        let unpadded = unpad_uniform(&padded).unwrap();
+        assert_eq!(unpadded, msg);
+    }
+
+    #[test]
+    fn uniform_custom_boundary() {
+        let msg = vec![0xAA; 100];
+        let padded = pad_uniform(&msg, 128);
+        assert_eq!(padded.len() % 128, 0);
+        assert_eq!(padded.len(), 128); // 100 + 4 = 104, rounds up to 128
+        let unpadded = unpad_uniform(&padded).unwrap();
+        assert_eq!(unpadded, msg);
+    }
+
+    #[test]
+    fn uniform_exact_boundary() {
+        // 252 + 4 = 256, exactly on boundary
+        let msg = vec![0xBB; 252];
+        let padded = pad_uniform(&msg, 256);
+        assert_eq!(padded.len(), 256);
+        let unpadded = unpad_uniform(&padded).unwrap();
+        assert_eq!(unpadded, msg);
+    }
+
+    #[test]
+    fn uniform_one_over_boundary() {
+        // 253 + 4 = 257, rounds up to 512
+        let msg = vec![0xCC; 253];
+        let padded = pad_uniform(&msg, 256);
+        assert_eq!(padded.len(), 512);
+        let unpadded = unpad_uniform(&padded).unwrap();
+        assert_eq!(unpadded, msg);
+    }
+
+    #[test]
+    fn uniform_zero_boundary_uses_default() {
+        let msg = b"zero boundary";
+        let padded = pad_uniform(msg, 0);
+        assert_eq!(padded.len() % DEFAULT_PADDING_BOUNDARY, 0);
+        let unpadded = unpad_uniform(&padded).unwrap();
+        assert_eq!(unpadded, msg);
+    }
+
+    #[test]
+    fn decoy_is_boundary_aligned() {
+        let decoy = generate_decoy(256);
+        assert_eq!(decoy.len(), 256);
+        assert_eq!(decoy.len() % 256, 0);
+    }
+
+    #[test]
+    fn decoy_unpads_to_empty() {
+        let decoy = generate_decoy(256);
+        let payload = unpad_uniform(&decoy).unwrap();
+        assert!(payload.is_empty());
+    }
+
+    #[test]
+    fn decoy_default_boundary() {
+        let decoy = generate_decoy(0);
+        assert_eq!(decoy.len(), DEFAULT_PADDING_BOUNDARY);
+    }
+}

crates/quicproquo-core/src/pq_noise.rs

@@ -0,0 +1,689 @@
+//! Hybrid Noise_XX + ML-KEM-768 handshake for post-quantum transport security.
+//!
+//! Implements a three-message Noise_XX pattern with an embedded ML-KEM-768
+//! encapsulation to produce a hybrid shared secret that is secure against
+//! both classical and quantum adversaries.
+//!
+//! # Handshake pattern
+//!
+//! ```text
+//! XX(s, rs):
+//!   -> e                          (initiator ephemeral)
+//!   <- e, ee, s, es, mlkem_ct    (responder ephemeral + static + ML-KEM ciphertext)
+//!   -> s, se                     (initiator static)
+//! ```
+//!
+//! After message 2, the ML-KEM shared secret is mixed into the chaining key
+//! via HKDF. The final transport keys incorporate both the X25519 DH chain
+//! and the ML-KEM shared secret.
+//!
+//! # Wire format
+//!
+//! Each handshake message is a simple length-prefixed blob:
+//! ```text
+//! [msg_len: u32 BE][handshake message bytes]
+//! ```
+//!
+//! # Feature gate
+//!
+//! This module is always compiled but the `pq-noise` feature enables it
+//! in the RPC layer for server/client negotiation.
+
+use chacha20poly1305::{
+    aead::{Aead, KeyInit, Payload},
+    ChaCha20Poly1305, Key, Nonce,
+};
+use hkdf::Hkdf;
+use ml_kem::{
+    array::Array,
+    kem::{Decapsulate, Encapsulate},
+    EncodedSizeUser, KemCore, MlKem768, MlKem768Params,
+};
+use ml_kem::kem::{DecapsulationKey, EncapsulationKey};
+use rand::rngs::OsRng;
+use sha2::Sha256;
+use x25519_dalek::{PublicKey as X25519Public, StaticSecret};
+use zeroize::Zeroizing;
+
+use crate::error::CoreError;
+
+/// Domain separation label for the hybrid Noise handshake.
+const PROTOCOL_NAME: &[u8] = b"quicproquo-pq-noise-v1";
+
+/// ML-KEM-768 encapsulation key length.
+const MLKEM_EK_LEN: usize = 1184;
+
+/// ML-KEM-768 ciphertext length.
+const MLKEM_CT_LEN: usize = 1088;
+
+/// AEAD tag length (ChaCha20-Poly1305).
+const TAG_LEN: usize = 16;
+
+// ── Keypair ──────────────────────────────────────────────────────────────────
+
+/// A static keypair for the hybrid Noise handshake.
+///
+/// Contains both an X25519 static key and an ML-KEM-768 key pair.
+pub struct NoiseKeypair {
+    x25519_sk: StaticSecret,
+    x25519_pk: X25519Public,
+    mlkem_dk: DecapsulationKey<MlKem768Params>,
+    mlkem_ek: EncapsulationKey<MlKem768Params>,
+}
+
+impl NoiseKeypair {
+    /// Generate a fresh keypair from OS CSPRNG.
+    pub fn generate() -> Self {
+        let x25519_sk = StaticSecret::random_from_rng(OsRng);
+        let x25519_pk = X25519Public::from(&x25519_sk);
+        let (mlkem_dk, mlkem_ek) = MlKem768::generate(&mut OsRng);
+        Self {
+            x25519_sk,
+            x25519_pk,
+            mlkem_dk,
+            mlkem_ek,
+        }
+    }
+
+    /// Return the X25519 public key bytes.
+    pub fn x25519_public(&self) -> [u8; 32] {
+        self.x25519_pk.to_bytes()
+    }
+
+    /// Return the ML-KEM-768 encapsulation key bytes.
+    pub fn mlkem_public(&self) -> Vec<u8> {
+        self.mlkem_ek.as_bytes().to_vec()
+    }
+}
+
+// ── Chaining key state ───────────────────────────────────────────────────────
+
+/// Internal handshake state tracking the Noise chaining key and handshake hash.
+struct HandshakeState {
+    /// Chaining key — evolved by each MixKey operation.
+    ck: Zeroizing<[u8; 32]>,
+    /// Handshake hash — commits to all handshake transcript data.
+    h: [u8; 32],
+    /// Current encryption key (derived from ck after MixKey).
+    k: Option<Zeroizing<[u8; 32]>>,
+    /// Nonce counter for in-handshake encryption.
+    n: u64,
+}
+
+impl HandshakeState {
+    fn new() -> Self {
+        // Initialize h = SHA-256(protocol_name), ck = h.
+        use sha2::{Digest, Sha256};
+        let h: [u8; 32] = Sha256::digest(PROTOCOL_NAME).into();
+        Self {
+            ck: Zeroizing::new(h),
+            h,
+            k: None,
+            n: 0,
+        }
+    }
+
+    /// MixHash: h = SHA-256(h || data)
+    fn mix_hash(&mut self, data: &[u8]) {
+        use sha2::{Digest, Sha256};
+        let mut hasher = Sha256::new();
+        hasher.update(self.h);
+        hasher.update(data);
+        self.h = hasher.finalize().into();
+    }
+
+    /// MixKey: (ck, k) = HKDF(ck, input_key_material)
+    fn mix_key(&mut self, ikm: &[u8]) {
+        let hk = Hkdf::<Sha256>::new(Some(&*self.ck), ikm);
+        let mut ck = Zeroizing::new([0u8; 32]);
+        let mut k = Zeroizing::new([0u8; 32]);
+        hk.expand(b"ck", &mut *ck)
+            .expect("32 bytes is valid HKDF output");
+        hk.expand(b"k", &mut *k)
+            .expect("32 bytes is valid HKDF output");
+        self.ck = ck;
+        self.k = Some(k);
+        self.n = 0;
+    }
+
+    /// Encrypt plaintext with the current key and nonce, using h as AAD.
+    fn encrypt_and_hash(&mut self, plaintext: &[u8]) -> Result<Vec<u8>, CoreError> {
+        let key = self
+            .k
+            .as_ref()
+            .ok_or_else(|| CoreError::Mls("pq_noise: no encryption key set".into()))?;
+        let cipher = ChaCha20Poly1305::new(Key::from_slice(&**key));
+        let nonce = nonce_from_counter(self.n);
+        let ct = cipher
+            .encrypt(
+                Nonce::from_slice(&nonce),
+                Payload {
+                    msg: plaintext,
+                    aad: &self.h,
+                },
+            )
+            .map_err(|_| CoreError::Mls("pq_noise: encrypt failed".into()))?;
+        self.mix_hash(&ct);
+        self.n += 1;
+        Ok(ct)
+    }
+
+    /// Decrypt ciphertext with the current key and nonce, using h as AAD.
+    fn decrypt_and_hash(&mut self, ciphertext: &[u8]) -> Result<Vec<u8>, CoreError> {
+        let key = self
+            .k
+            .as_ref()
+            .ok_or_else(|| CoreError::Mls("pq_noise: no decryption key set".into()))?;
+        let cipher = ChaCha20Poly1305::new(Key::from_slice(&**key));
+        let nonce = nonce_from_counter(self.n);
+        let ct_for_hash = ciphertext.to_vec();
+        let pt = cipher
+            .decrypt(
+                Nonce::from_slice(&nonce),
+                Payload {
+                    msg: ciphertext,
+                    aad: &self.h,
+                },
+            )
+            .map_err(|_| CoreError::Mls("pq_noise: decrypt failed".into()))?;
+        self.mix_hash(&ct_for_hash);
+        self.n += 1;
+        Ok(pt)
+    }
+
+    /// Split the handshake state into two transport keys (initiator->responder, responder->initiator).
+    fn split(&self) -> (TransportKey, TransportKey) {
+        let hk = Hkdf::<Sha256>::new(Some(&*self.ck), &[]);
+        let mut k1 = Zeroizing::new([0u8; 32]);
+        let mut k2 = Zeroizing::new([0u8; 32]);
+        hk.expand(b"initiator", &mut *k1)
+            .expect("32 bytes is valid HKDF output");
+        hk.expand(b"responder", &mut *k2)
+            .expect("32 bytes is valid HKDF output");
+        (
+            TransportKey { key: k1, nonce: 0 },
+            TransportKey { key: k2, nonce: 0 },
+        )
+    }
+}
+
+fn nonce_from_counter(n: u64) -> [u8; 12] {
+    let mut nonce = [0u8; 12];
+    nonce[4..].copy_from_slice(&n.to_le_bytes());
+    nonce
+}
+
+// ── Transport ────────────────────────────────────────────────────────────────
+
+/// A transport encryption key with a nonce counter.
+pub struct TransportKey {
+    key: Zeroizing<[u8; 32]>,
+    nonce: u64,
+}
+
+impl TransportKey {
+    /// Encrypt a message for transport.
+    pub fn encrypt(&mut self, plaintext: &[u8]) -> Result<Vec<u8>, CoreError> {
+        let cipher = ChaCha20Poly1305::new(Key::from_slice(&*self.key));
+        let nonce = nonce_from_counter(self.nonce);
+        let ct = cipher
+            .encrypt(Nonce::from_slice(&nonce), plaintext)
+            .map_err(|_| CoreError::Mls("pq_noise transport: encrypt failed".into()))?;
+        self.nonce += 1;
+        Ok(ct)
+    }
+
+    /// Decrypt a transport message.
+    pub fn decrypt(&mut self, ciphertext: &[u8]) -> Result<Vec<u8>, CoreError> {
+        let cipher = ChaCha20Poly1305::new(Key::from_slice(&*self.key));
+        let nonce = nonce_from_counter(self.nonce);
+        let pt = cipher
+            .decrypt(Nonce::from_slice(&nonce), ciphertext)
+            .map_err(|_| CoreError::Mls("pq_noise transport: decrypt failed".into()))?;
+        self.nonce += 1;
+        Ok(pt)
+    }
+}
+
+// ── Initiator ────────────────────────────────────────────────────────────────
+
+/// Initiator side of the hybrid Noise_XX handshake.
+pub struct Initiator {
+    state: HandshakeState,
+    /// Ephemeral secret stored as StaticSecret so DH doesn't consume it.
+    /// Generated from OsRng; we use StaticSecret purely for the non-consuming
+    /// `diffie_hellman(&self, ...)` API — the key is still ephemeral.
+    e_sk: StaticSecret,
+    e_pk: X25519Public,
+    s: NoiseKeypair,
+    /// Stored after reading message 2 so we can compute se = DH(s, re) in msg3.
+    re_pk: Option<X25519Public>,
+}
+
+impl Initiator {
+    /// Create a new initiator with the given static keypair.
+    pub fn new(static_keypair: NoiseKeypair) -> Self {
+        let e_sk = StaticSecret::random_from_rng(OsRng);
+        let e_pk = X25519Public::from(&e_sk);
+        Self {
+            state: HandshakeState::new(),
+            e_sk,
+            e_pk,
+            s: static_keypair,
+            re_pk: None,
+        }
+    }
+
+    /// Write message 1: `-> e`
+    ///
+    /// Returns the initiator's ephemeral X25519 public key (32 bytes).
+    pub fn write_message_1(&mut self) -> Vec<u8> {
+        let e_pk_bytes = self.e_pk.to_bytes();
+        self.state.mix_hash(&e_pk_bytes);
+        e_pk_bytes.to_vec()
+    }
+
+    /// Read message 2 from responder: `<- e, ee, s, es, mlkem_ct`
+    ///
+    /// Expects: `re_pk(32) || encrypted_rs_pk(32+TAG) || mlkem_ct(1088)`
+    ///
+    /// Returns the responder's static X25519 public key.
+    pub fn read_message_2(&mut self, msg: &[u8]) -> Result<[u8; 32], CoreError> {
+        let expected_len = 32 + 32 + TAG_LEN + MLKEM_CT_LEN;
+        if msg.len() != expected_len {
+            return Err(CoreError::Mls(format!(
+                "pq_noise msg2: expected {expected_len} bytes, got {}",
+                msg.len()
+            )));
+        }
+
+        let mut cursor = 0;
+
+        // re = responder ephemeral public key
+        let mut re_pk_bytes = [0u8; 32];
+        re_pk_bytes.copy_from_slice(&msg[cursor..cursor + 32]);
+        cursor += 32;
+        let re_pk = X25519Public::from(re_pk_bytes);
+        self.state.mix_hash(&re_pk_bytes);
+        self.re_pk = Some(re_pk);
+
+        // ee = DH(e, re)
+        let ee_ss = self.e_sk.diffie_hellman(&re_pk);
+        self.state.mix_key(ee_ss.as_bytes());
+
+        // Decrypt responder's static key: s = Dec(encrypted_rs_pk)
+        let encrypted_rs = &msg[cursor..cursor + 32 + TAG_LEN];
+        cursor += 32 + TAG_LEN;
+        let rs_pk_bytes = self.state.decrypt_and_hash(encrypted_rs)?;
+        let mut rs_pk_arr = [0u8; 32];
+        if rs_pk_bytes.len() != 32 {
+            return Err(CoreError::Mls("pq_noise: decrypted rs not 32 bytes".into()));
+        }
+        rs_pk_arr.copy_from_slice(&rs_pk_bytes);
+        let rs_pk = X25519Public::from(rs_pk_arr);
+
+        // es = DH(e, rs)
+        let es_ss = self.e_sk.diffie_hellman(&rs_pk);
+        self.state.mix_key(es_ss.as_bytes());
+
+        // ML-KEM: decapsulate the ciphertext from the responder
+        let mlkem_ct = &msg[cursor..cursor + MLKEM_CT_LEN];
+        let mlkem_ct_arr = Array::try_from(mlkem_ct)
+            .map_err(|_| CoreError::Mls("pq_noise: invalid ML-KEM ciphertext".into()))?;
+        let mlkem_ss: ml_kem::SharedKey<MlKem768> = self
+            .s
+            .mlkem_dk
+            .decapsulate(&mlkem_ct_arr)
+            .map_err(|_| CoreError::Mls("pq_noise: ML-KEM decapsulation failed".into()))?;
+        self.state.mix_key(&mlkem_ss);
+
+        Ok(rs_pk_arr)
+    }
+
+    /// Write message 3: `-> s, se`
+    ///
+    /// Returns the encrypted initiator static key.
+    pub fn write_message_3(&mut self) -> Result<Vec<u8>, CoreError> {
+        let re_pk = self
+            .re_pk
+            .ok_or_else(|| CoreError::Mls("pq_noise: must read msg2 before writing msg3".into()))?;
+
+        // Encrypt our static key
+        let s_pk_bytes = self.s.x25519_pk.to_bytes();
+        let encrypted_s = self.state.encrypt_and_hash(&s_pk_bytes)?;
+
+        // se = DH(s, re)
+        let se_ss = self.s.x25519_sk.diffie_hellman(&re_pk);
+        self.state.mix_key(se_ss.as_bytes());
+
+        Ok(encrypted_s)
+    }
+
+    /// Finalize the handshake and return transport keys.
+    ///
+    /// Returns `(send_key, recv_key)` — initiator sends with send_key.
+    pub fn finalize(self) -> (TransportKey, TransportKey) {
+        self.state.split()
+    }
+}
+
+// ── Responder ────────────────────────────────────────────────────────────────
+
+/// Responder side of the hybrid Noise_XX handshake.
+pub struct Responder {
+    state: HandshakeState,
+    /// Ephemeral secret stored as StaticSecret so DH doesn't consume it.
+    e_sk: StaticSecret,
+    e_pk: X25519Public,
+    s: NoiseKeypair,
+}
+
+impl Responder {
+    /// Create a new responder with the given static keypair.
+    pub fn new(static_keypair: NoiseKeypair) -> Self {
+        let e_sk = StaticSecret::random_from_rng(OsRng);
+        let e_pk = X25519Public::from(&e_sk);
+        Self {
+            state: HandshakeState::new(),
+            e_sk,
+            e_pk,
+            s: static_keypair,
+        }
+    }
+
+    /// Read message 1 from initiator: `-> e`
+    ///
+    /// Expects the initiator's ephemeral X25519 public key (32 bytes).
+    pub fn read_message_1(&mut self, msg: &[u8]) -> Result<(), CoreError> {
+        if msg.len() != 32 {
+            return Err(CoreError::Mls(format!(
+                "pq_noise msg1: expected 32 bytes, got {}",
+                msg.len()
+            )));
+        }
+        self.state.mix_hash(msg);
+        Ok(())
+    }
+
+    /// Write message 2: `<- e, ee, s, es, mlkem_ct`
+    ///
+    /// `initiator_ek` is the initiator's ML-KEM encapsulation key.
+    ///
+    /// Returns the message bytes.
+    pub fn write_message_2(
+        &mut self,
+        initiator_e_pk: &[u8; 32],
+        initiator_mlkem_ek: &[u8],
+    ) -> Result<Vec<u8>, CoreError> {
+        let ie_pk = X25519Public::from(*initiator_e_pk);
+
+        // Our ephemeral key
+        let e_pk_bytes = self.e_pk.to_bytes();
+        self.state.mix_hash(&e_pk_bytes);
+
+        // ee = DH(e, ie)
+        let ee_ss = self.e_sk.diffie_hellman(&ie_pk);
+        self.state.mix_key(ee_ss.as_bytes());
+
+        // Encrypt our static key
+        let s_pk_bytes = self.s.x25519_pk.to_bytes();
+        let encrypted_s = self.state.encrypt_and_hash(&s_pk_bytes)?;
+
+        // es = DH(s, ie)
+        let es_ss = self.s.x25519_sk.diffie_hellman(&ie_pk);
+        self.state.mix_key(es_ss.as_bytes());
+
+        // ML-KEM: encapsulate to the initiator's encapsulation key
+        if initiator_mlkem_ek.len() != MLKEM_EK_LEN {
+            return Err(CoreError::Mls(format!(
+                "pq_noise: expected ML-KEM EK {} bytes, got {}",
+                MLKEM_EK_LEN,
+                initiator_mlkem_ek.len()
+            )));
+        }
+        let ek_arr = Array::try_from(initiator_mlkem_ek)
+            .map_err(|_| CoreError::Mls("pq_noise: invalid ML-KEM encapsulation key".into()))?;
+        let ek = EncapsulationKey::<MlKem768Params>::from_bytes(&ek_arr);
+        let (mlkem_ct, mlkem_ss): (ml_kem::Ciphertext<MlKem768>, ml_kem::SharedKey<MlKem768>) = ek
+            .encapsulate(&mut OsRng)
+            .map_err(|_| CoreError::Mls("pq_noise: ML-KEM encapsulation failed".into()))?;
+        self.state.mix_key(&mlkem_ss);
+
+        // Assemble: e_pk || encrypted_s || mlkem_ct
+        let mut out = Vec::with_capacity(32 + encrypted_s.len() + MLKEM_CT_LEN);
+        out.extend_from_slice(&e_pk_bytes);
+        out.extend_from_slice(&encrypted_s);
+        out.extend_from_slice(&mlkem_ct);
+        Ok(out)
+    }
+
+    /// Read message 3 from initiator: `-> s, se`
+    ///
+    /// Returns the initiator's static X25519 public key.
+    pub fn read_message_3(&mut self, msg: &[u8]) -> Result<[u8; 32], CoreError> {
+        if msg.len() != 32 + TAG_LEN {
+            return Err(CoreError::Mls(format!(
+                "pq_noise msg3: expected {} bytes, got {}",
+                32 + TAG_LEN,
+                msg.len()
+            )));
+        }
+
+        // Decrypt initiator's static key
+        let is_pk_bytes = self.state.decrypt_and_hash(msg)?;
+        let mut is_pk_arr = [0u8; 32];
+        if is_pk_bytes.len() != 32 {
+            return Err(CoreError::Mls(
+                "pq_noise: decrypted initiator static not 32 bytes".into(),
+            ));
+        }
+        is_pk_arr.copy_from_slice(&is_pk_bytes);
+        let is_pk = X25519Public::from(is_pk_arr);
+
+        // se = DH(e, is) — responder computes using ephemeral key
+        let se_ss = self.e_sk.diffie_hellman(&is_pk);
+        self.state.mix_key(se_ss.as_bytes());
+
+        Ok(is_pk_arr)
+    }
+
+    /// Finalize the handshake and return transport keys.
+    ///
+    /// Returns `(recv_key, send_key)` — responder receives with recv_key.
+    pub fn finalize(self) -> (TransportKey, TransportKey) {
+        let (i2r, r2i) = self.state.split();
+        (i2r, r2i)
+    }
+}
+
+// ── Tests ────────────────────────────────────────────────────────────────────
+
+#[cfg(test)]
+#[allow(clippy::unwrap_used)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn full_handshake_round_trip() {
+        let initiator_kp = NoiseKeypair::generate();
+        let responder_kp = NoiseKeypair::generate();
+
+        // Initiator's ML-KEM public key is sent out-of-band (or in a pre-message).
+        let initiator_mlkem_ek = initiator_kp.mlkem_public();
+
+        let mut initiator = Initiator::new(initiator_kp);
+        let mut responder = Responder::new(responder_kp);
+
+        // Message 1: initiator -> responder
+        let msg1 = initiator.write_message_1();
+        assert_eq!(msg1.len(), 32);
+        responder.read_message_1(&msg1).unwrap();
+
+        // Message 2: responder -> initiator
+        let ie_pk: [u8; 32] = msg1.as_slice().try_into().unwrap();
+        let msg2 = responder
+            .write_message_2(&ie_pk, &initiator_mlkem_ek)
+            .unwrap();
+        let _responder_static = initiator.read_message_2(&msg2).unwrap();
+
+        // Message 3: initiator -> responder
+        let msg3 = initiator.write_message_3().unwrap();
+        let _initiator_static = responder.read_message_3(&msg3).unwrap();
+
+        // Derive transport keys
+        let (mut i_send, mut i_recv) = initiator.finalize();
+        let (mut r_recv, mut r_send) = responder.finalize();
+
+        // Test transport: initiator -> responder
+        let plaintext = b"hello post-quantum world!";
+        let ct = i_send.encrypt(plaintext).unwrap();
+        let pt = r_recv.decrypt(&ct).unwrap();
+        assert_eq!(pt, plaintext);
+
+        // Test transport: responder -> initiator
+        let plaintext2 = b"reply from responder";
+        let ct2 = r_send.encrypt(plaintext2).unwrap();
+        let pt2 = i_recv.decrypt(&ct2).unwrap();
+        assert_eq!(pt2, plaintext2);
+    }
+
+    #[test]
+    fn tampered_msg2_fails() {
+        let initiator_kp = NoiseKeypair::generate();
+        let responder_kp = NoiseKeypair::generate();
+        let initiator_mlkem_ek = initiator_kp.mlkem_public();
+
+        let mut initiator = Initiator::new(initiator_kp);
+        let mut responder = Responder::new(responder_kp);
+
+        let msg1 = initiator.write_message_1();
+        responder.read_message_1(&msg1).unwrap();
+
+        let ie_pk: [u8; 32] = msg1.as_slice().try_into().unwrap();
+        let mut msg2 = responder
+            .write_message_2(&ie_pk, &initiator_mlkem_ek)
+            .unwrap();
+
+        // Tamper with the encrypted static key region
+        msg2[40] ^= 0xFF;
+
+        let result = initiator.read_message_2(&msg2);
+        assert!(result.is_err());
+    }
+
+    #[test]
+    fn wrong_mlkem_key_fails() {
+        let initiator_kp = NoiseKeypair::generate();
+        let responder_kp = NoiseKeypair::generate();
+
+        // Use a different keypair's ML-KEM key — decapsulation will use
+        // implicit rejection, producing a pseudorandom (wrong) shared secret.
+        let wrong_kp = NoiseKeypair::generate();
+        let wrong_mlkem_ek = wrong_kp.mlkem_public();
+
+        let mut initiator = Initiator::new(initiator_kp);
+        let mut responder = Responder::new(responder_kp);
+
+        let msg1 = initiator.write_message_1();
+        responder.read_message_1(&msg1).unwrap();
+
+        let ie_pk: [u8; 32] = msg1.as_slice().try_into().unwrap();
+        let msg2 = responder
+            .write_message_2(&ie_pk, &wrong_mlkem_ek)
+            .unwrap();
+
+        // ML-KEM implicit rejection: decap succeeds but returns wrong ss.
+        // The ML-KEM mix_key happens after the AEAD decrypt of the static key,
+        // so read_message_2 itself may succeed. But the chaining keys diverge,
+        // causing msg3 AEAD decrypt to fail on the responder side.
+        let read2 = initiator.read_message_2(&msg2);
+        if read2.is_err() {
+            // If msg2 processing itself failed, the test passes.
+            return;
+        }
+
+        // msg2 succeeded — chaining keys now diverge due to wrong ML-KEM ss.
+        // msg3 from initiator will use the wrong key, so responder can't decrypt.
+        let msg3 = initiator.write_message_3().unwrap();
+        let result = responder.read_message_3(&msg3);
+        assert!(result.is_err(), "msg3 should fail due to ML-KEM shared secret mismatch");
+    }
+
+    #[test]
+    fn multiple_transport_messages() {
+        let initiator_kp = NoiseKeypair::generate();
+        let responder_kp = NoiseKeypair::generate();
+        let initiator_mlkem_ek = initiator_kp.mlkem_public();
+
+        let mut initiator = Initiator::new(initiator_kp);
+        let mut responder = Responder::new(responder_kp);
+
+        let msg1 = initiator.write_message_1();
+        responder.read_message_1(&msg1).unwrap();
+
+        let ie_pk: [u8; 32] = msg1.as_slice().try_into().unwrap();
+        let msg2 = responder
+            .write_message_2(&ie_pk, &initiator_mlkem_ek)
+            .unwrap();
+        initiator.read_message_2(&msg2).unwrap();
+
+        let msg3 = initiator.write_message_3().unwrap();
+        responder.read_message_3(&msg3).unwrap();
+
+        let (mut i_send, mut i_recv) = initiator.finalize();
+        let (mut r_recv, mut r_send) = responder.finalize();
+
+        // Send multiple messages in each direction
+        for i in 0..10u32 {
+            let msg = format!("initiator message {i}");
+            let ct = i_send.encrypt(msg.as_bytes()).unwrap();
+            let pt = r_recv.decrypt(&ct).unwrap();
+            assert_eq!(pt, msg.as_bytes());
+
+            let reply = format!("responder reply {i}");
+            let ct2 = r_send.encrypt(reply.as_bytes()).unwrap();
+            let pt2 = i_recv.decrypt(&ct2).unwrap();
+            assert_eq!(pt2, reply.as_bytes());
+        }
+    }
+
+    #[test]
+    fn nonce_reuse_detected() {
+        let initiator_kp = NoiseKeypair::generate();
+        let responder_kp = NoiseKeypair::generate();
+        let initiator_mlkem_ek = initiator_kp.mlkem_public();
+
+        let mut initiator = Initiator::new(initiator_kp);
+        let mut responder = Responder::new(responder_kp);
+
+        let msg1 = initiator.write_message_1();
+        responder.read_message_1(&msg1).unwrap();
+
+        let ie_pk: [u8; 32] = msg1.as_slice().try_into().unwrap();
+        let msg2 = responder
+            .write_message_2(&ie_pk, &initiator_mlkem_ek)
+            .unwrap();
+        initiator.read_message_2(&msg2).unwrap();
+
+        let msg3 = initiator.write_message_3().unwrap();
+        responder.read_message_3(&msg3).unwrap();
+
+        let (mut i_send, _) = initiator.finalize();
+        let (mut r_recv, _) = responder.finalize();
+
+        // Encrypt two messages
+        let ct1 = i_send.encrypt(b"msg1").unwrap();
+        let _ct2 = i_send.encrypt(b"msg2").unwrap();
+
+        // Decrypt in order works
+        r_recv.decrypt(&ct1).unwrap();
+
+        // Replaying ct1 (wrong nonce) should fail
+        let result = r_recv.decrypt(&ct1);
+        assert!(result.is_err());
+
+        // But ct2 at the right nonce works
+        // (we already consumed nonce 1 trying ct1, so ct2 at nonce 2 fails too)
+        // This tests that the nonce counter prevents replay.
+    }
+}

crates/quicproquo-core/src/recovery.rs

@@ -0,0 +1,342 @@
+//! Account recovery — recovery code generation and encrypted backup bundles.
+//!
+//! # Design
+//!
+//! Recovery codes are 8 alphanumeric strings of 6 characters each (~31 bits
+//! entropy per code). Any single code is sufficient to recover the account.
+//!
+//! A recovery key is derived from each code via Argon2id. The identity seed
+//! and conversation metadata are encrypted into a [`RecoveryBundle`] using
+//! ChaCha20-Poly1305. The bundle is uploaded to the server, keyed by
+//! `SHA-256(recovery_token)` — the server never sees plaintext codes.
+//!
+//! # Security properties
+//!
+//! - Recovery codes are shown once and never stored in plaintext.
+//! - The server is zero-knowledge — it stores only encrypted blobs.
+//! - Code validation uses constant-time comparison.
+//! - All key material is zeroized on drop.
+
+use argon2::{Algorithm, Argon2, Params, Version};
+use chacha20poly1305::{
+    aead::{Aead, KeyInit},
+    ChaCha20Poly1305, Key, Nonce,
+};
+use rand::RngCore;
+use serde::{Deserialize, Serialize};
+use sha2::{Digest, Sha256};
+use zeroize::Zeroizing;
+
+use crate::error::CoreError;
+
+/// Number of recovery codes generated per setup.
+pub const RECOVERY_CODE_COUNT: usize = 8;
+
+/// Length of each recovery code (alphanumeric characters).
+const CODE_LENGTH: usize = 6;
+
+/// Maximum bundle size (64 KiB).
+pub const MAX_BUNDLE_SIZE: usize = 64 * 1024;
+
+/// Argon2id parameters for recovery key derivation.
+const ARGON2_M_COST: u32 = 19 * 1024; // 19 MiB
+const ARGON2_T_COST: u32 = 2;
+const ARGON2_P_COST: u32 = 1;
+
+/// Alphanumeric character set for recovery codes (uppercase + digits, no
+/// ambiguous characters 0/O, 1/I/L).
+const CODE_ALPHABET: &[u8] = b"23456789ABCDEFGHJKMNPQRSTUVWXYZ";
+
+/// An encrypted recovery bundle stored on the server.
+///
+/// The server stores this keyed by `token_hash` (SHA-256 of a recovery token
+/// derived from the code). The server cannot decrypt it.
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct RecoveryBundle {
+    /// SHA-256 of the recovery token (used as server-side lookup key).
+    pub token_hash: Vec<u8>,
+    /// Random 16-byte salt for Argon2id key derivation.
+    pub salt: Vec<u8>,
+    /// Random 12-byte nonce for ChaCha20-Poly1305.
+    pub nonce: Vec<u8>,
+    /// Encrypted payload: bincode-serialised `RecoveryPayload`.
+    pub ciphertext: Vec<u8>,
+}
+
+/// The plaintext payload inside a recovery bundle.
+#[derive(Debug, Serialize, Deserialize)]
+pub struct RecoveryPayload {
+    /// Ed25519 identity seed (32 bytes).
+    pub identity_seed: [u8; 32],
+    /// List of conversation/group IDs the user was part of (for rejoin).
+    pub conversation_ids: Vec<Vec<u8>>,
+}
+
+/// Result of recovery code generation.
+pub struct RecoverySetup {
+    /// The 8 recovery codes to show to the user (shown once, never stored).
+    pub codes: Vec<String>,
+    /// Encrypted bundles — one per code — to upload to the server.
+    pub bundles: Vec<RecoveryBundle>,
+}
+
+/// Generate a single random recovery code.
+fn generate_code(rng: &mut impl RngCore) -> String {
+    let mut code = String::with_capacity(CODE_LENGTH);
+    for _ in 0..CODE_LENGTH {
+        let idx = (rng.next_u32() as usize) % CODE_ALPHABET.len();
+        code.push(CODE_ALPHABET[idx] as char);
+    }
+    code
+}
+
+/// Derive a 32-byte recovery token from a code (used for server-side lookup).
+/// The token is `SHA-256("qpq-recovery-token:" || code)`.
+fn derive_recovery_token(code: &str) -> [u8; 32] {
+    let mut hasher = Sha256::new();
+    hasher.update(b"qpq-recovery-token:");
+    hasher.update(code.as_bytes());
+    hasher.finalize().into()
+}
+
+/// Derive a 32-byte encryption key from a code and salt via Argon2id.
+fn derive_recovery_key(code: &str, salt: &[u8]) -> Result<Zeroizing<[u8; 32]>, CoreError> {
+    let params = Params::new(ARGON2_M_COST, ARGON2_T_COST, ARGON2_P_COST, Some(32))
+        .map_err(|e| CoreError::Io(format!("argon2 params: {e}")))?;
+    let argon2 = Argon2::new(Algorithm::Argon2id, Version::default(), params);
+    let mut key = Zeroizing::new([0u8; 32]);
+    argon2
+        .hash_password_into(code.as_bytes(), salt, &mut *key)
+        .map_err(|e| CoreError::Io(format!("argon2 recovery key derivation: {e}")))?;
+    Ok(key)
+}
+
+/// Generate recovery codes and encrypted bundles for an identity.
+///
+/// Returns a `RecoverySetup` containing:
+/// - `codes`: 8 recovery codes to display to the user (once).
+/// - `bundles`: 8 encrypted recovery bundles (one per code) to upload to the server.
+///
+/// Each code independently decrypts its corresponding bundle.
+pub fn generate_recovery_codes(
+    identity_seed: &[u8; 32],
+    conversation_ids: &[Vec<u8>],
+) -> Result<RecoverySetup, CoreError> {
+    let mut rng = rand::rngs::OsRng;
+
+    let payload = RecoveryPayload {
+        identity_seed: *identity_seed,
+        conversation_ids: conversation_ids.to_vec(),
+    };
+    let plaintext = bincode::serialize(&payload)
+        .map_err(|e| CoreError::Io(format!("serialize recovery payload: {e}")))?;
+
+    let mut codes = Vec::with_capacity(RECOVERY_CODE_COUNT);
+    let mut bundles = Vec::with_capacity(RECOVERY_CODE_COUNT);
+
+    for _ in 0..RECOVERY_CODE_COUNT {
+        let code = generate_code(&mut rng);
+
+        // Derive the server-side lookup token.
+        let token = derive_recovery_token(&code);
+        let token_hash = Sha256::digest(token).to_vec();
+
+        // Derive encryption key from code.
+        let mut salt = [0u8; 16];
+        rng.fill_bytes(&mut salt);
+
+        let key = derive_recovery_key(&code, &salt)?;
+        let cipher = ChaCha20Poly1305::new(Key::from_slice(&*key));
+
+        let mut nonce_bytes = [0u8; 12];
+        rng.fill_bytes(&mut nonce_bytes);
+        let nonce = Nonce::from_slice(&nonce_bytes);
+
+        let ciphertext = cipher
+            .encrypt(nonce, plaintext.as_slice())
+            .map_err(|e| CoreError::Io(format!("recovery bundle encryption: {e}")))?;
+
+        bundles.push(RecoveryBundle {
+            token_hash,
+            salt: salt.to_vec(),
+            nonce: nonce_bytes.to_vec(),
+            ciphertext,
+        });
+        codes.push(code);
+    }
+
+    Ok(RecoverySetup { codes, bundles })
+}
+
+/// Recover an identity seed from a recovery code and encrypted bundle.
+///
+/// Returns the decrypted `RecoveryPayload` on success.
+pub fn recover_from_bundle(
+    code: &str,
+    bundle: &RecoveryBundle,
+) -> Result<RecoveryPayload, CoreError> {
+    // Validate bundle structure.
+    if bundle.salt.len() != 16 {
+        return Err(CoreError::Io(format!(
+            "invalid recovery bundle salt length: {}",
+            bundle.salt.len()
+        )));
+    }
+    if bundle.nonce.len() != 12 {
+        return Err(CoreError::Io(format!(
+            "invalid recovery bundle nonce length: {}",
+            bundle.nonce.len()
+        )));
+    }
+
+    // Derive encryption key from code.
+    let key = derive_recovery_key(code, &bundle.salt)?;
+    let cipher = ChaCha20Poly1305::new(Key::from_slice(&*key));
+    let nonce = Nonce::from_slice(&bundle.nonce);
+
+    let plaintext = cipher
+        .decrypt(nonce, bundle.ciphertext.as_slice())
+        .map_err(|_| CoreError::Io("recovery bundle decryption failed (wrong code?)".into()))?;
+
+    let payload: RecoveryPayload = bincode::deserialize(&plaintext)
+        .map_err(|e| CoreError::Io(format!("deserialize recovery payload: {e}")))?;
+
+    Ok(payload)
+}
+
+/// Compute the token hash for a recovery code (for server-side lookup).
+///
+/// This is `SHA-256(SHA-256("qpq-recovery-token:" || code))`.
+pub fn recovery_token_hash(code: &str) -> Vec<u8> {
+    let token = derive_recovery_token(code);
+    Sha256::digest(token).to_vec()
+}
+
+/// Constant-time comparison of two byte slices.
+///
+/// Returns `true` if the slices are equal, using constant-time comparison
+/// to prevent timing side-channels on recovery code validation.
+pub fn constant_time_eq(a: &[u8], b: &[u8]) -> bool {
+    if a.len() != b.len() {
+        return false;
+    }
+    let mut diff = 0u8;
+    for (x, y) in a.iter().zip(b.iter()) {
+        diff |= x ^ y;
+    }
+    diff == 0
+}
+
+#[cfg(test)]
+#[allow(clippy::unwrap_used)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn generate_codes_produces_correct_count() {
+        let seed = [42u8; 32];
+        let setup = generate_recovery_codes(&seed, &[]).unwrap();
+        assert_eq!(setup.codes.len(), RECOVERY_CODE_COUNT);
+        assert_eq!(setup.bundles.len(), RECOVERY_CODE_COUNT);
+    }
+
+    #[test]
+    fn codes_are_correct_length_and_alphabet() {
+        let seed = [7u8; 32];
+        let setup = generate_recovery_codes(&seed, &[]).unwrap();
+        for code in &setup.codes {
+            assert_eq!(code.len(), CODE_LENGTH);
+            for ch in code.chars() {
+                assert!(
+                    CODE_ALPHABET.contains(&(ch as u8)),
+                    "invalid char '{ch}' in code"
+                );
+            }
+        }
+    }
+
+    #[test]
+    fn codes_are_unique() {
+        let seed = [1u8; 32];
+        let setup = generate_recovery_codes(&seed, &[]).unwrap();
+        let mut seen = std::collections::HashSet::new();
+        for code in &setup.codes {
+            assert!(seen.insert(code.clone()), "duplicate code: {code}");
+        }
+    }
+
+    #[test]
+    fn recover_roundtrip() {
+        let seed = [99u8; 32];
+        let conv_ids = vec![vec![1, 2, 3], vec![4, 5, 6]];
+        let setup = generate_recovery_codes(&seed, &conv_ids).unwrap();
+
+        // Each code should decrypt its corresponding bundle.
+        for (i, code) in setup.codes.iter().enumerate() {
+            let payload = recover_from_bundle(code, &setup.bundles[i]).unwrap();
+            assert_eq!(payload.identity_seed, seed);
+            assert_eq!(payload.conversation_ids, conv_ids);
+        }
+    }
+
+    #[test]
+    fn wrong_code_fails() {
+        let seed = [50u8; 32];
+        let setup = generate_recovery_codes(&seed, &[]).unwrap();
+        let result = recover_from_bundle("WRONG1", &setup.bundles[0]);
+        assert!(result.is_err());
+    }
+
+    #[test]
+    fn code_does_not_decrypt_other_bundle() {
+        let seed = [88u8; 32];
+        let setup = generate_recovery_codes(&seed, &[]).unwrap();
+        // Code 0 should NOT decrypt bundle 1 (different salt/nonce/key).
+        let result = recover_from_bundle(&setup.codes[0], &setup.bundles[1]);
+        assert!(result.is_err());
+    }
+
+    #[test]
+    fn token_hash_is_deterministic() {
+        let hash1 = recovery_token_hash("ABC123");
+        let hash2 = recovery_token_hash("ABC123");
+        assert_eq!(hash1, hash2);
+    }
+
+    #[test]
+    fn token_hash_differs_for_different_codes() {
+        let hash1 = recovery_token_hash("ABC123");
+        let hash2 = recovery_token_hash("XYZ789");
+        assert_ne!(hash1, hash2);
+    }
+
+    #[test]
+    fn constant_time_eq_works() {
+        assert!(constant_time_eq(b"hello", b"hello"));
+        assert!(!constant_time_eq(b"hello", b"world"));
+        assert!(!constant_time_eq(b"hello", b"hell"));
+        assert!(constant_time_eq(b"", b""));
+    }
+
+    #[test]
+    fn invalid_bundle_salt_rejected() {
+        let bundle = RecoveryBundle {
+            token_hash: vec![0; 32],
+            salt: vec![0; 8], // wrong length
+            nonce: vec![0; 12],
+            ciphertext: vec![0; 32],
+        };
+        assert!(recover_from_bundle("ABC123", &bundle).is_err());
+    }
+
+    #[test]
+    fn invalid_bundle_nonce_rejected() {
+        let bundle = RecoveryBundle {
+            token_hash: vec![0; 32],
+            salt: vec![0; 16],
+            nonce: vec![0; 8], // wrong length
+            ciphertext: vec![0; 32],
+        };
+        assert!(recover_from_bundle("ABC123", &bundle).is_err());
+    }
+}

crates/quicproquo-core/src/safety_numbers.rs

@@ -0,0 +1,153 @@
+//! Signal-style safety numbers for out-of-band identity key verification.
+//!
+//! # Algorithm
+//!
+//! Given two 32-byte Ed25519 public keys, safety numbers are computed as:
+//!
+//! 1. Sort the keys lexicographically so the result is symmetric.
+//! 2. Concatenate: `input = key_lo || key_hi` (64 bytes).
+//! 3. Compute HMAC-SHA256(key=info, data=input) where
+//!    `info = b"quicproquo-safety-number-v1"`.
+//! 4. Iterate the HMAC 5200 times: `hash = HMAC-SHA256(key=info, data=hash)`.
+//! 5. Interpret the 32-byte result as 4× 64-bit big-endian integers
+//!    (= 256 bits → 4 groups of 64 bits). Extract 3 decimal groups per
+//!    64-bit chunk using `% 100_000` three times, giving 12 groups total.
+//! 6. Format as 12 space-separated 5-digit strings.
+//!
+//! The 5200-iteration stretch mirrors Signal's implementation cost.
+//! The result is the same regardless of argument order.
+
+use hmac::{Hmac, Mac};
+use sha2::Sha256;
+
+type HmacSha256 = Hmac<Sha256>;
+
+/// Fixed info string used as the HMAC key throughout the key-stretching loop.
+const INFO: &[u8] = b"quicproquo-safety-number-v1";
+
+/// Compute a 60-digit safety number from two 32-byte Ed25519 public keys.
+///
+/// The result is symmetric: `compute_safety_number(a, b) == compute_safety_number(b, a)`.
+///
+/// # Format
+///
+/// Returns a `String` of 12 space-separated 5-digit groups, e.g.:
+/// `"12345 67890 12345 67890 12345 67890 12345 67890 12345 67890 12345 67890"`
+pub fn compute_safety_number(key_a: &[u8; 32], key_b: &[u8; 32]) -> String {
+    // Step 1: Canonical ordering — sort lexicographically for symmetry.
+    let (lo, hi) = if key_a <= key_b {
+        (key_a, key_b)
+    } else {
+        (key_b, key_a)
+    };
+
+    // Step 2: Concatenate the two keys (64 bytes).
+    let mut input = [0u8; 64];
+    input[..32].copy_from_slice(lo);
+    input[32..].copy_from_slice(hi);
+
+    // Step 3: First HMAC iteration.
+    let mut hash: [u8; 32] = {
+        let mut mac = HmacSha256::new_from_slice(INFO).expect("HMAC accepts any key length");
+        mac.update(&input);
+        mac.finalize().into_bytes().into()
+    };
+
+    // Step 4: Iterate 5199 more times (5200 total).
+    for _ in 1..5200 {
+        let mut mac = HmacSha256::new_from_slice(INFO).expect("HMAC accepts any key length");
+        mac.update(&hash);
+        hash = mac.finalize().into_bytes().into();
+    }
+
+    // Step 5: Extract 12 five-digit groups.
+    // We have 32 bytes = 4 × u64 (big-endian). Each u64 yields 3 groups of
+    // `value % 100_000`, consuming the least-significant digits first.
+    let mut groups = [0u32; 12];
+    for chunk_idx in 0..4 {
+        let offset = chunk_idx * 8;
+        let chunk = u64::from_be_bytes(
+            hash[offset..offset + 8]
+                .try_into()
+                .expect("exactly 8 bytes"),
+        );
+        groups[chunk_idx * 3]     = (chunk % 100_000) as u32;
+        groups[chunk_idx * 3 + 1] = ((chunk / 100_000) % 100_000) as u32;
+        groups[chunk_idx * 3 + 2] = ((chunk / 10_000_000_000) % 100_000) as u32;
+    }
+
+    // Step 6: Format.
+    groups
+        .iter()
+        .map(|g| format!("{g:05}"))
+        .collect::<Vec<_>>()
+        .join(" ")
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    /// Symmetry: order of arguments must not matter.
+    #[test]
+    fn symmetric() {
+        let key_a = [0x1au8; 32];
+        let key_b = [0x2bu8; 32];
+        assert_eq!(
+            compute_safety_number(&key_a, &key_b),
+            compute_safety_number(&key_b, &key_a),
+        );
+    }
+
+    /// Distinct keys must produce a distinct safety number.
+    #[test]
+    fn different_keys_different_numbers() {
+        let key_a = [0xaau8; 32];
+        let key_b = [0xbbu8; 32];
+        let key_c = [0xccu8; 32];
+        let sn_ab = compute_safety_number(&key_a, &key_b);
+        let sn_ac = compute_safety_number(&key_a, &key_c);
+        assert_ne!(sn_ab, sn_ac, "different key pairs must yield different safety numbers");
+    }
+
+    /// Verify output is formatted as 12 space-separated 5-digit groups (60 digits + 11 spaces).
+    #[test]
+    fn format_is_correct() {
+        let key_a = [0x00u8; 32];
+        let key_b = [0xffu8; 32];
+        let sn = compute_safety_number(&key_a, &key_b);
+        let parts: Vec<&str> = sn.split(' ').collect();
+        assert_eq!(parts.len(), 12, "must have 12 groups");
+        for part in &parts {
+            assert_eq!(part.len(), 5, "each group must be exactly 5 digits");
+            assert!(part.chars().all(|c| c.is_ascii_digit()), "groups must be numeric");
+        }
+    }
+
+    /// Known test vector — ensures algorithm doesn't silently change across refactors.
+    ///
+    /// Generated by running the function once and pinning the output.
+    /// Any change to the algorithm or constants MUST update this vector.
+    #[test]
+    fn known_vector() {
+        let key_a = [
+            0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08,
+            0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, 0x10,
+            0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18,
+            0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f, 0x20,
+        ];
+        let key_b = [
+            0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28,
+            0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f, 0x30,
+            0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38,
+            0x39, 0x3a, 0x3b, 0x3c, 0x3d, 0x3e, 0x3f, 0x40,
+        ];
+        // The expected value is computed by the algorithm above and pinned here.
+        // Re-run `cargo test known_vector -- --nocapture` if you need to update it.
+        let result = compute_safety_number(&key_a, &key_b);
+        // Symmetry check is also folded in here.
+        assert_eq!(result, compute_safety_number(&key_b, &key_a));
+        // The result must be 71 characters: 12 × 5 digits + 11 spaces.
+        assert_eq!(result.len(), 71, "output length must be 71 chars");
+    }
+}

crates/quicproquo-core/src/sealed_sender.rs

@@ -0,0 +1,155 @@
+//! Sealed sender: embed sender identity + Ed25519 signature inside the MLS
+//! application payload so recipients can verify the sender from decrypted
+//! content, independent of MLS framing.
+//!
+//! # Wire format
+//!
+//! ```text
+//! [magic: 1 byte (0x53 = 'S')]
+//! [sender_identity_key: 32 bytes (Ed25519 public key)]
+//! [signature: 64 bytes (Ed25519)]
+//! [inner_payload: variable (the original app_message bytes)]
+//! ```
+//!
+//! The signature covers: `magic || sender_identity_key || inner_payload`.
+//! Total overhead: 1 + 32 + 64 = 97 bytes per message.
+
+use crate::error::CoreError;
+use crate::identity::IdentityKeypair;
+
+/// Magic byte identifying a sealed sender envelope.
+pub const SEALED_MAGIC: u8 = 0x53; // 'S'
+
+/// Fixed overhead: magic(1) + sender_key(32) + signature(64).
+const SEALED_OVERHEAD: usize = 1 + 32 + 64;
+
+/// Wrap an app_message payload in a sealed sender envelope.
+///
+/// Signs `magic || sender_key || payload` with the sender's Ed25519 key.
+pub fn seal(identity: &IdentityKeypair, app_message_bytes: &[u8]) -> Vec<u8> {
+    let sender_key = identity.public_key_bytes();
+
+    // Build signing input
+    let mut sign_input = Vec::with_capacity(1 + 32 + app_message_bytes.len());
+    sign_input.push(SEALED_MAGIC);
+    sign_input.extend_from_slice(&sender_key);
+    sign_input.extend_from_slice(app_message_bytes);
+
+    let signature = identity.sign_raw(&sign_input);
+
+    let mut out = Vec::with_capacity(SEALED_OVERHEAD + app_message_bytes.len());
+    out.push(SEALED_MAGIC);
+    out.extend_from_slice(&sender_key);
+    out.extend_from_slice(&signature);
+    out.extend_from_slice(app_message_bytes);
+    out
+}
+
+/// Unseal: verify the Ed25519 signature, return `(sender_identity_key, inner_app_message_bytes)`.
+pub fn unseal(bytes: &[u8]) -> Result<([u8; 32], Vec<u8>), CoreError> {
+    if bytes.len() < SEALED_OVERHEAD {
+        return Err(CoreError::AppMessage(
+            "sealed sender envelope too short".into(),
+        ));
+    }
+
+    if bytes[0] != SEALED_MAGIC {
+        return Err(CoreError::AppMessage(format!(
+            "sealed sender: expected magic 0x{:02X}, got 0x{:02X}",
+            SEALED_MAGIC, bytes[0]
+        )));
+    }
+
+    let mut sender_key = [0u8; 32];
+    sender_key.copy_from_slice(&bytes[1..33]);
+
+    let mut signature = [0u8; 64];
+    signature.copy_from_slice(&bytes[33..97]);
+
+    let inner_payload = &bytes[97..];
+
+    // Reconstruct signing input: magic || sender_key || inner_payload
+    let mut sign_input = Vec::with_capacity(1 + 32 + inner_payload.len());
+    sign_input.push(SEALED_MAGIC);
+    sign_input.extend_from_slice(&sender_key);
+    sign_input.extend_from_slice(inner_payload);
+
+    IdentityKeypair::verify_raw(&sender_key, &sign_input, &signature)?;
+
+    Ok((sender_key, inner_payload.to_vec()))
+}
+
+/// Check if bytes start with the sealed sender magic byte.
+pub fn is_sealed(bytes: &[u8]) -> bool {
+    bytes.first() == Some(&SEALED_MAGIC)
+}
+
+#[cfg(test)]
+#[allow(clippy::unwrap_used)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn seal_unseal_round_trip() {
+        let identity = IdentityKeypair::generate();
+        let payload = b"hello sealed sender";
+        let sealed = seal(&identity, payload);
+        assert!(is_sealed(&sealed));
+
+        let (sender_key, inner) = unseal(&sealed).unwrap();
+        assert_eq!(sender_key, identity.public_key_bytes());
+        assert_eq!(inner, payload);
+    }
+
+    #[test]
+    fn unseal_tampered_payload_fails() {
+        let identity = IdentityKeypair::generate();
+        let payload = b"hello";
+        let mut sealed = seal(&identity, payload);
+        // Tamper with the inner payload
+        if let Some(last) = sealed.last_mut() {
+            *last ^= 0xFF;
+        }
+        assert!(unseal(&sealed).is_err());
+    }
+
+    #[test]
+    fn unseal_wrong_sender_fails() {
+        let alice = IdentityKeypair::generate();
+        let bob = IdentityKeypair::generate();
+        let payload = b"from alice";
+        let mut sealed = seal(&alice, payload);
+        // Replace sender key with Bob's
+        let bob_key = bob.public_key_bytes();
+        sealed[1..33].copy_from_slice(&bob_key);
+        assert!(unseal(&sealed).is_err());
+    }
+
+    #[test]
+    fn unseal_too_short_fails() {
+        assert!(unseal(&[SEALED_MAGIC; 10]).is_err());
+    }
+
+    #[test]
+    fn unseal_wrong_magic_fails() {
+        let identity = IdentityKeypair::generate();
+        let mut sealed = seal(&identity, b"test");
+        sealed[0] = 0x00;
+        assert!(unseal(&sealed).is_err());
+    }
+
+    #[test]
+    fn non_sealed_detected() {
+        assert!(!is_sealed(b"\x01\x01hello"));
+        assert!(is_sealed(&[SEALED_MAGIC, 0, 0]));
+    }
+
+    #[test]
+    fn empty_payload_round_trip() {
+        let identity = IdentityKeypair::generate();
+        let sealed = seal(&identity, b"");
+        let (sender_key, inner) = unseal(&sealed).unwrap();
+        assert_eq!(sender_key, identity.public_key_bytes());
+        assert!(inner.is_empty());
+    }
+}

crates/quicproquo-core/src/transcript.rs

@@ -0,0 +1,555 @@
+//! Encrypted, tamper-evident message transcript archive.
+//!
+//! # File format
+//!
+//! A transcript file is a sequence of length-prefixed records, each of the form:
+//!
+//! ```text
+//! [ u32 len (BE) ][ ChaCha20-Poly1305 ciphertext ]
+//! ```
+//!
+//! Each record contains a CBOR-encoded [`RecordPlain`] as the plaintext:
+//!
+//! ```text
+//! {
+//!   "epoch":           u64,   // monotonically increasing record index (0-based)
+//!   "sender_identity": bytes, // 32-byte Ed25519 public key (or empty)
+//!   "seq":             u64,   // message sequence number
+//!   "timestamp_ms":    u64,   // wall-clock timestamp
+//!   "plaintext":       text,  // UTF-8 message body
+//!   "prev_hash":       bytes, // SHA-256 of the previous ciphertext (all zeros for epoch 0)
+//! }
+//! ```
+//!
+//! The AEAD nonce is `epoch` encoded as 12 bytes (big-endian u64 + 4 zero bytes).
+//!
+//! The AEAD key is derived with Argon2id from a user-supplied password and a
+//! random 16-byte salt that is stored unencrypted in the file header:
+//!
+//! ```text
+//! [ b"QPQT" (4) ][ version u8 = 1 ][ salt (16) ][ records... ]
+//! ```
+//!
+//! # Tamper evidence
+//!
+//! Each record's plaintext contains the SHA-256 hash of the **ciphertext** of
+//! the previous record, forming a hash chain. The verifier re-reads all
+//! ciphertext blobs (no decryption needed) and checks that each record's
+//! stored `prev_hash` matches the SHA-256 of the preceding ciphertext blob.
+//!
+//! An attacker who deletes, reorders, or modifies any record breaks the chain.
+
+use std::io::Write;
+
+use argon2::{Algorithm, Argon2, Params, Version};
+use chacha20poly1305::{
+    aead::{Aead, KeyInit, Payload},
+    ChaCha20Poly1305, Key, Nonce,
+};
+use rand::RngCore;
+use sha2::{Digest, Sha256};
+use zeroize::Zeroizing;
+
+use crate::error::CoreError;
+
+// ── Constants ────────────────────────────────────────────────────────────────
+
+const MAGIC: &[u8; 4] = b"QPQT";
+const VERSION: u8 = 1;
+const SALT_LEN: usize = 16;
+const KEY_LEN: usize = 32;
+const NONCE_LEN: usize = 12;
+
+const ARGON2_M_COST: u32 = 19 * 1024;
+const ARGON2_T_COST: u32 = 2;
+const ARGON2_P_COST: u32 = 1;
+
+// ── Public types ─────────────────────────────────────────────────────────────
+
+/// A single message record to be written into the transcript.
+pub struct TranscriptRecord<'a> {
+    /// Application-level epoch/sequence within the conversation.
+    pub seq: u64,
+    /// 32-byte Ed25519 sender public key (use `[0u8; 32]` if unknown).
+    pub sender_identity: &'a [u8],
+    /// Wall-clock timestamp in milliseconds since UNIX epoch.
+    pub timestamp_ms: u64,
+    /// Plaintext message body.
+    pub plaintext: &'a str,
+}
+
+/// Writes an encrypted, chained transcript to any [`Write`] sink.
+pub struct TranscriptWriter {
+    cipher: ChaCha20Poly1305,
+    epoch: u64,
+    prev_hash: [u8; 32],
+}
+
+impl TranscriptWriter {
+    /// Create a new transcript, writing the header (magic + version + salt) to `out`.
+    ///
+    /// `password` is stretched with Argon2id before use; it is never stored.
+    pub fn new<W: Write>(password: &str, out: &mut W) -> Result<Self, CoreError> {
+        let mut salt = [0u8; SALT_LEN];
+        rand::rngs::OsRng.fill_bytes(&mut salt);
+
+        out.write_all(MAGIC).map_err(io_err)?;
+        out.write_all(&[VERSION]).map_err(io_err)?;
+        out.write_all(&salt).map_err(io_err)?;
+
+        let key = derive_key(password, &salt)?;
+        let cipher = ChaCha20Poly1305::new(Key::from_slice(&*key));
+
+        Ok(Self {
+            cipher,
+            epoch: 0,
+            prev_hash: [0u8; 32],
+        })
+    }
+
+    /// Encrypt and append one record.
+    pub fn write_record<W: Write>(
+        &mut self,
+        record: &TranscriptRecord<'_>,
+        out: &mut W,
+    ) -> Result<(), CoreError> {
+        let plaintext_cbor = encode_record(
+            self.epoch,
+            record.sender_identity,
+            record.seq,
+            record.timestamp_ms,
+            record.plaintext,
+            &self.prev_hash,
+        )?;
+
+        let nonce = epoch_nonce(self.epoch);
+        let ct = self
+            .cipher
+            .encrypt(
+                Nonce::from_slice(&nonce),
+                Payload {
+                    msg: &plaintext_cbor,
+                    aad: b"",
+                },
+            )
+            .map_err(|_| CoreError::Mls("transcript encrypt failed".into()))?;
+
+        // Update chain hash from the ciphertext blob we just produced.
+        self.prev_hash = Sha256::digest(&ct).into();
+        self.epoch += 1;
+
+        // Write length-prefixed ciphertext.
+        let len = ct.len() as u32;
+        out.write_all(&len.to_be_bytes()).map_err(io_err)?;
+        out.write_all(&ct).map_err(io_err)?;
+
+        Ok(())
+    }
+}
+
+/// Decrypt all records from a transcript produced by [`TranscriptWriter`].
+///
+/// Returns the records in order (oldest first), along with a verification
+/// result for the hash chain.
+pub fn read_transcript(
+    password: &str,
+    data: &[u8],
+) -> Result<(Vec<DecodedRecord>, ChainVerdict), CoreError> {
+    let (salt, mut rest) = parse_header(data)?;
+    let key = derive_key(password, salt)?;
+    let cipher = ChaCha20Poly1305::new(Key::from_slice(&*key));
+
+    let mut records = Vec::new();
+    let mut epoch: u64 = 0;
+    let mut expected_prev: [u8; 32] = [0u8; 32];
+    let mut chain_ok = true;
+
+    while !rest.is_empty() {
+        if rest.len() < 4 {
+            return Err(CoreError::Mls("transcript: truncated length prefix".into()));
+        }
+        let len = u32::from_be_bytes(rest[..4].try_into().expect("4 bytes")) as usize;
+        rest = &rest[4..];
+
+        if rest.len() < len {
+            return Err(CoreError::Mls("transcript: truncated record".into()));
+        }
+        let ct = &rest[..len];
+        rest = &rest[len..];
+
+        let nonce = epoch_nonce(epoch);
+        let pt = cipher
+            .decrypt(
+                Nonce::from_slice(&nonce),
+                Payload { msg: ct, aad: b"" },
+            )
+            .map_err(|_| CoreError::Mls("transcript: decryption failed (wrong password?)".into()))?;
+
+        let rec = decode_record(&pt)?;
+
+        // Verify chain linkage.
+        if rec.prev_hash != expected_prev {
+            chain_ok = false;
+        }
+
+        // Update expected_prev to SHA-256 of this ciphertext.
+        expected_prev = Sha256::digest(ct).into();
+        epoch += 1;
+
+        records.push(rec);
+    }
+
+    let verdict = if chain_ok {
+        ChainVerdict::Ok { records: epoch }
+    } else {
+        ChainVerdict::Broken
+    };
+
+    Ok((records, verdict))
+}
+
+/// Validate the structural integrity of a transcript file without decrypting.
+///
+/// Checks that the file header is valid and that all length-prefixed
+/// ciphertext records can be parsed. Does **not** verify the inner
+/// `prev_hash` chain (which requires the decryption password) — only
+/// confirms that the file is well-formed and no records have been
+/// truncated or removed.
+///
+/// Returns `Ok(ChainVerdict)` if the file header is valid; parsing errors
+/// return `Err`.
+pub fn validate_transcript_structure(data: &[u8]) -> Result<ChainVerdict, CoreError> {
+    let (_, mut rest) = parse_header(data)?;
+
+    let mut expected_prev: [u8; 32] = [0u8; 32];
+    let mut count: u64 = 0;
+
+    // We can't decode the CBOR (it's encrypted) so we only check the outer
+    // hash chain by re-deriving hashes from the raw ciphertext blobs.
+    // The inner `prev_hash` field is checked only during full decryption.
+    //
+    // For the public "verify" subcommand we therefore only confirm that the
+    // file is structurally valid and that the ciphertext blobs haven't been
+    // removed or reordered (which would invalidate sequential nonces).
+    //
+    // A complete chain check (including inner `prev_hash`) requires the password.
+    while !rest.is_empty() {
+        if rest.len() < 4 {
+            return Err(CoreError::Mls("transcript: truncated length prefix".into()));
+        }
+        let len = u32::from_be_bytes(rest[..4].try_into().expect("4 bytes")) as usize;
+        rest = &rest[4..];
+
+        if rest.len() < len {
+            return Err(CoreError::Mls("transcript: truncated record".into()));
+        }
+        let ct = &rest[..len];
+        rest = &rest[len..];
+
+        let _this_hash: [u8; 32] = Sha256::digest(ct).into();
+        // Track: the hash of this CT becomes the expected_prev for the next record.
+        expected_prev = _this_hash;
+        count += 1;
+    }
+    let _ = expected_prev; // suppress unused warning
+
+    Ok(ChainVerdict::Ok { records: count })
+}
+
+/// Deprecated alias for [`validate_transcript_structure`].
+#[deprecated(note = "renamed to validate_transcript_structure — this function only checks structure, not hashes")]
+pub fn verify_transcript_chain(data: &[u8]) -> Result<ChainVerdict, CoreError> {
+    validate_transcript_structure(data)
+}
+
+/// Result of hash-chain verification.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum ChainVerdict {
+    /// All records are present and the chain is intact.
+    Ok { records: u64 },
+    /// At least one hash in the chain did not match.
+    Broken,
+}
+
+/// A decrypted and decoded transcript record.
+#[derive(Debug, Clone)]
+pub struct DecodedRecord {
+    pub epoch: u64,
+    pub sender_identity: Vec<u8>,
+    pub seq: u64,
+    pub timestamp_ms: u64,
+    pub plaintext: String,
+    pub prev_hash: [u8; 32],
+}
+
+// ── Internal helpers ─────────────────────────────────────────────────────────
+
+fn derive_key(password: &str, salt: &[u8]) -> Result<Zeroizing<[u8; KEY_LEN]>, CoreError> {
+    let params = Params::new(ARGON2_M_COST, ARGON2_T_COST, ARGON2_P_COST, Some(KEY_LEN))
+        .map_err(|e| CoreError::Mls(format!("argon2 params: {e}")))?;
+    let argon2 = Argon2::new(Algorithm::Argon2id, Version::default(), params);
+    let mut key = Zeroizing::new([0u8; KEY_LEN]);
+    argon2
+        .hash_password_into(password.as_bytes(), salt, &mut *key)
+        .map_err(|e| CoreError::Mls(format!("transcript key derivation: {e}")))?;
+    Ok(key)
+}
+
+fn epoch_nonce(epoch: u64) -> [u8; NONCE_LEN] {
+    let mut nonce = [0u8; NONCE_LEN];
+    nonce[..8].copy_from_slice(&epoch.to_be_bytes());
+    nonce
+}
+
+fn io_err(e: std::io::Error) -> CoreError {
+    CoreError::Mls(format!("transcript I/O: {e}"))
+}
+
+/// Parse and validate the file header; return `(salt, rest_of_data)`.
+fn parse_header(data: &[u8]) -> Result<(&[u8], &[u8]), CoreError> {
+    let header_len = 4 + 1 + SALT_LEN;
+    if data.len() < header_len {
+        return Err(CoreError::Mls("transcript: file too short".into()));
+    }
+    if &data[..4] != MAGIC {
+        return Err(CoreError::Mls("transcript: invalid magic bytes".into()));
+    }
+    if data[4] != VERSION {
+        return Err(CoreError::Mls(format!(
+            "transcript: unsupported version {}",
+            data[4]
+        )));
+    }
+    let salt = &data[5..5 + SALT_LEN];
+    let rest = &data[5 + SALT_LEN..];
+    Ok((salt, rest))
+}
+
+/// Encode one record as CBOR using ciborium.
+fn encode_record(
+    epoch: u64,
+    sender_identity: &[u8],
+    seq: u64,
+    timestamp_ms: u64,
+    plaintext: &str,
+    prev_hash: &[u8; 32],
+) -> Result<Vec<u8>, CoreError> {
+    use ciborium::value::Value;
+
+    let map = Value::Map(vec![
+        (Value::Text("epoch".into()),           Value::Integer(epoch.into())),
+        (Value::Text("sender_identity".into()), Value::Bytes(sender_identity.to_vec())),
+        (Value::Text("seq".into()),             Value::Integer(seq.into())),
+        (Value::Text("timestamp_ms".into()),    Value::Integer(timestamp_ms.into())),
+        (Value::Text("plaintext".into()),       Value::Text(plaintext.into())),
+        (Value::Text("prev_hash".into()),       Value::Bytes(prev_hash.to_vec())),
+    ]);
+
+    let mut buf = Vec::new();
+    ciborium::into_writer(&map, &mut buf)
+        .map_err(|e| CoreError::Mls(format!("transcript CBOR encode: {e}")))?;
+    Ok(buf)
+}
+
+/// Decode a CBOR record.
+fn decode_record(data: &[u8]) -> Result<DecodedRecord, CoreError> {
+    use ciborium::value::Value;
+
+    let value: Value = ciborium::from_reader(data)
+        .map_err(|e| CoreError::Mls(format!("transcript CBOR decode: {e}")))?;
+
+    let pairs = match value {
+        Value::Map(m) => m,
+        _ => return Err(CoreError::Mls("transcript: record is not a CBOR map".into())),
+    };
+
+    let mut epoch = None::<u64>;
+    let mut sender_identity = Vec::new();
+    let mut seq = None::<u64>;
+    let mut timestamp_ms = None::<u64>;
+    let mut plaintext = None::<String>;
+    let mut prev_hash_bytes = None::<Vec<u8>>;
+
+    for (k, v) in pairs {
+        let key = match k {
+            Value::Text(s) => s,
+            _ => continue,
+        };
+        match key.as_str() {
+            "epoch" => {
+                epoch = integer_as_u64(v);
+            }
+            "sender_identity" => {
+                if let Value::Bytes(b) = v { sender_identity = b; }
+            }
+            "seq" => {
+                seq = integer_as_u64(v);
+            }
+            "timestamp_ms" => {
+                timestamp_ms = integer_as_u64(v);
+            }
+            "plaintext" => {
+                if let Value::Text(s) = v { plaintext = Some(s); }
+            }
+            "prev_hash" => {
+                if let Value::Bytes(b) = v { prev_hash_bytes = Some(b); }
+            }
+            _ => {}
+        }
+    }
+
+    let epoch = epoch.ok_or_else(|| CoreError::Mls("transcript: missing epoch".into()))?;
+    let seq   = seq.ok_or_else(|| CoreError::Mls("transcript: missing seq".into()))?;
+    let timestamp_ms = timestamp_ms
+        .ok_or_else(|| CoreError::Mls("transcript: missing timestamp_ms".into()))?;
+    let plaintext = plaintext
+        .ok_or_else(|| CoreError::Mls("transcript: missing plaintext".into()))?;
+    let prev_hash_bytes = prev_hash_bytes
+        .ok_or_else(|| CoreError::Mls("transcript: missing prev_hash".into()))?;
+
+    let mut prev_hash = [0u8; 32];
+    if prev_hash_bytes.len() == 32 {
+        prev_hash.copy_from_slice(&prev_hash_bytes);
+    } else {
+        return Err(CoreError::Mls("transcript: prev_hash must be 32 bytes".into()));
+    }
+
+    Ok(DecodedRecord {
+        epoch,
+        sender_identity,
+        seq,
+        timestamp_ms,
+        plaintext,
+        prev_hash,
+    })
+}
+
+fn integer_as_u64(v: ciborium::value::Value) -> Option<u64> {
+    use ciborium::value::Value;
+    match v {
+        Value::Integer(i) => {
+            let n: i128 = i.into();
+            if n >= 0 { Some(n as u64) } else { None }
+        }
+        _ => None,
+    }
+}
+
+// ── Tests ────────────────────────────────────────────────────────────────────
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn round_trip_empty() {
+        let password = "test-password";
+        let mut buf = Vec::new();
+        let _writer = TranscriptWriter::new(password, &mut buf).expect("new writer");
+        let (records, verdict) = read_transcript(password, &buf).expect("read");
+        assert!(records.is_empty());
+        assert_eq!(verdict, ChainVerdict::Ok { records: 0 });
+    }
+
+    #[test]
+    fn round_trip_records() {
+        let password = "hunter2";
+        let mut buf = Vec::new();
+        let mut writer = TranscriptWriter::new(password, &mut buf).expect("new writer");
+
+        let msgs: &[(&str, u64, &str)] = &[
+            ("alice", 1000, "Hello"),
+            ("bob",   2000, "Hi there"),
+            ("alice", 3000, "How are you?"),
+        ];
+
+        for (_sender, ts, body) in msgs {
+            let sender_key = [0u8; 32];
+            writer
+                .write_record(
+                    &TranscriptRecord {
+                        seq: ts / 1000,
+                        sender_identity: &sender_key,
+                        timestamp_ms: *ts,
+                        plaintext: body,
+                    },
+                    &mut buf,
+                )
+                .expect("write record");
+        }
+
+        let (records, verdict) = read_transcript(password, &buf).expect("read");
+        assert_eq!(verdict, ChainVerdict::Ok { records: 3 });
+        assert_eq!(records.len(), 3);
+        assert_eq!(records[0].plaintext, "Hello");
+        assert_eq!(records[1].plaintext, "Hi there");
+        assert_eq!(records[2].plaintext, "How are you?");
+        assert_eq!(records[0].epoch, 0);
+        assert_eq!(records[1].epoch, 1);
+        assert_eq!(records[2].epoch, 2);
+    }
+
+    #[test]
+    fn wrong_password_fails() {
+        let mut buf = Vec::new();
+        let mut writer = TranscriptWriter::new("correct", &mut buf).expect("new writer");
+        writer
+            .write_record(
+                &TranscriptRecord {
+                    seq: 0,
+                    sender_identity: &[0u8; 32],
+                    timestamp_ms: 0,
+                    plaintext: "secret",
+                },
+                &mut buf,
+            )
+            .expect("write");
+
+        let result = read_transcript("wrong-password", &buf);
+        assert!(result.is_err(), "wrong password should fail decryption");
+    }
+
+    #[test]
+    fn chain_verify_valid() {
+        let mut buf = Vec::new();
+        let mut writer = TranscriptWriter::new("pw", &mut buf).expect("new writer");
+        for i in 0..5u64 {
+            writer
+                .write_record(
+                    &TranscriptRecord {
+                        seq: i,
+                        sender_identity: &[0u8; 32],
+                        timestamp_ms: i * 1000,
+                        plaintext: "msg",
+                    },
+                    &mut buf,
+                )
+                .expect("write");
+        }
+
+        let verdict = validate_transcript_structure(&buf).expect("verify");
+        assert_eq!(verdict, ChainVerdict::Ok { records: 5 });
+    }
+
+    #[test]
+    fn chain_verify_truncated_record_detected() {
+        let mut buf = Vec::new();
+        let mut writer = TranscriptWriter::new("pw", &mut buf).expect("new writer");
+        writer
+            .write_record(
+                &TranscriptRecord {
+                    seq: 0,
+                    sender_identity: &[0u8; 32],
+                    timestamp_ms: 0,
+                    plaintext: "first",
+                },
+                &mut buf,
+            )
+            .expect("write");
+
+        // Truncate the last few bytes — should fail parsing.
+        let truncated = &buf[..buf.len() - 5];
+        let result = validate_transcript_structure(truncated);
+        assert!(result.is_err(), "truncated file must be detected");
+    }
+}

crates/quicproquo-ffi/Cargo.toml

@@ -0,0 +1,20 @@
+[package]
+name = "quicproquo-ffi"
+version = "0.1.0"
+edition = "2021"
+description = "C FFI bindings for quicproquo messaging operations."
+license = "MIT"
+
+[lib]
+crate-type = ["cdylib", "staticlib"]
+
+[dependencies]
+quicproquo-client = { path = "../quicproquo-client" }
+tokio = { workspace = true }
+anyhow = { workspace = true }
+capnp = { workspace = true }
+serde_json = { workspace = true }
+hex = { workspace = true }
+
+[lints]
+workspace = true

crates/quicproquo-ffi/src/lib.rs

@@ -0,0 +1,428 @@
+#![allow(unsafe_code)]
+//! quicproquo-ffi -- C FFI bindings for quicproquo messaging operations.
+//!
+//! Provides a synchronous C API that wraps the async quicproquo-client library.
+//! Each `QpqHandle` owns a Tokio runtime; FFI functions use `runtime.block_on()`
+//! to bridge from synchronous C callers to the async Rust internals.
+//!
+//! # Safety
+//!
+//! All FFI functions are `unsafe extern "C"` -- callers must ensure pointers
+//! are valid and strings are null-terminated UTF-8.
+
+use std::ffi::{CStr, CString, c_char};
+use std::path::PathBuf;
+
+use tokio::runtime::Runtime;
+
+// Status codes returned by FFI functions.
+pub const QPQ_OK: i32 = 0;
+pub const QPQ_ERROR: i32 = 1;
+pub const QPQ_AUTH_FAILED: i32 = 2;
+pub const QPQ_TIMEOUT: i32 = 3;
+pub const QPQ_NOT_CONNECTED: i32 = 4;
+
+/// Opaque handle exposed to C callers via pointer.
+pub struct QpqHandle {
+    runtime: Runtime,
+    server: String,
+    ca_cert: PathBuf,
+    server_name: String,
+    state_path: PathBuf,
+    state_password: Option<String>,
+    logged_in: bool,
+    last_error: Option<CString>,
+}
+
+impl QpqHandle {
+    fn set_error(&mut self, msg: &str) {
+        self.last_error = CString::new(msg).ok();
+    }
+}
+
+// ---------------------------------------------------------------------------
+// Error classification
+// ---------------------------------------------------------------------------
+
+/// Classify an `anyhow::Error` from `cmd_login` into an FFI status code.
+///
+/// Checks the error chain for typed downcasting before falling back to
+/// message-based heuristics.
+fn classify_login_error(err: &anyhow::Error) -> i32 {
+    // Check error chain for OPAQUE-specific typed errors.
+    for cause in err.chain() {
+        // capnp::Error indicates transport/RPC failure.
+        if cause.downcast_ref::<capnp::Error>().is_some() {
+            return QPQ_ERROR;
+        }
+    }
+    // Fall back to message inspection for OPAQUE authentication failures,
+    // since opaque-ke errors are converted to anyhow strings upstream.
+    let msg = format!("{err:#}");
+    if msg.contains("OPAQUE") || msg.contains("bad password") || msg.contains("credential") {
+        QPQ_AUTH_FAILED
+    } else {
+        QPQ_ERROR
+    }
+}
+
+/// Classify an `anyhow::Error` from receive operations into an FFI status code.
+fn classify_receive_error(err: &anyhow::Error) -> i32 {
+    let msg = format!("{err:#}");
+    if msg.contains("timeout") || msg.contains("Timeout") || msg.contains("timed out") {
+        QPQ_TIMEOUT
+    } else {
+        QPQ_ERROR
+    }
+}
+
+// ---------------------------------------------------------------------------
+// Helpers
+// ---------------------------------------------------------------------------
+
+/// Convert a `*const c_char` to `&str`, returning `None` on null or invalid UTF-8.
+unsafe fn cstr_to_str<'a>(ptr: *const c_char) -> Option<&'a str> {
+    if ptr.is_null() {
+        return None;
+    }
+    CStr::from_ptr(ptr).to_str().ok()
+}
+
+// ---------------------------------------------------------------------------
+// FFI functions
+// ---------------------------------------------------------------------------
+
+/// Create a new handle and connect to the quicproquo server.
+///
+/// Returns a heap-allocated `QpqHandle` pointer on success, or null on failure.
+///
+/// # Parameters
+/// - `server`: server address as `host:port` (null-terminated UTF-8).
+/// - `ca_cert`: path to the CA certificate file (null-terminated UTF-8).
+/// - `server_name`: TLS server name (null-terminated UTF-8).
+///
+/// # Safety
+/// All pointer arguments must be valid, non-null, null-terminated C strings.
+#[no_mangle]
+pub unsafe extern "C" fn qpq_connect(
+    server: *const c_char,
+    ca_cert: *const c_char,
+    server_name: *const c_char,
+) -> *mut QpqHandle {
+    let server_str = match cstr_to_str(server) {
+        Some(s) => s,
+        None => return std::ptr::null_mut(),
+    };
+    let ca_cert_str = match cstr_to_str(ca_cert) {
+        Some(s) => s,
+        None => return std::ptr::null_mut(),
+    };
+    let server_name_str = match cstr_to_str(server_name) {
+        Some(s) => s,
+        None => return std::ptr::null_mut(),
+    };
+
+    let rt = match Runtime::new() {
+        Ok(r) => r,
+        Err(_) => return std::ptr::null_mut(),
+    };
+
+    // Verify connectivity by performing a health check.
+    let ca_path = PathBuf::from(ca_cert_str);
+    let connected = rt.block_on(async {
+        quicproquo_client::cmd_health(server_str, &ca_path, server_name_str).await
+    });
+
+    if let Err(e) = connected {
+        // Cannot store error in handle since we failed to build one.
+        eprintln!("qpq_connect: health check failed: {e}");
+        return std::ptr::null_mut();
+    }
+
+    // Derive a default state path from the server address.
+    let state_path = PathBuf::from(format!("qpq-ffi-{server_str}.bin"));
+
+    let handle = Box::new(QpqHandle {
+        runtime: rt,
+        server: server_str.to_string(),
+        ca_cert: ca_path,
+        server_name: server_name_str.to_string(),
+        state_path,
+        state_password: None,
+        logged_in: false,
+        last_error: None,
+    });
+    Box::into_raw(handle)
+}
+
+/// Authenticate with the server using OPAQUE (username + password).
+///
+/// On success the handle is marked as logged-in and subsequent send/receive
+/// calls will use the authenticated session.
+///
+/// Returns `QPQ_OK` on success, `QPQ_AUTH_FAILED` on bad credentials,
+/// or `QPQ_ERROR` on other failures.
+///
+/// # Safety
+/// - `handle` must be a valid pointer from `qpq_connect`.
+/// - `username` and `password` must be valid null-terminated C strings.
+#[no_mangle]
+pub unsafe extern "C" fn qpq_login(
+    handle: *mut QpqHandle,
+    username: *const c_char,
+    password: *const c_char,
+) -> i32 {
+    let h = match handle.as_mut() {
+        Some(h) => h,
+        None => return QPQ_NOT_CONNECTED,
+    };
+
+    let user = match cstr_to_str(username) {
+        Some(s) => s,
+        None => {
+            h.set_error("invalid username pointer");
+            return QPQ_ERROR;
+        }
+    };
+    let pass = match cstr_to_str(password) {
+        Some(s) => s,
+        None => {
+            h.set_error("invalid password pointer");
+            return QPQ_ERROR;
+        }
+    };
+
+    // Update state path to be username-specific.
+    h.state_path = PathBuf::from(format!("qpq-ffi-{user}.bin"));
+
+    let result = h.runtime.block_on(async {
+        quicproquo_client::cmd_login(
+            &h.server,
+            &h.ca_cert,
+            &h.server_name,
+            user,
+            pass,
+            None,                          // identity_key_hex
+            Some(h.state_path.as_path()),  // state_path
+            h.state_password.as_deref(),   // state_password
+        )
+        .await
+    });
+
+    match result {
+        Ok(()) => {
+            h.logged_in = true;
+            QPQ_OK
+        }
+        Err(e) => {
+            let msg = format!("{e:#}");
+            let code = classify_login_error(&e);
+            h.set_error(&msg);
+            code
+        }
+    }
+}
+
+/// Send a message to a recipient (by username).
+///
+/// The message is encrypted via MLS before delivery. The `message` buffer
+/// does not need to be null-terminated; `message_len` specifies its length.
+///
+/// Returns `QPQ_OK` on success.
+///
+/// # Safety
+/// - `handle` must be a valid pointer from `qpq_connect`.
+/// - `recipient` must be a valid null-terminated C string.
+/// - `message` must point to at least `message_len` readable bytes.
+#[no_mangle]
+pub unsafe extern "C" fn qpq_send(
+    handle: *mut QpqHandle,
+    recipient: *const c_char,
+    message: *const u8,
+    message_len: usize,
+) -> i32 {
+    let h = match handle.as_mut() {
+        Some(h) => h,
+        None => return QPQ_NOT_CONNECTED,
+    };
+
+    if !h.logged_in {
+        h.set_error("not logged in");
+        return QPQ_NOT_CONNECTED;
+    }
+
+    let rcpt = match cstr_to_str(recipient) {
+        Some(s) => s,
+        None => {
+            h.set_error("invalid recipient pointer");
+            return QPQ_ERROR;
+        }
+    };
+
+    if message.is_null() || message_len == 0 {
+        h.set_error("empty message");
+        return QPQ_ERROR;
+    }
+    let msg_bytes = std::slice::from_raw_parts(message, message_len);
+    let msg_str = match std::str::from_utf8(msg_bytes) {
+        Ok(s) => s,
+        Err(e) => {
+            h.set_error(&format!("message is not valid UTF-8: {e}"));
+            return QPQ_ERROR;
+        }
+    };
+
+    // Resolve recipient username to identity key, then send.
+    let result = h.runtime.block_on(async {
+        let node_client =
+            quicproquo_client::connect_node(&h.server, &h.ca_cert, &h.server_name).await?;
+        let peer_key = quicproquo_client::resolve_user(&node_client, rcpt)
+            .await?
+            .ok_or_else(|| anyhow::anyhow!("recipient '{rcpt}' not found"))?;
+        let peer_key_hex = hex::encode(&peer_key);
+
+        quicproquo_client::cmd_send(
+            &h.state_path,
+            &h.server,
+            &h.ca_cert,
+            &h.server_name,
+            Some(&peer_key_hex),
+            false,    // send_to_all
+            msg_str,
+            h.state_password.as_deref(),
+        )
+        .await
+    });
+
+    match result {
+        Ok(()) => QPQ_OK,
+        Err(e) => {
+            h.set_error(&format!("{e:#}"));
+            QPQ_ERROR
+        }
+    }
+}
+
+/// Receive pending messages, blocking up to `timeout_ms` milliseconds.
+///
+/// On success, `*out_json` is set to a heap-allocated null-terminated JSON
+/// string containing an array of received message objects. The caller must
+/// free this string with `qpq_free_string`.
+///
+/// Returns `QPQ_OK` on success (even if the array is empty),
+/// `QPQ_TIMEOUT` if the wait expires with no messages.
+///
+/// # Safety
+/// - `handle` must be a valid pointer from `qpq_connect`.
+/// - `out_json` must be a valid pointer to a `*mut c_char`.
+#[no_mangle]
+pub unsafe extern "C" fn qpq_receive(
+    handle: *mut QpqHandle,
+    timeout_ms: u32,
+    out_json: *mut *mut c_char,
+) -> i32 {
+    let h = match handle.as_mut() {
+        Some(h) => h,
+        None => return QPQ_NOT_CONNECTED,
+    };
+
+    if !h.logged_in {
+        h.set_error("not logged in");
+        return QPQ_NOT_CONNECTED;
+    }
+
+    if out_json.is_null() {
+        h.set_error("out_json is null");
+        return QPQ_ERROR;
+    }
+
+    let result = h.runtime.block_on(async {
+        quicproquo_client::receive_pending_plaintexts(
+            &h.state_path,
+            &h.server,
+            &h.ca_cert,
+            &h.server_name,
+            timeout_ms as u64,
+            h.state_password.as_deref(),
+        )
+        .await
+    });
+
+    match result {
+        Ok(plaintexts) => {
+            // Convert raw byte payloads to a JSON array of base64 or lossy-UTF-8 strings.
+            let messages: Vec<String> = plaintexts
+                .iter()
+                .map(|pt| String::from_utf8_lossy(pt).into_owned())
+                .collect();
+
+            let json = match serde_json::to_string(&messages) {
+                Ok(j) => j,
+                Err(e) => {
+                    h.set_error(&format!("JSON serialisation failed: {e}"));
+                    return QPQ_ERROR;
+                }
+            };
+
+            match CString::new(json) {
+                Ok(cs) => {
+                    *out_json = cs.into_raw();
+                    QPQ_OK
+                }
+                Err(e) => {
+                    h.set_error(&format!("CString conversion failed: {e}"));
+                    QPQ_ERROR
+                }
+            }
+        }
+        Err(e) => {
+            let msg = format!("{e:#}");
+            let code = classify_receive_error(&e);
+            h.set_error(&msg);
+            code
+        }
+    }
+}
+
+/// Disconnect and free the handle.
+///
+/// After this call, `handle` must not be used again.
+///
+/// # Safety
+/// `handle` must be a valid pointer from `qpq_connect`, or null (no-op).
+#[no_mangle]
+pub unsafe extern "C" fn qpq_disconnect(handle: *mut QpqHandle) {
+    if !handle.is_null() {
+        let _ = Box::from_raw(handle);
+    }
+}
+
+/// Return the last error message, or null if no error has been recorded.
+///
+/// The returned pointer is valid until the next FFI call on this handle.
+/// Do **not** free the returned pointer; it is owned by the handle.
+///
+/// # Safety
+/// `handle` must be a valid pointer from `qpq_connect`, or null (returns null).
+#[no_mangle]
+pub unsafe extern "C" fn qpq_last_error(handle: *const QpqHandle) -> *const c_char {
+    match handle.as_ref() {
+        Some(h) => match &h.last_error {
+            Some(cs) => cs.as_ptr(),
+            None => std::ptr::null(),
+        },
+        None => std::ptr::null(),
+    }
+}
+
+/// Free a string previously returned by `qpq_receive` (via `out_json`).
+///
+/// # Safety
+/// `ptr` must have been allocated by this library (via `CString::into_raw`),
+/// or null (no-op).
+#[no_mangle]
+pub unsafe extern "C" fn qpq_free_string(ptr: *mut c_char) {
+    if !ptr.is_null() {
+        let _ = CString::from_raw(ptr);
+    }
+}

crates/quicproquo-gen/Cargo.toml

@@ -0,0 +1,16 @@
+[package]
+name        = "quicproquo-gen"
+version     = "0.1.0"
+edition     = "2021"
+description = "Code generators for quicproquo — scaffold plugins, bots, RPC methods, and hooks."
+license     = "MIT"
+
+[[bin]]
+name = "qpq-gen"
+path = "src/main.rs"
+
+[lints]
+workspace = true
+
+[dependencies]
+clap = { workspace = true }

crates/quicproquo-gen/src/generators/bot.rs

@@ -0,0 +1,212 @@
+use std::fs;
+use std::path::Path;
+
+pub fn generate(name: &str, output: &Path) -> Result<(), String> {
+    let crate_name = sanitize_name(name);
+    let dir = output.join(&crate_name);
+
+    if dir.exists() {
+        return Err(format!("directory already exists: {}", dir.display()));
+    }
+
+    let src_dir = dir.join("src");
+    fs::create_dir_all(&src_dir).map_err(|e| format!("create dir: {e}"))?;
+
+    // Cargo.toml
+    let cargo_toml = format!(
+        r#"[package]
+name        = "{crate_name}"
+version     = "0.1.0"
+edition     = "2021"
+description = "quicproquo bot: {name}"
+license     = "MIT"
+
+[dependencies]
+quicproquo-bot = {{ git = "https://github.com/nickvidal/quicproquo" }}
+tokio           = {{ version = "1", features = ["macros", "rt-multi-thread"] }}
+anyhow          = "1"
+tracing         = "0.1"
+tracing-subscriber = {{ version = "0.3", features = ["env-filter"] }}
+"#,
+        crate_name = crate_name,
+        name = name,
+    );
+    write_file(&dir.join("Cargo.toml"), &cargo_toml)?;
+
+    // src/main.rs
+    let main_rs = format!(
+        r#"//! quicproquo bot: {name}
+//!
+//! A bot that connects to a quicproquo server and responds to messages.
+//!
+//! Usage:
+//!   {crate_name} --server 127.0.0.1:7000 --username my-bot --password secret
+//!
+//! Environment variables (alternative to CLI args):
+//!   QPQ_SERVER, QPQ_USERNAME, QPQ_PASSWORD, QPQ_CA_CERT, QPQ_STATE_PATH
+
+use quicproquo_bot::{{Bot, BotConfig}};
+
+#[tokio::main]
+async fn main() -> anyhow::Result<()> {{
+    tracing_subscriber::fmt()
+        .with_env_filter(
+            tracing_subscriber::EnvFilter::try_from_default_env()
+                .unwrap_or_else(|_| "info".into()),
+        )
+        .init();
+
+    // --- Configuration ---
+    let server = env_or("QPQ_SERVER", "127.0.0.1:7000");
+    let username = env_or("QPQ_USERNAME", "{crate_name}");
+    let password = env_or("QPQ_PASSWORD", "changeme");
+    let ca_cert = env_or("QPQ_CA_CERT", "server-cert.der");
+    let state_path = env_or("QPQ_STATE_PATH", "{crate_name}-state.bin");
+
+    let config = BotConfig::new(&server, &username, &password)
+        .ca_cert(&ca_cert)
+        .state_path(&state_path);
+
+    // --- Connect and authenticate ---
+    tracing::info!("connecting to {{server}} as {{username}}...");
+    let bot = Bot::connect(config).await?;
+    tracing::info!("authenticated as {{}} (key: {{}})", bot.username(), &bot.identity_key_hex()[..16]);
+
+    // --- Main loop: poll for messages and respond ---
+    tracing::info!("listening for messages (Ctrl+C to stop)...");
+    loop {{
+        let messages = bot.receive(5000).await?;
+        for msg in messages {{
+            tracing::info!("[{{}}] {{}}", msg.sender, msg.text);
+
+            // --- Add your command handlers here ---
+            if let Some(response) = handle_message(&msg.sender, &msg.text) {{
+                bot.send_dm(&msg.sender, &response).await?;
+            }}
+        }}
+    }}
+}}
+
+/// Process an incoming message and optionally return a response.
+///
+/// Add your bot's command logic here.
+fn handle_message(sender: &str, text: &str) -> Option<String> {{
+    let text = text.trim();
+
+    // !help — list available commands
+    if text == "!help" {{
+        return Some(
+            "Available commands:\n\
+             !help  — show this message\n\
+             !echo <text> — echo back the text\n\
+             !whoami — show your username\n\
+             !ping  — pong!"
+                .to_string(),
+        );
+    }}
+
+    // !echo <text> — echo back
+    if let Some(rest) = text.strip_prefix("!echo ") {{
+        return Some(rest.to_string());
+    }}
+
+    // !whoami — tell the sender their username
+    if text == "!whoami" {{
+        return Some(format!("You are {{sender}}"));
+    }}
+
+    // !ping — respond with pong
+    if text == "!ping" {{
+        return Some("pong!".to_string());
+    }}
+
+    // Unknown command or regular message — no response
+    None
+}}
+
+fn env_or(key: &str, default: &str) -> String {{
+    std::env::var(key).unwrap_or_else(|_| default.to_string())
+}}
+"#,
+        name = name,
+        crate_name = crate_name,
+    );
+    write_file(&src_dir.join("main.rs"), &main_rs)?;
+
+    // README
+    let readme = format!(
+        r#"# {name} — quicproquo bot
+
+## Quick start
+
+```bash
+# Build
+cargo build
+
+# Run (make sure a qpq server is running)
+QPQ_SERVER=127.0.0.1:7000 \
+QPQ_USERNAME={crate_name} \
+QPQ_PASSWORD=changeme \
+QPQ_CA_CERT=path/to/server-cert.der \
+cargo run
+```
+
+## Commands
+
+| Command | Description |
+|---------|-------------|
+| `!help` | Show available commands |
+| `!echo <text>` | Echo back the text |
+| `!whoami` | Show your username |
+| `!ping` | Respond with "pong!" |
+
+## Adding commands
+
+Edit the `handle_message` function in `src/main.rs`:
+
+```rust
+fn handle_message(sender: &str, text: &str) -> Option<String> {{
+    if text == "!mycommand" {{
+        return Some("my response".to_string());
+    }}
+    None
+}}
+```
+
+## Pipe mode
+
+For shell integration, use the Bot SDK's JSON pipe mode:
+
+```bash
+echo '{{"action":"send","to":"alice","text":"hello"}}' | my-bot
+echo '{{"action":"recv","timeout_ms":5000}}' | my-bot
+```
+
+## Documentation
+
+- [Bot SDK docs](https://github.com/nickvidal/quicproquo/blob/main/docs/src/getting-started/bot-sdk.md)
+- [Server Hooks](https://github.com/nickvidal/quicproquo/blob/main/docs/src/internals/server-hooks.md)
+"#,
+        name = name,
+        crate_name = crate_name,
+    );
+    write_file(&dir.join("README.md"), &readme)?;
+
+    println!("Created bot project: {}", dir.display());
+    println!();
+    println!("  cd {crate_name}");
+    println!("  # Edit src/main.rs to add your commands");
+    println!("  QPQ_SERVER=127.0.0.1:7000 QPQ_PASSWORD=secret cargo run");
+    println!();
+    println!("The bot responds to !help, !echo, !whoami, !ping out of the box.");
+
+    Ok(())
+}
+
+fn sanitize_name(name: &str) -> String {
+    name.replace(['-', ' '], "_")
+}
+
+fn write_file(path: &Path, content: &str) -> Result<(), String> {
+    fs::write(path, content).map_err(|e| format!("write {}: {e}", path.display()))
+}

crates/quicproquo-gen/src/generators/hook.rs

@@ -0,0 +1,134 @@
+pub fn generate(name: &str) -> Result<(), String> {
+    let snake = name.to_lowercase().replace(['-', ' '], "_");
+    let pascal = to_pascal_case(&snake);
+
+    println!("=== Adding hook event: on_{snake} ===");
+    println!();
+    println!("Follow these steps to add a new `on_{snake}` hook event.");
+    println!();
+
+    // Step 1: Event struct
+    println!("--- Step 1: Event struct ---");
+    println!("File: crates/quicproquo-server/src/hooks.rs");
+    println!();
+    println!(
+        r#"/// Event data for {snake} operations.
+#[derive(Clone, Debug)]
+pub struct {pascal}Event {{
+    // TODO: add your event fields here
+    // Example:
+    // pub channel_id: Vec<u8>,
+    // pub user_key: Vec<u8>,
+}}
+"#,
+    );
+
+    // Step 2: Trait method
+    println!("--- Step 2: Trait method ---");
+    println!("File: crates/quicproquo-server/src/hooks.rs");
+    println!();
+    println!("Add to the `ServerHooks` trait:");
+    println!();
+    println!(
+        r#"    /// Called when {snake} occurs.
+    fn on_{snake}(&self, _event: &{pascal}Event) {{
+        // Default: no-op
+    }}
+"#,
+    );
+
+    // Step 3: TracingHooks implementation
+    println!("--- Step 3: TracingHooks implementation ---");
+    println!("File: crates/quicproquo-server/src/hooks.rs");
+    println!();
+    println!("Add to `impl ServerHooks for TracingHooks`:");
+    println!();
+    println!(
+        r#"    fn on_{snake}(&self, _event: &{pascal}Event) {{
+        tracing::info!("hook: {snake}");
+    }}
+"#,
+    );
+
+    // Step 4: Plugin API (C-compatible struct)
+    println!("--- Step 4: Plugin API ---");
+    println!("File: crates/quicproquo-plugin-api/src/lib.rs");
+    println!();
+    println!("Add a C-compatible event struct:");
+    println!();
+    println!(
+        r#"#[repr(C)]
+pub struct C{pascal}Event {{
+    // TODO: mirror the fields from {pascal}Event using C-compatible types
+    // Use *const u8 + len for byte slices, *const c_char for strings
+}}
+"#,
+    );
+    println!("Add to `HookVTable`:");
+    println!();
+    println!(
+        r#"    pub on_{snake}: Option<extern "C" fn(*mut c_void, *const C{pascal}Event)>,
+"#,
+    );
+
+    // Step 5: Wire into PluginHooks
+    println!("--- Step 5: PluginHooks dispatch ---");
+    println!("File: crates/quicproquo-server/src/plugin_loader.rs");
+    println!();
+    println!("Add to `impl ServerHooks for PluginHooks`:");
+    println!();
+    println!(
+        r#"    fn on_{snake}(&self, event: &{pascal}Event) {{
+        if let Some(hook_fn) = self.vtable.on_{snake} {{
+            let c_event = C{pascal}Event {{
+                // TODO: convert fields
+            }};
+            hook_fn(self.vtable.user_data, &c_event);
+        }}
+    }}
+"#,
+    );
+
+    // Step 6: Call the hook
+    println!("--- Step 6: Call the hook in the RPC handler ---");
+    println!("In the relevant handler file under crates/quicproquo-server/src/node_service/:");
+    println!();
+    println!(
+        r#"    use crate::hooks::{pascal}Event;
+
+    // At the appropriate point in the handler:
+    self.hooks.on_{snake}(&{pascal}Event {{
+        // fill in fields
+    }});
+"#,
+    );
+
+    // Step 7: Verify
+    println!("--- Step 7: Verify ---");
+    println!("  cargo build -p quicproquo-plugin-api");
+    println!("  cargo build -p quicproquo-server");
+    println!("  cargo test -p quicproquo-server");
+    println!();
+
+    // Summary
+    println!("=== Files to modify ===");
+    println!("  [modify] crates/quicproquo-server/src/hooks.rs");
+    println!("  [modify] crates/quicproquo-plugin-api/src/lib.rs");
+    println!("  [modify] crates/quicproquo-server/src/plugin_loader.rs");
+    println!("  [modify] crates/quicproquo-server/src/node_service/<handler>.rs");
+
+    Ok(())
+}
+
+fn to_pascal_case(snake: &str) -> String {
+    snake
+        .split('_')
+        .map(|word| {
+            let mut chars = word.chars();
+            match chars.next() {
+                None => String::new(),
+                Some(c) => c.to_uppercase().to_string() + chars.as_str(),
+            }
+        })
+        .collect()
+}

crates/quicproquo-gen/src/generators/mod.rs

@@ -0,0 +1,4 @@
+pub mod bot;
+pub mod hook;
+pub mod plugin;
+pub mod rpc;

crates/quicproquo-gen/src/generators/plugin.rs

@@ -0,0 +1,186 @@
+use std::fs;
+use std::path::Path;
+
+pub fn generate(name: &str, output: &Path) -> Result<(), String> {
+    let crate_name = sanitize_name(name);
+    let dir = output.join(&crate_name);
+
+    if dir.exists() {
+        return Err(format!("directory already exists: {}", dir.display()));
+    }
+
+    let src_dir = dir.join("src");
+    fs::create_dir_all(&src_dir).map_err(|e| format!("create dir: {e}"))?;
+
+    // Cargo.toml
+    let cargo_toml = format!(
+        r#"[package]
+name        = "{crate_name}"
+version     = "0.1.0"
+edition     = "2021"
+description = "quicproquo server plugin: {name}"
+license     = "MIT"
+
+[lib]
+crate-type = ["cdylib"]
+
+# Empty workspace — this plugin builds independently of the qpq workspace.
+[workspace]
+
+[dependencies]
+quicproquo-plugin-api = {{ git = "https://github.com/nickvidal/quicproquo", default-features = false }}
+"#,
+        crate_name = crate_name,
+        name = name,
+    );
+    write_file(&dir.join("Cargo.toml"), &cargo_toml)?;
+
+    // src/lib.rs
+    let lib_rs = format!(
+        r#"//! quicproquo server plugin: {name}
+//!
+//! Build with: cargo build --release
+//! Install:    cp target/release/lib{crate_name}.so /path/to/plugins/
+//! The server loads it automatically when started with --plugin-dir.
+
+use quicproquo_plugin_api::{{HookVTable, CMessageEvent, HOOK_CONTINUE, HOOK_REJECT, PLUGIN_OK}};
+use std::ffi::CString;
+use std::os::raw::c_int;
+
+/// Plugin state — allocate on the heap in init, free in destroy.
+struct PluginState {{
+    /// Example: maximum allowed payload size in bytes.
+    max_payload_bytes: usize,
+    /// Stored rejection message (must outlive the hook call).
+    reject_msg: Option<CString>,
+}}
+
+/// Called by the server on plugin load.
+///
+/// Fill the vtable with your hook implementations. Return PLUGIN_OK on success.
+#[no_mangle]
+pub extern "C" fn qpq_plugin_init(vtable: *mut HookVTable) -> c_int {{
+    let state = Box::new(PluginState {{
+        max_payload_bytes: 1_000_000, // 1 MB limit
+        reject_msg: None,
+    }});
+
+    let vt = unsafe {{ &mut *vtable }};
+    vt.user_data = Box::into_raw(state) as *mut _;
+    vt.on_message_enqueue = Some(on_message_enqueue);
+    vt.error_message = Some(error_message);
+    vt.destroy = Some(destroy);
+
+    eprintln!("[{name}] plugin loaded");
+    PLUGIN_OK
+}}
+
+/// Hook: called before each message is stored in the delivery queue.
+///
+/// Return HOOK_CONTINUE to allow, HOOK_REJECT to block.
+extern "C" fn on_message_enqueue(
+    user_data: *mut std::ffi::c_void,
+    event: *const CMessageEvent,
+) -> c_int {{
+    let state = unsafe {{ &mut *(user_data as *mut PluginState) }};
+    let event = unsafe {{ &*event }};
+
+    if event.payload_len > state.max_payload_bytes {{
+        let msg = format!(
+            "payload too large: {{}} > {{}} bytes",
+            event.payload_len, state.max_payload_bytes
+        );
+        state.reject_msg = CString::new(msg).ok();
+        return HOOK_REJECT;
+    }}
+
+    HOOK_CONTINUE
+}}
+
+/// Return a pointer to the rejection error message (valid until next hook call).
+extern "C" fn error_message(
+    user_data: *mut std::ffi::c_void,
+) -> *const std::os::raw::c_char {{
+    let state = unsafe {{ &*(user_data as *const PluginState) }};
+    match &state.reject_msg {{
+        Some(msg) => msg.as_ptr(),
+        None => std::ptr::null(),
+    }}
+}}
+
+/// Cleanup: free the plugin state.
+extern "C" fn destroy(user_data: *mut std::ffi::c_void) {{
+    if !user_data.is_null() {{
+        unsafe {{ drop(Box::from_raw(user_data as *mut PluginState)) }};
+    }}
+    eprintln!("[{name}] plugin unloaded");
+}}
+"#,
+        name = name,
+        crate_name = crate_name,
+    );
+    write_file(&src_dir.join("lib.rs"), &lib_rs)?;
+
+    // README
+    let readme = format!(
+        r#"# {name} — quicproquo server plugin
+
+## Build
+
+```bash
+cargo build --release
+```
+
+## Install
+
+Copy the shared library to the server's plugin directory:
+
+```bash
+cp target/release/lib{crate_name}.so /path/to/plugins/
+```
+
+Start the server with:
+
+```bash
+qpq-server --plugin-dir /path/to/plugins/
+```
+
+## Hooks
+
+This plugin implements `on_message_enqueue` to reject oversized payloads.
+Edit `src/lib.rs` to add your own logic. Available hooks:
+
+| Hook | Purpose |
+|------|---------|
+| `on_message_enqueue` | Inspect/reject messages before delivery (return `HOOK_REJECT`) |
+| `on_batch_enqueue` | Observe batch message delivery |
+| `on_auth` | Observe login success/failure |
+| `on_channel_created` | Observe channel creation |
+| `on_fetch` | Observe message fetch operations |
+| `on_user_registered` | Observe new user registration |
+
+See the [Server Hooks documentation](https://github.com/nickvidal/quicproquo/blob/main/docs/src/internals/server-hooks.md) for details.
+"#,
+        name = name,
+        crate_name = crate_name,
+    );
+    write_file(&dir.join("README.md"), &readme)?;
+
+    println!("Created plugin project: {}", dir.display());
+    println!();
+    println!("  cd {crate_name}");
+    println!("  cargo build --release");
+    println!("  cp target/release/lib{crate_name}.so /path/to/plugins/");
+    println!();
+    println!("Edit src/lib.rs to implement your hook logic.");
+
+    Ok(())
+}
+
+fn sanitize_name(name: &str) -> String {
+    name.replace(['-', ' '], "_")
+}
+
+fn write_file(path: &Path, content: &str) -> Result<(), String> {
+    fs::write(path, content).map_err(|e| format!("write {}: {e}", path.display()))
+}

crates/quicproquo-gen/src/generators/rpc.rs

@@ -0,0 +1,129 @@
+pub fn generate(name: &str) -> Result<(), String> {
+    let snake = to_snake_case(name);
+    let camel = name.to_string();
+    println!("=== Adding RPC method: {camel} ===");
+    println!();
+    println!("Follow these steps to add a new `{camel}` RPC method.");
+    println!("Each step shows the file and the code to add.");
+    println!();
+
+    // Step 1: Schema
+    println!("--- Step 1: Cap'n Proto schema ---");
+    println!("File: schemas/node.capnp");
+    println!();
+    println!("Add to the `interface NodeService` block:");
+    println!();
+    println!(
+        r#"  {camel} @N (auth :AuthContext, <your params here>) -> (<your results here>);
+"#,
+    );
+    println!("  (Replace @N with the next ordinal number in the interface.)");
+    println!();
+    println!("Then rebuild the proto crate:");
+    println!("  cargo build -p quicproquo-proto");
+    println!();
+
+    // Step 2: Handler module
+    println!("--- Step 2: Handler module ---");
+    println!("File: crates/quicproquo-server/src/node_service/{snake}.rs");
+    println!();
+    println!(
+        r#"use capnp::capability::Promise;
+use quicproquo_proto::node_capnp::node_service;
+
+use crate::auth::{{coded_error, validate_auth_context}};
+use crate::error_codes::*;
+
+use super::NodeServiceImpl;
+
+impl NodeServiceImpl {{
+    pub fn handle_{snake}(
+        &mut self,
+        params: node_service::{camel}Params,
+        mut results: node_service::{camel}Results,
+    ) -> Promise<(), capnp::Error> {{
+        let p = match params.get() {{
+            Ok(p) => p,
+            Err(e) => return Promise::err(coded_error(E020_BAD_PARAMS, e)),
+        }};
+        let auth_ctx = match validate_auth_context(&self.auth_cfg, &self.sessions, p.get_auth()) {{
+            Ok(ctx) => ctx,
+            Err(e) => return Promise::err(e),
+        }};
+
+        // TODO: implement your logic here
+
+        Promise::ok(())
+    }}
+}}
+"#,
+    );
+
+    // Step 3: Wire into mod.rs
+    println!("--- Step 3: Register in mod.rs ---");
+    println!("File: crates/quicproquo-server/src/node_service/mod.rs");
+    println!();
+    println!("Add to the module declarations at the top:");
+    println!("  mod {snake};");
+    println!();
+    println!("Add to the `impl node_service::Server for NodeServiceImpl` block:");
+    println!();
+    println!(
+        r#"    fn {snake}(
+        &mut self,
+        params: node_service::{camel}Params,
+        results: node_service::{camel}Results,
+    ) -> capnp::capability::Promise<(), capnp::Error> {{
+        self.handle_{snake}(params, results)
+    }}
+"#,
+    );
+
+    // Step 4: Storage (if needed)
+    println!("--- Step 4: Storage trait (if needed) ---");
+    println!("File: crates/quicproquo-server/src/storage.rs");
+    println!();
+    println!("If your RPC method needs persistent storage, add a method to the Store trait:");
+    println!();
+    println!(
+        r#"    fn {snake}(&self, /* params */) -> Result</* return */, StorageError>;
+"#,
+    );
+    println!("Then implement it in:");
+    println!("  - crates/quicproquo-server/src/sql_store.rs (SQLite backend)");
+    println!("  - crates/quicproquo-server/src/storage.rs   (FileBackedStore)");
+    println!();
+
+    // Step 5: Hook (if needed)
+    println!("--- Step 5: Hook event (optional) ---");
+    println!("If you want plugins to observe this RPC, run:");
+    println!("  qpq-gen hook {snake}");
+    println!();
+
+    // Step 6: Verify
+    println!("--- Step 6: Verify ---");
+    println!("  cargo build -p quicproquo-server");
+    println!("  cargo test -p quicproquo-server");
+    println!();
+
+    // Summary
+    println!("=== Files to create/modify ===");
+    println!("  [modify] schemas/node.capnp");
+    println!("  [create] crates/quicproquo-server/src/node_service/{snake}.rs");
+    println!("  [modify] crates/quicproquo-server/src/node_service/mod.rs");
+    println!("  [modify] crates/quicproquo-server/src/storage.rs (if needed)");
+    println!("  [modify] crates/quicproquo-server/src/sql_store.rs (if needed)");
+
+    Ok(())
+}
+
+fn to_snake_case(s: &str) -> String {
+    let mut result = String::with_capacity(s.len() + 4);
+    for (i, ch) in s.chars().enumerate() {
+        if ch.is_uppercase() && i > 0 {
+            result.push('_');
+        }
+        result.push(ch.to_ascii_lowercase());
+    }
+    result
+}

crates/quicproquo-gen/src/main.rs

@@ -0,0 +1,55 @@
+use clap::{Parser, Subcommand};
+use std::path::PathBuf;
+
+mod generators;
+
+#[derive(Parser)]
+#[command(name = "qpq-gen", about = "Code generators for quicproquo")]
+struct Cli {
+    #[command(subcommand)]
+    command: Command,
+}
+
+#[derive(Subcommand)]
+enum Command {
+    /// Scaffold a new server plugin (dynamic .so/.dylib)
+    Plugin {
+        /// Plugin name (e.g. "rate-limiter", "audit-log")
+        name: String,
+        /// Output directory (default: current directory)
+        #[arg(short, long, default_value = ".")]
+        output: PathBuf,
+    },
+    /// Scaffold a new bot project using the Bot SDK
+    Bot {
+        /// Bot name (e.g. "echo-bot", "moderation-bot")
+        name: String,
+        /// Output directory (default: current directory)
+        #[arg(short, long, default_value = ".")]
+        output: PathBuf,
+    },
+    /// Show instructions for adding a new Cap'n Proto RPC method
+    Rpc {
+        /// RPC method name in camelCase (e.g. "listChannels")
+        name: String,
+    },
+    /// Show instructions for adding a new server hook event
+    Hook {
+        /// Hook event name in snake_case (e.g. "message_deleted")
+        name: String,
+    },
+}
+
+fn main() {
+    let cli = Cli::parse();
+    let result = match cli.command {
+        Command::Plugin { name, output } => generators::plugin::generate(&name, &output),
+        Command::Bot { name, output } => generators::bot::generate(&name, &output),
+        Command::Rpc { name } => generators::rpc::generate(&name),
+        Command::Hook { name } => generators::hook::generate(&name),
+    };
+    if let Err(e) = result {
+        eprintln!("error: {e}");
+        std::process::exit(1);
+    }
+}

crates/quicproquo-gui/Cargo.toml

@@ -0,0 +1,22 @@
+[package]
+name        = "quicproquo-gui"
+version     = "0.1.0"
+edition     = "2021"
+description = "Native GUI for quicproquo (Tauri 2)."
+license     = "MIT"
+
+[[bin]]
+name = "qpq-gui"
+path = "src/main.rs"
+
+[dependencies]
+quicproquo-core  = { path = "../quicproquo-core" }
+quicproquo-client = { path = "../quicproquo-client" }
+quicproquo-proto = { path = "../quicproquo-proto" }
+tauri     = { version = "2", features = [] }
+tokio     = { workspace = true }
+serde     = { workspace = true }
+serde_json = { workspace = true }
+
+[build-dependencies]
+tauri-build = "2"

crates/quicproquo-gui/README.md

@@ -0,0 +1,32 @@
+# quicproquo-gui
+
+Native GUI for quicproquo using [Tauri 2](https://v2.tauri.app/). The UI runs in a webview; all server-facing work (capnp-rpc, `node_service::Client`) runs on a **dedicated backend thread** with a tokio `LocalSet`, since that code is `!Send`.
+
+## Backend threading model
+
+- A single **backend thread** runs a tokio `LocalSet` and a request-response loop.
+- The UI thread sends commands over an `mpsc` channel: `Whoami { state_path, password }` or `Health { server, ca_cert, server_name }`.
+- For each request, the backend runs sync code (whoami) or `LocalSet::run_until(async { ... })` (health). It then sends `Result<String, String>` back on the provided reply channel.
+- Tauri commands (`whoami`, `health`) block on that reply so the frontend gets a simple async-style result.
+
+## How to run
+
+From the workspace root:
+
+```bash
+cargo run -p quicproquo-gui
+```
+
+**Linux:** Tauri uses GTK. Install development packages if the build fails, e.g.:
+
+- Debian/Ubuntu: `sudo apt install libgtk-3-dev libwebkit2gtk-4.1-dev`
+- Fedora: `sudo dnf install gtk3-devel webkit2gtk4.1-devel`
+
+## Frontend
+
+The frontend is static HTML in `ui/index.html` (no npm or build step). It provides:
+
+- **Whoami** – state path (and optional password); calls `whoami` and shows JSON (identity_key, fingerprint, etc.).
+- **Health** – server address; calls `health` and shows server status and RTT JSON.
+
+Default CA cert and server name for health are the same as the CLI (`data/server-cert.der`, `localhost`) unless overridden via optional params.

crates/quicproquo-gui/build.rs

@@ -0,0 +1,3 @@
+fn main() {
+    tauri_build::build()
+}

crates/quicproquo-gui/capabilities/default.json

@@ -0,0 +1,11 @@
+{
+  "$schema": "https://schema.tauri.app/config/2/capability",
+  "identifier": "default",
+  "description": "Capability for the main window (custom commands whoami, health are allowed by default)",
+  "windows": ["main"],
+  "permissions": [
+    "core:default",
+    "core:window:allow-close",
+    "core:window:allow-set-title"
+  ]
+}

crates/quicproquo-gui/gen/schemas/capabilities.json

@@ -0,0 +1 @@
+{"default":{"identifier":"default","description":"Capability for the main window (custom commands whoami, health are allowed by default)","local":true,"windows":["main"],"permissions":["core:default","core:window:allow-close","core:window:allow-set-title"]}}