chore: rename quicproquo → quicprochat in Rust workspace

Rename all crate directories, package names, binary names, proto
package/module paths, ALPN strings, env var prefixes, config filenames,
mDNS service names, and plugin ABI symbols from quicproquo/qpq to
quicprochat/qpc.

crates/quicprochat-server/Cargo.toml

@@ -0,0 +1,91 @@
+[package]
+name        = "quicprochat-server"
+version     = "0.1.0"
+edition.workspace     = true
+description = "Delivery Service and Authentication Service for quicprochat."
+license     = "AGPL-3.0-only"
+repository.workspace  = true
+
+[features]
+traffic-resistance = []
+webtransport = ["dep:h3", "dep:h3-quinn", "dep:h3-webtransport", "dep:http"]
+
+[[bin]]
+name = "qpc-server"
+path = "src/main.rs"
+
+[dependencies]
+quicprochat-core       = { path = "../quicprochat-core" }
+quicprochat-proto      = { path = "../quicprochat-proto" }
+quicprochat-plugin-api = { path = "../quicprochat-plugin-api" }
+quicprochat-kt         = { path = "../quicprochat-kt" }
+quicprochat-rpc        = { path = "../quicprochat-rpc" }
+
+# Dynamic plugin loading
+libloading = "0.8"
+
+# Serialisation + RPC
+capnp         = { workspace = true }
+capnp-rpc     = { workspace = true }
+prost         = { workspace = true }
+bytes         = { workspace = true }
+
+# Async
+tokio         = { workspace = true }
+tokio-util    = { workspace = true }
+futures       = { workspace = true }
+
+# Server utilities
+dashmap       = { workspace = true }
+hex           = { 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 }
+x509-parser   = { workspace = true }
+
+# Crypto — OPAQUE PAKE
+opaque-ke     = { workspace = true }
+rand          = { workspace = true }
+subtle        = { workspace = true }
+zeroize       = { workspace = true }
+
+# Database
+rusqlite      = { workspace = true }
+
+# Error handling
+anyhow        = { workspace = true }
+thiserror     = { workspace = true }
+bincode       = { workspace = true }
+serde         = { workspace = true }
+serde_json    = { workspace = true }
+
+# CLI
+clap          = { workspace = true }
+toml          = { version = "0.8" }
+
+# WebSocket JSON-RPC bridge for browser clients
+tokio-tungstenite = "0.26"
+base64            = "0.22"
+
+# Metrics (Prometheus)
+metrics                    = "0.22"
+metrics-exporter-prometheus = "0.15"
+
+# mDNS service announcement for local mesh / Freifunk node discovery.
+mdns-sd = "0.12"
+
+# WebTransport (HTTP/3) — feature-gated, for browser clients.
+h3                = { version = "0.0.8", optional = true }
+h3-quinn          = { version = "0.0.10", features = ["datagram"], optional = true }
+h3-webtransport   = { version = "0.1", optional = true }
+http              = { version = "1", optional = true }
+
+[lints]
+workspace = true
+
+[dev-dependencies]
+tempfile = "3"

crates/quicprochat-server/migrations/001_initial.sql

@@ -0,0 +1,47 @@
+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'))
+);

crates/quicprochat-server/migrations/002_add_seq.sql

@@ -0,0 +1,21 @@
+-- Migration 002: add per-inbox delivery sequence numbers.
+--
+-- Adds a `seq` column to the deliveries table and a separate counter table
+-- that tracks the next sequence number per (recipient_key, channel_id) inbox.
+-- The counter is atomically incremented on each enqueue via an UPSERT so
+-- sequence numbers are gapless even under concurrent inserts.
+--
+-- Requires SQLite >= 3.35 (RETURNING clause support; available on Ubuntu 22.04+).
+
+ALTER TABLE deliveries ADD COLUMN seq INTEGER NOT NULL DEFAULT 0;
+
+CREATE TABLE IF NOT EXISTS delivery_seq_counters (
+    recipient_key BLOB    NOT NULL,
+    channel_id    BLOB    NOT NULL,
+    next_seq      INTEGER NOT NULL DEFAULT 0,
+    PRIMARY KEY (recipient_key, channel_id)
+);
+
+-- Index lets ORDER BY seq queries use an index scan instead of a sort.
+CREATE INDEX IF NOT EXISTS idx_del_seq
+    ON deliveries (recipient_key, channel_id, seq);

crates/quicprochat-server/migrations/003_channels.sql

@@ -0,0 +1,13 @@
+-- Migration 003: 1:1 DM channels.
+-- channel_id is 16 bytes (UUID); member_a and member_b are identity keys in sorted order.
+-- Unique on (member_a, member_b) prevents duplicate channels between the same pair.
+
+CREATE TABLE IF NOT EXISTS channels (
+    channel_id BLOB PRIMARY KEY,
+    member_a   BLOB NOT NULL,
+    member_b   BLOB NOT NULL,
+    UNIQUE(member_a, member_b)
+);
+
+CREATE INDEX IF NOT EXISTS idx_channels_members
+    ON channels(member_a, member_b);

crates/quicprochat-server/migrations/004_federation.sql

@@ -0,0 +1,16 @@
+-- 004_federation.sql: Federation support tables.
+
+-- Map identity keys to their home server domain.
+-- Used for routing: if a recipient's home_server != local domain, relay via federation.
+CREATE TABLE IF NOT EXISTS identity_home_servers (
+    identity_key BLOB PRIMARY KEY,
+    home_server  TEXT NOT NULL,
+    updated_at   INTEGER NOT NULL
+);
+
+-- Known federation peers (other quicnprotochat servers).
+CREATE TABLE IF NOT EXISTS federation_peers (
+    domain    TEXT PRIMARY KEY,
+    last_seen INTEGER NOT NULL,
+    is_active INTEGER NOT NULL DEFAULT 1
+);

crates/quicprochat-server/migrations/005_signing_key.sql

@@ -0,0 +1,4 @@
+CREATE TABLE IF NOT EXISTS server_signing_key (
+    id        INTEGER PRIMARY KEY CHECK (id = 1),
+    seed_data BLOB NOT NULL
+);

crates/quicprochat-server/migrations/006_kt_log.sql

@@ -0,0 +1,4 @@
+CREATE TABLE IF NOT EXISTS kt_log (
+    id       INTEGER PRIMARY KEY CHECK (id = 1),
+    log_data BLOB NOT NULL
+);

crates/quicprochat-server/migrations/007_add_expiry.sql

@@ -0,0 +1,2 @@
+ALTER TABLE deliveries ADD COLUMN expires_at INTEGER;
+CREATE INDEX idx_deliveries_expires ON deliveries(expires_at) WHERE expires_at IS NOT NULL;

crates/quicprochat-server/migrations/008_devices.sql

@@ -0,0 +1,8 @@
+CREATE TABLE IF NOT EXISTS devices (
+    identity_key BLOB NOT NULL,
+    device_id BLOB NOT NULL,
+    device_name TEXT NOT NULL DEFAULT '',
+    registered_at INTEGER NOT NULL DEFAULT (strftime('%s','now')),
+    PRIMARY KEY (identity_key, device_id)
+);
+CREATE INDEX IF NOT EXISTS idx_devices_identity ON devices(identity_key);

crates/quicprochat-server/migrations/009_sessions.sql

@@ -0,0 +1,8 @@
+CREATE TABLE IF NOT EXISTS sessions (
+    token BLOB PRIMARY KEY,
+    username TEXT NOT NULL,
+    identity_key BLOB NOT NULL,
+    created_at INTEGER NOT NULL,
+    expires_at INTEGER NOT NULL
+);
+CREATE INDEX IF NOT EXISTS idx_sessions_expires ON sessions(expires_at);

crates/quicprochat-server/migrations/010_blobs.sql

@@ -0,0 +1,15 @@
+CREATE TABLE IF NOT EXISTS blobs (
+    blob_id BLOB PRIMARY KEY,
+    data BLOB NOT NULL,
+    total_size INTEGER NOT NULL,
+    mime_type TEXT NOT NULL DEFAULT '',
+    uploaded_at INTEGER NOT NULL
+);
+CREATE TABLE IF NOT EXISTS blob_staging (
+    blob_hash BLOB NOT NULL,
+    offset INTEGER NOT NULL,
+    chunk BLOB NOT NULL,
+    total_size INTEGER NOT NULL,
+    mime_type TEXT NOT NULL DEFAULT '',
+    PRIMARY KEY (blob_hash, offset)
+);

crates/quicprochat-server/migrations/011_recovery_bundles.sql

@@ -0,0 +1,7 @@
+-- Recovery bundle storage: encrypted bundles keyed by token_hash.
+CREATE TABLE IF NOT EXISTS recovery_bundles (
+    token_hash BLOB PRIMARY KEY,
+    bundle     BLOB NOT NULL,
+    ttl_secs   INTEGER NOT NULL DEFAULT 0,
+    created_at INTEGER NOT NULL DEFAULT (strftime('%s', 'now'))
+);

crates/quicprochat-server/migrations/012_moderation.sql

@@ -0,0 +1,20 @@
+-- Moderation tables: reports and bans.
+
+CREATE TABLE IF NOT EXISTS reports (
+    id                  INTEGER PRIMARY KEY AUTOINCREMENT,
+    encrypted_report    BLOB NOT NULL,
+    conversation_id     BLOB NOT NULL,
+    reporter_identity   BLOB NOT NULL,
+    created_at          INTEGER NOT NULL DEFAULT (strftime('%s', 'now'))
+);
+
+CREATE INDEX IF NOT EXISTS idx_reports_created ON reports(created_at);
+
+CREATE TABLE IF NOT EXISTS bans (
+    identity_key    BLOB PRIMARY KEY,
+    reason          TEXT NOT NULL DEFAULT '',
+    banned_at       INTEGER NOT NULL DEFAULT (strftime('%s', 'now')),
+    expires_at      INTEGER NOT NULL DEFAULT 0
+);
+
+CREATE INDEX IF NOT EXISTS idx_bans_expires ON bans(expires_at);

crates/quicprochat-server/src/audit.rs

@@ -0,0 +1,232 @@
+//! Structured audit log — persistent, machine-readable event journal.
+//!
+//! Events are serialized as JSON lines and appended to a file or SQL table.
+//! Each event carries a correlation `trace_id` for cross-referencing with
+//! RPC request traces.
+
+use std::fs::OpenOptions;
+use std::io::Write as IoWrite;
+use std::path::{Path, PathBuf};
+use std::sync::Mutex;
+
+use serde::Serialize;
+
+// ── Audit event types ─────────────────────────────────────────────────────
+
+/// Action categories for the audit log.
+#[derive(Debug, Clone, Serialize)]
+#[serde(rename_all = "snake_case")]
+pub enum AuditAction {
+    AuthRegister,
+    AuthLoginSuccess,
+    AuthLoginFailure,
+    Enqueue,
+    BatchEnqueue,
+    Fetch,
+    FetchWait,
+    KeyUpload,
+    HybridKeyUpload,
+    BanUser,
+    UnbanUser,
+    ReportMessage,
+    AccountDelete,
+    DeviceRegister,
+    DeviceRevoke,
+    BlobUpload,
+    RecoveryStore,
+    RecoveryFetch,
+    RecoveryDelete,
+}
+
+/// Outcome of an audited action.
+#[derive(Debug, Clone, Serialize)]
+#[serde(rename_all = "snake_case")]
+pub enum AuditOutcome {
+    Success,
+    Denied,
+    Error,
+    RateLimited,
+}
+
+/// A single audit event record.
+#[derive(Debug, Clone, Serialize)]
+pub struct AuditEvent {
+    /// ISO-8601 timestamp.
+    pub timestamp: String,
+    /// RPC correlation ID.
+    pub trace_id: String,
+    /// Hex-encoded actor identity key (truncated for privacy when redact=true).
+    pub actor: String,
+    /// The action performed.
+    pub action: AuditAction,
+    /// Target identifier (recipient key, username, etc.).
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub target: Option<String>,
+    /// Outcome of the action.
+    pub outcome: AuditOutcome,
+    /// Free-form details.
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub details: Option<String>,
+}
+
+// ── Audit logger trait ────────────────────────────────────────────────────
+
+/// Trait for audit log backends.
+pub trait AuditLogger: Send + Sync {
+    fn log(&self, event: AuditEvent);
+}
+
+// ── File-backed implementation ───────────────────────────────────────────
+
+/// Appends JSON-line events to a file.
+pub struct FileAuditLogger {
+    path: PathBuf,
+    file: Mutex<std::fs::File>,
+}
+
+impl FileAuditLogger {
+    /// Open (or create) the audit log file at `path`.
+    pub fn open(path: &Path) -> Result<Self, std::io::Error> {
+        let file = OpenOptions::new()
+            .create(true)
+            .append(true)
+            .open(path)?;
+        Ok(Self {
+            path: path.to_path_buf(),
+            file: Mutex::new(file),
+        })
+    }
+
+    /// Return the path to the audit log file.
+    pub fn path(&self) -> &Path {
+        &self.path
+    }
+}
+
+impl AuditLogger for FileAuditLogger {
+    fn log(&self, event: AuditEvent) {
+        let Ok(mut line) = serde_json::to_string(&event) else {
+            tracing::warn!("audit: failed to serialize event");
+            return;
+        };
+        line.push('\n');
+
+        let Ok(mut f) = self.file.lock() else {
+            tracing::warn!("audit: log file lock poisoned");
+            return;
+        };
+        if let Err(e) = f.write_all(line.as_bytes()) {
+            tracing::warn!(error = %e, "audit: failed to write event");
+        }
+    }
+}
+
+// ── No-op implementation ─────────────────────────────────────────────────
+
+/// Does nothing. Used when audit logging is disabled.
+pub struct NoopAuditLogger;
+
+impl AuditLogger for NoopAuditLogger {
+    fn log(&self, _event: AuditEvent) {}
+}
+
+// ── Helpers ──────────────────────────────────────────────────────────────
+
+/// Format identity key bytes as hex, optionally truncated for privacy.
+pub fn format_actor(identity_key: &[u8], redact: bool) -> String {
+    let full = hex::encode(identity_key);
+    if redact && full.len() > 12 {
+        format!("{}...", &full[..12])
+    } else {
+        full
+    }
+}
+
+/// Current ISO-8601 UTC timestamp.
+pub fn now_iso8601() -> String {
+    // Use SystemTime to avoid pulling in chrono.
+    let d = std::time::SystemTime::now()
+        .duration_since(std::time::UNIX_EPOCH)
+        .unwrap_or_default();
+    let secs = d.as_secs();
+    // Simple UTC formatting: enough for audit logs.
+    format!("{secs}")
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::io::Read;
+
+    #[test]
+    fn file_audit_logger_writes_json_lines() {
+        let dir = tempfile::tempdir().expect("tempdir");
+        let path = dir.path().join("audit.jsonl");
+        let logger = FileAuditLogger::open(&path).expect("open");
+
+        logger.log(AuditEvent {
+            timestamp: "1709500000".to_string(),
+            trace_id: "test-trace-001".to_string(),
+            actor: "abcdef123456".to_string(),
+            action: AuditAction::Enqueue,
+            target: Some("recipient-hex".to_string()),
+            outcome: AuditOutcome::Success,
+            details: None,
+        });
+
+        logger.log(AuditEvent {
+            timestamp: "1709500001".to_string(),
+            trace_id: "test-trace-002".to_string(),
+            actor: "abcdef123456".to_string(),
+            action: AuditAction::AuthLoginFailure,
+            target: None,
+            outcome: AuditOutcome::Denied,
+            details: Some("bad password".to_string()),
+        });
+
+        drop(logger);
+
+        let mut content = String::new();
+        std::fs::File::open(&path)
+            .expect("open for read")
+            .read_to_string(&mut content)
+            .expect("read");
+
+        let lines: Vec<&str> = content.trim().split('\n').collect();
+        assert_eq!(lines.len(), 2);
+
+        // Verify JSON parses.
+        let v: serde_json::Value = serde_json::from_str(lines[0]).expect("parse line 0");
+        assert_eq!(v["action"], "enqueue");
+        assert_eq!(v["outcome"], "success");
+        assert_eq!(v["trace_id"], "test-trace-001");
+
+        let v: serde_json::Value = serde_json::from_str(lines[1]).expect("parse line 1");
+        assert_eq!(v["action"], "auth_login_failure");
+        assert_eq!(v["details"], "bad password");
+    }
+
+    #[test]
+    fn format_actor_truncates_when_redacted() {
+        let key = vec![0xAA; 32];
+        let full = format_actor(&key, false);
+        assert_eq!(full.len(), 64);
+        let redacted = format_actor(&key, true);
+        assert!(redacted.ends_with("..."));
+        assert_eq!(redacted.len(), 15); // 12 hex chars + "..."
+    }
+
+    #[test]
+    fn noop_logger_does_not_panic() {
+        let logger = NoopAuditLogger;
+        logger.log(AuditEvent {
+            timestamp: "0".to_string(),
+            trace_id: "noop".to_string(),
+            actor: "none".to_string(),
+            action: AuditAction::Fetch,
+            target: None,
+            outcome: AuditOutcome::Success,
+            details: None,
+        });
+    }
+}

crates/quicprochat-server/src/auth.rs

@@ -0,0 +1,304 @@
+use std::net::IpAddr;
+use std::sync::Arc;
+
+use dashmap::DashMap;
+use quicprochat_proto::node_capnp::auth;
+use sha2::Digest;
+use subtle::ConstantTimeEq;
+use tokio::sync::Notify;
+use zeroize::Zeroizing;
+
+use crate::error_codes::*;
+
+pub const SESSION_TTL_SECS: u64 = 24 * 60 * 60; // 24 hours
+pub const PENDING_LOGIN_TTL_SECS: u64 = 300; // 5 minutes
+pub const RATE_LIMIT_WINDOW_SECS: u64 = 60;
+pub const RATE_LIMIT_MAX_ENQUEUES: u32 = 100;
+
+#[derive(Clone)]
+pub struct AuthConfig {
+    /// Server bearer token — zeroized on drop to prevent memory disclosure.
+    pub required_token: Option<Zeroizing<Vec<u8>>>,
+    /// When true, a valid bearer token (no session) is accepted and the request's identity/key is used (dev/e2e only).
+    /// CLI flag: --allow-insecure-auth / QPQ_ALLOW_INSECURE_AUTH.
+    pub allow_insecure_identity_from_request: bool,
+}
+
+impl std::fmt::Debug for AuthConfig {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("AuthConfig")
+            .field("required_token", &self.required_token.as_ref().map(|_| "[REDACTED]"))
+            .field("allow_insecure_identity_from_request", &self.allow_insecure_identity_from_request)
+            .finish()
+    }
+}
+
+impl AuthConfig {
+    pub fn new(required_token: Option<String>, allow_insecure_identity_from_request: bool) -> Self {
+        let required_token = required_token
+            .filter(|s| !s.is_empty())
+            .map(|s| Zeroizing::new(s.into_bytes()));
+        Self {
+            required_token,
+            allow_insecure_identity_from_request,
+        }
+    }
+}
+
+#[derive(Clone)]
+pub struct SessionInfo {
+    #[allow(dead_code)]
+    pub username: String,
+    pub identity_key: Vec<u8>,
+    #[allow(dead_code)]
+    pub created_at: u64,
+    pub expires_at: u64,
+}
+
+pub struct PendingLogin {
+    pub state_bytes: Vec<u8>,
+    pub created_at: u64,
+}
+
+pub struct RateEntry {
+    pub count: u32,
+    pub window_start: u64,
+}
+
+#[derive(Clone)]
+pub struct AuthContext {
+    pub token: Vec<u8>,
+    pub identity_key: Option<Vec<u8>>,
+}
+
+pub fn current_timestamp() -> u64 {
+    match std::time::SystemTime::now().duration_since(std::time::UNIX_EPOCH) {
+        Ok(d) => d.as_secs(),
+        Err(_) => {
+            tracing::warn!("system time is before UNIX_EPOCH; using 0 for session/rate-limit timestamps");
+            0
+        }
+    }
+}
+
+pub fn check_rate_limit(
+    rate_limits: &DashMap<Vec<u8>, RateEntry>,
+    token: &[u8],
+) -> Result<(), capnp::Error> {
+    let now = current_timestamp();
+    let mut entry = rate_limits.entry(token.to_vec()).or_insert(RateEntry {
+        count: 0,
+        window_start: now,
+    });
+
+    if now - entry.window_start >= RATE_LIMIT_WINDOW_SECS {
+        entry.count = 1;
+        entry.window_start = now;
+    } else {
+        entry.count += 1;
+        if entry.count > RATE_LIMIT_MAX_ENQUEUES {
+            return Err(crate::error_codes::coded_error(
+                E014_RATE_LIMITED,
+                format!(
+                    "rate limit exceeded: {} enqueues in {}s window",
+                    RATE_LIMIT_MAX_ENQUEUES, RATE_LIMIT_WINDOW_SECS
+                ),
+            ));
+        }
+    }
+    Ok(())
+}
+
+pub fn validate_auth(
+    cfg: &AuthConfig,
+    sessions: &DashMap<Vec<u8>, SessionInfo>,
+    auth: Result<auth::Reader<'_>, capnp::Error>,
+) -> Result<(), capnp::Error> {
+    validate_auth_context(cfg, sessions, auth).map(|_| ())
+}
+
+pub fn validate_auth_context(
+    cfg: &AuthConfig,
+    sessions: &DashMap<Vec<u8>, SessionInfo>,
+    auth: Result<auth::Reader<'_>, capnp::Error>,
+) -> Result<AuthContext, capnp::Error> {
+    let auth = auth?;
+    let version = auth.get_version();
+
+    if version != 1 {
+        return Err(crate::error_codes::coded_error(
+            E001_BAD_AUTH_VERSION,
+            format!("unsupported auth version {} (expected 1)", version),
+        ));
+    }
+
+    let token = auth
+        .get_access_token()
+        .map_err(|e| crate::error_codes::coded_error(E020_BAD_PARAMS, format!("auth.accessToken: {e}")))?
+        .to_vec();
+
+    if token.is_empty() {
+        return Err(crate::error_codes::coded_error(
+            E002_EMPTY_TOKEN,
+            "auth.version=1 requires non-empty accessToken",
+        ));
+    }
+
+    if let Some(expected) = &cfg.required_token {
+        if expected.len() == token.len() && bool::from(expected.as_slice().ct_eq(&token)) {
+            return Ok(AuthContext {
+                token,
+                identity_key: None,
+            });
+        }
+    }
+
+    if let Some(session) = sessions.get(&token) {
+        let now = current_timestamp();
+        if session.expires_at > now {
+            let identity = if session.identity_key.is_empty() {
+                None
+            } else {
+                Some(session.identity_key.clone())
+            };
+
+            return Ok(AuthContext {
+                token,
+                identity_key: identity,
+            });
+        }
+        drop(session);
+        sessions.remove(&token);
+        return Err(crate::error_codes::coded_error(
+            E017_SESSION_EXPIRED,
+            "session token has expired",
+        ));
+    }
+
+    Err(crate::error_codes::coded_error(E003_INVALID_TOKEN, "invalid accessToken"))
+}
+
+/// Validate a raw bearer token (no Cap'n Proto dependency).
+/// Used by the WebSocket JSON-RPC bridge.
+pub fn validate_token_raw(
+    cfg: &AuthConfig,
+    sessions: &DashMap<Vec<u8>, SessionInfo>,
+    token: &[u8],
+) -> Result<AuthContext, String> {
+    if token.is_empty() {
+        return Err("empty access token".to_string());
+    }
+
+    // Check static bearer token.
+    if let Some(expected) = &cfg.required_token {
+        if expected.len() == token.len() && bool::from(expected.as_slice().ct_eq(token)) {
+            return Ok(AuthContext {
+                token: token.to_vec(),
+                identity_key: None,
+            });
+        }
+    }
+
+    // Check session tokens.
+    if let Some(session) = sessions.get(token) {
+        let now = current_timestamp();
+        if session.expires_at > now {
+            let identity = if session.identity_key.is_empty() {
+                None
+            } else {
+                Some(session.identity_key.clone())
+            };
+            return Ok(AuthContext {
+                token: token.to_vec(),
+                identity_key: identity,
+            });
+        }
+        drop(session);
+        sessions.remove(token);
+        return Err("session token has expired".to_string());
+    }
+
+    Err("invalid access token".to_string())
+}
+
+pub fn require_identity(auth_ctx: &AuthContext) -> Result<&[u8], capnp::Error> {
+    match auth_ctx.identity_key.as_deref() {
+        Some(ik) => Ok(ik),
+        None => Err(crate::error_codes::coded_error(
+            E003_INVALID_TOKEN,
+            "access token is not identity-bound; login required",
+        )),
+    }
+}
+
+pub fn require_identity_match(auth_ctx: &AuthContext, expected: &[u8]) -> Result<(), capnp::Error> {
+    let ik = require_identity(auth_ctx)?;
+    if ik.len() != expected.len() || !bool::from(ik.ct_eq(expected)) {
+        return Err(crate::error_codes::coded_error(
+            E016_IDENTITY_MISMATCH,
+            "access token is bound to a different identity",
+        ));
+    }
+    Ok(())
+}
+
+/// When the token is a valid session, require it to match `request_identity`.
+/// When the token is a bearer token (no identity) and `allow_insecure_identity_from_request` is true, accept the request identity (dev/e2e).
+pub fn require_identity_or_request(
+    auth_ctx: &AuthContext,
+    request_identity: &[u8],
+    allow_insecure: bool,
+) -> Result<(), capnp::Error> {
+    match auth_ctx.identity_key.as_deref() {
+        Some(_) => require_identity_match(auth_ctx, request_identity),
+        None if allow_insecure => Ok(()),
+        None => Err(crate::error_codes::coded_error(
+            E003_INVALID_TOKEN,
+            "access token is not identity-bound; login required",
+        )),
+    }
+}
+
+pub fn fmt_hex(bytes: &[u8]) -> String {
+    let hex: String = bytes.iter().map(|b| format!("{b:02x}")).collect();
+    format!("{hex}…")
+}
+
+pub fn waiter(waiters: &DashMap<Vec<u8>, Arc<Notify>>, recipient_key: &[u8]) -> Arc<Notify> {
+    waiters
+        .entry(recipient_key.to_vec())
+        .or_insert_with(|| Arc::new(Notify::new()))
+        .clone()
+}
+
+pub const CONN_RATE_LIMIT_WINDOW_SECS: u64 = 60;
+pub const CONN_RATE_LIMIT_MAX: u32 = 50;
+
+/// Per-IP connection rate limiter. Returns `true` if the connection is allowed.
+pub fn check_conn_rate_limit(
+    conn_rate_limits: &DashMap<IpAddr, RateEntry>,
+    ip: IpAddr,
+) -> bool {
+    let now = current_timestamp();
+    let mut entry = conn_rate_limits.entry(ip).or_insert(RateEntry {
+        count: 0,
+        window_start: now,
+    });
+
+    if now - entry.window_start >= CONN_RATE_LIMIT_WINDOW_SECS {
+        entry.count = 1;
+        entry.window_start = now;
+        true
+    } else {
+        entry.count += 1;
+        entry.count <= CONN_RATE_LIMIT_MAX
+    }
+}
+
+pub fn fingerprint(data: &[u8]) -> Vec<u8> {
+    sha2::Sha256::digest(data).to_vec()
+}
+
+pub fn coded_error(code: &str, msg: impl std::fmt::Display) -> capnp::Error {
+    crate::error_codes::coded_error(code, msg)
+}

crates/quicprochat-server/src/config.rs

@@ -0,0 +1,350 @@
+use std::path::{Path, PathBuf};
+
+use anyhow::Context;
+use serde::Deserialize;
+
+pub const DEFAULT_LISTEN: &str = "0.0.0.0:7000";
+pub const DEFAULT_DATA_DIR: &str = "data";
+pub const DEFAULT_TLS_CERT: &str = "data/server-cert.der";
+pub const DEFAULT_TLS_KEY: &str = "data/server-key.der";
+pub const DEFAULT_STORE_BACKEND: &str = "file";
+pub const DEFAULT_DB_PATH: &str = "data/qpc.db";
+
+#[derive(Debug, Default, Deserialize)]
+pub struct FileConfig {
+    pub listen: Option<String>,
+    pub data_dir: Option<String>,
+    pub tls_cert: Option<PathBuf>,
+    pub tls_key: Option<PathBuf>,
+    pub auth_token: Option<String>,
+    pub allow_insecure_auth: Option<bool>,
+    /// When true, enqueue does not require an identity-bound session: only a valid token is required.
+    /// The server does not associate the request with a specific sender (Sealed Sender).
+    #[serde(default)]
+    pub sealed_sender: Option<bool>,
+    pub store_backend: Option<String>,
+    pub db_path: Option<PathBuf>,
+    pub db_key: Option<String>,
+    /// Metrics HTTP listen address (e.g. "0.0.0.0:9090"). If set, /metrics is served there.
+    pub metrics_listen: Option<String>,
+    /// When true and metrics_listen is set, start the metrics server.
+    #[serde(default)]
+    pub metrics_enabled: Option<bool>,
+    pub federation: Option<FederationFileConfig>,
+    /// Directory containing plugin `.so` / `.dylib` files to load at startup.
+    pub plugin_dir: Option<PathBuf>,
+    /// When true, audit logs hash identity key prefixes and omit payload sizes.
+    #[serde(default)]
+    pub redact_logs: Option<bool>,
+    /// WebSocket JSON-RPC bridge listen address (e.g. "0.0.0.0:9000").
+    pub ws_listen: Option<String>,
+    /// WebTransport (HTTP/3) listen address for browser clients (e.g. "0.0.0.0:7443").
+    pub webtransport_listen: Option<String>,
+    /// Graceful shutdown drain timeout in seconds.
+    pub drain_timeout_secs: Option<u64>,
+    /// Default per-RPC timeout in seconds.
+    pub rpc_timeout_secs: Option<u64>,
+    /// Storage/database operation timeout in seconds.
+    pub storage_timeout_secs: Option<u64>,
+}
+
+#[derive(Debug)]
+pub struct EffectiveConfig {
+    pub listen: String,
+    pub data_dir: String,
+    pub tls_cert: PathBuf,
+    pub tls_key: PathBuf,
+    pub auth_token: Option<String>,
+    pub allow_insecure_auth: bool,
+    /// When true, enqueue does not require identity; valid token only (Sealed Sender).
+    pub sealed_sender: bool,
+    pub store_backend: String,
+    pub db_path: PathBuf,
+    pub db_key: String,
+    /// If Some(addr), metrics server listens here (e.g. "0.0.0.0:9090").
+    pub metrics_listen: Option<String>,
+    /// Start metrics server only when true and metrics_listen is set.
+    pub metrics_enabled: bool,
+    pub federation: Option<EffectiveFederationConfig>,
+    /// Directory to scan for plugin `.so` / `.dylib` files at startup. None = no plugins.
+    pub plugin_dir: Option<PathBuf>,
+    /// When true, audit logs hash identity key prefixes and omit payload sizes.
+    pub redact_logs: bool,
+    /// WebSocket JSON-RPC bridge listen address. If set, the bridge is started.
+    pub ws_listen: Option<String>,
+    /// WebTransport (HTTP/3) listen address. If set, the WebTransport endpoint is started.
+    pub webtransport_listen: Option<String>,
+    /// Graceful shutdown drain timeout in seconds.
+    pub drain_timeout_secs: u64,
+    /// Default per-RPC timeout in seconds.
+    pub rpc_timeout_secs: u64,
+    /// Storage/database operation timeout in seconds.
+    pub storage_timeout_secs: u64,
+}
+
+pub const DEFAULT_DRAIN_TIMEOUT_SECS: u64 = 30;
+pub const DEFAULT_RPC_TIMEOUT_SECS: u64 = 30;
+pub const DEFAULT_STORAGE_TIMEOUT_SECS: u64 = 10;
+
+#[derive(Debug, Default, Deserialize)]
+pub struct FederationFileConfig {
+    pub enabled: Option<bool>,
+    pub domain: Option<String>,
+    pub listen: Option<String>,
+    pub federation_cert: Option<PathBuf>,
+    pub federation_key: Option<PathBuf>,
+    pub federation_ca: Option<PathBuf>,
+    #[serde(default)]
+    pub peers: Vec<FederationPeerConfig>,
+}
+
+#[derive(Debug, Clone, Deserialize)]
+pub struct FederationPeerConfig {
+    pub domain: String,
+    pub address: String,
+}
+
+#[derive(Debug)]
+#[allow(dead_code)] // federation not yet wired up
+pub struct EffectiveFederationConfig {
+    pub enabled: bool,
+    pub domain: String,
+    pub listen: String,
+    pub federation_cert: PathBuf,
+    pub federation_key: PathBuf,
+    pub federation_ca: PathBuf,
+    pub peers: Vec<FederationPeerConfig>,
+}
+
+pub fn load_config(path: Option<&Path>) -> anyhow::Result<FileConfig> {
+    let path = match path {
+        Some(p) => PathBuf::from(p),
+        None => PathBuf::from("qpc-server.toml"),
+    };
+
+    if !path.exists() {
+        return Ok(FileConfig::default());
+    }
+
+    let contents =
+        std::fs::read_to_string(&path).with_context(|| format!("read config file {path:?}"))?;
+    let cfg: FileConfig =
+        toml::from_str(&contents).with_context(|| format!("parse config file {path:?}"))?;
+    Ok(cfg)
+}
+
+pub fn merge_config(args: &crate::Args, file: &FileConfig) -> EffectiveConfig {
+    let listen = if args.listen == DEFAULT_LISTEN {
+        file.listen
+            .clone()
+            .unwrap_or_else(|| DEFAULT_LISTEN.to_string())
+    } else {
+        args.listen.clone()
+    };
+
+    let data_dir = if args.data_dir == DEFAULT_DATA_DIR {
+        file.data_dir
+            .clone()
+            .unwrap_or_else(|| DEFAULT_DATA_DIR.to_string())
+    } else {
+        args.data_dir.clone()
+    };
+
+    let tls_cert = if args.tls_cert == Path::new(DEFAULT_TLS_CERT) {
+        file.tls_cert
+            .clone()
+            .unwrap_or_else(|| PathBuf::from(DEFAULT_TLS_CERT))
+    } else {
+        args.tls_cert.clone()
+    };
+
+    let tls_key = if args.tls_key == Path::new(DEFAULT_TLS_KEY) {
+        file.tls_key
+            .clone()
+            .unwrap_or_else(|| PathBuf::from(DEFAULT_TLS_KEY))
+    } else {
+        args.tls_key.clone()
+    };
+
+    let auth_token = if args.auth_token.is_some() {
+        args.auth_token.clone()
+    } else {
+        file.auth_token.clone()
+    };
+
+    let allow_insecure_auth = if args.allow_insecure_auth {
+        true
+    } else {
+        file.allow_insecure_auth.unwrap_or(false)
+    };
+
+    let sealed_sender = args.sealed_sender || file.sealed_sender.unwrap_or(false);
+
+    let store_backend = if args.store_backend == DEFAULT_STORE_BACKEND {
+        file.store_backend
+            .clone()
+            .unwrap_or_else(|| DEFAULT_STORE_BACKEND.to_string())
+    } else {
+        args.store_backend.clone()
+    };
+
+    let db_path = if args.db_path == Path::new(DEFAULT_DB_PATH) {
+        file.db_path
+            .clone()
+            .unwrap_or_else(|| PathBuf::from(DEFAULT_DB_PATH))
+    } else {
+        args.db_path.clone()
+    };
+
+    let db_key = if args.db_key.is_empty() {
+        file.db_key.clone().unwrap_or_else(|| args.db_key.clone())
+    } else {
+        args.db_key.clone()
+    };
+
+    let metrics_listen = args
+        .metrics_listen
+        .clone()
+        .or_else(|| file.metrics_listen.clone());
+    let metrics_enabled = args
+        .metrics_enabled
+        .or(file.metrics_enabled)
+        .unwrap_or(metrics_listen.is_some());
+
+    let federation = {
+        let file_fed = file.federation.as_ref();
+        let enabled = args.federation_enabled
+            || file_fed.and_then(|f| f.enabled).unwrap_or(false);
+
+        if enabled {
+            let domain = args.federation_domain.clone()
+                .or_else(|| file_fed.and_then(|f| f.domain.clone()))
+                .unwrap_or_default();
+            let listen_fed = args.federation_listen.clone()
+                .or_else(|| file_fed.and_then(|f| f.listen.clone()))
+                .unwrap_or_else(|| "0.0.0.0:7001".to_string());
+            let federation_cert = file_fed.and_then(|f| f.federation_cert.clone())
+                .unwrap_or_else(|| PathBuf::from("data/federation-cert.der"));
+            let federation_key = file_fed.and_then(|f| f.federation_key.clone())
+                .unwrap_or_else(|| PathBuf::from("data/federation-key.der"));
+            let federation_ca = file_fed.and_then(|f| f.federation_ca.clone())
+                .unwrap_or_else(|| PathBuf::from("data/federation-ca.der"));
+            let peers = file_fed
+                .map(|f| f.peers.clone())
+                .unwrap_or_default();
+
+            Some(EffectiveFederationConfig {
+                enabled,
+                domain,
+                listen: listen_fed,
+                federation_cert,
+                federation_key,
+                federation_ca,
+                peers,
+            })
+        } else {
+            None
+        }
+    };
+
+    let plugin_dir = args.plugin_dir.clone().or_else(|| file.plugin_dir.clone());
+    let redact_logs = args.redact_logs || file.redact_logs.unwrap_or(false);
+    let ws_listen = args
+        .ws_listen
+        .clone()
+        .or_else(|| file.ws_listen.clone());
+
+    let webtransport_listen = args
+        .webtransport_listen
+        .clone()
+        .or_else(|| file.webtransport_listen.clone());
+
+    let drain_timeout_secs = if args.drain_timeout == DEFAULT_DRAIN_TIMEOUT_SECS {
+        file.drain_timeout_secs.unwrap_or(DEFAULT_DRAIN_TIMEOUT_SECS)
+    } else {
+        args.drain_timeout
+    };
+    let rpc_timeout_secs = if args.rpc_timeout == DEFAULT_RPC_TIMEOUT_SECS {
+        file.rpc_timeout_secs.unwrap_or(DEFAULT_RPC_TIMEOUT_SECS)
+    } else {
+        args.rpc_timeout
+    };
+    let storage_timeout_secs = if args.storage_timeout == DEFAULT_STORAGE_TIMEOUT_SECS {
+        file.storage_timeout_secs.unwrap_or(DEFAULT_STORAGE_TIMEOUT_SECS)
+    } else {
+        args.storage_timeout
+    };
+
+    EffectiveConfig {
+        listen,
+        data_dir,
+        tls_cert,
+        tls_key,
+        auth_token,
+        allow_insecure_auth,
+        sealed_sender,
+        store_backend,
+        db_path,
+        db_key,
+        metrics_listen,
+        metrics_enabled,
+        federation,
+        plugin_dir,
+        redact_logs,
+        ws_listen,
+        webtransport_listen,
+        drain_timeout_secs,
+        rpc_timeout_secs,
+        storage_timeout_secs,
+    }
+}
+
+pub fn validate_production_config(effective: &EffectiveConfig) -> anyhow::Result<()> {
+    if effective.allow_insecure_auth {
+        anyhow::bail!("production forbids --allow-insecure-auth");
+    }
+    let token = effective
+        .auth_token
+        .as_deref()
+        .filter(|s| !s.is_empty())
+        .ok_or_else(|| {
+            anyhow::anyhow!("production requires QPQ_AUTH_TOKEN (non-empty)")
+        })?;
+    if token == "devtoken" {
+        anyhow::bail!(
+            "production forbids auth_token 'devtoken'; set a strong QPQ_AUTH_TOKEN"
+        );
+    }
+    if token.len() < 16 {
+        anyhow::bail!(
+            "production requires QPQ_AUTH_TOKEN of at least 16 characters (got {})",
+            token.len()
+        );
+    }
+    if effective.store_backend == "sql" && effective.db_key.is_empty() {
+        anyhow::bail!("production with store_backend=sql requires non-empty QPQ_DB_KEY");
+    }
+    if effective.store_backend == "sql" {
+        let db_dir = effective
+            .db_path
+            .parent()
+            .unwrap_or_else(|| Path::new("."));
+        // Verify the directory exists and is writable by creating+removing a probe file.
+        let probe = db_dir.join(".qpc-write-probe");
+        std::fs::write(&probe, b"probe")
+            .with_context(|| format!("DB path parent {:?} is not writable", db_dir))?;
+        let _ = std::fs::remove_file(&probe);
+    }
+    if effective.store_backend != "sql" {
+        tracing::warn!(
+            "production is using file-backed storage; \
+             consider store_backend=sql with QPQ_DB_KEY for encryption at rest"
+        );
+    }
+    if !effective.tls_cert.exists() || !effective.tls_key.exists() {
+        anyhow::bail!(
+            "production requires existing TLS cert and key (no auto-generation); provide QPQ_TLS_CERT and QPQ_TLS_KEY"
+        );
+    }
+    Ok(())
+}

crates/quicprochat-server/src/domain/account.rs

@@ -0,0 +1,28 @@
+//! Account domain logic — account deletion with KT tombstone.
+
+use std::sync::{Arc, Mutex};
+
+use quicprochat_kt::MerkleLog;
+
+use crate::storage::Store;
+
+use super::types::DomainError;
+
+/// Domain service for account lifecycle operations.
+pub struct AccountService {
+    pub store: Arc<dyn Store>,
+    pub kt_log: Arc<Mutex<MerkleLog>>,
+}
+
+impl AccountService {
+    pub fn delete_account(&self, caller_identity_key: &[u8]) -> Result<(), DomainError> {
+        self.store.delete_account(caller_identity_key)?;
+
+        // Append a KT tombstone entry so the deletion is auditable.
+        if let Ok(mut log) = self.kt_log.lock() {
+            log.append("__tombstone__", caller_identity_key);
+        }
+
+        Ok(())
+    }
+}

crates/quicprochat-server/src/domain/auth.rs

@@ -0,0 +1,72 @@
+//! Authentication domain logic — OPAQUE registration and login.
+//!
+//! This module contains the pure business logic for OPAQUE auth,
+//! extracted from `node_service/auth_ops.rs`. It operates on domain
+//! types and the `Store` trait, with no dependency on Cap'n Proto or Protobuf.
+
+use std::sync::Arc;
+
+use dashmap::DashMap;
+use opaque_ke::ServerSetup;
+use quicprochat_core::opaque_auth::OpaqueSuite;
+
+use crate::auth::{AuthConfig, PendingLogin, SessionInfo};
+use crate::storage::{Store, StorageError};
+
+use super::types::*;
+
+/// Shared state needed by auth operations.
+pub struct AuthService {
+    pub store: Arc<dyn Store>,
+    pub opaque_setup: Arc<ServerSetup<OpaqueSuite>>,
+    pub pending_logins: Arc<DashMap<String, PendingLogin>>,
+    pub sessions: Arc<DashMap<Vec<u8>, SessionInfo>>,
+    pub auth_cfg: Arc<AuthConfig>,
+}
+
+impl AuthService {
+    /// Validate a session token and return the caller's auth context.
+    pub fn validate_session(&self, token: &[u8]) -> Option<CallerAuth> {
+        let info = self.sessions.get(token)?;
+        if info.expires_at <= crate::auth::current_timestamp() {
+            self.sessions.remove(token);
+            return None;
+        }
+        Some(CallerAuth {
+            identity_key: info.identity_key.clone(),
+            token: token.to_vec(),
+            device_id: None,
+        })
+    }
+
+    /// Start OPAQUE registration.
+    pub fn register_start(&self, req: RegisterStartReq) -> Result<RegisterStartResp, StorageError> {
+        use opaque_ke::ServerRegistration;
+
+        let result = ServerRegistration::<OpaqueSuite>::start(
+            &self.opaque_setup,
+            opaque_ke::RegistrationRequest::deserialize(&req.request_bytes)
+                .map_err(|e| StorageError::Io(format!("bad registration request: {e}")))?,
+            req.username.as_bytes(),
+        )
+        .map_err(|e| StorageError::Io(format!("OPAQUE register start: {e}")))?;
+
+        let response_bytes = result.message.serialize().to_vec();
+        Ok(RegisterStartResp { response_bytes })
+    }
+
+    /// Finish OPAQUE registration — persist user record and identity key.
+    pub fn register_finish(&self, req: RegisterFinishReq) -> Result<RegisterFinishResp, StorageError> {
+        let upload = opaque_ke::RegistrationUpload::<OpaqueSuite>::deserialize(&req.upload_bytes)
+            .map_err(|e| StorageError::Io(format!("bad registration upload: {e}")))?;
+
+        let record = opaque_ke::ServerRegistration::<OpaqueSuite>::finish(upload);
+        let serialized = record.serialize().to_vec();
+
+        self.store.store_user_record(&req.username, serialized)?;
+        self.store
+            .store_user_identity_key(&req.username, req.identity_key)?;
+
+        Ok(RegisterFinishResp { success: true })
+    }
+}

crates/quicprochat-server/src/domain/blobs.rs

@@ -0,0 +1,193 @@
+//! Blob domain logic — chunked file upload/download with SHA-256 verification.
+
+use std::io::{Read, Seek, SeekFrom, Write};
+use std::path::PathBuf;
+
+use sha2::{Digest, Sha256};
+
+use super::types::*;
+
+/// Maximum blob size: 100 MB.
+const MAX_BLOB_SIZE: u64 = 100 * 1024 * 1024;
+
+/// Maximum download chunk size: 256 KB.
+const MAX_DOWNLOAD_CHUNK: u32 = 256 * 1024;
+
+/// Metadata stored alongside each completed blob.
+#[derive(serde::Serialize, serde::Deserialize)]
+struct BlobMeta {
+    mime_type: String,
+    total_size: u64,
+    uploaded_at: u64,
+}
+
+/// Domain service for blob (file attachment) storage.
+pub struct BlobService {
+    pub data_dir: PathBuf,
+}
+
+impl BlobService {
+    fn blobs_dir(&self) -> PathBuf {
+        self.data_dir.join("blobs")
+    }
+
+    pub fn upload_blob(
+        &self,
+        req: UploadBlobReq,
+        _auth: &CallerAuth,
+    ) -> Result<UploadBlobResp, DomainError> {
+        if req.blob_hash.len() != 32 {
+            return Err(DomainError::BlobHashLength(req.blob_hash.len()));
+        }
+        if req.total_size > MAX_BLOB_SIZE {
+            return Err(DomainError::BlobTooLarge(req.total_size));
+        }
+        if req.total_size == 0 {
+            return Err(DomainError::BadParams("total_size must be > 0".into()));
+        }
+        if req
+            .offset
+            .checked_add(req.chunk.len() as u64)
+            .is_none_or(|end| end > req.total_size)
+        {
+            return Err(DomainError::BadParams(format!(
+                "chunk out of bounds: offset={} + chunk_len={} > total_size={}",
+                req.offset,
+                req.chunk.len(),
+                req.total_size
+            )));
+        }
+
+        let blob_hex = hex::encode(&req.blob_hash);
+        let dir = self.blobs_dir();
+
+        std::fs::create_dir_all(&dir)
+            .map_err(|e| DomainError::Io(format!("create blobs directory: {e}")))?;
+
+        let part_path = dir.join(format!("{blob_hex}.part"));
+        let final_path = dir.join(&blob_hex);
+        let meta_path = dir.join(format!("{blob_hex}.meta"));
+
+        // Already fully uploaded.
+        if final_path.exists() {
+            return Ok(UploadBlobResp {
+                blob_id: req.blob_hash,
+            });
+        }
+
+        // Write chunk at offset.
+        let mut file = std::fs::OpenOptions::new()
+            .create(true)
+            .write(true)
+            .truncate(false)
+            .open(&part_path)
+            .map_err(|e| DomainError::Io(format!("open .part file: {e}")))?;
+        file.seek(SeekFrom::Start(req.offset))
+            .map_err(|e| DomainError::Io(format!("seek: {e}")))?;
+        file.write_all(&req.chunk)
+            .map_err(|e| DomainError::Io(format!("write chunk: {e}")))?;
+        file.sync_all()
+            .map_err(|e| DomainError::Io(format!("sync: {e}")))?;
+
+        // Check if upload is complete.
+        let end = req.offset + req.chunk.len() as u64;
+        if end == req.total_size {
+            // Verify SHA-256.
+            let mut vfile = std::fs::File::open(&part_path)
+                .map_err(|e| DomainError::Io(format!("open for verify: {e}")))?;
+            let mut hasher = Sha256::new();
+            let mut buf = [0u8; 64 * 1024];
+            loop {
+                let n = vfile
+                    .read(&mut buf)
+                    .map_err(|e| DomainError::Io(format!("read: {e}")))?;
+                if n == 0 {
+                    break;
+                }
+                hasher.update(&buf[..n]);
+            }
+            let computed: [u8; 32] = hasher.finalize().into();
+            if computed[..] != req.blob_hash[..] {
+                let _ = std::fs::remove_file(&part_path);
+                return Err(DomainError::BlobHashMismatch);
+            }
+
+            // Finalize.
+            std::fs::rename(&part_path, &final_path)
+                .map_err(|e| DomainError::Io(format!("rename .part: {e}")))?;
+
+            // Write metadata.
+            let now = std::time::SystemTime::now()
+                .duration_since(std::time::UNIX_EPOCH)
+                .unwrap_or_default()
+                .as_secs();
+            let meta = BlobMeta {
+                mime_type: req.mime_type,
+                total_size: req.total_size,
+                uploaded_at: now,
+            };
+            if let Ok(json) = serde_json::to_string_pretty(&meta) {
+                let _ = std::fs::write(&meta_path, json.as_bytes());
+            }
+        }
+
+        Ok(UploadBlobResp {
+            blob_id: req.blob_hash,
+        })
+    }
+
+    pub fn download_blob(
+        &self,
+        req: DownloadBlobReq,
+        _auth: &CallerAuth,
+    ) -> Result<DownloadBlobResp, DomainError> {
+        if req.blob_id.len() != 32 {
+            return Err(DomainError::BlobHashLength(req.blob_id.len()));
+        }
+
+        let blob_hex = hex::encode(&req.blob_id);
+        let dir = self.blobs_dir();
+        let blob_path = dir.join(&blob_hex);
+        let meta_path = dir.join(format!("{blob_hex}.meta"));
+
+        if !blob_path.exists() {
+            return Err(DomainError::BlobNotFound);
+        }
+
+        // Read metadata.
+        let meta_json = std::fs::read_to_string(&meta_path)
+            .map_err(|e| DomainError::Io(format!("read blob metadata: {e}")))?;
+        let meta: BlobMeta = serde_json::from_str(&meta_json)
+            .map_err(|e| DomainError::Io(format!("corrupt blob metadata: {e}")))?;
+
+        // Read chunk.
+        let mut file = std::fs::File::open(&blob_path)
+            .map_err(|e| DomainError::Io(format!("open blob: {e}")))?;
+        let file_len = file
+            .metadata()
+            .map_err(|e| DomainError::Io(format!("file metadata: {e}")))?
+            .len();
+
+        if req.offset >= file_len {
+            return Ok(DownloadBlobResp {
+                chunk: vec![],
+                total_size: meta.total_size,
+                mime_type: meta.mime_type,
+            });
+        }
+
+        file.seek(SeekFrom::Start(req.offset))
+            .map_err(|e| DomainError::Io(format!("seek: {e}")))?;
+        let remaining = (file_len - req.offset) as usize;
+        let to_read = remaining.min(req.length.min(MAX_DOWNLOAD_CHUNK) as usize);
+        let mut chunk = vec![0u8; to_read];
+        file.read_exact(&mut chunk)
+            .map_err(|e| DomainError::Io(format!("read chunk: {e}")))?;
+
+        Ok(DownloadBlobResp {
+            chunk,
+            total_size: meta.total_size,
+            mime_type: meta.mime_type,
+        })
+    }
+}

crates/quicprochat-server/src/domain/channels.rs

@@ -0,0 +1,38 @@
+//! Channel domain logic — 1:1 DM channel creation.
+
+use std::sync::Arc;
+
+use crate::storage::Store;
+
+use super::types::*;
+
+/// Domain service for 1:1 channel management.
+pub struct ChannelService {
+    pub store: Arc<dyn Store>,
+}
+
+impl ChannelService {
+    pub fn create_channel(
+        &self,
+        req: CreateChannelReq,
+        caller_identity_key: &[u8],
+    ) -> Result<CreateChannelResp, DomainError> {
+        if req.peer_key.len() != 32 {
+            return Err(DomainError::InvalidIdentityKey(req.peer_key.len()));
+        }
+        if caller_identity_key == req.peer_key.as_slice() {
+            return Err(DomainError::BadParams(
+                "peer_key must not equal caller identity".into(),
+            ));
+        }
+
+        let (channel_id, was_new) = self
+            .store
+            .create_channel(caller_identity_key, &req.peer_key)?;
+
+        Ok(CreateChannelResp {
+            channel_id,
+            was_new,
+        })
+    }
+}

crates/quicprochat-server/src/domain/delivery.rs

@@ -0,0 +1,352 @@
+//! Delivery domain logic — enqueue, fetch, peek, ack.
+//!
+//! Pure business logic operating on `Store` trait and domain types.
+//!
+//! ## Multi-device delivery
+//!
+//! When a message is enqueued for a recipient identity, the service resolves
+//! all registered device IDs for that identity and enqueues a copy of the
+//! payload to each device-scoped queue. The queue key is a composite of
+//! `identity_key + device_id`, so each device maintains its own sequence
+//! counter and ack state.
+//!
+//! If the recipient has no registered devices, the message is delivered to
+//! the bare `identity_key` queue (backwards compatible with single-device
+//! clients).
+
+use std::sync::Arc;
+
+use dashmap::DashMap;
+use tokio::sync::Notify;
+
+use crate::storage::Store;
+
+use super::types::*;
+
+/// Build a device-scoped recipient key: `identity_key || device_id`.
+/// When `device_id` is empty, returns a clone of `identity_key` (single-device compat).
+fn device_recipient_key(identity_key: &[u8], device_id: &[u8]) -> Vec<u8> {
+    if device_id.is_empty() {
+        return identity_key.to_vec();
+    }
+    let mut key = Vec::with_capacity(identity_key.len() + device_id.len());
+    key.extend_from_slice(identity_key);
+    key.extend_from_slice(device_id);
+    key
+}
+
+/// Shared state needed by delivery operations.
+pub struct DeliveryService {
+    pub store: Arc<dyn Store>,
+    pub waiters: Arc<DashMap<Vec<u8>, Arc<Notify>>>,
+}
+
+impl DeliveryService {
+    /// Resolve the device-scoped recipient keys for an identity.
+    /// Returns a list of composite keys (identity_key + device_id) for each
+    /// registered device. If no devices are registered, returns a single-element
+    /// list with the bare identity_key for backwards compatibility.
+    fn resolve_device_keys(&self, identity_key: &[u8]) -> Vec<Vec<u8>> {
+        let devices = self.store.list_devices(identity_key).unwrap_or_default();
+        if devices.is_empty() {
+            vec![identity_key.to_vec()]
+        } else {
+            devices
+                .into_iter()
+                .map(|(device_id, _, _)| device_recipient_key(identity_key, &device_id))
+                .collect()
+        }
+    }
+
+    /// Wake any long-polling waiter for the given recipient key.
+    fn wake_waiter(&self, recipient_key: &[u8]) {
+        if let Some(notify) = self.waiters.get(recipient_key) {
+            notify.notify_one();
+        }
+    }
+
+    /// Enqueue a payload for delivery to all devices of the recipient.
+    ///
+    /// Returns the sequence number from the *first* device queue (for backwards
+    /// compatibility with single-device callers).
+    pub fn enqueue(&self, req: EnqueueReq) -> Result<EnqueueResp, crate::storage::StorageError> {
+        let ttl = if req.ttl_secs > 0 {
+            Some(req.ttl_secs)
+        } else {
+            None
+        };
+
+        let device_keys = self.resolve_device_keys(&req.recipient_key);
+        let mut first_seq = 0;
+
+        for (i, dk) in device_keys.iter().enumerate() {
+            let seq = self.store.enqueue(
+                dk,
+                &req.channel_id,
+                req.payload.clone(),
+                ttl,
+            )?;
+            if i == 0 {
+                first_seq = seq;
+            }
+            self.wake_waiter(dk);
+        }
+
+        // Also wake the bare identity_key waiter (legacy clients).
+        self.wake_waiter(&req.recipient_key);
+
+        Ok(EnqueueResp {
+            seq: first_seq,
+            delivery_proof: Vec::new(), // Proof generated at RPC handler layer (see v2_handlers/delivery.rs)
+        })
+    }
+
+    /// Fetch and drain queued messages for a specific device.
+    ///
+    /// The `recipient_key` should be the device-scoped composite key
+    /// (`identity_key + device_id`) or bare `identity_key` for single-device.
+    pub fn fetch(&self, req: FetchReq) -> Result<FetchResp, crate::storage::StorageError> {
+        let messages = if req.limit > 0 {
+            self.store
+                .fetch_limited(&req.recipient_key, &req.channel_id, req.limit as usize)?
+        } else {
+            self.store.fetch(&req.recipient_key, &req.channel_id)?
+        };
+
+        Ok(FetchResp {
+            payloads: messages
+                .into_iter()
+                .map(|(seq, data)| Envelope { seq, data })
+                .collect(),
+        })
+    }
+
+    /// Peek at messages without removing them.
+    pub fn peek(&self, req: PeekReq) -> Result<PeekResp, crate::storage::StorageError> {
+        let messages = self.store.peek(
+            &req.recipient_key,
+            &req.channel_id,
+            if req.limit > 0 { req.limit as usize } else { 0 },
+        )?;
+
+        Ok(PeekResp {
+            payloads: messages
+                .into_iter()
+                .map(|(seq, data)| Envelope { seq, data })
+                .collect(),
+        })
+    }
+
+    /// Acknowledge messages up to a sequence number.
+    pub fn ack(&self, req: AckReq) -> Result<(), crate::storage::StorageError> {
+        self.store
+            .ack(&req.recipient_key, &req.channel_id, req.seq_up_to)?;
+        Ok(())
+    }
+
+    /// Batch enqueue to multiple recipients (with multi-device fan-out for each).
+    ///
+    /// Returns one sequence number per recipient identity (from the first device queue).
+    pub fn batch_enqueue(
+        &self,
+        req: BatchEnqueueReq,
+    ) -> Result<BatchEnqueueResp, crate::storage::StorageError> {
+        let ttl = if req.ttl_secs > 0 {
+            Some(req.ttl_secs)
+        } else {
+            None
+        };
+
+        let mut seqs = Vec::with_capacity(req.recipient_keys.len());
+        for rk in &req.recipient_keys {
+            let device_keys = self.resolve_device_keys(rk);
+            let mut first_seq = 0;
+
+            for (i, dk) in device_keys.iter().enumerate() {
+                let seq = self.store.enqueue(dk, &req.channel_id, req.payload.clone(), ttl)?;
+                if i == 0 {
+                    first_seq = seq;
+                }
+                self.wake_waiter(dk);
+            }
+
+            self.wake_waiter(rk);
+            seqs.push(first_seq);
+        }
+
+        Ok(BatchEnqueueResp { seqs })
+    }
+
+    /// Build a device-scoped recipient key from identity_key and device_id.
+    /// Public helper for RPC handlers to build the correct fetch/ack key.
+    pub fn device_recipient_key(identity_key: &[u8], device_id: &[u8]) -> Vec<u8> {
+        device_recipient_key(identity_key, device_id)
+    }
+}
+
+#[cfg(test)]
+#[allow(clippy::unwrap_used)]
+mod tests {
+    use super::*;
+    use crate::storage::FileBackedStore;
+
+    fn test_service() -> (tempfile::TempDir, DeliveryService) {
+        let dir = tempfile::tempdir().unwrap();
+        let store = Arc::new(FileBackedStore::open(dir.path()).unwrap());
+        let svc = DeliveryService {
+            store,
+            waiters: Arc::new(DashMap::new()),
+        };
+        (dir, svc)
+    }
+
+    #[test]
+    fn enqueue_single_device_backwards_compat() {
+        let (_dir, svc) = test_service();
+        let ik = vec![1u8; 32];
+        let ch = vec![0u8; 16];
+
+        // No devices registered — should enqueue to bare identity_key.
+        let resp = svc
+            .enqueue(EnqueueReq {
+                recipient_key: ik.clone(),
+                payload: b"hello".to_vec(),
+                channel_id: ch.clone(),
+                ttl_secs: 0,
+            })
+            .unwrap();
+        assert_eq!(resp.seq, 0);
+
+        // Fetch from bare identity_key.
+        let fetched = svc
+            .fetch(FetchReq {
+                recipient_key: ik,
+                channel_id: ch,
+                limit: 10,
+            })
+            .unwrap();
+        assert_eq!(fetched.payloads.len(), 1);
+        assert_eq!(fetched.payloads[0].data, b"hello");
+    }
+
+    #[test]
+    fn enqueue_multi_device_fanout() {
+        let (_dir, svc) = test_service();
+        let ik = vec![2u8; 32];
+        let ch = vec![0u8; 16];
+        let dev_a = b"device-a".to_vec();
+        let dev_b = b"device-b".to_vec();
+
+        // Register two devices.
+        svc.store
+            .register_device(&ik, &dev_a, "Phone")
+            .unwrap();
+        svc.store
+            .register_device(&ik, &dev_b, "Laptop")
+            .unwrap();
+
+        // Enqueue a message.
+        svc.enqueue(EnqueueReq {
+            recipient_key: ik.clone(),
+            payload: b"fanout-msg".to_vec(),
+            channel_id: ch.clone(),
+            ttl_secs: 0,
+        })
+        .unwrap();
+
+        // Each device should receive the message on its own queue.
+        let key_a = device_recipient_key(&ik, &dev_a);
+        let key_b = device_recipient_key(&ik, &dev_b);
+
+        let msgs_a = svc
+            .fetch(FetchReq {
+                recipient_key: key_a,
+                channel_id: ch.clone(),
+                limit: 10,
+            })
+            .unwrap();
+        assert_eq!(msgs_a.payloads.len(), 1);
+        assert_eq!(msgs_a.payloads[0].data, b"fanout-msg");
+
+        let msgs_b = svc
+            .fetch(FetchReq {
+                recipient_key: key_b,
+                channel_id: ch.clone(),
+                limit: 10,
+            })
+            .unwrap();
+        assert_eq!(msgs_b.payloads.len(), 1);
+        assert_eq!(msgs_b.payloads[0].data, b"fanout-msg");
+
+        // Bare identity_key queue should be empty (not used when devices exist).
+        let msgs_bare = svc
+            .fetch(FetchReq {
+                recipient_key: ik,
+                channel_id: ch,
+                limit: 10,
+            })
+            .unwrap();
+        assert!(msgs_bare.payloads.is_empty());
+    }
+
+    #[test]
+    fn batch_enqueue_multi_device() {
+        let (_dir, svc) = test_service();
+        let ik1 = vec![3u8; 32];
+        let ik2 = vec![4u8; 32];
+        let ch = vec![0u8; 16];
+        let dev = b"dev1".to_vec();
+
+        // ik1 has a device, ik2 has none.
+        svc.store
+            .register_device(&ik1, &dev, "Phone")
+            .unwrap();
+
+        let resp = svc
+            .batch_enqueue(BatchEnqueueReq {
+                recipient_keys: vec![ik1.clone(), ik2.clone()],
+                payload: b"batch-msg".to_vec(),
+                channel_id: ch.clone(),
+                ttl_secs: 0,
+            })
+            .unwrap();
+        assert_eq!(resp.seqs.len(), 2);
+
+        // ik1 device should have the message.
+        let key_1 = device_recipient_key(&ik1, &dev);
+        let msgs_1 = svc
+            .fetch(FetchReq {
+                recipient_key: key_1,
+                channel_id: ch.clone(),
+                limit: 10,
+            })
+            .unwrap();
+        assert_eq!(msgs_1.payloads.len(), 1);
+
+        // ik2 (no devices) should have it on bare key.
+        let msgs_2 = svc
+            .fetch(FetchReq {
+                recipient_key: ik2,
+                channel_id: ch,
+                limit: 10,
+            })
+            .unwrap();
+        assert_eq!(msgs_2.payloads.len(), 1);
+    }
+
+    #[test]
+    fn device_recipient_key_construction() {
+        let ik = vec![1u8; 32];
+        let dev = b"my-device".to_vec();
+
+        // With device_id.
+        let key = device_recipient_key(&ik, &dev);
+        assert_eq!(key.len(), 32 + dev.len());
+        assert_eq!(&key[..32], &ik[..]);
+        assert_eq!(&key[32..], dev.as_slice());
+
+        // Empty device_id returns bare identity_key.
+        let bare = device_recipient_key(&ik, &[]);
+        assert_eq!(bare, ik);
+    }
+}

crates/quicprochat-server/src/domain/devices.rs

@@ -0,0 +1,76 @@
+//! Device registry domain logic — register, list, revoke devices.
+
+use std::sync::Arc;
+
+use crate::storage::Store;
+
+use super::types::*;
+
+const MAX_DEVICES_PER_IDENTITY: usize = 5;
+
+/// Domain service for multi-device management.
+pub struct DeviceService {
+    pub store: Arc<dyn Store>,
+}
+
+impl DeviceService {
+    pub fn register_device(
+        &self,
+        req: RegisterDeviceReq,
+        caller_identity_key: &[u8],
+    ) -> Result<RegisterDeviceResp, DomainError> {
+        if req.device_id.is_empty() {
+            return Err(DomainError::BadParams(
+                "device_id must not be empty".into(),
+            ));
+        }
+
+        let count = self.store.device_count(caller_identity_key)?;
+        if count >= MAX_DEVICES_PER_IDENTITY {
+            return Err(DomainError::DeviceLimit(MAX_DEVICES_PER_IDENTITY));
+        }
+
+        let success =
+            self.store
+                .register_device(caller_identity_key, &req.device_id, &req.device_name)?;
+
+        Ok(RegisterDeviceResp { success })
+    }
+
+    pub fn list_devices(
+        &self,
+        caller_identity_key: &[u8],
+    ) -> Result<ListDevicesResp, DomainError> {
+        let raw = self.store.list_devices(caller_identity_key)?;
+        let devices = raw
+            .into_iter()
+            .map(|(device_id, device_name, registered_at)| DeviceInfo {
+                device_id,
+                device_name,
+                registered_at,
+            })
+            .collect();
+        Ok(ListDevicesResp { devices })
+    }
+
+    pub fn revoke_device(
+        &self,
+        req: RevokeDeviceReq,
+        caller_identity_key: &[u8],
+    ) -> Result<RevokeDeviceResp, DomainError> {
+        if req.device_id.is_empty() {
+            return Err(DomainError::BadParams(
+                "device_id must not be empty".into(),
+            ));
+        }
+
+        let success = self
+            .store
+            .revoke_device(caller_identity_key, &req.device_id)?;
+        if !success {
+            return Err(DomainError::DeviceNotFound);
+        }
+
+        Ok(RevokeDeviceResp { success })
+    }
+}

crates/quicprochat-server/src/domain/groups.rs

@@ -0,0 +1,208 @@
+//! Group management domain logic — metadata, membership tracking.
+
+use std::sync::Arc;
+
+use crate::storage::Store;
+
+use super::types::*;
+
+/// Domain service for group metadata and membership.
+pub struct GroupService {
+    pub store: Arc<dyn Store>,
+}
+
+impl GroupService {
+    /// Update group metadata (name, description, avatar_hash).
+    pub fn update_metadata(
+        &self,
+        req: UpdateGroupMetadataReq,
+        caller_identity_key: &[u8],
+    ) -> Result<(), DomainError> {
+        if req.group_id.is_empty() {
+            return Err(DomainError::BadParams("group_id must not be empty".into()));
+        }
+
+        self.store.store_group_metadata(
+            &req.group_id,
+            &req.name,
+            &req.description,
+            &req.avatar_hash,
+            caller_identity_key,
+        )?;
+
+        Ok(())
+    }
+
+    /// List group members with resolved usernames.
+    pub fn list_members(
+        &self,
+        req: ListGroupMembersReq,
+    ) -> Result<ListGroupMembersResp, DomainError> {
+        if req.group_id.is_empty() {
+            return Err(DomainError::BadParams("group_id must not be empty".into()));
+        }
+
+        let raw = self.store.list_group_members(&req.group_id)?;
+        let members = raw
+            .into_iter()
+            .map(|(identity_key, joined_at)| {
+                let username = self
+                    .store
+                    .resolve_identity_key(&identity_key)
+                    .ok()
+                    .flatten()
+                    .unwrap_or_default();
+                GroupMemberInfo {
+                    identity_key,
+                    username,
+                    joined_at,
+                }
+            })
+            .collect();
+        Ok(ListGroupMembersResp { members })
+    }
+
+    /// Track a member addition in the server-side membership table.
+    pub fn add_member(
+        &self,
+        group_id: &[u8],
+        identity_key: &[u8],
+    ) -> Result<(), DomainError> {
+        self.store.add_group_member(group_id, identity_key)?;
+        Ok(())
+    }
+
+    /// Track a member removal in the server-side membership table.
+    pub fn remove_member(
+        &self,
+        group_id: &[u8],
+        identity_key: &[u8],
+    ) -> Result<bool, DomainError> {
+        let removed = self.store.remove_group_member(group_id, identity_key)?;
+        Ok(removed)
+    }
+
+    /// Get group metadata.
+    pub fn get_metadata(
+        &self,
+        group_id: &[u8],
+    ) -> Result<Option<GroupMetadata>, DomainError> {
+        if group_id.is_empty() {
+            return Err(DomainError::BadParams("group_id must not be empty".into()));
+        }
+
+        match self.store.get_group_metadata(group_id)? {
+            Some((name, description, avatar_hash, creator_key, created_at)) => {
+                Ok(Some(GroupMetadata {
+                    group_id: group_id.to_vec(),
+                    name,
+                    description,
+                    avatar_hash,
+                    creator_key,
+                    created_at,
+                }))
+            }
+            None => Ok(None),
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::storage::FileBackedStore;
+
+    fn make_service() -> (GroupService, tempfile::TempDir) {
+        let dir = tempfile::tempdir().expect("tempdir");
+        let store = FileBackedStore::open(dir.path()).expect("open store");
+        let svc = GroupService {
+            store: Arc::new(store),
+        };
+        (svc, dir)
+    }
+
+    #[test]
+    fn update_and_get_metadata() {
+        let (svc, _dir) = make_service();
+        let group_id = b"test-group-00001".to_vec();
+        let caller = b"caller-key".to_vec();
+
+        svc.update_metadata(
+            UpdateGroupMetadataReq {
+                group_id: group_id.clone(),
+                name: "Test Group".into(),
+                description: "A test group".into(),
+                avatar_hash: vec![0xAB],
+            },
+            &caller,
+        )
+        .expect("update_metadata should succeed");
+
+        let meta = svc.get_metadata(&group_id).expect("get_metadata should succeed");
+        let meta = meta.expect("metadata should exist");
+        assert_eq!(meta.name, "Test Group");
+        assert_eq!(meta.description, "A test group");
+        assert_eq!(meta.avatar_hash, vec![0xAB]);
+        assert_eq!(meta.creator_key, caller);
+    }
+
+    #[test]
+    fn get_metadata_nonexistent_returns_none() {
+        let (svc, _dir) = make_service();
+        let result = svc.get_metadata(b"no-such-group").expect("should not error");
+        assert!(result.is_none());
+    }
+
+    #[test]
+    fn empty_group_id_rejected() {
+        let (svc, _dir) = make_service();
+        let err = svc.update_metadata(
+            UpdateGroupMetadataReq {
+                group_id: Vec::new(),
+                name: "X".into(),
+                description: String::new(),
+                avatar_hash: Vec::new(),
+            },
+            b"caller",
+        );
+        assert!(err.is_err());
+    }
+
+    #[test]
+    fn add_list_remove_members() {
+        let (svc, _dir) = make_service();
+        let group_id = b"membership-group".to_vec();
+        let member_a = b"member-a-key".to_vec();
+        let member_b = b"member-b-key".to_vec();
+
+        svc.add_member(&group_id, &member_a).expect("add a");
+        svc.add_member(&group_id, &member_b).expect("add b");
+
+        let resp = svc
+            .list_members(ListGroupMembersReq {
+                group_id: group_id.clone(),
+            })
+            .expect("list members");
+        assert_eq!(resp.members.len(), 2);
+
+        let removed = svc.remove_member(&group_id, &member_a).expect("remove a");
+        assert!(removed);
+
+        let resp = svc
+            .list_members(ListGroupMembersReq {
+                group_id: group_id.clone(),
+            })
+            .expect("list members after removal");
+        assert_eq!(resp.members.len(), 1);
+        assert_eq!(resp.members[0].identity_key, member_b);
+    }
+
+    #[test]
+    fn remove_nonexistent_member_returns_false() {
+        let (svc, _dir) = make_service();
+        let removed = svc
+            .remove_member(b"group", b"nobody")
+            .expect("remove nonexistent");
+        assert!(!removed);
+    }
+}

crates/quicprochat-server/src/domain/keys.rs

@@ -0,0 +1,93 @@
+//! Key management domain logic — KeyPackage and hybrid key operations.
+
+use std::sync::Arc;
+
+use sha2::{Digest, Sha256};
+
+use crate::storage::Store;
+
+use super::types::*;
+
+const MAX_KEYPACKAGE_BYTES: usize = 1024 * 1024; // 1 MB
+
+/// Domain service for MLS KeyPackage and hybrid (PQ) key management.
+pub struct KeyService {
+    pub store: Arc<dyn Store>,
+}
+
+impl KeyService {
+    pub fn upload_key_package(
+        &self,
+        req: UploadKeyPackageReq,
+        _auth: &CallerAuth,
+    ) -> Result<UploadKeyPackageResp, DomainError> {
+        if req.identity_key.len() != 32 {
+            return Err(DomainError::InvalidIdentityKey(req.identity_key.len()));
+        }
+        if req.package.is_empty() {
+            return Err(DomainError::EmptyPackage);
+        }
+        if req.package.len() > MAX_KEYPACKAGE_BYTES {
+            return Err(DomainError::PackageTooLarge(req.package.len()));
+        }
+
+        let fingerprint: Vec<u8> = Sha256::digest(&req.package).to_vec();
+        self.store
+            .upload_key_package(&req.identity_key, req.package)?;
+
+        Ok(UploadKeyPackageResp { fingerprint })
+    }
+
+    pub fn fetch_key_package(
+        &self,
+        req: FetchKeyPackageReq,
+        _auth: &CallerAuth,
+    ) -> Result<FetchKeyPackageResp, DomainError> {
+        let package = self.store.fetch_key_package(&req.identity_key)?;
+        Ok(FetchKeyPackageResp {
+            package: package.unwrap_or_default(),
+        })
+    }
+
+    pub fn upload_hybrid_key(
+        &self,
+        req: UploadHybridKeyReq,
+        _auth: &CallerAuth,
+    ) -> Result<(), DomainError> {
+        if req.identity_key.len() != 32 {
+            return Err(DomainError::InvalidIdentityKey(req.identity_key.len()));
+        }
+        if req.hybrid_public_key.is_empty() {
+            return Err(DomainError::EmptyHybridKey);
+        }
+
+        self.store
+            .upload_hybrid_key(&req.identity_key, req.hybrid_public_key)?;
+        Ok(())
+    }
+
+    pub fn fetch_hybrid_key(
+        &self,
+        req: FetchHybridKeyReq,
+        _auth: &CallerAuth,
+    ) -> Result<FetchHybridKeyResp, DomainError> {
+        let hybrid_public_key = self
+            .store
+            .fetch_hybrid_key(&req.identity_key)?
+            .unwrap_or_default();
+        Ok(FetchHybridKeyResp { hybrid_public_key })
+    }
+
+    pub fn fetch_hybrid_keys(
+        &self,
+        req: FetchHybridKeysReq,
+        _auth: &CallerAuth,
+    ) -> Result<FetchHybridKeysResp, DomainError> {
+        let mut keys = Vec::with_capacity(req.identity_keys.len());
+        for ik in &req.identity_keys {
+            let pk = self.store.fetch_hybrid_key(ik)?.unwrap_or_default();
+            keys.push(pk);
+        }
+        Ok(FetchHybridKeysResp { keys })
+    }
+}

crates/quicprochat-server/src/domain/mod.rs

@@ -0,0 +1,24 @@
+//! Domain types and service logic — protocol-agnostic.
+//!
+//! These types define the server's business logic independently of any
+//! serialization format (Cap'n Proto, Protobuf). RPC handlers translate
+//! wire-format messages into these types, call service functions, and
+//! translate the results back.
+
+pub mod types;
+pub mod auth;
+pub mod delivery;
+pub mod keys;
+pub mod channels;
+pub mod users;
+pub mod blobs;
+pub mod devices;
+pub mod groups;
+pub mod p2p;
+pub mod account;
+pub mod moderation;
+pub mod notification;
+pub mod rate_limit;
+pub mod recovery;
+#[cfg(feature = "traffic-resistance")]
+pub mod traffic_resistance;

crates/quicprochat-server/src/domain/moderation.rs

@@ -0,0 +1,304 @@
+//! Moderation domain logic — report, ban, unban, list.
+//!
+//! Pure business logic operating on `Store` trait and domain types.
+
+use std::sync::Arc;
+
+use crate::storage::Store;
+
+use super::types::*;
+
+/// Shared state needed by moderation operations.
+pub struct ModerationService {
+    pub store: Arc<dyn Store>,
+}
+
+impl ModerationService {
+    /// Submit an encrypted report for a message.
+    pub fn report_message(
+        &self,
+        req: ReportMessageReq,
+    ) -> Result<ReportMessageResp, DomainError> {
+        if req.encrypted_report.is_empty() {
+            return Err(DomainError::BadParams(
+                "encrypted report must not be empty".into(),
+            ));
+        }
+
+        self.store
+            .store_report(
+                &req.encrypted_report,
+                &req.conversation_id,
+                &req.reporter_identity,
+            )
+            .map_err(DomainError::Storage)?;
+
+        tracing::info!(
+            reporter_prefix = %hex_prefix(&req.reporter_identity),
+            "audit: message reported"
+        );
+
+        Ok(ReportMessageResp { accepted: true })
+    }
+
+    /// Ban a user by identity key.
+    pub fn ban_user(&self, req: BanUserReq) -> Result<BanUserResp, DomainError> {
+        if req.identity_key.len() != 32 {
+            return Err(DomainError::InvalidIdentityKey(req.identity_key.len()));
+        }
+
+        let expires_at = if req.duration_secs == 0 {
+            0 // permanent
+        } else {
+            now_secs() + req.duration_secs
+        };
+
+        self.store
+            .ban_user(&req.identity_key, &req.reason, expires_at)
+            .map_err(DomainError::Storage)?;
+
+        tracing::info!(
+            identity_prefix = %hex_prefix(&req.identity_key),
+            reason = %req.reason,
+            expires_at,
+            "audit: user banned"
+        );
+
+        Ok(BanUserResp { success: true })
+    }
+
+    /// Unban a user by identity key.
+    pub fn unban_user(&self, req: UnbanUserReq) -> Result<UnbanUserResp, DomainError> {
+        if req.identity_key.len() != 32 {
+            return Err(DomainError::InvalidIdentityKey(req.identity_key.len()));
+        }
+
+        let removed = self
+            .store
+            .unban_user(&req.identity_key)
+            .map_err(DomainError::Storage)?;
+
+        if removed {
+            tracing::info!(
+                identity_prefix = %hex_prefix(&req.identity_key),
+                "audit: user unbanned"
+            );
+        }
+
+        Ok(UnbanUserResp { success: removed })
+    }
+
+    /// Check if a user is currently banned.
+    pub fn check_ban(&self, identity_key: &[u8]) -> Result<Option<String>, DomainError> {
+        self.store
+            .is_banned(identity_key)
+            .map_err(DomainError::Storage)
+    }
+
+    /// List reports with pagination.
+    pub fn list_reports(&self, req: ListReportsReq) -> Result<ListReportsResp, DomainError> {
+        let raw = self
+            .store
+            .list_reports(req.limit, req.offset)
+            .map_err(DomainError::Storage)?;
+
+        let reports = raw
+            .into_iter()
+            .map(
+                |(id, encrypted_report, conversation_id, reporter_identity, timestamp)| {
+                    ReportEntry {
+                        id,
+                        encrypted_report,
+                        conversation_id,
+                        reporter_identity,
+                        timestamp,
+                    }
+                },
+            )
+            .collect();
+
+        Ok(ListReportsResp { reports })
+    }
+
+    /// List all currently banned users.
+    pub fn list_banned(&self) -> Result<ListBannedResp, DomainError> {
+        let raw = self.store.list_banned().map_err(DomainError::Storage)?;
+
+        let users = raw
+            .into_iter()
+            .map(
+                |(identity_key, reason, banned_at, expires_at)| BannedUserEntry {
+                    identity_key,
+                    reason,
+                    banned_at,
+                    expires_at,
+                },
+            )
+            .collect();
+
+        Ok(ListBannedResp { users })
+    }
+}
+
+fn now_secs() -> u64 {
+    std::time::SystemTime::now()
+        .duration_since(std::time::UNIX_EPOCH)
+        .unwrap_or_default()
+        .as_secs()
+}
+
+fn hex_prefix(bytes: &[u8]) -> String {
+    let len = bytes.len().min(4);
+    let hex: String = bytes[..len].iter().map(|b| format!("{b:02x}")).collect();
+    format!("{hex}...")
+}
+
+#[cfg(test)]
+#[allow(clippy::unwrap_used)]
+mod tests {
+    use super::*;
+    use crate::storage::FileBackedStore;
+
+    fn test_service() -> (tempfile::TempDir, ModerationService) {
+        let dir = tempfile::tempdir().unwrap();
+        let store = Arc::new(FileBackedStore::open(dir.path()).unwrap());
+        let svc = ModerationService { store };
+        (dir, svc)
+    }
+
+    #[test]
+    fn report_store_and_list() {
+        let (_dir, svc) = test_service();
+
+        let resp = svc
+            .report_message(ReportMessageReq {
+                encrypted_report: vec![1, 2, 3],
+                conversation_id: vec![10; 16],
+                reporter_identity: vec![20; 32],
+            })
+            .unwrap();
+        assert!(resp.accepted);
+
+        let reports = svc
+            .list_reports(ListReportsReq {
+                limit: 10,
+                offset: 0,
+            })
+            .unwrap();
+        assert_eq!(reports.reports.len(), 1);
+        assert_eq!(reports.reports[0].encrypted_report, vec![1, 2, 3]);
+        assert_eq!(reports.reports[0].conversation_id, vec![10; 16]);
+        assert_eq!(reports.reports[0].reporter_identity, vec![20; 32]);
+    }
+
+    #[test]
+    fn report_empty_rejected() {
+        let (_dir, svc) = test_service();
+        let result = svc.report_message(ReportMessageReq {
+            encrypted_report: vec![],
+            conversation_id: vec![10; 16],
+            reporter_identity: vec![20; 32],
+        });
+        assert!(result.is_err());
+    }
+
+    #[test]
+    fn ban_unban_lifecycle() {
+        let (_dir, svc) = test_service();
+        let ik = vec![1u8; 32];
+
+        // Not banned initially.
+        assert!(svc.check_ban(&ik).unwrap().is_none());
+
+        // Ban permanently.
+        let resp = svc
+            .ban_user(BanUserReq {
+                identity_key: ik.clone(),
+                reason: "spam".into(),
+                duration_secs: 0,
+            })
+            .unwrap();
+        assert!(resp.success);
+
+        // Now banned.
+        let reason = svc.check_ban(&ik).unwrap();
+        assert_eq!(reason, Some("spam".to_string()));
+
+        // Listed in banned users.
+        let banned = svc.list_banned().unwrap();
+        assert_eq!(banned.users.len(), 1);
+        assert_eq!(banned.users[0].identity_key, ik);
+        assert_eq!(banned.users[0].reason, "spam");
+        assert_eq!(banned.users[0].expires_at, 0); // permanent
+
+        // Unban.
+        let resp = svc.unban_user(UnbanUserReq { identity_key: ik.clone() }).unwrap();
+        assert!(resp.success);
+
+        // No longer banned.
+        assert!(svc.check_ban(&ik).unwrap().is_none());
+        assert!(svc.list_banned().unwrap().users.is_empty());
+    }
+
+    #[test]
+    fn ban_invalid_identity_key() {
+        let (_dir, svc) = test_service();
+        let result = svc.ban_user(BanUserReq {
+            identity_key: vec![1u8; 16], // wrong length
+            reason: "test".into(),
+            duration_secs: 0,
+        });
+        assert!(result.is_err());
+    }
+
+    #[test]
+    fn list_reports_pagination() {
+        let (_dir, svc) = test_service();
+
+        for i in 0..5u8 {
+            svc.report_message(ReportMessageReq {
+                encrypted_report: vec![i],
+                conversation_id: vec![10; 16],
+                reporter_identity: vec![20; 32],
+            })
+            .unwrap();
+        }
+
+        let page1 = svc
+            .list_reports(ListReportsReq {
+                limit: 2,
+                offset: 0,
+            })
+            .unwrap();
+        assert_eq!(page1.reports.len(), 2);
+        assert_eq!(page1.reports[0].encrypted_report, vec![0]);
+
+        let page2 = svc
+            .list_reports(ListReportsReq {
+                limit: 2,
+                offset: 2,
+            })
+            .unwrap();
+        assert_eq!(page2.reports.len(), 2);
+        assert_eq!(page2.reports[0].encrypted_report, vec![2]);
+
+        let page3 = svc
+            .list_reports(ListReportsReq {
+                limit: 2,
+                offset: 4,
+            })
+            .unwrap();
+        assert_eq!(page3.reports.len(), 1);
+    }
+
+    #[test]
+    fn unban_nonexistent_returns_false() {
+        let (_dir, svc) = test_service();
+        let resp = svc
+            .unban_user(UnbanUserReq {
+                identity_key: vec![99u8; 32],
+            })
+            .unwrap();
+        assert!(!resp.success);
+    }
+}

crates/quicprochat-server/src/domain/notification.rs

@@ -0,0 +1,131 @@
+//! Cross-node notification bus for message delivery fan-out.
+//!
+//! When a message is enqueued, the bus publishes a notification so that
+//! any node running a `fetch_wait` long-poll for that recipient can
+//! wake up — even if the enqueue happened on a different node.
+//!
+//! Two backends:
+//! - `InMemoryNotificationBus`: single-node, tokio::sync::Notify (default)
+//! - Redis pub/sub (feature-gated `redis-pubsub`, implemented externally)
+
+use std::sync::Arc;
+use dashmap::DashMap;
+use tokio::sync::Notify;
+
+// ── Trait ────────────────────────────────────────────────────────────────────
+
+/// Cross-node notification bus.
+///
+/// Publishers call `publish` when a message is enqueued.
+/// Subscribers call `subscribe` to get a future that resolves when
+/// a notification arrives for the given topic.
+pub trait NotificationBus: Send + Sync {
+    /// Notify all waiters for `topic` that new data is available.
+    fn publish(&self, topic: &[u8]);
+
+    /// Return a future that completes when `topic` receives a notification.
+    /// The returned `Notify` can be `.notified().await`'d.
+    fn subscribe(&self, topic: &[u8]) -> Arc<Notify>;
+}
+
+// ── In-memory implementation ────────────────────────────────────────────────
+
+/// Single-node notification bus backed by `tokio::sync::Notify`.
+///
+/// This is the default for single-node deployments. For multi-node,
+/// replace with a Redis pub/sub or NATS implementation.
+pub struct InMemoryNotificationBus {
+    waiters: DashMap<Vec<u8>, Arc<Notify>>,
+}
+
+impl InMemoryNotificationBus {
+    pub fn new() -> Self {
+        Self {
+            waiters: DashMap::new(),
+        }
+    }
+}
+
+impl Default for InMemoryNotificationBus {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl NotificationBus for InMemoryNotificationBus {
+    fn publish(&self, topic: &[u8]) {
+        if let Some(notify) = self.waiters.get(topic) {
+            notify.notify_waiters();
+        }
+    }
+
+    fn subscribe(&self, topic: &[u8]) -> Arc<Notify> {
+        self.waiters
+            .entry(topic.to_vec())
+            .or_insert_with(|| Arc::new(Notify::new()))
+            .clone()
+    }
+}
+
+/// Create the default notification bus (in-memory, single-node).
+pub fn default_notification_bus() -> Arc<dyn NotificationBus> {
+    Arc::new(InMemoryNotificationBus::new())
+}
+
+// ── Tests ───────────────────────────────────────────────────────────────────
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::time::Duration;
+
+    #[tokio::test]
+    async fn publish_wakes_subscriber() {
+        let bus = InMemoryNotificationBus::new();
+        let topic = b"user:alice";
+
+        let notify = bus.subscribe(topic);
+        let notified = notify.notified();
+
+        // Publish from another "node" (same process in this case).
+        bus.publish(topic);
+
+        // Should resolve immediately since we published.
+        tokio::time::timeout(Duration::from_millis(100), notified)
+            .await
+            .expect("notification should arrive");
+    }
+
+    #[tokio::test]
+    async fn no_publish_times_out() {
+        let bus = InMemoryNotificationBus::new();
+        let topic = b"user:bob";
+
+        let notify = bus.subscribe(topic);
+        let notified = notify.notified();
+
+        let result = tokio::time::timeout(Duration::from_millis(50), notified).await;
+        assert!(result.is_err(), "should time out without publish");
+    }
+
+    #[tokio::test]
+    async fn independent_topics() {
+        let bus = InMemoryNotificationBus::new();
+
+        let notify_a = bus.subscribe(b"topic-a");
+        let notified_a = notify_a.notified();
+
+        let notify_b = bus.subscribe(b"topic-b");
+        let notified_b = notify_b.notified();
+
+        // Only publish to topic-a.
+        bus.publish(b"topic-a");
+
+        tokio::time::timeout(Duration::from_millis(100), notified_a)
+            .await
+            .expect("topic-a should wake");
+
+        let result = tokio::time::timeout(Duration::from_millis(50), notified_b).await;
+        assert!(result.is_err(), "topic-b should not wake");
+    }
+}

crates/quicprochat-server/src/domain/p2p.rs

@@ -0,0 +1,50 @@
+//! P2P endpoint domain logic — publish, resolve, health.
+
+use std::sync::Arc;
+
+use crate::storage::Store;
+
+use super::types::*;
+
+/// Domain service for P2P endpoint management and health checks.
+pub struct P2pService {
+    pub store: Arc<dyn Store>,
+}
+
+impl P2pService {
+    pub fn publish_endpoint(
+        &self,
+        req: PublishEndpointReq,
+        _auth: &CallerAuth,
+    ) -> Result<(), DomainError> {
+        if req.identity_key.len() != 32 {
+            return Err(DomainError::InvalidIdentityKey(req.identity_key.len()));
+        }
+
+        self.store
+            .publish_endpoint(&req.identity_key, req.node_addr)?;
+        Ok(())
+    }
+
+    pub fn resolve_endpoint(
+        &self,
+        req: ResolveEndpointReq,
+        _auth: &CallerAuth,
+    ) -> Result<ResolveEndpointResp, DomainError> {
+        if req.identity_key.len() != 32 {
+            return Err(DomainError::InvalidIdentityKey(req.identity_key.len()));
+        }
+
+        let node_addr = self
+            .store
+            .resolve_endpoint(&req.identity_key)?
+            .unwrap_or_default();
+        Ok(ResolveEndpointResp { node_addr })
+    }
+
+    pub fn health() -> HealthResp {
+        HealthResp {
+            status: "ok".into(),
+        }
+    }
+}

crates/quicprochat-server/src/domain/rate_limit.rs

@@ -0,0 +1,257 @@
+//! Distributed rate limiting — sliding window algorithm.
+//!
+//! Two backends:
+//! - `InMemoryRateLimiter`: single-process, DashMap-based (default)
+//! - `RedisRateLimiter`: shared across nodes via Redis (feature-gated `redis-ratelimit`)
+
+use std::sync::Arc;
+use std::time::{Duration, Instant};
+
+use dashmap::DashMap;
+
+// ── Public types ────────────────────────────────────────────────────────────
+
+/// Result of a rate-limit check.
+#[derive(Debug, Clone)]
+pub struct RateResult {
+    /// Whether the request is allowed.
+    pub allowed: bool,
+    /// Remaining requests in the current window.
+    pub remaining: u32,
+    /// When the window resets (seconds from now).
+    pub retry_after_secs: u32,
+}
+
+/// Configuration for a specific rate-limit bucket.
+#[derive(Debug, Clone)]
+pub struct RateLimitConfig {
+    /// Maximum number of requests in the window.
+    pub max_requests: u32,
+    /// Length of the sliding window.
+    pub window: Duration,
+}
+
+impl Default for RateLimitConfig {
+    fn default() -> Self {
+        Self {
+            max_requests: 100,
+            window: Duration::from_secs(60),
+        }
+    }
+}
+
+// ── Trait ────────────────────────────────────────────────────────────────────
+
+/// Abstraction over rate-limit backends.
+pub trait RateLimiter: Send + Sync {
+    /// Check whether `key` is within its rate limit. If allowed, the counter
+    /// is incremented atomically.
+    fn check_rate(&self, key: &str, config: &RateLimitConfig) -> RateResult;
+}
+
+// ── In-memory sliding window ────────────────────────────────────────────────
+
+/// Per-key state for the sliding window algorithm.
+struct SlidingWindow {
+    /// Timestamps of recent requests within the window.
+    timestamps: Vec<u64>,
+}
+
+/// In-memory rate limiter using a sliding window log.
+pub struct InMemoryRateLimiter {
+    buckets: DashMap<String, SlidingWindow>,
+    /// Last time we ran GC on expired entries.
+    last_gc: std::sync::Mutex<Instant>,
+}
+
+impl InMemoryRateLimiter {
+    pub fn new() -> Self {
+        Self {
+            buckets: DashMap::new(),
+            last_gc: std::sync::Mutex::new(Instant::now()),
+        }
+    }
+
+    fn now_millis() -> u64 {
+        std::time::SystemTime::now()
+            .duration_since(std::time::UNIX_EPOCH)
+            .unwrap_or_default()
+            .as_millis() as u64
+    }
+
+    /// Remove entries whose entire window has expired. Called lazily.
+    fn gc_if_needed(&self, window: Duration) {
+        let should_gc = {
+            let Ok(last) = self.last_gc.lock() else {
+                return;
+            };
+            last.elapsed() > Duration::from_secs(60)
+        };
+
+        if !should_gc {
+            return;
+        }
+
+        if let Ok(mut last) = self.last_gc.lock() {
+            *last = Instant::now();
+        }
+
+        let now_ms = Self::now_millis();
+        let window_ms = window.as_millis() as u64;
+
+        self.buckets.retain(|_key, window_state| {
+            // Keep if any timestamp is within the window.
+            window_state
+                .timestamps
+                .iter()
+                .any(|&ts| now_ms.saturating_sub(ts) < window_ms)
+        });
+    }
+}
+
+impl Default for InMemoryRateLimiter {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl RateLimiter for InMemoryRateLimiter {
+    fn check_rate(&self, key: &str, config: &RateLimitConfig) -> RateResult {
+        let now_ms = Self::now_millis();
+        let window_ms = config.window.as_millis() as u64;
+
+        self.gc_if_needed(config.window);
+
+        let mut entry = self.buckets.entry(key.to_string()).or_insert(SlidingWindow {
+            timestamps: Vec::new(),
+        });
+
+        // Evict timestamps outside the sliding window.
+        let cutoff = now_ms.saturating_sub(window_ms);
+        entry.timestamps.retain(|&ts| ts > cutoff);
+
+        let count = entry.timestamps.len() as u32;
+
+        if count >= config.max_requests {
+            // Find earliest timestamp to compute retry-after.
+            let earliest = entry.timestamps.iter().copied().min().unwrap_or(now_ms);
+            let retry_after_ms = (earliest + window_ms).saturating_sub(now_ms);
+            return RateResult {
+                allowed: false,
+                remaining: 0,
+                retry_after_secs: (retry_after_ms / 1000).max(1) as u32,
+            };
+        }
+
+        entry.timestamps.push(now_ms);
+        let remaining = config.max_requests.saturating_sub(count + 1);
+
+        RateResult {
+            allowed: true,
+            remaining,
+            retry_after_secs: 0,
+        }
+    }
+}
+
+/// Create the default rate limiter (in-memory).
+pub fn default_rate_limiter() -> Arc<dyn RateLimiter> {
+    Arc::new(InMemoryRateLimiter::new())
+}
+
+// ── Tests ───────────────────────────────────────────────────────────────────
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn allows_within_limit() {
+        let limiter = InMemoryRateLimiter::new();
+        let config = RateLimitConfig {
+            max_requests: 3,
+            window: Duration::from_secs(60),
+        };
+
+        for _ in 0..3 {
+            let result = limiter.check_rate("user1", &config);
+            assert!(result.allowed);
+        }
+    }
+
+    #[test]
+    fn blocks_over_limit() {
+        let limiter = InMemoryRateLimiter::new();
+        let config = RateLimitConfig {
+            max_requests: 2,
+            window: Duration::from_secs(60),
+        };
+
+        assert!(limiter.check_rate("user1", &config).allowed);
+        assert!(limiter.check_rate("user1", &config).allowed);
+        let result = limiter.check_rate("user1", &config);
+        assert!(!result.allowed);
+        assert_eq!(result.remaining, 0);
+        assert!(result.retry_after_secs > 0);
+    }
+
+    #[test]
+    fn independent_keys() {
+        let limiter = InMemoryRateLimiter::new();
+        let config = RateLimitConfig {
+            max_requests: 1,
+            window: Duration::from_secs(60),
+        };
+
+        assert!(limiter.check_rate("user1", &config).allowed);
+        assert!(!limiter.check_rate("user1", &config).allowed);
+        // Different key should still be allowed.
+        assert!(limiter.check_rate("user2", &config).allowed);
+    }
+
+    #[test]
+    fn remaining_decreases() {
+        let limiter = InMemoryRateLimiter::new();
+        let config = RateLimitConfig {
+            max_requests: 5,
+            window: Duration::from_secs(60),
+        };
+
+        let r1 = limiter.check_rate("user1", &config);
+        assert_eq!(r1.remaining, 4);
+        let r2 = limiter.check_rate("user1", &config);
+        assert_eq!(r2.remaining, 3);
+    }
+
+    #[test]
+    fn concurrent_access_is_safe() {
+        use std::sync::Arc;
+        use std::thread;
+
+        let limiter = Arc::new(InMemoryRateLimiter::new());
+        let config = RateLimitConfig {
+            max_requests: 1000,
+            window: Duration::from_secs(60),
+        };
+
+        let handles: Vec<_> = (0..10)
+            .map(|_| {
+                let l = Arc::clone(&limiter);
+                let c = config.clone();
+                thread::spawn(move || {
+                    for _ in 0..100 {
+                        l.check_rate("shared_key", &c);
+                    }
+                })
+            })
+            .collect();
+
+        for h in handles {
+            h.join().expect("thread panicked");
+        }
+
+        // After 1000 requests exactly, next should be blocked.
+        let result = limiter.check_rate("shared_key", &config);
+        assert!(!result.allowed);
+    }
+}

crates/quicprochat-server/src/domain/recovery.rs

@@ -0,0 +1,76 @@
+//! Recovery domain logic — encrypted recovery bundle CRUD.
+
+use std::sync::Arc;
+
+use crate::storage::Store;
+
+use super::types::DomainError;
+
+/// Maximum recovery bundle size: 64 KiB.
+const MAX_BUNDLE_SIZE: usize = 64 * 1024;
+
+/// Default TTL for recovery bundles: 90 days.
+pub const DEFAULT_TTL_SECS: u64 = 90 * 24 * 60 * 60;
+
+/// Domain service for recovery bundle operations.
+pub struct RecoveryService {
+    pub store: Arc<dyn Store>,
+}
+
+impl RecoveryService {
+    /// Store an encrypted recovery bundle.
+    ///
+    /// `token_hash` is the SHA-256 of a recovery token derived from the code.
+    /// `bundle` is the encrypted blob (opaque to server).
+    /// `ttl_secs` is the time-to-live; 0 uses the default (90 days).
+    pub fn store_bundle(
+        &self,
+        token_hash: &[u8],
+        bundle: Vec<u8>,
+        ttl_secs: u64,
+    ) -> Result<(), DomainError> {
+        if token_hash.len() != 32 {
+            return Err(DomainError::BadParams(format!(
+                "token_hash must be 32 bytes, got {}",
+                token_hash.len()
+            )));
+        }
+        if bundle.is_empty() {
+            return Err(DomainError::BadParams("recovery bundle must not be empty".into()));
+        }
+        if bundle.len() > MAX_BUNDLE_SIZE {
+            return Err(DomainError::BadParams(format!(
+                "recovery bundle exceeds max size ({} > {MAX_BUNDLE_SIZE})",
+                bundle.len()
+            )));
+        }
+
+        let ttl = if ttl_secs == 0 { DEFAULT_TTL_SECS } else { ttl_secs };
+        self.store.store_recovery_bundle(token_hash, bundle, ttl)?;
+        Ok(())
+    }
+
+    /// Fetch an encrypted recovery bundle by token_hash.
+    pub fn fetch_bundle(&self, token_hash: &[u8]) -> Result<Option<Vec<u8>>, DomainError> {
+        if token_hash.len() != 32 {
+            return Err(DomainError::BadParams(format!(
+                "token_hash must be 32 bytes, got {}",
+                token_hash.len()
+            )));
+        }
+        let bundle = self.store.get_recovery_bundle(token_hash)?;
+        Ok(bundle)
+    }
+
+    /// Delete an encrypted recovery bundle by token_hash.
+    pub fn delete_bundle(&self, token_hash: &[u8]) -> Result<bool, DomainError> {
+        if token_hash.len() != 32 {
+            return Err(DomainError::BadParams(format!(
+                "token_hash must be 32 bytes, got {}",
+                token_hash.len()
+            )));
+        }
+        let deleted = self.store.delete_recovery_bundle(token_hash)?;
+        Ok(deleted)
+    }
+}

crates/quicprochat-server/src/domain/traffic_resistance.rs

@@ -0,0 +1,249 @@
+//! Traffic analysis resistance — decoy traffic generation and timing jitter.
+//!
+//! When enabled (via the `traffic-resistance` feature), the server:
+//!
+//! 1. Pads all enqueued payloads to a uniform boundary using [`quicprochat_core::padding::pad_uniform`].
+//! 2. Injects random jitter delays before enqueue responses to mask timing patterns.
+//! 3. Runs a background decoy traffic generator that enqueues fake encrypted messages
+//!    at a configurable rate to connected recipients.
+//!
+//! Decoy messages are indistinguishable from real padded messages on the wire.
+//! Recipients detect and discard them by unpadding to an empty payload.
+
+use std::sync::Arc;
+
+use rand::Rng;
+use tokio::sync::Notify;
+
+use super::delivery::DeliveryService;
+use super::types::EnqueueReq;
+
+/// Configuration for traffic analysis resistance.
+#[derive(Clone, Debug)]
+pub struct TrafficResistanceConfig {
+    /// Padding boundary in bytes (default 256). All enqueued payloads are
+    /// padded to the nearest multiple of this value.
+    pub padding_boundary: usize,
+
+    /// Mean interval in milliseconds between decoy messages per recipient.
+    /// Set to 0 to disable decoy traffic.
+    pub decoy_interval_ms: u64,
+
+    /// Maximum random jitter in milliseconds added before enqueue responses.
+    /// Set to 0 to disable jitter.
+    pub jitter_max_ms: u64,
+}
+
+impl Default for TrafficResistanceConfig {
+    fn default() -> Self {
+        Self {
+            padding_boundary: quicprochat_core::padding::DEFAULT_PADDING_BOUNDARY,
+            decoy_interval_ms: 5000,
+            jitter_max_ms: 50,
+        }
+    }
+}
+
+/// Pad a payload to the configured uniform boundary.
+pub fn pad_payload(payload: &[u8], config: &TrafficResistanceConfig) -> Vec<u8> {
+    quicprochat_core::padding::pad_uniform(payload, config.padding_boundary)
+}
+
+/// Apply random jitter delay to mask timing patterns.
+///
+/// Sleeps for a random duration in `[0, config.jitter_max_ms)` milliseconds.
+/// Does nothing if `jitter_max_ms` is 0.
+pub async fn apply_jitter(config: &TrafficResistanceConfig) {
+    if config.jitter_max_ms == 0 {
+        return;
+    }
+    let jitter_ms = rand::thread_rng().gen_range(0..config.jitter_max_ms);
+    if jitter_ms > 0 {
+        tokio::time::sleep(std::time::Duration::from_millis(jitter_ms)).await;
+    }
+}
+
+/// Spawn a background task that generates decoy traffic.
+///
+/// Sends decoy messages to the provided `recipient_keys` at random intervals
+/// around `config.decoy_interval_ms`. The task runs until `shutdown` is notified.
+///
+/// Returns a `JoinHandle` for the spawned task.
+pub fn spawn_decoy_generator(
+    delivery: Arc<DeliveryService>,
+    recipient_keys: Vec<Vec<u8>>,
+    channel_id: Vec<u8>,
+    config: TrafficResistanceConfig,
+    shutdown: Arc<Notify>,
+) -> tokio::task::JoinHandle<()> {
+    tokio::spawn(async move {
+        if config.decoy_interval_ms == 0 || recipient_keys.is_empty() {
+            // Decoy traffic disabled or no recipients — wait for shutdown.
+            shutdown.notified().await;
+            return;
+        }
+
+        let base_interval = std::time::Duration::from_millis(config.decoy_interval_ms);
+
+        loop {
+            // Randomize interval: 50%–150% of base to avoid periodic patterns.
+            let jitter_factor: f64 = rand::thread_rng().gen_range(0.5..1.5);
+            let interval = base_interval.mul_f64(jitter_factor);
+
+            tokio::select! {
+                () = tokio::time::sleep(interval) => {}
+                () = shutdown.notified() => {
+                    tracing::debug!("decoy traffic generator shutting down");
+                    return;
+                }
+            }
+
+            // Pick a random recipient.
+            let idx = rand::thread_rng().gen_range(0..recipient_keys.len());
+            let recipient_key = &recipient_keys[idx];
+
+            // Generate a decoy payload that is indistinguishable from a real padded message.
+            let decoy = quicprochat_core::padding::generate_decoy(config.padding_boundary);
+
+            let req = EnqueueReq {
+                recipient_key: recipient_key.clone(),
+                payload: decoy,
+                channel_id: channel_id.clone(),
+                ttl_secs: 60, // Short TTL for decoys.
+            };
+
+            match delivery.enqueue(req) {
+                Ok(_) => {
+                    tracing::trace!("decoy message injected");
+                }
+                Err(e) => {
+                    tracing::warn!(error = %e, "failed to inject decoy message");
+                }
+            }
+        }
+    })
+}
+
+#[cfg(test)]
+#[allow(clippy::unwrap_used)]
+mod tests {
+    use super::*;
+    use crate::storage::FileBackedStore;
+    use dashmap::DashMap;
+
+    fn test_delivery() -> (tempfile::TempDir, Arc<DeliveryService>) {
+        let dir = tempfile::tempdir().unwrap();
+        let store = Arc::new(FileBackedStore::open(dir.path()).unwrap());
+        let svc = Arc::new(DeliveryService {
+            store,
+            waiters: Arc::new(DashMap::new()),
+        });
+        (dir, svc)
+    }
+
+    #[test]
+    fn pad_payload_is_boundary_aligned() {
+        let config = TrafficResistanceConfig {
+            padding_boundary: 256,
+            ..Default::default()
+        };
+        let payload = b"test message";
+        let padded = pad_payload(payload, &config);
+        assert_eq!(padded.len() % 256, 0);
+
+        // Unpad should recover original.
+        let unpadded = quicprochat_core::padding::unpad_uniform(&padded).unwrap();
+        assert_eq!(unpadded, payload);
+    }
+
+    #[test]
+    fn pad_payload_custom_boundary() {
+        let config = TrafficResistanceConfig {
+            padding_boundary: 512,
+            ..Default::default()
+        };
+        let payload = vec![0xAA; 300];
+        let padded = pad_payload(&payload, &config);
+        assert_eq!(padded.len() % 512, 0);
+        assert_eq!(padded.len(), 512);
+    }
+
+    #[tokio::test]
+    async fn jitter_zero_is_noop() {
+        let config = TrafficResistanceConfig {
+            jitter_max_ms: 0,
+            ..Default::default()
+        };
+        let start = std::time::Instant::now();
+        apply_jitter(&config).await;
+        // Should return almost immediately.
+        assert!(start.elapsed() < std::time::Duration::from_millis(5));
+    }
+
+    #[tokio::test]
+    async fn decoy_generator_produces_messages() {
+        let (_dir, delivery) = test_delivery();
+        let recipient = vec![0xFFu8; 32];
+        let channel = vec![0u8; 16];
+        let shutdown = Arc::new(Notify::new());
+
+        let config = TrafficResistanceConfig {
+            padding_boundary: 256,
+            decoy_interval_ms: 50, // Fast interval for testing.
+            jitter_max_ms: 0,
+        };
+
+        let handle = spawn_decoy_generator(
+            Arc::clone(&delivery),
+            vec![recipient.clone()],
+            channel.clone(),
+            config,
+            Arc::clone(&shutdown),
+        );
+
+        // Wait enough time for at least one decoy.
+        tokio::time::sleep(std::time::Duration::from_millis(200)).await;
+        shutdown.notify_one();
+        handle.await.unwrap();
+
+        // Check that decoy messages were enqueued.
+        let fetched = delivery
+            .fetch(super::super::types::FetchReq {
+                recipient_key: recipient,
+                channel_id: channel,
+                limit: 100,
+            })
+            .unwrap();
+
+        assert!(!fetched.payloads.is_empty(), "decoy generator should have enqueued at least one message");
+
+        // Every decoy should unpad to an empty payload.
+        for env in &fetched.payloads {
+            let unpadded = quicprochat_core::padding::unpad_uniform(&env.data).unwrap();
+            assert!(unpadded.is_empty(), "decoy payload should unpad to empty");
+        }
+    }
+
+    #[tokio::test]
+    async fn decoy_generator_disabled_when_zero_interval() {
+        let (_dir, delivery) = test_delivery();
+        let shutdown = Arc::new(Notify::new());
+
+        let config = TrafficResistanceConfig {
+            decoy_interval_ms: 0,
+            ..Default::default()
+        };
+
+        let handle = spawn_decoy_generator(
+            delivery,
+            vec![vec![1u8; 32]],
+            vec![0u8; 16],
+            config,
+            Arc::clone(&shutdown),
+        );
+
+        // Signal shutdown immediately — should return without having sent anything.
+        shutdown.notify_one();
+        handle.await.unwrap();
+    }
+}

crates/quicprochat-server/src/domain/types.rs

@@ -0,0 +1,441 @@
+//! Plain Rust request/response types for server domain logic.
+//!
+//! No proto, no capnp — just Rust structs.
+
+use crate::storage::StorageError;
+
+// ── Domain Error ────────────────────────────────────────────────────────────
+
+/// Errors returned by domain service methods.
+#[derive(thiserror::Error, Debug)]
+pub enum DomainError {
+    #[error("identity key must be exactly 32 bytes, got {0}")]
+    InvalidIdentityKey(usize),
+
+    #[error("key package must not be empty")]
+    EmptyPackage,
+
+    #[error("key package exceeds max size ({0} bytes)")]
+    PackageTooLarge(usize),
+
+    #[error("hybrid public key must not be empty")]
+    EmptyHybridKey,
+
+    #[error("username must not be empty")]
+    EmptyUsername,
+
+    #[error("blob hash must be exactly 32 bytes, got {0}")]
+    BlobHashLength(usize),
+
+    #[error("blob exceeds max size ({0} bytes)")]
+    BlobTooLarge(u64),
+
+    #[error("SHA-256 of uploaded data does not match blob hash")]
+    BlobHashMismatch,
+
+    #[error("blob not found")]
+    BlobNotFound,
+
+    #[error("maximum {0} devices per identity")]
+    DeviceLimit(usize),
+
+    #[error("device not found")]
+    DeviceNotFound,
+
+    #[error("group not found")]
+    GroupNotFound,
+
+    #[error("bad parameters: {0}")]
+    BadParams(String),
+
+    #[error("I/O error: {0}")]
+    Io(String),
+
+    #[error("storage error: {0}")]
+    Storage(#[from] StorageError),
+}
+
+// ── Auth ─────────────────────────────────────────────────────────────────────
+
+/// Caller authentication context (resolved from session token).
+#[derive(Debug, Clone)]
+pub struct CallerAuth {
+    /// Ed25519 identity key of the authenticated caller (32 bytes).
+    pub identity_key: Vec<u8>,
+    /// Session token bytes.
+    pub token: Vec<u8>,
+    /// Device ID (optional, for auditing).
+    pub device_id: Option<Vec<u8>>,
+}
+
+/// OPAQUE registration start.
+pub struct RegisterStartReq {
+    pub username: String,
+    pub request_bytes: Vec<u8>,
+}
+
+pub struct RegisterStartResp {
+    pub response_bytes: Vec<u8>,
+}
+
+/// OPAQUE registration finish.
+pub struct RegisterFinishReq {
+    pub username: String,
+    pub upload_bytes: Vec<u8>,
+    pub identity_key: Vec<u8>,
+}
+
+pub struct RegisterFinishResp {
+    pub success: bool,
+}
+
+/// OPAQUE login start.
+pub struct LoginStartReq {
+    pub username: String,
+    pub request_bytes: Vec<u8>,
+}
+
+pub struct LoginStartResp {
+    pub response_bytes: Vec<u8>,
+}
+
+/// OPAQUE login finish.
+pub struct LoginFinishReq {
+    pub username: String,
+    pub finalization_bytes: Vec<u8>,
+    pub identity_key: Vec<u8>,
+}
+
+pub struct LoginFinishResp {
+    pub session_token: Vec<u8>,
+}
+
+// ── Delivery ─────────────────────────────────────────────────────────────────
+
+/// An envelope pairing a sequence number with an opaque payload.
+#[derive(Debug, Clone)]
+pub struct Envelope {
+    pub seq: u64,
+    pub data: Vec<u8>,
+}
+
+pub struct EnqueueReq {
+    pub recipient_key: Vec<u8>,
+    pub payload: Vec<u8>,
+    pub channel_id: Vec<u8>,
+    pub ttl_secs: u32,
+}
+
+pub struct EnqueueResp {
+    pub seq: u64,
+    pub delivery_proof: Vec<u8>,
+}
+
+pub struct FetchReq {
+    pub recipient_key: Vec<u8>,
+    pub channel_id: Vec<u8>,
+    pub limit: u32,
+}
+
+pub struct FetchResp {
+    pub payloads: Vec<Envelope>,
+}
+
+pub struct PeekReq {
+    pub recipient_key: Vec<u8>,
+    pub channel_id: Vec<u8>,
+    pub limit: u32,
+}
+
+pub struct PeekResp {
+    pub payloads: Vec<Envelope>,
+}
+
+pub struct AckReq {
+    pub recipient_key: Vec<u8>,
+    pub channel_id: Vec<u8>,
+    pub seq_up_to: u64,
+}
+
+pub struct BatchEnqueueReq {
+    pub recipient_keys: Vec<Vec<u8>>,
+    pub payload: Vec<u8>,
+    pub channel_id: Vec<u8>,
+    pub ttl_secs: u32,
+}
+
+pub struct BatchEnqueueResp {
+    pub seqs: Vec<u64>,
+}
+
+// ── Keys ─────────────────────────────────────────────────────────────────────
+
+pub struct UploadKeyPackageReq {
+    pub identity_key: Vec<u8>,
+    pub package: Vec<u8>,
+}
+
+pub struct UploadKeyPackageResp {
+    pub fingerprint: Vec<u8>,
+}
+
+pub struct FetchKeyPackageReq {
+    pub identity_key: Vec<u8>,
+}
+
+pub struct FetchKeyPackageResp {
+    pub package: Vec<u8>,
+}
+
+pub struct UploadHybridKeyReq {
+    pub identity_key: Vec<u8>,
+    pub hybrid_public_key: Vec<u8>,
+}
+
+pub struct FetchHybridKeyReq {
+    pub identity_key: Vec<u8>,
+}
+
+pub struct FetchHybridKeyResp {
+    pub hybrid_public_key: Vec<u8>,
+}
+
+pub struct FetchHybridKeysReq {
+    pub identity_keys: Vec<Vec<u8>>,
+}
+
+pub struct FetchHybridKeysResp {
+    pub keys: Vec<Vec<u8>>,
+}
+
+// ── Key Transparency / Revocation ────────────────────────────────────
+
+pub struct RevokeKeyReq {
+    pub identity_key: Vec<u8>,
+    pub reason: String,
+}
+
+pub struct RevokeKeyResp {
+    pub success: bool,
+    pub leaf_index: u64,
+}
+
+pub struct CheckRevocationReq {
+    pub identity_key: Vec<u8>,
+}
+
+pub struct CheckRevocationResp {
+    pub revoked: bool,
+    pub reason: String,
+    pub timestamp_ms: u64,
+}
+
+pub struct AuditKeyTransparencyReq {
+    pub start: u64,
+    pub end: u64,
+}
+
+pub struct AuditLogEntry {
+    pub index: u64,
+    pub leaf_hash: Vec<u8>,
+}
+
+pub struct AuditKeyTransparencyResp {
+    pub entries: Vec<AuditLogEntry>,
+    pub tree_size: u64,
+    pub root: Vec<u8>,
+}
+
+// ── Channel ──────────────────────────────────────────────────────────────────
+
+pub struct CreateChannelReq {
+    pub peer_key: Vec<u8>,
+}
+
+pub struct CreateChannelResp {
+    pub channel_id: Vec<u8>,
+    pub was_new: bool,
+}
+
+// ── User ─────────────────────────────────────────────────────────────────────
+
+pub struct ResolveUserReq {
+    pub username: String,
+}
+
+pub struct ResolveUserResp {
+    pub identity_key: Vec<u8>,
+    pub inclusion_proof: Vec<u8>,
+}
+
+pub struct ResolveIdentityReq {
+    pub identity_key: Vec<u8>,
+}
+
+pub struct ResolveIdentityResp {
+    pub username: String,
+}
+
+// ── Blob ─────────────────────────────────────────────────────────────────────
+
+pub struct UploadBlobReq {
+    pub blob_hash: Vec<u8>,
+    pub chunk: Vec<u8>,
+    pub offset: u64,
+    pub total_size: u64,
+    pub mime_type: String,
+}
+
+pub struct UploadBlobResp {
+    pub blob_id: Vec<u8>,
+}
+
+pub struct DownloadBlobReq {
+    pub blob_id: Vec<u8>,
+    pub offset: u64,
+    pub length: u32,
+}
+
+pub struct DownloadBlobResp {
+    pub chunk: Vec<u8>,
+    pub total_size: u64,
+    pub mime_type: String,
+}
+
+// ── Device ───────────────────────────────────────────────────────────────────
+
+pub struct RegisterDeviceReq {
+    pub device_id: Vec<u8>,
+    pub device_name: String,
+}
+
+pub struct RegisterDeviceResp {
+    pub success: bool,
+}
+
+pub struct DeviceInfo {
+    pub device_id: Vec<u8>,
+    pub device_name: String,
+    pub registered_at: u64,
+}
+
+pub struct ListDevicesResp {
+    pub devices: Vec<DeviceInfo>,
+}
+
+pub struct RevokeDeviceReq {
+    pub device_id: Vec<u8>,
+}
+
+pub struct RevokeDeviceResp {
+    pub success: bool,
+}
+
+// ── Group metadata ───────────────────────────────────────────────────
+
+pub struct GroupMetadata {
+    pub group_id: Vec<u8>,
+    pub name: String,
+    pub description: String,
+    pub avatar_hash: Vec<u8>,
+    pub creator_key: Vec<u8>,
+    pub created_at: u64,
+}
+
+pub struct UpdateGroupMetadataReq {
+    pub group_id: Vec<u8>,
+    pub name: String,
+    pub description: String,
+    pub avatar_hash: Vec<u8>,
+}
+
+pub struct ListGroupMembersReq {
+    pub group_id: Vec<u8>,
+}
+
+pub struct GroupMemberInfo {
+    pub identity_key: Vec<u8>,
+    pub username: String,
+    pub joined_at: u64,
+}
+
+pub struct ListGroupMembersResp {
+    pub members: Vec<GroupMemberInfo>,
+}
+
+// ── Moderation ───────────────────────────────────────────────────────────────
+
+pub struct ReportMessageReq {
+    pub encrypted_report: Vec<u8>,
+    pub conversation_id: Vec<u8>,
+    pub reporter_identity: Vec<u8>,
+}
+
+pub struct ReportMessageResp {
+    pub accepted: bool,
+}
+
+pub struct BanUserReq {
+    pub identity_key: Vec<u8>,
+    pub reason: String,
+    pub duration_secs: u64,
+}
+
+pub struct BanUserResp {
+    pub success: bool,
+}
+
+pub struct UnbanUserReq {
+    pub identity_key: Vec<u8>,
+}
+
+pub struct UnbanUserResp {
+    pub success: bool,
+}
+
+pub struct ListReportsReq {
+    pub limit: u32,
+    pub offset: u32,
+}
+
+pub struct ReportEntry {
+    pub id: u64,
+    pub encrypted_report: Vec<u8>,
+    pub conversation_id: Vec<u8>,
+    pub reporter_identity: Vec<u8>,
+    pub timestamp: u64,
+}
+
+pub struct ListReportsResp {
+    pub reports: Vec<ReportEntry>,
+}
+
+pub struct BannedUserEntry {
+    pub identity_key: Vec<u8>,
+    pub reason: String,
+    pub banned_at: u64,
+    pub expires_at: u64,
+}
+
+pub struct ListBannedResp {
+    pub users: Vec<BannedUserEntry>,
+}
+
+// ── P2P ──────────────────────────────────────────────────────────────────────
+
+pub struct PublishEndpointReq {
+    pub identity_key: Vec<u8>,
+    pub node_addr: Vec<u8>,
+}
+
+pub struct ResolveEndpointReq {
+    pub identity_key: Vec<u8>,
+}
+
+pub struct ResolveEndpointResp {
+    pub node_addr: Vec<u8>,
+}
+
+pub struct HealthResp {
+    pub status: String,
+}

crates/quicprochat-server/src/domain/users.rs

@@ -0,0 +1,146 @@
+//! User resolution domain logic — username <-> identity key lookups.
+
+use std::sync::{Arc, Mutex};
+
+use quicprochat_kt::{MerkleLog, RevocationLog, RevocationReason};
+
+use crate::storage::Store;
+
+use super::types::*;
+
+/// Domain service for user/identity resolution.
+pub struct UserService {
+    pub store: Arc<dyn Store>,
+    pub kt_log: Arc<Mutex<MerkleLog>>,
+    pub revocation_log: Arc<Mutex<RevocationLog>>,
+}
+
+impl UserService {
+    pub fn resolve_user(&self, req: ResolveUserReq) -> Result<ResolveUserResp, DomainError> {
+        if req.username.is_empty() {
+            return Err(DomainError::EmptyUsername);
+        }
+
+        let identity_key = self
+            .store
+            .get_user_identity_key(&req.username)?
+            .unwrap_or_default();
+
+        let mut inclusion_proof = Vec::new();
+
+        if !identity_key.is_empty() {
+            if let Ok(log) = self.kt_log.lock() {
+                if let Some(leaf_idx) = log.find(&req.username, &identity_key) {
+                    if let Ok(proof) = log.inclusion_proof(leaf_idx) {
+                        if let Ok(bytes) = proof.to_bytes() {
+                            inclusion_proof = bytes;
+                        }
+                    }
+                }
+            }
+        }
+
+        Ok(ResolveUserResp {
+            identity_key,
+            inclusion_proof,
+        })
+    }
+
+    pub fn resolve_identity(
+        &self,
+        req: ResolveIdentityReq,
+    ) -> Result<ResolveIdentityResp, DomainError> {
+        if req.identity_key.len() != 32 {
+            return Err(DomainError::InvalidIdentityKey(req.identity_key.len()));
+        }
+
+        let username = self
+            .store
+            .resolve_identity_key(&req.identity_key)?
+            .unwrap_or_default();
+
+        Ok(ResolveIdentityResp { username })
+    }
+
+    /// Revoke an identity key in the Key Transparency log.
+    pub fn revoke_key(&self, req: RevokeKeyReq) -> Result<RevokeKeyResp, DomainError> {
+        if req.identity_key.len() != 32 {
+            return Err(DomainError::InvalidIdentityKey(req.identity_key.len()));
+        }
+
+        let reason = RevocationReason::from_tag(&req.reason)
+            .ok_or_else(|| DomainError::BadParams(format!("invalid revocation reason: {}", req.reason)))?;
+
+        let timestamp_ms = std::time::SystemTime::now()
+            .duration_since(std::time::UNIX_EPOCH)
+            .map(|d| d.as_millis() as u64)
+            .unwrap_or(0);
+
+        let mut kt = self.kt_log.lock().map_err(|e| DomainError::Io(e.to_string()))?;
+        let mut revlog = self.revocation_log.lock().map_err(|e| DomainError::Io(e.to_string()))?;
+
+        let leaf_index = revlog
+            .revoke(&mut kt, &req.identity_key, reason, timestamp_ms)
+            .map_err(|e| DomainError::BadParams(e.to_string()))?;
+
+        // Persist updated logs.
+        if let Ok(bytes) = kt.to_bytes() {
+            let _ = self.store.save_kt_log(bytes);
+        }
+        if let Ok(bytes) = revlog.to_bytes() {
+            let _ = self.store.save_revocation_log(bytes);
+        }
+
+        Ok(RevokeKeyResp {
+            success: true,
+            leaf_index,
+        })
+    }
+
+    /// Check if an identity key has been revoked.
+    pub fn check_revocation(&self, req: CheckRevocationReq) -> Result<CheckRevocationResp, DomainError> {
+        let revlog = self.revocation_log.lock().map_err(|e| DomainError::Io(e.to_string()))?;
+
+        if let Some(entry) = revlog.get(&req.identity_key) {
+            Ok(CheckRevocationResp {
+                revoked: true,
+                reason: entry.reason.as_tag().to_string(),
+                timestamp_ms: entry.timestamp_ms,
+            })
+        } else {
+            Ok(CheckRevocationResp {
+                revoked: false,
+                reason: String::new(),
+                timestamp_ms: 0,
+            })
+        }
+    }
+
+    /// Return a range of KT log entries for client-side audit.
+    pub fn audit_key_transparency(
+        &self,
+        req: AuditKeyTransparencyReq,
+    ) -> Result<AuditKeyTransparencyResp, DomainError> {
+        let kt = self.kt_log.lock().map_err(|e| DomainError::Io(e.to_string()))?;
+
+        let end = if req.end == 0 { kt.len() } else { req.end };
+        let log_entries = kt.audit_log(req.start, end);
+
+        let entries: Vec<AuditLogEntry> = log_entries
+            .into_iter()
+            .map(|(index, hash)| AuditLogEntry {
+                index,
+                leaf_hash: hash.to_vec(),
+            })
+            .collect();
+
+        let tree_size = kt.len();
+        let root = kt.root().map(|r| r.to_vec()).unwrap_or_default();
+
+        Ok(AuditKeyTransparencyResp {
+            entries,
+            tree_size,
+            root,
+        })
+    }
+}

crates/quicprochat-server/src/error_codes.rs

@@ -0,0 +1,46 @@
+//! Structured error codes for server RPC responses.
+//!
+//! Every `capnp::Error::failed()` message is prefixed with a stable code
+//! (E001–E020) so clients can match on the code without parsing free-text.
+
+pub const E001_BAD_AUTH_VERSION: &str = "E001";
+pub const E002_EMPTY_TOKEN: &str = "E002";
+pub const E003_INVALID_TOKEN: &str = "E003";
+pub const E004_IDENTITY_KEY_LENGTH: &str = "E004";
+pub const E005_PAYLOAD_EMPTY: &str = "E005";
+pub const E006_PAYLOAD_TOO_LARGE: &str = "E006";
+pub const E007_PACKAGE_EMPTY: &str = "E007";
+pub const E008_PACKAGE_TOO_LARGE: &str = "E008";
+pub const E009_STORAGE_ERROR: &str = "E009";
+pub const E010_OPAQUE_ERROR: &str = "E010";
+pub const E011_USERNAME_EMPTY: &str = "E011";
+pub const E012_WIRE_VERSION: &str = "E012";
+pub const E013_HYBRID_KEY_EMPTY: &str = "E013";
+pub const E014_RATE_LIMITED: &str = "E014";
+pub const E015_QUEUE_FULL: &str = "E015";
+pub const E016_IDENTITY_MISMATCH: &str = "E016";
+pub const E017_SESSION_EXPIRED: &str = "E017";
+pub const E018_USER_EXISTS: &str = "E018";
+pub const E019_NO_PENDING_LOGIN: &str = "E019";
+pub const E020_BAD_PARAMS: &str = "E020";
+pub const E021_CIPHERSUITE_NOT_ALLOWED: &str = "E021";
+pub const E022_CHANNEL_ACCESS_DENIED: &str = "E022";
+pub const E023_CHANNEL_NOT_FOUND: &str = "E023";
+pub const E024_BLOB_TOO_LARGE: &str = "E024";
+pub const E025_BLOB_HASH_LENGTH: &str = "E025";
+pub const E026_BLOB_HASH_MISMATCH: &str = "E026";
+pub const E027_BLOB_NOT_FOUND: &str = "E027";
+pub const E028_ACCOUNT_DELETION_FAILED: &str = "E028";
+pub const E029_DEVICE_LIMIT: &str = "E029";
+pub const E030_DEVICE_NOT_FOUND: &str = "E030";
+#[allow(dead_code)] // used by v2 RPC moderation handlers
+pub const E031_USER_BANNED: &str = "E031";
+#[allow(dead_code)] // used by v2 RPC moderation handlers
+pub const E032_REPORT_EMPTY: &str = "E032";
+#[allow(dead_code)] // used by v2 RPC moderation handlers
+pub const E033_ADMIN_REQUIRED: &str = "E033";
+
+/// Build a `capnp::Error::failed()` with the structured code prefix.
+pub fn coded_error(code: &str, msg: impl std::fmt::Display) -> capnp::Error {
+    capnp::Error::failed(format!("{code}: {msg}"))
+}

crates/quicprochat-server/src/federation/address.rs

@@ -0,0 +1,80 @@
+//! Parse `username@domain` federated addresses.
+//!
+//! A bare `username` (no `@`) is treated as local.
+
+#![allow(dead_code)] // federation not yet wired up
+
+/// A parsed federated address.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct FederatedAddress {
+    pub username: String,
+    pub domain: Option<String>,
+}
+
+impl FederatedAddress {
+    /// Parse a `user@domain` string. Bare `user` → domain is `None`.
+    pub fn parse(input: &str) -> Self {
+        // Split on the *last* '@' so usernames can contain '@' in theory.
+        match input.rsplit_once('@') {
+            Some((user, domain)) if !domain.is_empty() && !user.is_empty() => Self {
+                username: user.to_string(),
+                domain: Some(domain.to_string()),
+            },
+            _ => Self {
+                username: input.to_string(),
+                domain: None,
+            },
+        }
+    }
+
+    /// Returns true if this address refers to a local user (no domain or domain matches local).
+    pub fn is_local(&self, local_domain: &str) -> bool {
+        match &self.domain {
+            None => true,
+            Some(d) => d == local_domain,
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn bare_username() {
+        let addr = FederatedAddress::parse("alice");
+        assert_eq!(addr.username, "alice");
+        assert_eq!(addr.domain, None);
+        assert!(addr.is_local("example.com"));
+    }
+
+    #[test]
+    fn user_at_domain() {
+        let addr = FederatedAddress::parse("alice@remote.example.com");
+        assert_eq!(addr.username, "alice");
+        assert_eq!(addr.domain, Some("remote.example.com".into()));
+        assert!(!addr.is_local("local.example.com"));
+        assert!(addr.is_local("remote.example.com"));
+    }
+
+    #[test]
+    fn trailing_at_is_bare() {
+        let addr = FederatedAddress::parse("alice@");
+        assert_eq!(addr.username, "alice@");
+        assert_eq!(addr.domain, None);
+    }
+
+    #[test]
+    fn leading_at_is_bare() {
+        let addr = FederatedAddress::parse("@domain.com");
+        assert_eq!(addr.username, "@domain.com");
+        assert_eq!(addr.domain, None);
+    }
+
+    #[test]
+    fn multiple_at_uses_last() {
+        let addr = FederatedAddress::parse("user@org@domain.com");
+        assert_eq!(addr.username, "user@org");
+        assert_eq!(addr.domain, Some("domain.com".into()));
+    }
+}

crates/quicprochat-server/src/federation/client.rs

@@ -0,0 +1,288 @@
+//! Outbound federation client: connects to peer servers to relay messages.
+//!
+//! Uses a lazy connection pool (DashMap) to reuse QUIC connections to known peers.
+
+#![allow(dead_code)] // federation not yet wired up
+
+use std::collections::HashMap;
+use std::net::SocketAddr;
+
+use anyhow::Context;
+use dashmap::DashMap;
+use quinn::Endpoint;
+
+use crate::config::EffectiveFederationConfig;
+
+/// Outbound federation client for relaying to peer servers.
+pub struct FederationClient {
+    /// Peer domain → address mapping from config.
+    peer_addresses: HashMap<String, SocketAddr>,
+    /// Lazy QUIC connection pool: domain → active Connection.
+    connections: DashMap<String, quinn::Connection>,
+    /// Local QUIC endpoint (shared for all outbound federation connections).
+    endpoint: Endpoint,
+    /// Local domain (for the FederationAuth.origin field).
+    local_domain: String,
+}
+
+impl FederationClient {
+    /// Create a new federation client from config.
+    ///
+    /// The `endpoint` should be configured with mTLS client credentials.
+    pub fn new(
+        config: &EffectiveFederationConfig,
+        endpoint: Endpoint,
+    ) -> anyhow::Result<Self> {
+        let mut peer_addresses = HashMap::new();
+        for peer in &config.peers {
+            let addr: SocketAddr = peer.address.parse().with_context(|| {
+                format!("parse federation peer address '{}' for '{}'", peer.address, peer.domain)
+            })?;
+            peer_addresses.insert(peer.domain.clone(), addr);
+        }
+
+        Ok(Self {
+            peer_addresses,
+            connections: DashMap::new(),
+            endpoint,
+            local_domain: config.domain.clone(),
+        })
+    }
+
+    /// Check if we have a configured peer for the given domain.
+    pub fn has_peer(&self, domain: &str) -> bool {
+        self.peer_addresses.contains_key(domain)
+    }
+
+    /// List all configured peer domains.
+    pub fn peer_domains(&self) -> Vec<String> {
+        self.peer_addresses.keys().cloned().collect()
+    }
+
+    /// Get the local domain.
+    pub fn local_domain(&self) -> &str {
+        &self.local_domain
+    }
+
+    /// Relay a single enqueue to a remote peer. Returns the seq assigned by the remote server.
+    pub async fn relay_enqueue(
+        &self,
+        domain: &str,
+        recipient_key: &[u8],
+        payload: &[u8],
+        channel_id: &[u8],
+    ) -> anyhow::Result<u64> {
+        let conn = self.get_or_connect(domain).await?;
+        let (send, recv) = conn.open_bi().await.context("open bi stream to peer")?;
+
+        let (reader, writer) = (
+            tokio_util::compat::TokioAsyncReadCompatExt::compat(recv),
+            tokio_util::compat::TokioAsyncWriteCompatExt::compat_write(send),
+        );
+
+        let rpc_network = capnp_rpc::twoparty::VatNetwork::new(
+            reader,
+            writer,
+            capnp_rpc::rpc_twoparty_capnp::Side::Client,
+            Default::default(),
+        );
+
+        let mut rpc_system = capnp_rpc::RpcSystem::new(Box::new(rpc_network), None);
+        let client: quicprochat_proto::federation_capnp::federation_service::Client =
+            rpc_system.bootstrap(capnp_rpc::rpc_twoparty_capnp::Side::Server);
+
+        tokio::task::spawn_local(rpc_system);
+
+        let mut req = client.relay_enqueue_request();
+        {
+            let mut builder = req.get();
+            builder.set_recipient_key(recipient_key);
+            builder.set_payload(payload);
+            builder.set_channel_id(channel_id);
+            builder.set_version(1);
+            let mut auth = builder.init_auth();
+            auth.set_origin(&self.local_domain);
+        }
+
+        let response = req.send().promise.await
+            .map_err(|e| anyhow::anyhow!("federation relay_enqueue failed: {e}"))?;
+        let seq = response.get()
+            .map_err(|e| anyhow::anyhow!("read relay_enqueue response: {e}"))?
+            .get_seq();
+
+        Ok(seq)
+    }
+
+    /// Proxy a key package fetch to a remote peer.
+    pub async fn proxy_fetch_key_package(
+        &self,
+        domain: &str,
+        identity_key: &[u8],
+    ) -> anyhow::Result<Option<Vec<u8>>> {
+        let conn = self.get_or_connect(domain).await?;
+        let (send, recv) = conn.open_bi().await.context("open bi stream to peer")?;
+
+        let (reader, writer) = (
+            tokio_util::compat::TokioAsyncReadCompatExt::compat(recv),
+            tokio_util::compat::TokioAsyncWriteCompatExt::compat_write(send),
+        );
+
+        let rpc_network = capnp_rpc::twoparty::VatNetwork::new(
+            reader,
+            writer,
+            capnp_rpc::rpc_twoparty_capnp::Side::Client,
+            Default::default(),
+        );
+
+        let mut rpc_system = capnp_rpc::RpcSystem::new(Box::new(rpc_network), None);
+        let client: quicprochat_proto::federation_capnp::federation_service::Client =
+            rpc_system.bootstrap(capnp_rpc::rpc_twoparty_capnp::Side::Server);
+
+        tokio::task::spawn_local(rpc_system);
+
+        let mut req = client.proxy_fetch_key_package_request();
+        {
+            let mut builder = req.get();
+            builder.set_identity_key(identity_key);
+            let mut auth = builder.init_auth();
+            auth.set_origin(&self.local_domain);
+        }
+
+        let response = req.send().promise.await
+            .map_err(|e| anyhow::anyhow!("federation proxy_fetch_key_package failed: {e}"))?;
+        let pkg = response.get()
+            .map_err(|e| anyhow::anyhow!("read proxy_fetch_key_package response: {e}"))?
+            .get_package()
+            .map_err(|e| anyhow::anyhow!("get package: {e}"))?;
+
+        if pkg.is_empty() {
+            Ok(None)
+        } else {
+            Ok(Some(pkg.to_vec()))
+        }
+    }
+
+    /// Proxy a hybrid key fetch to a remote peer.
+    pub async fn proxy_fetch_hybrid_key(
+        &self,
+        domain: &str,
+        identity_key: &[u8],
+    ) -> anyhow::Result<Option<Vec<u8>>> {
+        let conn = self.get_or_connect(domain).await?;
+        let (send, recv) = conn.open_bi().await.context("open bi stream to peer")?;
+
+        let (reader, writer) = (
+            tokio_util::compat::TokioAsyncReadCompatExt::compat(recv),
+            tokio_util::compat::TokioAsyncWriteCompatExt::compat_write(send),
+        );
+
+        let rpc_network = capnp_rpc::twoparty::VatNetwork::new(
+            reader,
+            writer,
+            capnp_rpc::rpc_twoparty_capnp::Side::Client,
+            Default::default(),
+        );
+
+        let mut rpc_system = capnp_rpc::RpcSystem::new(Box::new(rpc_network), None);
+        let client: quicprochat_proto::federation_capnp::federation_service::Client =
+            rpc_system.bootstrap(capnp_rpc::rpc_twoparty_capnp::Side::Server);
+
+        tokio::task::spawn_local(rpc_system);
+
+        let mut req = client.proxy_fetch_hybrid_key_request();
+        {
+            let mut builder = req.get();
+            builder.set_identity_key(identity_key);
+            let mut auth = builder.init_auth();
+            auth.set_origin(&self.local_domain);
+        }
+
+        let response = req.send().promise.await
+            .map_err(|e| anyhow::anyhow!("federation proxy_fetch_hybrid_key failed: {e}"))?;
+        let pk = response.get()
+            .map_err(|e| anyhow::anyhow!("read proxy_fetch_hybrid_key response: {e}"))?
+            .get_hybrid_public_key()
+            .map_err(|e| anyhow::anyhow!("get hybrid_public_key: {e}"))?;
+
+        if pk.is_empty() {
+            Ok(None)
+        } else {
+            Ok(Some(pk.to_vec()))
+        }
+    }
+
+    /// Proxy a user resolution to a remote peer.
+    pub async fn proxy_resolve_user(
+        &self,
+        domain: &str,
+        username: &str,
+    ) -> anyhow::Result<Option<Vec<u8>>> {
+        let conn = self.get_or_connect(domain).await?;
+        let (send, recv) = conn.open_bi().await.context("open bi stream to peer")?;
+
+        let (reader, writer) = (
+            tokio_util::compat::TokioAsyncReadCompatExt::compat(recv),
+            tokio_util::compat::TokioAsyncWriteCompatExt::compat_write(send),
+        );
+
+        let rpc_network = capnp_rpc::twoparty::VatNetwork::new(
+            reader,
+            writer,
+            capnp_rpc::rpc_twoparty_capnp::Side::Client,
+            Default::default(),
+        );
+
+        let mut rpc_system = capnp_rpc::RpcSystem::new(Box::new(rpc_network), None);
+        let client: quicprochat_proto::federation_capnp::federation_service::Client =
+            rpc_system.bootstrap(capnp_rpc::rpc_twoparty_capnp::Side::Server);
+
+        tokio::task::spawn_local(rpc_system);
+
+        let mut req = client.proxy_resolve_user_request();
+        {
+            let mut builder = req.get();
+            builder.set_username(username);
+            let mut auth = builder.init_auth();
+            auth.set_origin(&self.local_domain);
+        }
+
+        let response = req.send().promise.await
+            .map_err(|e| anyhow::anyhow!("federation proxy_resolve_user failed: {e}"))?;
+        let key = response.get()
+            .map_err(|e| anyhow::anyhow!("read proxy_resolve_user response: {e}"))?
+            .get_identity_key()
+            .map_err(|e| anyhow::anyhow!("get identity_key: {e}"))?;
+
+        if key.is_empty() {
+            Ok(None)
+        } else {
+            Ok(Some(key.to_vec()))
+        }
+    }
+
+    /// Get an existing connection or create a new one to a peer domain.
+    async fn get_or_connect(&self, domain: &str) -> anyhow::Result<quinn::Connection> {
+        // Check for cached connection that's still alive.
+        if let Some(conn) = self.connections.get(domain) {
+            if conn.close_reason().is_none() {
+                return Ok(conn.clone());
+            }
+        }
+
+        let addr = self.peer_addresses.get(domain).ok_or_else(|| {
+            anyhow::anyhow!("no federation peer configured for domain '{domain}'")
+        })?;
+
+        tracing::info!(domain = domain, addr = %addr, "connecting to federation peer");
+
+        let conn = self
+            .endpoint
+            .connect(*addr, domain)
+            .map_err(|e| anyhow::anyhow!("federation connect to {domain}: {e}"))?
+            .await
+            .with_context(|| format!("federation QUIC handshake with {domain}"))?;
+
+        self.connections.insert(domain.to_string(), conn.clone());
+        Ok(conn)
+    }
+}

crates/quicprochat-server/src/federation/mod.rs

@@ -0,0 +1,14 @@
+//! Federation subsystem: server-to-server message relay over mutual TLS + QUIC.
+//!
+//! When federation is enabled, the server binds a second QUIC endpoint on a
+//! dedicated port (default 7001) that only accepts connections from known peers
+//! authenticated via mTLS. Inbound requests are handled by [`service::FederationServiceImpl`],
+//! which delegates to the local [`Store`]. Outbound relay uses [`client::FederationClient`].
+
+pub mod address;
+pub mod client;
+pub mod routing;
+pub mod service;
+pub mod tls;
+
+pub use client::FederationClient;

crates/quicprochat-server/src/federation/routing.rs

@@ -0,0 +1,45 @@
+//! Federation routing: determine whether a recipient is local or remote.
+
+use std::sync::Arc;
+
+use crate::storage::Store;
+
+/// Where a message should be delivered.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum Destination {
+    /// Recipient is on this server.
+    Local,
+    /// Recipient's home server is the given domain.
+    Remote(String),
+}
+
+/// Resolve a recipient identity key to a routing destination.
+///
+/// 1. Check the `identity_home_servers` table for an explicit mapping.
+/// 2. If no mapping exists, assume local (backwards compatible with single-server deployments).
+pub fn resolve_destination(
+    store: &Arc<dyn Store>,
+    recipient_key: &[u8],
+    local_domain: &str,
+) -> Destination {
+    match store.get_identity_home_server(recipient_key) {
+        Ok(Some(domain)) if domain != local_domain => Destination::Remote(domain),
+        _ => Destination::Local,
+    }
+}
+
+#[cfg(test)]
+#[allow(clippy::unwrap_used)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn unknown_identity_routes_local() {
+        let store: Arc<dyn Store> =
+            Arc::new(crate::storage::FileBackedStore::open(
+                tempfile::tempdir().unwrap().path(),
+            ).unwrap());
+        let dest = resolve_destination(&store, &[1u8; 32], "local.example.com");
+        assert_eq!(dest, Destination::Local);
+    }
+}

crates/quicprochat-server/src/federation/service.rs

@@ -0,0 +1,349 @@
+//! Inbound federation handler: implements `FederationService` Cap'n Proto interface.
+//!
+//! Delegates all operations to the local [`Store`], acting as a trusted relay
+//! from authenticated peer servers.
+//!
+//! **Security:** Each handler validates the request's `origin` field against
+//! the `verified_peer_domain` extracted from the mTLS client certificate at
+//! connection time. Per-peer rate limits prevent abuse.
+
+use std::sync::Arc;
+
+use capnp::capability::Promise;
+use dashmap::DashMap;
+use quicprochat_proto::federation_capnp::federation_service;
+use tokio::sync::Notify;
+
+use crate::auth::RateEntry;
+use crate::storage::Store;
+
+/// Per-peer federation rate limit: max requests within a 60-second window.
+const FED_RATE_LIMIT_WINDOW_SECS: u64 = 60;
+const FED_RATE_LIMIT_MAX: u32 = 200;
+
+/// Inbound federation RPC handler.
+pub struct FederationServiceImpl {
+    pub store: Arc<dyn Store>,
+    pub waiters: Arc<DashMap<Vec<u8>, Arc<Notify>>>,
+    pub local_domain: String,
+    /// The peer domain extracted from the mTLS client certificate's CN/SAN
+    /// at connection time. All requests must declare an `origin` matching this.
+    pub verified_peer_domain: Option<String>,
+    /// Per-peer rate limiter (keyed by peer domain).
+    pub rate_limits: Arc<DashMap<String, RateEntry>>,
+}
+
+/// Validate that the request's `origin` matches the mTLS-verified peer domain.
+fn validate_origin(
+    verified: &Option<String>,
+    declared: &str,
+) -> Result<(), capnp::Error> {
+    match verified {
+        Some(ref expected) if expected == declared => Ok(()),
+        Some(ref expected) => Err(capnp::Error::failed(format!(
+            "federation auth: origin '{}' does not match mTLS cert '{}'",
+            declared, expected
+        ))),
+        None => Err(capnp::Error::failed(
+            "federation auth: no verified peer domain (mTLS required)".into(),
+        )),
+    }
+}
+
+/// Extract and validate the origin string from the request's auth field.
+fn extract_and_validate_origin(
+    service: &FederationServiceImpl,
+    get_auth: Result<quicprochat_proto::federation_capnp::federation_auth::Reader<'_>, capnp::Error>,
+) -> Result<String, capnp::Error> {
+    let auth = get_auth
+        .map_err(|_| capnp::Error::failed("federation auth: missing auth field".into()))?;
+    let origin_reader = auth.get_origin()
+        .map_err(|_| capnp::Error::failed("federation auth: missing origin".into()))?;
+    let origin = origin_reader.to_str()
+        .map_err(|_| capnp::Error::failed("federation auth: origin is not valid UTF-8".into()))?;
+
+    if origin.is_empty() {
+        return Err(capnp::Error::failed("federation auth: origin must not be empty".into()));
+    }
+
+    validate_origin(&service.verified_peer_domain, origin)?;
+    check_federation_rate_limit(&service.rate_limits, origin)?;
+
+    Ok(origin.to_string())
+}
+
+/// Per-peer federation rate limiter.
+fn check_federation_rate_limit(
+    rate_limits: &DashMap<String, RateEntry>,
+    peer_domain: &str,
+) -> Result<(), capnp::Error> {
+    let now = crate::auth::current_timestamp();
+    let mut entry = rate_limits.entry(peer_domain.to_string()).or_insert(RateEntry {
+        count: 0,
+        window_start: now,
+    });
+
+    if now - entry.window_start >= FED_RATE_LIMIT_WINDOW_SECS {
+        entry.count = 1;
+        entry.window_start = now;
+    } else {
+        entry.count += 1;
+        if entry.count > FED_RATE_LIMIT_MAX {
+            return Err(capnp::Error::failed(format!(
+                "federation rate limit exceeded for peer '{peer_domain}'"
+            )));
+        }
+    }
+    Ok(())
+}
+
+impl federation_service::Server for FederationServiceImpl {
+    fn relay_enqueue(
+        &mut self,
+        params: federation_service::RelayEnqueueParams,
+        mut results: federation_service::RelayEnqueueResults,
+    ) -> Promise<(), capnp::Error> {
+        let p = match params.get() {
+            Ok(p) => p,
+            Err(e) => return Promise::err(capnp::Error::failed(format!("bad params: {e}"))),
+        };
+
+        // Validate origin against mTLS cert and apply rate limit.
+        let origin = match extract_and_validate_origin(self, p.get_auth()) {
+            Ok(o) => o,
+            Err(e) => return Promise::err(e),
+        };
+
+        let recipient_key = match p.get_recipient_key() {
+            Ok(v) => v.to_vec(),
+            Err(e) => return Promise::err(capnp::Error::failed(format!("bad recipient_key: {e}"))),
+        };
+        let payload = match p.get_payload() {
+            Ok(v) => v.to_vec(),
+            Err(e) => return Promise::err(capnp::Error::failed(format!("bad payload: {e}"))),
+        };
+        let channel_id = p.get_channel_id().unwrap_or_default().to_vec();
+
+        if recipient_key.len() != 32 {
+            return Promise::err(capnp::Error::failed("recipient_key must be 32 bytes".into()));
+        }
+        if payload.is_empty() {
+            return Promise::err(capnp::Error::failed("payload must not be empty".into()));
+        }
+
+        let seq = match self.store.enqueue(&recipient_key, &channel_id, payload, None) {
+            Ok(s) => s,
+            Err(e) => return Promise::err(capnp::Error::failed(format!("store error: {e}"))),
+        };
+
+        results.get().set_seq(seq);
+
+        // Wake any waiting fetchWait clients.
+        if let Some(waiter) = self.waiters.get(&recipient_key) {
+            waiter.notify_waiters();
+        }
+
+        tracing::info!(
+            origin = %origin,
+            recipient_prefix = %hex::encode(&recipient_key[..4]),
+            seq = seq,
+            "federation: relayed enqueue"
+        );
+
+        Promise::ok(())
+    }
+
+    fn relay_batch_enqueue(
+        &mut self,
+        params: federation_service::RelayBatchEnqueueParams,
+        mut results: federation_service::RelayBatchEnqueueResults,
+    ) -> Promise<(), capnp::Error> {
+        let p = match params.get() {
+            Ok(p) => p,
+            Err(e) => return Promise::err(capnp::Error::failed(format!("bad params: {e}"))),
+        };
+
+        // Validate origin against mTLS cert and apply rate limit.
+        let _origin = match extract_and_validate_origin(self, p.get_auth()) {
+            Ok(o) => o,
+            Err(e) => return Promise::err(e),
+        };
+
+        let recipient_keys = match p.get_recipient_keys() {
+            Ok(v) => v,
+            Err(e) => return Promise::err(capnp::Error::failed(format!("bad recipient_keys: {e}"))),
+        };
+        let payload = match p.get_payload() {
+            Ok(v) => v.to_vec(),
+            Err(e) => return Promise::err(capnp::Error::failed(format!("bad payload: {e}"))),
+        };
+        let channel_id = p.get_channel_id().unwrap_or_default().to_vec();
+
+        let mut seqs = Vec::with_capacity(recipient_keys.len() as usize);
+        for i in 0..recipient_keys.len() {
+            let rk = match recipient_keys.get(i) {
+                Ok(v) => v.to_vec(),
+                Err(e) => return Promise::err(capnp::Error::failed(format!("bad key[{i}]: {e}"))),
+            };
+            if rk.len() != 32 {
+                return Promise::err(capnp::Error::failed(
+                    format!("recipient_key[{i}] must be 32 bytes"),
+                ));
+            }
+            let seq = match self.store.enqueue(&rk, &channel_id, payload.clone(), None) {
+                Ok(s) => s,
+                Err(e) => return Promise::err(capnp::Error::failed(format!("store error: {e}"))),
+            };
+            seqs.push(seq);
+            if let Some(waiter) = self.waiters.get(&rk) {
+                waiter.notify_waiters();
+            }
+        }
+
+        let mut list = results.get().init_seqs(seqs.len() as u32);
+        for (i, seq) in seqs.iter().enumerate() {
+            list.set(i as u32, *seq);
+        }
+
+        tracing::info!(
+            recipient_count = recipient_keys.len(),
+            "federation: relayed batch_enqueue"
+        );
+
+        Promise::ok(())
+    }
+
+    fn proxy_fetch_key_package(
+        &mut self,
+        params: federation_service::ProxyFetchKeyPackageParams,
+        mut results: federation_service::ProxyFetchKeyPackageResults,
+    ) -> Promise<(), capnp::Error> {
+        let p = match params.get() {
+            Ok(p) => p,
+            Err(e) => return Promise::err(capnp::Error::failed(format!("bad params: {e}"))),
+        };
+
+        // Validate origin against mTLS cert and apply rate limit.
+        if let Err(e) = extract_and_validate_origin(self, p.get_auth()) {
+            return Promise::err(e);
+        }
+
+        let identity_key = match p.get_identity_key() {
+            Ok(v) => v.to_vec(),
+            Err(e) => return Promise::err(capnp::Error::failed(format!("bad identity_key: {e}"))),
+        };
+
+        match self.store.fetch_key_package(&identity_key) {
+            Ok(Some(pkg)) => results.get().set_package(&pkg),
+            Ok(None) => results.get().set_package(&[]),
+            Err(e) => return Promise::err(capnp::Error::failed(format!("store error: {e}"))),
+        }
+
+        Promise::ok(())
+    }
+
+    fn proxy_fetch_hybrid_key(
+        &mut self,
+        params: federation_service::ProxyFetchHybridKeyParams,
+        mut results: federation_service::ProxyFetchHybridKeyResults,
+    ) -> Promise<(), capnp::Error> {
+        let p = match params.get() {
+            Ok(p) => p,
+            Err(e) => return Promise::err(capnp::Error::failed(format!("bad params: {e}"))),
+        };
+
+        // Validate origin against mTLS cert and apply rate limit.
+        if let Err(e) = extract_and_validate_origin(self, p.get_auth()) {
+            return Promise::err(e);
+        }
+
+        let identity_key = match p.get_identity_key() {
+            Ok(v) => v.to_vec(),
+            Err(e) => return Promise::err(capnp::Error::failed(format!("bad identity_key: {e}"))),
+        };
+
+        match self.store.fetch_hybrid_key(&identity_key) {
+            Ok(Some(pk)) => results.get().set_hybrid_public_key(&pk),
+            Ok(None) => results.get().set_hybrid_public_key(&[]),
+            Err(e) => return Promise::err(capnp::Error::failed(format!("store error: {e}"))),
+        }
+
+        Promise::ok(())
+    }
+
+    fn proxy_resolve_user(
+        &mut self,
+        params: federation_service::ProxyResolveUserParams,
+        mut results: federation_service::ProxyResolveUserResults,
+    ) -> Promise<(), capnp::Error> {
+        let p = match params.get() {
+            Ok(p) => p,
+            Err(e) => return Promise::err(capnp::Error::failed(format!("bad params: {e}"))),
+        };
+
+        // Validate origin against mTLS cert and apply rate limit.
+        if let Err(e) = extract_and_validate_origin(self, p.get_auth()) {
+            return Promise::err(e);
+        }
+
+        let username = match p.get_username() {
+            Ok(u) => match u.to_str() {
+                Ok(s) => s.to_string(),
+                Err(e) => return Promise::err(capnp::Error::failed(format!("bad utf-8: {e}"))),
+            },
+            Err(e) => return Promise::err(capnp::Error::failed(format!("bad params: {e}"))),
+        };
+
+        match self.store.get_user_identity_key(&username) {
+            Ok(Some(key)) => results.get().set_identity_key(&key),
+            Ok(None) => results.get().set_identity_key(&[]),
+            Err(e) => return Promise::err(capnp::Error::failed(format!("store error: {e}"))),
+        }
+
+        Promise::ok(())
+    }
+
+    fn federation_health(
+        &mut self,
+        _params: federation_service::FederationHealthParams,
+        mut results: federation_service::FederationHealthResults,
+    ) -> Promise<(), capnp::Error> {
+        // Health check does not require origin validation (diagnostic endpoint).
+        results.get().set_status("ok");
+        results.get().set_server_domain(&self.local_domain);
+        Promise::ok(())
+    }
+}
+
+/// Extract the peer domain from the mTLS client certificate's first SAN (DNS name)
+/// or CN, given the QUIC connection's peer identity (a certificate chain).
+pub fn extract_peer_domain(conn: &quinn::Connection) -> Option<String> {
+    let identity = conn.peer_identity()?;
+    let certs = identity.downcast::<Vec<rustls::pki_types::CertificateDer<'static>>>().ok()?;
+    let first_cert = certs.first()?;
+
+    // Parse the DER certificate to extract SAN DNS names or CN.
+    let (_, parsed) = x509_parser::parse_x509_certificate(first_cert.as_ref()).ok()?;
+
+    // Prefer SAN DNS names.
+    if let Ok(Some(san)) = parsed.subject_alternative_name() {
+        for name in &san.value.general_names {
+            if let x509_parser::extensions::GeneralName::DNSName(dns) = name {
+                return Some(dns.to_string());
+            }
+        }
+    }
+
+    // Fall back to CN.
+    for rdn in parsed.subject().iter() {
+        for attr in rdn.iter() {
+            if attr.attr_type() == &x509_parser::oid_registry::OID_X509_COMMON_NAME {
+                if let Ok(cn) = attr.as_str() {
+                    return Some(cn.to_string());
+                }
+            }
+        }
+    }
+
+    None
+}

crates/quicprochat-server/src/federation/tls.rs

@@ -0,0 +1,85 @@
+//! Build mTLS server/client configs for the federation endpoint.
+//!
+//! Federation uses a separate CA from the public-facing QUIC endpoint.
+//! Both server and client present certificates; the server verifies the client
+//! cert is signed by the federation CA.
+
+use std::path::Path;
+use std::sync::Arc;
+
+use anyhow::Context;
+use quinn::ServerConfig;
+use quinn_proto::crypto::rustls::QuicServerConfig;
+use rustls::pki_types::{CertificateDer, PrivateKeyDer};
+use rustls::version::TLS13;
+
+/// Build a QUIC server config for the federation listener with mutual TLS.
+///
+/// `cert`/`key`: this server's federation certificate and private key.
+/// `ca`: the federation CA certificate used to verify peer certificates.
+pub fn build_federation_server_config(
+    cert_path: &Path,
+    key_path: &Path,
+    ca_path: &Path,
+) -> anyhow::Result<ServerConfig> {
+    let cert_bytes = std::fs::read(cert_path)
+        .with_context(|| format!("read federation cert: {:?}", cert_path))?;
+    let key_bytes = std::fs::read(key_path)
+        .with_context(|| format!("read federation key: {:?}", key_path))?;
+    let ca_bytes = std::fs::read(ca_path)
+        .with_context(|| format!("read federation CA: {:?}", ca_path))?;
+
+    let cert_chain = vec![CertificateDer::from(cert_bytes)];
+    let key = PrivateKeyDer::try_from(key_bytes)
+        .map_err(|_| anyhow::anyhow!("invalid federation private key"))?;
+
+    // Build a root cert store with the federation CA for client verification.
+    let mut root_store = rustls::RootCertStore::empty();
+    root_store
+        .add(CertificateDer::from(ca_bytes))
+        .context("add federation CA to root store")?;
+
+    let client_verifier = rustls::server::WebPkiClientVerifier::builder(Arc::new(root_store))
+        .build()
+        .context("build client cert verifier")?;
+
+    let mut tls = rustls::ServerConfig::builder_with_protocol_versions(&[&TLS13])
+        .with_client_cert_verifier(client_verifier)
+        .with_single_cert(cert_chain, key)?;
+    tls.alpn_protocols = vec![b"quicprochat/federation/1".to_vec()];
+
+    let crypto = QuicServerConfig::try_from(tls)
+        .map_err(|e| anyhow::anyhow!("invalid federation server TLS config: {e}"))?;
+
+    Ok(ServerConfig::with_crypto(Arc::new(crypto)))
+}
+
+/// Build a QUIC client config for connecting to a federation peer with mutual TLS.
+pub fn build_federation_client_config(
+    cert_path: &Path,
+    key_path: &Path,
+    ca_path: &Path,
+) -> anyhow::Result<rustls::ClientConfig> {
+    let cert_bytes = std::fs::read(cert_path)
+        .with_context(|| format!("read federation cert: {:?}", cert_path))?;
+    let key_bytes = std::fs::read(key_path)
+        .with_context(|| format!("read federation key: {:?}", key_path))?;
+    let ca_bytes = std::fs::read(ca_path)
+        .with_context(|| format!("read federation CA: {:?}", ca_path))?;
+
+    let cert_chain = vec![CertificateDer::from(cert_bytes)];
+    let key = PrivateKeyDer::try_from(key_bytes)
+        .map_err(|_| anyhow::anyhow!("invalid federation client private key"))?;
+
+    let mut root_store = rustls::RootCertStore::empty();
+    root_store
+        .add(CertificateDer::from(ca_bytes))
+        .context("add federation CA to root store")?;
+
+    let tls = rustls::ClientConfig::builder_with_protocol_versions(&[&TLS13])
+        .with_root_certificates(root_store)
+        .with_client_auth_cert(cert_chain, key)
+        .context("set client auth cert")?;
+
+    Ok(tls)
+}

crates/quicprochat-server/src/hooks.rs

@@ -0,0 +1,198 @@
+//! Server-side plugin hooks for extending quicprochat.
+//!
+//! Implement the [`ServerHooks`] trait to intercept server events — message delivery,
+//! authentication, channel creation, and more. Hooks fire after validation but before
+//! storage, so they can inspect, log, or reject operations.
+//!
+//! # Built-in implementations
+//!
+//! - [`NoopHooks`] — does nothing (default when no hooks are configured)
+//! - [`TracingHooks`] — logs all events via `tracing` at info/debug level
+//!
+//! # Writing a custom hook
+//!
+//! ```rust,ignore
+//! use quicprochat_server::hooks::{ServerHooks, HookAction, MessageEvent};
+//!
+//! struct ModeratorHook {
+//!     banned_words: Vec<String>,
+//! }
+//!
+//! impl ServerHooks for ModeratorHook {
+//!     fn on_message_enqueue(&self, event: &MessageEvent) -> HookAction {
+//!         // Can't inspect encrypted content (E2E), but can enforce rate limits,
+//!         // payload size limits, or sender restrictions.
+//!         if event.payload_len > 1_000_000 {
+//!             return HookAction::Reject("payload too large".into());
+//!         }
+//!         HookAction::Continue
+//!     }
+//! }
+//! ```
+
+/// The result of a hook invocation.
+#[derive(Clone, Debug)]
+pub enum HookAction {
+    /// Allow the operation to proceed.
+    Continue,
+    /// Reject the operation with a reason (returned to the client as an error).
+    Reject(String),
+}
+
+/// Event data for message enqueue operations.
+#[derive(Clone, Debug)]
+pub struct MessageEvent {
+    /// Sender's identity key (32 bytes), if known (None in sealed sender mode).
+    pub sender_identity: Option<Vec<u8>>,
+    /// Recipient's identity key (32 bytes).
+    pub recipient_key: Vec<u8>,
+    /// Channel ID (16 bytes) if this is a DM channel message.
+    pub channel_id: Vec<u8>,
+    /// Length of the encrypted payload in bytes.
+    pub payload_len: usize,
+    /// Server-assigned sequence number.
+    pub seq: u64,
+}
+
+/// Event data for authentication operations.
+#[derive(Clone, Debug)]
+pub struct AuthEvent {
+    /// The username attempting to authenticate.
+    pub username: String,
+    /// Whether the authentication succeeded.
+    pub success: bool,
+    /// Failure reason (empty on success).
+    pub failure_reason: String,
+}
+
+/// Event data for channel creation operations.
+#[derive(Clone, Debug)]
+pub struct ChannelEvent {
+    /// The channel's unique ID (16 bytes).
+    pub channel_id: Vec<u8>,
+    /// Identity key of the initiator.
+    pub initiator_key: Vec<u8>,
+    /// Identity key of the peer.
+    pub peer_key: Vec<u8>,
+    /// True if this is a newly created channel (initiator creates the MLS group).
+    pub was_new: bool,
+}
+
+/// Event data for message fetch operations.
+#[derive(Clone, Debug)]
+pub struct FetchEvent {
+    /// Identity key of the fetcher.
+    pub recipient_key: Vec<u8>,
+    /// Channel ID being fetched from.
+    pub channel_id: Vec<u8>,
+    /// Number of messages returned.
+    pub message_count: usize,
+}
+
+/// Trait for server-side plugin hooks.
+///
+/// All methods have default implementations that return [`HookAction::Continue`],
+/// so you only need to override the events you care about.
+///
+/// Hooks are called synchronously in the RPC handler path. Keep them fast —
+/// offload heavy work (HTTP calls, disk I/O) to background tasks.
+pub trait ServerHooks: Send + Sync {
+    /// Called after validation, before a message is stored in the delivery queue.
+    ///
+    /// Return `HookAction::Reject` to prevent delivery.
+    fn on_message_enqueue(&self, _event: &MessageEvent) -> HookAction {
+        HookAction::Continue
+    }
+
+    /// Called after a batch of messages is enqueued.
+    fn on_batch_enqueue(&self, _events: &[MessageEvent]) {
+        // Default: no-op
+    }
+
+    /// Called after a successful or failed login attempt.
+    fn on_auth(&self, _event: &AuthEvent) {
+        // Default: no-op
+    }
+
+    /// Called after a channel is created or looked up.
+    fn on_channel_created(&self, _event: &ChannelEvent) {
+        // Default: no-op
+    }
+
+    /// Called after messages are fetched from the delivery queue.
+    fn on_fetch(&self, _event: &FetchEvent) {
+        // Default: no-op
+    }
+
+    /// Called when a user registers (OPAQUE registration complete).
+    fn on_user_registered(&self, _username: &str, _identity_key: &[u8]) {
+        // Default: no-op
+    }
+}
+
+/// No-op hook implementation (default).
+pub struct NoopHooks;
+
+impl ServerHooks for NoopHooks {}
+
+/// Hook implementation that logs all events via `tracing`.
+pub struct TracingHooks;
+
+impl ServerHooks for TracingHooks {
+    fn on_message_enqueue(&self, event: &MessageEvent) -> HookAction {
+        tracing::info!(
+            recipient_prefix = %hex_prefix(&event.recipient_key),
+            payload_len = event.payload_len,
+            seq = event.seq,
+            has_sender = event.sender_identity.is_some(),
+            "hook: message enqueued"
+        );
+        HookAction::Continue
+    }
+
+    fn on_batch_enqueue(&self, events: &[MessageEvent]) {
+        tracing::info!(
+            count = events.len(),
+            "hook: batch enqueue"
+        );
+    }
+
+    fn on_auth(&self, event: &AuthEvent) {
+        if event.success {
+            tracing::info!(username = %event.username, "hook: login success");
+        } else {
+            tracing::warn!(
+                username = %event.username,
+                reason = %event.failure_reason,
+                "hook: login failure"
+            );
+        }
+    }
+
+    fn on_channel_created(&self, event: &ChannelEvent) {
+        tracing::info!(
+            channel_id = %hex_prefix(&event.channel_id),
+            was_new = event.was_new,
+            "hook: channel created"
+        );
+    }
+
+    fn on_fetch(&self, event: &FetchEvent) {
+        if event.message_count > 0 {
+            tracing::debug!(
+                recipient_prefix = %hex_prefix(&event.recipient_key),
+                count = event.message_count,
+                "hook: messages fetched"
+            );
+        }
+    }
+
+    fn on_user_registered(&self, username: &str, _identity_key: &[u8]) {
+        tracing::info!(username = %username, "hook: user registered");
+    }
+}
+
+fn hex_prefix(bytes: &[u8]) -> String {
+    let n = bytes.len().min(4);
+    hex::encode(&bytes[..n])
+}

crates/quicprochat-server/src/main.rs

@@ -0,0 +1,783 @@
+//! qpc-server — unified Authentication + Delivery service.
+//!
+//! The server hosts Authentication + Delivery services over QUIC + Cap'n Proto.
+
+use std::{net::IpAddr, net::SocketAddr, path::PathBuf, sync::Arc};
+
+use anyhow::Context;
+use clap::Parser;
+use dashmap::DashMap;
+use opaque_ke::ServerSetup;
+use quicprochat_core::opaque_auth::OpaqueSuite;
+use quicprochat_kt::MerkleLog;
+use quinn::Endpoint;
+use rand::rngs::OsRng;
+use tokio::sync::Notify;
+use tokio::task::LocalSet;
+
+pub mod audit;
+mod auth;
+mod config;
+pub mod domain;
+mod error_codes;
+mod federation;
+pub mod hooks;
+mod metrics;
+mod node_service;
+#[allow(unsafe_code)] // FFI: C-ABI plugin interaction requires unsafe blocks
+mod plugin_loader;
+mod sql_store;
+mod tls;
+mod storage;
+pub mod v2_handlers;
+mod ws_bridge;
+#[cfg(feature = "webtransport")]
+mod webtransport;
+
+use auth::{AuthConfig, PendingLogin, RateEntry, SessionInfo};
+use config::{
+    load_config, merge_config, validate_production_config, DEFAULT_DATA_DIR, DEFAULT_DB_PATH,
+    DEFAULT_LISTEN, DEFAULT_STORE_BACKEND, DEFAULT_TLS_CERT, DEFAULT_TLS_KEY,
+};
+use node_service::{handle_node_connection, spawn_cleanup_task};
+use sql_store::SqlStore;
+use storage::{FileBackedStore, Store};
+use tls::build_server_config;
+
+// ── CLI ───────────────────────────────────────────────────────────────────────
+
+#[derive(Debug, Parser)]
+#[command(
+    name = "qpc-server",
+    about = "quicprochat Delivery Service + Authentication Service",
+    version
+)]
+struct Args {
+    /// Optional path to a TOML config file (fields map to CLI flags).
+    #[arg(long, env = "QPQ_CONFIG")]
+    config: Option<PathBuf>,
+
+    /// QUIC listen address (host:port).
+    #[arg(long, default_value = DEFAULT_LISTEN, env = "QPQ_LISTEN")]
+    listen: String,
+
+    /// Directory for persisted server data (KeyPackages + delivery queues).
+    #[arg(long, default_value = DEFAULT_DATA_DIR, env = "QPQ_DATA_DIR")]
+    data_dir: String,
+
+    /// TLS certificate path (generated automatically if missing).
+    #[arg(long, default_value = DEFAULT_TLS_CERT, env = "QPQ_TLS_CERT")]
+    tls_cert: PathBuf,
+
+    /// TLS private key path (generated automatically if missing).
+    #[arg(long, default_value = DEFAULT_TLS_KEY, env = "QPQ_TLS_KEY")]
+    tls_key: PathBuf,
+
+    /// Required bearer token for auth.version=1 requests. Use --allow-insecure-auth to run without it (dev only).
+    #[arg(long, env = "QPQ_AUTH_TOKEN")]
+    auth_token: Option<String>,
+
+    /// Allow running without QPQ_AUTH_TOKEN (development only).
+    #[arg(long, env = "QPQ_ALLOW_INSECURE_AUTH", default_value_t = false)]
+    allow_insecure_auth: bool,
+
+    /// Enable Sealed Sender: enqueue does not require identity-bound session, only a valid token.
+    #[arg(long, env = "QPQ_SEALED_SENDER", default_value_t = false)]
+    sealed_sender: bool,
+
+    /// Storage backend: "file" (bincode) or "sql" (SQLCipher-encrypted).
+    #[arg(long, default_value = DEFAULT_STORE_BACKEND, env = "QPQ_STORE_BACKEND")]
+    store_backend: String,
+
+    /// Path to the SQLCipher database file (only used when --store-backend=sql).
+    #[arg(long, default_value = DEFAULT_DB_PATH, env = "QPQ_DB_PATH")]
+    db_path: PathBuf,
+
+    /// SQLCipher encryption key. Empty string disables encryption.
+    #[arg(long, default_value = "", env = "QPQ_DB_KEY")]
+    db_key: String,
+
+    /// Metrics HTTP listen address (e.g. 0.0.0.0:9090). If set and metrics enabled, /metrics is served.
+    #[arg(long, env = "QPQ_METRICS_LISTEN")]
+    metrics_listen: Option<String>,
+
+    /// Enable metrics server when metrics_listen is set.
+    #[arg(long, env = "QPQ_METRICS_ENABLED")]
+    metrics_enabled: Option<bool>,
+
+    /// Enable federation (server-to-server message relay).
+    #[arg(long, env = "QPQ_FEDERATION_ENABLED", default_value_t = false)]
+    federation_enabled: bool,
+
+    /// This server's domain for federation addressing (e.g. "chat.example.com").
+    #[arg(long, env = "QPQ_FEDERATION_DOMAIN")]
+    federation_domain: Option<String>,
+
+    /// Federation QUIC listen address (default: 0.0.0.0:7001).
+    #[arg(long, env = "QPQ_FEDERATION_LISTEN")]
+    federation_listen: Option<String>,
+
+    /// Directory containing plugin `.so` / `.dylib` files to load at startup.
+    /// Each library must export `extern "C" fn qpc_plugin_init(vtable: *mut HookVTable) -> i32`.
+    #[arg(long, env = "QPQ_PLUGIN_DIR")]
+    plugin_dir: Option<PathBuf>,
+
+    /// Redact identity key prefixes and payload sizes in audit logs for metadata minimization.
+    #[arg(long, env = "QPQ_REDACT_LOGS", default_value_t = false)]
+    redact_logs: bool,
+
+    /// WebSocket JSON-RPC bridge listen address (e.g. 0.0.0.0:9000). Enables browser connectivity.
+    #[arg(long, env = "QPQ_WS_LISTEN")]
+    ws_listen: Option<String>,
+
+    /// WebTransport (HTTP/3) listen address for browser clients (e.g. 0.0.0.0:7443).
+    /// Requires --features webtransport.
+    #[arg(long, env = "QPQ_WEBTRANSPORT_LISTEN")]
+    webtransport_listen: Option<String>,
+
+    /// Graceful shutdown drain timeout in seconds (default: 30). In-flight RPCs get this
+    /// long to finish after a shutdown signal before connections are forcefully closed.
+    #[arg(long, env = "QPQ_DRAIN_TIMEOUT", default_value_t = config::DEFAULT_DRAIN_TIMEOUT_SECS)]
+    drain_timeout: u64,
+
+    /// Default per-RPC timeout in seconds (default: 30). Individual methods may override.
+    #[arg(long, env = "QPQ_RPC_TIMEOUT", default_value_t = config::DEFAULT_RPC_TIMEOUT_SECS)]
+    rpc_timeout: u64,
+
+    /// Storage/database operation timeout in seconds (default: 10).
+    #[arg(long, env = "QPQ_STORAGE_TIMEOUT", default_value_t = config::DEFAULT_STORAGE_TIMEOUT_SECS)]
+    storage_timeout: u64,
+}
+
+// ── Entry point ───────────────────────────────────────────────────────────────
+
+#[tokio::main]
+async fn main() -> anyhow::Result<()> {
+    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("info")),
+        )
+        .init();
+
+    let args = Args::parse();
+    let file_cfg = load_config(args.config.as_deref())?;
+    let effective = merge_config(&args, &file_cfg);
+
+    let production = std::env::var("QPQ_PRODUCTION")
+        .map(|v| matches!(v.to_lowercase().as_str(), "1" | "true" | "yes"))
+        .unwrap_or(false);
+    if production {
+        validate_production_config(&effective)?;
+    }
+
+    // Optional metrics server: only start when metrics_enabled and metrics_listen are set.
+    if effective.metrics_enabled {
+        if let Some(addr_str) = &effective.metrics_listen {
+            let addr: std::net::SocketAddr = addr_str
+                .parse()
+                .context("metrics_listen must be host:port (e.g. 0.0.0.0:9090)")?;
+            metrics_exporter_prometheus::PrometheusBuilder::new()
+                .with_http_listener(addr)
+                .install()
+                .context("failed to install Prometheus metrics exporter")?;
+            tracing::info!(addr = %addr_str, "metrics server listening on /metrics");
+        }
+    }
+
+    // In non-production, require an explicit opt-out before running without a static token.
+    if !production
+        && effective
+            .auth_token
+            .as_deref()
+            .map(|s| s.is_empty())
+            .unwrap_or(true)
+        && !effective.allow_insecure_auth
+    {
+        anyhow::bail!(
+            "missing QPQ_AUTH_TOKEN; set one or pass --allow-insecure-auth for development"
+        );
+    }
+
+    if effective.allow_insecure_auth
+        && effective
+            .auth_token
+            .as_deref()
+            .map(|s| s.is_empty())
+            .unwrap_or(true)
+    {
+        tracing::warn!("running without QPQ_AUTH_TOKEN (allow-insecure-auth enabled); development only");
+    }
+
+    let listen: SocketAddr = effective
+        .listen
+        .parse()
+        .context("--listen must be host:port")?;
+
+    let mut server_config = build_server_config(&effective.tls_cert, &effective.tls_key, production)
+        .context("failed to build TLS/QUIC server config")?;
+
+    // Harden QUIC transport: idle timeout, limit stream concurrency.
+    let mut transport = quinn::TransportConfig::default();
+    transport.max_idle_timeout(Some(
+        std::time::Duration::from_secs(300)
+            .try_into()
+            .map_err(|e| anyhow::anyhow!("idle timeout: {e}"))?,
+    ));
+    transport.max_concurrent_bidi_streams(1u32.into());
+    transport.max_concurrent_uni_streams(0u32.into());
+    server_config.transport_config(Arc::new(transport));
+
+    // Shared storage — persisted to disk for restart safety.
+    let store: Arc<dyn Store> = match effective.store_backend.as_str() {
+        "sql" => {
+            if let Some(parent) = effective.db_path.parent() {
+                std::fs::create_dir_all(parent).context("create db dir")?;
+            }
+            tracing::info!(
+                path = %effective.db_path.display(),
+                encrypted = !effective.db_key.is_empty(),
+                "opening SQLCipher store"
+            );
+            if effective.db_key.is_empty() {
+                tracing::warn!("db_key is empty; SQL store will be plaintext (development only)");
+            }
+            Arc::new(SqlStore::open(&effective.db_path, &effective.db_key)?)
+        }
+        _ => {
+            tracing::info!(dir = %effective.data_dir, "opening file-backed store");
+            Arc::new(FileBackedStore::open(&effective.data_dir)?)
+        }
+    };
+
+    // Ensure blobs directory exists for file transfer support.
+    std::fs::create_dir_all(PathBuf::from(&effective.data_dir).join("blobs"))
+        .context("create blobs directory")?;
+
+    let auth_cfg = Arc::new(AuthConfig::new(
+        effective.auth_token.clone(),
+        effective.allow_insecure_auth,
+    ));
+    let waiters: Arc<DashMap<Vec<u8>, Arc<Notify>>> = Arc::new(DashMap::new());
+
+    // OPAQUE ServerSetup: load from storage or generate fresh.
+    let opaque_setup: Arc<ServerSetup<OpaqueSuite>> = match store.get_server_setup() {
+        Ok(Some(bytes)) => {
+            let setup = ServerSetup::<OpaqueSuite>::deserialize(&bytes)
+                .map_err(|e| anyhow::anyhow!("corrupt OPAQUE server setup: {e}"))?;
+            tracing::info!("loaded persisted OPAQUE ServerSetup");
+            Arc::new(setup)
+        }
+        Ok(None) => {
+            let setup = ServerSetup::<OpaqueSuite>::new(&mut OsRng);
+            let bytes = setup.serialize().to_vec();
+            store
+                .store_server_setup(bytes)
+                .context("persist OPAQUE ServerSetup")?;
+            tracing::info!("generated and persisted new OPAQUE ServerSetup");
+            Arc::new(setup)
+        }
+        Err(e) => return Err(anyhow::anyhow!("load OPAQUE server setup: {e}")),
+    };
+
+    // Server Ed25519 signing key for delivery proofs: load from storage or generate fresh.
+    let signing_key: Arc<quicprochat_core::IdentityKeypair> = match store.get_signing_key_seed() {
+        Ok(Some(seed_bytes)) => {
+            let seed: [u8; 32] = seed_bytes
+                .as_slice()
+                .try_into()
+                .context("signing key seed must be 32 bytes")?;
+            tracing::info!("loaded persisted server signing key");
+            Arc::new(quicprochat_core::IdentityKeypair::from_seed(seed))
+        }
+        Ok(None) => {
+            let kp = quicprochat_core::IdentityKeypair::generate();
+            store
+                .store_signing_key_seed(kp.seed_bytes().to_vec())
+                .context("persist server signing key")?;
+            tracing::info!("generated and persisted new server signing key");
+            Arc::new(kp)
+        }
+        Err(e) => return Err(anyhow::anyhow!("load server signing key: {e}")),
+    };
+
+    // Key Transparency Merkle log: load from storage or start fresh.
+    let kt_log: Arc<std::sync::Mutex<MerkleLog>> = match store.load_kt_log() {
+        Ok(Some(bytes)) => {
+            match MerkleLog::from_bytes(&bytes) {
+                Ok(log) => {
+                    tracing::info!(entries = log.len(), "loaded persisted KT Merkle log");
+                    Arc::new(std::sync::Mutex::new(log))
+                }
+                Err(e) => {
+                    tracing::warn!(error = %e, "KT log deserialise failed; starting fresh");
+                    Arc::new(std::sync::Mutex::new(MerkleLog::new()))
+                }
+            }
+        }
+        Ok(None) => {
+            tracing::info!("no KT log found; starting fresh");
+            Arc::new(std::sync::Mutex::new(MerkleLog::new()))
+        }
+        Err(e) => return Err(anyhow::anyhow!("load KT log: {e}")),
+    };
+
+    // ── Plugin hooks ──────────────────────────────────────────────────────────
+    let hooks: Arc<dyn hooks::ServerHooks> = if let Some(dir) = &effective.plugin_dir {
+        let plugins = plugin_loader::load_plugins_from_dir(dir);
+        if plugins.is_empty() {
+            tracing::info!(dir = %dir.display(), "plugin_dir set but no plugins loaded");
+            Arc::new(hooks::NoopHooks)
+        } else {
+            tracing::info!(count = plugins.len(), "plugins loaded");
+            let boxed: Vec<Box<dyn hooks::ServerHooks>> = plugins
+                .into_iter()
+                .map(|p| Box::new(p) as Box<dyn hooks::ServerHooks>)
+                .collect();
+            Arc::new(plugin_loader::ChainedHooks::new(boxed))
+        }
+    } else {
+        Arc::new(hooks::NoopHooks)
+    };
+
+    let pending_logins: Arc<DashMap<String, PendingLogin>> = Arc::new(DashMap::new());
+    let sessions: Arc<DashMap<Vec<u8>, SessionInfo>> = Arc::new(DashMap::new());
+    let rate_limits: Arc<DashMap<Vec<u8>, RateEntry>> = Arc::new(DashMap::new());
+    let conn_rate_limits: Arc<DashMap<IpAddr, RateEntry>> = Arc::new(DashMap::new());
+
+    // Background cleanup task (expire sessions, pending logins, rate limits, and stale messages).
+    spawn_cleanup_task(
+        Arc::clone(&sessions),
+        Arc::clone(&pending_logins),
+        Arc::clone(&rate_limits),
+        Arc::clone(&conn_rate_limits),
+        Arc::clone(&store),
+        Arc::clone(&waiters),
+    );
+
+    // ── WebSocket JSON-RPC bridge ──────────────────────────────────────────
+    if let Some(ws_addr_str) = &effective.ws_listen {
+        let ws_addr: SocketAddr = ws_addr_str
+            .parse()
+            .context("--ws-listen must be host:port (e.g. 0.0.0.0:9000)")?;
+        let ws_state = Arc::new(ws_bridge::WsBridgeState {
+            store: Arc::clone(&store),
+            waiters: Arc::clone(&waiters),
+            auth_cfg: Arc::clone(&auth_cfg),
+            sessions: Arc::clone(&sessions),
+            rate_limits: Arc::clone(&rate_limits),
+            sealed_sender: effective.sealed_sender,
+            allow_insecure_auth: effective.allow_insecure_auth,
+        });
+        ws_bridge::spawn_ws_bridge(ws_addr, ws_state);
+    }
+
+    // ── WebTransport (HTTP/3) endpoint ─────────────────────────────────────
+    #[cfg(feature = "webtransport")]
+    if let Some(wt_addr_str) = &effective.webtransport_listen {
+        let wt_addr: SocketAddr = wt_addr_str
+            .parse()
+            .context("--webtransport-listen must be host:port (e.g. 0.0.0.0:7443)")?;
+
+        let wt_server_config = webtransport::build_webtransport_server_config(
+            &effective.tls_cert,
+            &effective.tls_key,
+        )
+        .context("build WebTransport server config")?;
+
+        let wt_state = Arc::new(v2_handlers::ServerState {
+            store: Arc::clone(&store),
+            waiters: Arc::clone(&waiters),
+            auth_cfg: Arc::clone(&auth_cfg),
+            opaque_setup: Arc::clone(&opaque_setup),
+            pending_logins: Arc::clone(&pending_logins),
+            sessions: Arc::clone(&sessions),
+            rate_limits: Arc::clone(&rate_limits),
+            sealed_sender: effective.sealed_sender,
+            hooks: Arc::clone(&hooks),
+            signing_key: Arc::clone(&signing_key),
+            kt_log: Arc::clone(&kt_log),
+            revocation_log: Arc::new(std::sync::Mutex::new(
+                quicprochat_kt::RevocationLog::new(),
+            )),
+            data_dir: PathBuf::from(&effective.data_dir),
+            redact_logs: effective.redact_logs,
+            audit_logger: Arc::new(audit::NoopAuditLogger),
+            draining: Arc::new(std::sync::atomic::AtomicBool::new(false)),
+            seen_message_ids: Arc::new(DashMap::new()),
+            banned_users: Arc::new(DashMap::new()),
+            moderation_reports: Arc::new(std::sync::Mutex::new(Vec::new())),
+            node_id: format!("wt-{}", hex::encode(&signing_key.public_key_bytes()[..4])),
+            start_time: std::time::Instant::now(),
+            storage_backend: effective.store_backend.clone(),
+            federation_client: None,
+            local_domain: effective.federation.as_ref().map(|f| f.domain.clone()).unwrap_or_default(),
+        });
+
+        let wt_registry = Arc::new(v2_handlers::build_registry(
+            std::time::Duration::from_secs(effective.rpc_timeout_secs),
+        ));
+
+        webtransport::spawn_webtransport_listener(wt_addr, wt_server_config, wt_state, wt_registry)
+            .context("spawn WebTransport listener")?;
+    }
+
+    let endpoint = Endpoint::server(server_config, listen)?;
+
+    tracing::info!(
+        addr = %effective.listen,
+        "accepting QUIC connections"
+    );
+
+    // ── Federation setup ─────────────────────────────────────────────────────
+    let federation_client: Option<Arc<federation::FederationClient>> =
+        if let Some(fed_cfg) = &effective.federation {
+            tracing::info!(
+                domain = %fed_cfg.domain,
+                listen = %fed_cfg.listen,
+                peers = fed_cfg.peers.len(),
+                "federation enabled"
+            );
+
+            // Build a client endpoint for outbound federation connections.
+            // For now we create a simple endpoint; full mTLS is used when certs are provided.
+            let client_config = if fed_cfg.federation_cert.exists()
+                && fed_cfg.federation_key.exists()
+                && fed_cfg.federation_ca.exists()
+            {
+                let tls_cfg = federation::tls::build_federation_client_config(
+                    &fed_cfg.federation_cert,
+                    &fed_cfg.federation_key,
+                    &fed_cfg.federation_ca,
+                )
+                .context("build federation client TLS config")?;
+
+                let crypto = quinn::crypto::rustls::QuicClientConfig::try_from(tls_cfg)
+                    .map_err(|e| anyhow::anyhow!("invalid federation client QUIC config: {e}"))?;
+                let mut qc = quinn::ClientConfig::new(Arc::new(crypto));
+                let mut transport = quinn::TransportConfig::default();
+                transport.max_idle_timeout(Some(
+                    std::time::Duration::from_secs(120)
+                        .try_into()
+                        .map_err(|e| anyhow::anyhow!("idle timeout: {e}"))?,
+                ));
+                qc.transport_config(Arc::new(transport));
+                Some(qc)
+            } else {
+                tracing::warn!("federation cert/key/CA not found; outbound federation connections will fail");
+                None
+            };
+
+            let fed_bind: SocketAddr = SocketAddr::from(([0, 0, 0, 0], 0));
+            let mut fed_endpoint = Endpoint::client(fed_bind)
+                .context("create federation client endpoint")?;
+            if let Some(cc) = client_config {
+                fed_endpoint.set_default_client_config(cc);
+            }
+
+            let client = federation::FederationClient::new(fed_cfg, fed_endpoint)
+                .context("create federation client")?;
+
+            // Register configured peers in storage.
+            for peer in &fed_cfg.peers {
+                if let Err(e) = store.upsert_federation_peer(&peer.domain, true) {
+                    tracing::warn!(domain = %peer.domain, error = %e, "failed to register federation peer");
+                }
+            }
+
+            Some(Arc::new(client))
+        } else {
+            None
+        };
+
+    let local_domain: Option<String> = effective.federation.as_ref().map(|f| f.domain.clone());
+
+    // ── Federation listener ──────────────────────────────────────────────────
+    let federation_endpoint: Option<Endpoint> =
+        if let Some(fed_cfg) = &effective.federation {
+            if fed_cfg.federation_cert.exists()
+                && fed_cfg.federation_key.exists()
+                && fed_cfg.federation_ca.exists()
+            {
+                let fed_server_config = federation::tls::build_federation_server_config(
+                    &fed_cfg.federation_cert,
+                    &fed_cfg.federation_key,
+                    &fed_cfg.federation_ca,
+                )
+                .context("build federation server TLS config")?;
+
+                let fed_listen: SocketAddr = fed_cfg
+                    .listen
+                    .parse()
+                    .context("federation listen must be host:port")?;
+
+                let ep = Endpoint::server(fed_server_config, fed_listen)
+                    .context("bind federation QUIC endpoint")?;
+
+                tracing::info!(addr = %fed_cfg.listen, "federation endpoint listening");
+                Some(ep)
+            } else {
+                tracing::warn!("federation certs not found; federation listener not started");
+                None
+            }
+        } else {
+            None
+        };
+
+    // ── mDNS local mesh discovery ─────────────────────────────────────────────
+    // Announce this server on the local network so mesh-mode clients (and other
+    // Freifunk nodes) can discover it automatically without manual configuration.
+    // Non-critical: failures are logged as warnings; the server starts regardless.
+    let _mdns_daemon = {
+        let listen_port: u16 = listen.port();
+        // Use the federation domain as the mDNS instance name when available.
+        let mdns_instance = effective
+            .federation
+            .as_ref()
+            .map(|f| f.domain.clone())
+            .unwrap_or_else(|| "qpc-server".to_string());
+        // mDNS host names must end with a dot.
+        let mdns_host = if mdns_instance.ends_with('.') {
+            mdns_instance.clone()
+        } else {
+            format!("{mdns_instance}.local.")
+        };
+
+        match mdns_sd::ServiceDaemon::new() {
+            Ok(daemon) => {
+                let mut props = std::collections::HashMap::new();
+                props.insert("ver".to_string(), "1".to_string());
+                props.insert("server".to_string(), effective.listen.clone());
+                props.insert("domain".to_string(), mdns_instance.clone());
+
+                match mdns_sd::ServiceInfo::new(
+                    "_quicprochat._udp.local.",
+                    &mdns_instance,
+                    &mdns_host,
+                    &[] as &[std::net::IpAddr],
+                    listen_port,
+                    Some(props),
+                ) {
+                    Ok(info) => match daemon.register(info) {
+                        Ok(()) => {
+                            tracing::info!(
+                                instance = %mdns_instance,
+                                port = listen_port,
+                                "mDNS: announced qpc server on local network (_quicprochat._udp.local.)"
+                            );
+                        }
+                        Err(e) => {
+                            tracing::warn!(error = %e, "mDNS: service registration failed; mesh discovery disabled");
+                        }
+                    },
+                    Err(e) => {
+                        tracing::warn!(error = %e, "mDNS: failed to build service info; mesh discovery disabled");
+                    }
+                }
+                Some(daemon)
+            }
+            Err(e) => {
+                tracing::warn!(error = %e, "mDNS: daemon start failed; mesh discovery disabled");
+                None
+            }
+        }
+    };
+
+    // capnp-rpc is !Send (Rc internals), so all RPC tasks must stay on a LocalSet.
+    let local = LocalSet::new();
+    local
+        .run_until(async move {
+            // Spawn federation acceptor if enabled.
+            if let Some(fed_ep) = federation_endpoint {
+                let fed_store = Arc::clone(&store);
+                let fed_waiters = Arc::clone(&waiters);
+                let fed_domain = local_domain.clone().unwrap_or_default();
+                tokio::task::spawn_local(async move {
+                    loop {
+                        let incoming = match fed_ep.accept().await {
+                            Some(i) => i,
+                            None => break,
+                        };
+                        let connecting = match incoming.accept() {
+                            Ok(c) => c,
+                            Err(e) => {
+                                tracing::warn!(error = %e, "federation: accept error");
+                                continue;
+                            }
+                        };
+                        let store = Arc::clone(&fed_store);
+                        let waiters = Arc::clone(&fed_waiters);
+                        let domain = fed_domain.clone();
+                        tokio::task::spawn_local(async move {
+                            match connecting.await {
+                                Ok(conn) => {
+                                    tracing::info!(
+                                        peer = %conn.remote_address(),
+                                        "federation: peer connected"
+                                    );
+                                    let (send, recv) = match conn.accept_bi().await {
+                                        Ok(s) => s,
+                                        Err(e) => {
+                                            tracing::warn!(error = %e, "federation: accept bi error");
+                                            return;
+                                        }
+                                    };
+                                    let reader = tokio_util::compat::TokioAsyncReadCompatExt::compat(recv);
+                                    let writer = tokio_util::compat::TokioAsyncWriteCompatExt::compat_write(send);
+
+                                    let network = capnp_rpc::twoparty::VatNetwork::new(
+                                        reader,
+                                        writer,
+                                        capnp_rpc::rpc_twoparty_capnp::Side::Server,
+                                        Default::default(),
+                                    );
+
+                                    let verified_peer_domain =
+                                        federation::service::extract_peer_domain(&conn);
+                                    if let Some(ref peer) = verified_peer_domain {
+                                        tracing::info!(peer_domain = %peer, "federation: mTLS peer authenticated");
+                                    } else {
+                                        tracing::warn!(peer = %conn.remote_address(), "federation: could not extract peer domain from mTLS cert");
+                                    }
+
+                                    let service_impl = federation::service::FederationServiceImpl {
+                                        store,
+                                        waiters,
+                                        local_domain: domain,
+                                        verified_peer_domain,
+                                        rate_limits: Arc::new(dashmap::DashMap::new()),
+                                    };
+                                    let client: quicprochat_proto::federation_capnp::federation_service::Client =
+                                        capnp_rpc::new_client(service_impl);
+
+                                    if let Err(e) = capnp_rpc::RpcSystem::new(
+                                        Box::new(network),
+                                        Some(client.client),
+                                    ).await {
+                                        tracing::warn!(error = %e, "federation: RPC error");
+                                    }
+                                }
+                                Err(e) => {
+                                    tracing::warn!(error = %e, "federation: connection error");
+                                }
+                            }
+                        });
+                    }
+                });
+            }
+
+            loop {
+                tokio::select! {
+                    biased;
+
+                    incoming = endpoint.accept() => {
+                        let incoming = match incoming {
+                            Some(i) => i,
+                            None => break,
+                        };
+
+                        // Per-IP connection rate limiting.
+                        let remote_ip = incoming.remote_address().ip();
+                        if !auth::check_conn_rate_limit(&conn_rate_limits, remote_ip) {
+                            tracing::warn!(ip = %remote_ip, "connection rate limit exceeded, dropping");
+                            incoming.refuse();
+                            continue;
+                        }
+
+                        let connecting = match incoming.accept() {
+                            Ok(c) => c,
+                            Err(e) => {
+                                tracing::warn!(error = %e, "failed to accept incoming connection");
+                                continue;
+                            }
+                        };
+
+                        let store = Arc::clone(&store);
+                        let waiters = Arc::clone(&waiters);
+                        let auth_cfg = Arc::clone(&auth_cfg);
+                        let opaque_setup = Arc::clone(&opaque_setup);
+                        let pending_logins = Arc::clone(&pending_logins);
+                        let sessions = Arc::clone(&sessions);
+                        let rate_limits = Arc::clone(&rate_limits);
+                        let sealed_sender = effective.sealed_sender;
+                        let fed_client = federation_client.clone();
+                        let local_dom = local_domain.clone();
+                        let sk = Arc::clone(&signing_key);
+                        let conn_hooks = Arc::clone(&hooks);
+                        let conn_kt_log = Arc::clone(&kt_log);
+                        let conn_data_dir = PathBuf::from(&effective.data_dir);
+                        let conn_redact_logs = effective.redact_logs;
+
+                        tokio::task::spawn_local(async move {
+                            if let Err(e) = handle_node_connection(
+                                connecting,
+                                store,
+                                waiters,
+                                auth_cfg,
+                                opaque_setup,
+                                pending_logins,
+                                sessions,
+                                rate_limits,
+                                sealed_sender,
+                                fed_client,
+                                local_dom,
+                                sk,
+                                conn_hooks,
+                                conn_kt_log,
+                                conn_data_dir,
+                                conn_redact_logs,
+                            )
+                            .await
+                            {
+                                tracing::warn!(error = %e, "connection error");
+                            }
+                        });
+                    }
+
+                    _ = shutdown_signal() => {
+                        tracing::info!("shutdown signal received, draining QUIC connections");
+                        // Stop accepting new connections immediately.
+                        endpoint.close(0u32.into(), b"server shutdown");
+                        break;
+                    }
+                }
+            }
+
+            // Grace period: let in-flight RPC tasks on the LocalSet finish.
+            let drain_secs = effective.drain_timeout_secs;
+            tracing::info!(drain_timeout_secs = drain_secs, "waiting for in-flight RPCs to complete");
+            tokio::time::sleep(std::time::Duration::from_secs(drain_secs)).await;
+
+            Ok::<(), anyhow::Error>(())
+        })
+        .await?;
+
+    Ok(())
+}
+
+/// Wait for either SIGINT (Ctrl-C) or SIGTERM (Unix only).
+///
+/// Load balancers typically send SIGTERM during rolling deploys. The server
+/// should stop accepting new connections, return "draining" from the health
+/// endpoint, and wait for in-flight RPCs to finish (up to the drain timeout).
+async fn shutdown_signal() {
+    let ctrl_c = tokio::signal::ctrl_c();
+
+    #[cfg(unix)]
+    {
+        let mut sigterm =
+            tokio::signal::unix::signal(tokio::signal::unix::SignalKind::terminate())
+                .expect("failed to install SIGTERM handler");
+        tokio::select! {
+            _ = ctrl_c => {},
+            _ = sigterm.recv() => {},
+        }
+    }
+
+    #[cfg(not(unix))]
+    {
+        ctrl_c.await.ok();
+    }
+}

crates/quicprochat-server/src/metrics.rs

@@ -0,0 +1,64 @@
+//! Prometheus metrics for the server.
+//!
+//! All counters/histograms/gauges use the `metrics` crate and are exported
+//! via metrics-exporter-prometheus on a configurable HTTP port (e.g. /metrics).
+
+/// Record one enqueue (success). Call after a message is enqueued.
+pub fn record_enqueue_total() {
+    metrics::counter!("enqueue_total").increment(1);
+}
+
+/// Record enqueued payload size in bytes.
+pub fn record_enqueue_bytes(bytes: u64) {
+    metrics::counter!("enqueue_bytes_total").increment(bytes);
+}
+
+/// Record one fetch (success). Call when fetch returns.
+pub fn record_fetch_total() {
+    metrics::counter!("fetch_total").increment(1);
+}
+
+/// Record one fetch_wait (success). Call when fetch_wait returns.
+pub fn record_fetch_wait_total() {
+    metrics::counter!("fetch_wait_total").increment(1);
+}
+
+/// Set the delivery queue depth gauge (sample). Updated at enqueue/fetch time.
+pub fn record_delivery_queue_depth(depth: usize) {
+    metrics::gauge!("delivery_queue_depth").set(depth as f64);
+}
+
+/// Record one KeyPackage upload (success).
+pub fn record_key_package_upload_total() {
+    metrics::counter!("key_package_upload_total").increment(1);
+}
+
+/// Record successful auth login (session token issued).
+pub fn record_auth_login_success_total() {
+    metrics::counter!("auth_login_success_total").increment(1);
+}
+
+/// Record failed auth login attempt.
+pub fn record_auth_login_failure_total() {
+    metrics::counter!("auth_login_failure_total").increment(1);
+}
+
+/// Record rate limit hit (enqueue rejected).
+pub fn record_rate_limit_hit_total() {
+    metrics::counter!("rate_limit_hit_total").increment(1);
+}
+
+// ── Storage operation latency ───────────────────────────────────────────────
+
+/// Record storage operation latency. Called by instrumented Store wrappers.
+pub fn record_storage_latency(operation: &'static str, duration: std::time::Duration) {
+    metrics::histogram!("storage_operation_duration_seconds", "op" => operation)
+        .record(duration.as_secs_f64());
+}
+
+// ── Server info ────────────────────────────────────────────────────────────
+
+/// Record the server uptime in seconds (set periodically).
+pub fn record_uptime_seconds(secs: f64) {
+    metrics::gauge!("server_uptime_seconds").set(secs);
+}

crates/quicprochat-server/src/node_service/account_ops.rs

@@ -0,0 +1,63 @@
+use capnp::capability::Promise;
+use quicprochat_proto::node_capnp::node_service;
+
+use crate::auth::{coded_error, require_identity, validate_auth_context};
+use crate::error_codes::*;
+
+use super::NodeServiceImpl;
+
+impl NodeServiceImpl {
+    pub fn handle_delete_account(
+        &mut self,
+        params: node_service::DeleteAccountParams,
+        mut results: node_service::DeleteAccountResults,
+    ) -> Promise<(), capnp::Error> {
+        let p = match params.get() {
+            Ok(p) => p,
+            Err(e) => return Promise::err(coded_error(E020_BAD_PARAMS, e)),
+        };
+
+        // Validate auth and require an identity-bound session.
+        let auth_ctx = match validate_auth_context(&self.auth_cfg, &self.sessions, p.get_auth()) {
+            Ok(ctx) => ctx,
+            Err(e) => return Promise::err(e),
+        };
+
+        let identity_key = match require_identity(&auth_ctx) {
+            Ok(ik) => ik.to_vec(),
+            Err(e) => return Promise::err(e),
+        };
+
+        let identity_prefix = crate::auth::fmt_hex(&identity_key[..8.min(identity_key.len())]);
+
+        // Delete account data from the store.
+        if let Err(e) = self.store.delete_account(&identity_key) {
+            tracing::error!(identity = %identity_prefix, error = %e, "account deletion failed");
+            return Promise::err(coded_error(
+                E028_ACCOUNT_DELETION_FAILED,
+                format!("account deletion failed: {e}"),
+            ));
+        }
+
+        // Invalidate all sessions for this identity.
+        let tokens_to_remove: Vec<Vec<u8>> = self
+            .sessions
+            .iter()
+            .filter(|entry| entry.value().identity_key == identity_key)
+            .map(|entry| entry.key().clone())
+            .collect();
+
+        for token in &tokens_to_remove {
+            self.sessions.remove(token);
+        }
+
+        tracing::info!(
+            identity = %identity_prefix,
+            sessions_invalidated = tokens_to_remove.len(),
+            "audit: account deleted"
+        );
+
+        results.get().set_success(true);
+        Promise::ok(())
+    }
+}

crates/quicprochat-server/src/node_service/auth_ops.rs

@@ -0,0 +1,412 @@
+use capnp::capability::Promise;
+use opaque_ke::{
+    CredentialFinalization, CredentialRequest, RegistrationRequest, RegistrationUpload,
+    ServerLogin, ServerRegistration,
+};
+use quicprochat_core::opaque_auth::OpaqueSuite;
+use quicprochat_proto::node_capnp::node_service;
+
+use crate::auth::{coded_error, current_timestamp, PendingLogin, SESSION_TTL_SECS};
+use crate::error_codes::*;
+use crate::metrics;
+use crate::storage::StorageError;
+
+use crate::hooks::AuthEvent;
+
+use super::NodeServiceImpl;
+
+// Audit events in this module must never include secrets (no session tokens, passwords, or raw keys).
+
+fn storage_err(err: StorageError) -> capnp::Error {
+    coded_error(E009_STORAGE_ERROR, err)
+}
+
+/// Parse username from Cap'n Proto reader; requires valid UTF-8.
+fn parse_username_param(
+    result: Result<capnp::text::Reader<'_>, capnp::Error>,
+) -> Result<String, capnp::Error> {
+    let reader = result.map_err(|e| coded_error(E020_BAD_PARAMS, e))?;
+    reader
+        .to_string()
+        .map_err(|_| coded_error(E020_BAD_PARAMS, "username must be valid UTF-8"))
+}
+
+impl NodeServiceImpl {
+    pub fn handle_opaque_login_start(
+        &mut self,
+        params: node_service::OpaqueLoginStartParams,
+        mut results: node_service::OpaqueLoginStartResults,
+    ) -> Promise<(), capnp::Error> {
+        let p = match params.get() {
+            Ok(p) => p,
+            Err(e) => return Promise::err(coded_error(E020_BAD_PARAMS, e)),
+        };
+        let username = match parse_username_param(p.get_username()) {
+            Ok(s) => s,
+            Err(e) => return Promise::err(e),
+        };
+        let request_bytes = match p.get_request() {
+            Ok(v) => v.to_vec(),
+            Err(e) => return Promise::err(coded_error(E020_BAD_PARAMS, e)),
+        };
+
+        if username.is_empty() {
+            return Promise::err(coded_error(E011_USERNAME_EMPTY, "username must not be empty"));
+        }
+
+        // Check for existing recent pending login before expensive OPAQUE/storage work (DoS mitigation).
+        if let Some(existing) = self.pending_logins.get(&username) {
+            let age = current_timestamp().saturating_sub(existing.created_at);
+            if age < 60 {
+                return Promise::err(coded_error(E010_OPAQUE_ERROR, "login already in progress"));
+            }
+        }
+
+        let credential_request = match CredentialRequest::<OpaqueSuite>::deserialize(&request_bytes) {
+            Ok(r) => r,
+            Err(e) => {
+                return Promise::err(coded_error(
+                    E010_OPAQUE_ERROR,
+                    format!("invalid credential request: {e}"),
+                ))
+            }
+        };
+
+        let password_file = match self.store.get_user_record(&username) {
+            Ok(Some(bytes)) => match ServerRegistration::<OpaqueSuite>::deserialize(&bytes) {
+                Ok(pf) => Some(pf),
+                Err(e) => {
+                    return Promise::err(coded_error(
+                        E010_OPAQUE_ERROR,
+                        format!("corrupt user record: {e}"),
+                    ))
+                }
+            },
+            Ok(None) => None,
+            Err(e) => return Promise::err(storage_err(e)),
+        };
+
+        let mut rng = rand::rngs::OsRng;
+        let result = match ServerLogin::<OpaqueSuite>::start(
+            &mut rng,
+            &self.opaque_setup,
+            password_file,
+            credential_request,
+            username.as_bytes(),
+            Default::default(),
+        ) {
+            Ok(r) => r,
+            Err(e) => {
+                return Promise::err(coded_error(
+                    E010_OPAQUE_ERROR,
+                    format!("OPAQUE login start failed: {e}"),
+                ))
+            }
+        };
+
+        let state_bytes = result.state.serialize().to_vec();
+        self.pending_logins.insert(
+            username.clone(),
+            PendingLogin {
+                state_bytes,
+                created_at: current_timestamp(),
+            },
+        );
+
+        let response_bytes = result.message.serialize();
+        results.get().set_response(&response_bytes);
+
+        tracing::info!(user = %username, "OPAQUE login started");
+        Promise::ok(())
+    }
+
+    pub fn handle_opaque_register_start(
+        &mut self,
+        params: node_service::OpaqueRegisterStartParams,
+        mut results: node_service::OpaqueRegisterStartResults,
+    ) -> Promise<(), capnp::Error> {
+        let p = match params.get() {
+            Ok(p) => p,
+            Err(e) => return Promise::err(coded_error(E020_BAD_PARAMS, e)),
+        };
+        let username = match parse_username_param(p.get_username()) {
+            Ok(s) => s,
+            Err(e) => return Promise::err(e),
+        };
+        let request_bytes = match p.get_request() {
+            Ok(v) => v.to_vec(),
+            Err(e) => return Promise::err(coded_error(E020_BAD_PARAMS, e)),
+        };
+
+        if username.is_empty() {
+            return Promise::err(coded_error(E011_USERNAME_EMPTY, "username must not be empty"));
+        }
+
+        if let Ok(true) = self.store.has_user_record(&username) {
+            return Promise::err(coded_error(
+                E018_USER_EXISTS,
+                format!("user '{}' already registered", username),
+            ));
+        }
+
+        let registration_request = match RegistrationRequest::<OpaqueSuite>::deserialize(&request_bytes) {
+            Ok(r) => r,
+            Err(e) => {
+                return Promise::err(coded_error(
+                    E010_OPAQUE_ERROR,
+                    format!("invalid registration request: {e}"),
+                ))
+            }
+        };
+
+        let result = match ServerRegistration::<OpaqueSuite>::start(
+            &self.opaque_setup,
+            registration_request,
+            username.as_bytes(),
+        ) {
+            Ok(r) => r,
+            Err(e) => {
+                return Promise::err(coded_error(
+                    E010_OPAQUE_ERROR,
+                    format!("OPAQUE registration start failed: {e}"),
+                ))
+            }
+        };
+
+        let response_bytes = result.message.serialize();
+        results.get().set_response(&response_bytes);
+
+        tracing::info!(user = %username, "OPAQUE registration started");
+        Promise::ok(())
+    }
+
+    pub fn handle_opaque_login_finish(
+        &mut self,
+        params: node_service::OpaqueLoginFinishParams,
+        mut results: node_service::OpaqueLoginFinishResults,
+    ) -> Promise<(), capnp::Error> {
+        let p = match params.get() {
+            Ok(p) => p,
+            Err(e) => return Promise::err(coded_error(E020_BAD_PARAMS, e)),
+        };
+        let username = match parse_username_param(p.get_username()) {
+            Ok(s) => s,
+            Err(e) => return Promise::err(e),
+        };
+        let finalization_bytes = match p.get_finalization() {
+            Ok(v) => v.to_vec(),
+            Err(e) => return Promise::err(coded_error(E020_BAD_PARAMS, e)),
+        };
+        let identity_key = p.get_identity_key().unwrap_or_default().to_vec();
+
+        if username.is_empty() {
+            return Promise::err(coded_error(E011_USERNAME_EMPTY, "username must not be empty"));
+        }
+
+        let pending = match self.pending_logins.remove(&username) {
+            Some((_, pl)) => pl,
+            None => {
+                // Audit: login failure — do not log secrets (no token, no password).
+                tracing::warn!(user = %username, "audit: auth login failure (no pending login)");
+                metrics::record_auth_login_failure_total();
+                self.hooks.on_auth(&AuthEvent {
+                    username: username.clone(),
+                    success: false,
+                    failure_reason: "no pending login".to_string(),
+                });
+                return Promise::err(coded_error(E019_NO_PENDING_LOGIN, "no pending login for this username"))
+            }
+        };
+
+        let server_login = match ServerLogin::<OpaqueSuite>::deserialize(&pending.state_bytes) {
+            Ok(s) => s,
+            Err(e) => {
+                return Promise::err(coded_error(
+                    E010_OPAQUE_ERROR,
+                    format!("corrupt login state: {e}"),
+                ))
+            }
+        };
+
+        let finalization = match CredentialFinalization::<OpaqueSuite>::deserialize(&finalization_bytes) {
+            Ok(f) => f,
+            Err(e) => {
+                return Promise::err(coded_error(
+                    E010_OPAQUE_ERROR,
+                    format!("invalid credential finalization: {e}"),
+                ))
+            }
+        };
+
+        let _result = match server_login.finish(finalization, Default::default()) {
+            Ok(r) => r,
+            Err(e) => {
+                tracing::warn!(user = %username, "audit: auth login failure (OPAQUE finish failed)");
+                metrics::record_auth_login_failure_total();
+                self.hooks.on_auth(&AuthEvent {
+                    username: username.clone(),
+                    success: false,
+                    failure_reason: format!("OPAQUE finish failed: {e}"),
+                });
+                return Promise::err(coded_error(
+                    E010_OPAQUE_ERROR,
+                    format!("OPAQUE login finish failed (bad password?): {e}"),
+                ))
+            }
+        };
+
+        if identity_key.is_empty() {
+            metrics::record_auth_login_failure_total();
+            return Promise::err(coded_error(
+                E016_IDENTITY_MISMATCH,
+                "identity key required to bind session token",
+            ));
+        }
+
+        if let Ok(Some(stored_ik)) = self.store.get_user_identity_key(&username) {
+            if stored_ik != identity_key {
+                tracing::warn!(user = %username, "audit: auth login failure (identity mismatch)");
+                metrics::record_auth_login_failure_total();
+                self.hooks.on_auth(&AuthEvent {
+                    username: username.clone(),
+                    success: false,
+                    failure_reason: "identity key mismatch".to_string(),
+                });
+                return Promise::err(coded_error(
+                    E016_IDENTITY_MISMATCH,
+                    "identity key does not match registered key",
+                ));
+            }
+        }
+
+        let mut token = [0u8; 32];
+        rand::RngCore::fill_bytes(&mut rand::rngs::OsRng, &mut token);
+        let token_vec = token.to_vec();
+
+        let now = current_timestamp();
+        self.sessions.insert(
+            token_vec.clone(),
+            crate::auth::SessionInfo {
+                username: username.clone(),
+                identity_key,
+                created_at: now,
+                expires_at: now + SESSION_TTL_SECS,
+            },
+        );
+
+        results.get().set_session_token(&token_vec);
+
+        // Hook: on_auth — fires after successful login.
+        self.hooks.on_auth(&AuthEvent {
+            username: username.clone(),
+            success: true,
+            failure_reason: String::new(),
+        });
+
+        // Audit: login success — do not log session token or any secrets.
+        metrics::record_auth_login_success_total();
+        tracing::info!(user = %username, "audit: auth login success — session token issued");
+        Promise::ok(())
+    }
+
+    pub fn handle_opaque_register_finish(
+        &mut self,
+        params: node_service::OpaqueRegisterFinishParams,
+        mut results: node_service::OpaqueRegisterFinishResults,
+    ) -> Promise<(), capnp::Error> {
+        let p = match params.get() {
+            Ok(p) => p,
+            Err(e) => return Promise::err(coded_error(E020_BAD_PARAMS, e)),
+        };
+        let username = match parse_username_param(p.get_username()) {
+            Ok(s) => s,
+            Err(e) => return Promise::err(e),
+        };
+        let upload_bytes = match p.get_upload() {
+            Ok(v) => v.to_vec(),
+            Err(e) => return Promise::err(coded_error(E020_BAD_PARAMS, e)),
+        };
+        let identity_key = p.get_identity_key().unwrap_or_default().to_vec();
+
+        if username.is_empty() {
+            return Promise::err(coded_error(E011_USERNAME_EMPTY, "username must not be empty"));
+        }
+
+        match self.store.has_user_record(&username) {
+            Ok(true) => {
+                return Promise::err(coded_error(
+                    E018_USER_EXISTS,
+                    format!("user '{}' already registered", username),
+                ))
+            }
+            Err(e) => return Promise::err(storage_err(e)),
+            _ => {}
+        }
+
+        let upload = match RegistrationUpload::<OpaqueSuite>::deserialize(&upload_bytes) {
+            Ok(u) => u,
+            Err(e) => {
+                return Promise::err(coded_error(
+                    E010_OPAQUE_ERROR,
+                    format!("invalid registration upload: {e}"),
+                ))
+            }
+        };
+
+        let password_file = ServerRegistration::<OpaqueSuite>::finish(upload);
+        let record_bytes = password_file.serialize().to_vec();
+
+        match self
+            .store
+            .store_user_record(&username, record_bytes)
+        {
+            Ok(()) => {}
+            Err(crate::storage::StorageError::DuplicateUser(_)) => {
+                return Promise::err(coded_error(
+                    E018_USER_EXISTS,
+                    format!("user '{}' already registered", username),
+                ))
+            }
+            Err(e) => return Promise::err(storage_err(e)),
+        }
+
+        // Hook: on_user_registered — fires after successful registration.
+        self.hooks.on_user_registered(&username, &identity_key);
+
+        if !identity_key.is_empty() {
+            if let Err(e) = self
+                .store
+                .store_user_identity_key(&username, identity_key.clone())
+                .map_err(storage_err)
+            {
+                return Promise::err(e);
+            }
+
+            // Append (username, identity_key) to the Key Transparency Merkle log.
+            match self.kt_log.lock() {
+                Ok(mut log) => {
+                    log.append(&username, &identity_key);
+                    // Persist after each append (small extra cost, but ensures durability).
+                    match log.to_bytes() {
+                        Ok(bytes) => {
+                            if let Err(e) = self.store.save_kt_log(bytes) {
+                                tracing::warn!(user = %username, error = %e, "KT log persist failed");
+                            }
+                        }
+                        Err(e) => {
+                            tracing::warn!(user = %username, error = %e, "KT log serialise failed");
+                        }
+                    }
+                    tracing::info!(user = %username, tree_size = log.len(), "KT: appended identity binding");
+                }
+                Err(e) => {
+                    tracing::warn!(user = %username, error = %e, "KT log lock poisoned; skipping append");
+                }
+            }
+        }
+
+        results.get().set_success(true);
+        tracing::info!(user = %username, "OPAQUE registration complete");
+        Promise::ok(())
+    }
+}

crates/quicprochat-server/src/node_service/blob_ops.rs

@@ -0,0 +1,326 @@
+//! uploadBlob / downloadBlob RPCs: chunked file transfer with SHA-256 integrity verification.
+
+use std::io::{Read, Seek, SeekFrom, Write};
+use std::path::PathBuf;
+
+use capnp::capability::Promise;
+use quicprochat_proto::node_capnp::node_service;
+use sha2::{Digest, Sha256};
+
+use crate::auth::{coded_error, fmt_hex, validate_auth_context};
+use crate::error_codes::*;
+
+use super::NodeServiceImpl;
+
+/// Maximum blob size: 50 MB.
+const MAX_BLOB_SIZE: u64 = 50 * 1024 * 1024;
+
+/// Maximum download chunk size: 256 KB.
+const MAX_DOWNLOAD_CHUNK: u32 = 256 * 1024;
+
+/// Metadata stored alongside each completed blob.
+#[derive(serde::Serialize, serde::Deserialize)]
+struct BlobMeta {
+    mime_type: String,
+    total_size: u64,
+    uploaded_at: u64,
+    uploader_key_prefix: String,
+}
+
+/// Resolve the blobs directory from the server's data_dir.
+fn blobs_dir(data_dir: &std::path::Path) -> PathBuf {
+    data_dir.join("blobs")
+}
+
+impl NodeServiceImpl {
+    pub fn handle_upload_blob(
+        &mut self,
+        params: node_service::UploadBlobParams,
+        mut results: node_service::UploadBlobResults,
+    ) -> 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),
+        };
+
+        let blob_hash = match p.get_blob_hash() {
+            Ok(v) => v.to_vec(),
+            Err(e) => return Promise::err(coded_error(E020_BAD_PARAMS, e)),
+        };
+        let chunk = match p.get_chunk() {
+            Ok(v) => v.to_vec(),
+            Err(e) => return Promise::err(coded_error(E020_BAD_PARAMS, e)),
+        };
+        let offset = p.get_offset();
+        let total_size = p.get_total_size();
+        let mime_type = match p.get_mime_type() {
+            Ok(v) => match v.to_str() {
+                Ok(s) => s.to_string(),
+                Err(e) => return Promise::err(coded_error(E020_BAD_PARAMS, e)),
+            },
+            Err(e) => return Promise::err(coded_error(E020_BAD_PARAMS, e)),
+        };
+
+        // Validate blobHash length.
+        if blob_hash.len() != 32 {
+            return Promise::err(coded_error(
+                E025_BLOB_HASH_LENGTH,
+                format!("blobHash must be exactly 32 bytes, got {}", blob_hash.len()),
+            ));
+        }
+
+        // Validate totalSize.
+        if total_size > MAX_BLOB_SIZE {
+            return Promise::err(coded_error(
+                E024_BLOB_TOO_LARGE,
+                format!("totalSize {} exceeds max blob size ({} bytes)", total_size, MAX_BLOB_SIZE),
+            ));
+        }
+        if total_size == 0 {
+            return Promise::err(coded_error(E020_BAD_PARAMS, "totalSize must be > 0"));
+        }
+
+        // Validate chunk bounds.
+        if offset.checked_add(chunk.len() as u64).is_none_or(|end| end > total_size) {
+            return Promise::err(coded_error(
+                E020_BAD_PARAMS,
+                format!(
+                    "chunk out of bounds: offset={} + chunk_len={} > totalSize={}",
+                    offset,
+                    chunk.len(),
+                    total_size
+                ),
+            ));
+        }
+
+        let blob_hex = hex::encode(&blob_hash);
+        let dir = blobs_dir(&self.data_dir);
+
+        // Ensure blobs directory exists.
+        if let Err(e) = std::fs::create_dir_all(&dir) {
+            return Promise::err(coded_error(
+                E009_STORAGE_ERROR,
+                format!("failed to create blobs directory: {e}"),
+            ));
+        }
+
+        let part_path = dir.join(format!("{blob_hex}.part"));
+        let final_path = dir.join(&blob_hex);
+        let meta_path = dir.join(format!("{blob_hex}.meta"));
+
+        // All file I/O is delegated to spawn_blocking to avoid stalling the Tokio event loop.
+        let uploader_prefix = auth_ctx
+            .identity_key
+            .as_deref()
+            .filter(|k| k.len() >= 4)
+            .map(|k| hex::encode(&k[..4]))
+            .unwrap_or_default();
+
+        Promise::from_future(async move {
+            let blob_hash_clone = blob_hash.clone();
+            let part_path_clone = part_path.clone();
+            let final_path_clone = final_path.clone();
+            let meta_path_clone = meta_path.clone();
+            let chunk_clone = chunk;
+            let mime_clone = mime_type.clone();
+            let prefix_clone = uploader_prefix.clone();
+
+            let io_result = tokio::task::spawn_blocking(move || -> Result<Option<bool>, String> {
+                // If the blob already exists (fully uploaded), return immediately.
+                if final_path_clone.exists() {
+                    return Ok(None); // signals "already done"
+                }
+
+                // Write chunk at the given offset.
+                let mut file = std::fs::OpenOptions::new()
+                    .create(true)
+                    .write(true)
+                    .truncate(false)
+                    .open(&part_path_clone)
+                    .map_err(|e| format!("open .part file: {e}"))?;
+                file.seek(SeekFrom::Start(offset))
+                    .map_err(|e| format!("seek: {e}"))?;
+                file.write_all(&chunk_clone)
+                    .map_err(|e| format!("write chunk: {e}"))?;
+                file.sync_all()
+                    .map_err(|e| format!("sync: {e}"))?;
+
+                // Check if the blob is complete.
+                let end = offset + chunk_clone.len() as u64;
+                if end == total_size {
+                    // Verify SHA-256 of the complete file.
+                    let mut vfile = std::fs::File::open(&part_path_clone)
+                        .map_err(|e| format!("open for verify: {e}"))?;
+                    let mut hasher = Sha256::new();
+                    let mut buf = [0u8; 64 * 1024];
+                    loop {
+                        let n = vfile.read(&mut buf).map_err(|e| format!("read: {e}"))?;
+                        if n == 0 {
+                            break;
+                        }
+                        hasher.update(&buf[..n]);
+                    }
+                    let computed: [u8; 32] = hasher.finalize().into();
+                    if computed != blob_hash_clone.as_slice() {
+                        let _ = std::fs::remove_file(&part_path_clone);
+                        return Ok(Some(false)); // hash mismatch
+                    }
+
+                    // Hash matches — finalize the blob.
+                    std::fs::rename(&part_path_clone, &final_path_clone)
+                        .map_err(|e| format!("rename .part to final: {e}"))?;
+
+                    // Write metadata file.
+                    let now = std::time::SystemTime::now()
+                        .duration_since(std::time::UNIX_EPOCH)
+                        .unwrap_or_default()
+                        .as_secs();
+
+                    let meta = BlobMeta {
+                        mime_type: mime_clone,
+                        total_size,
+                        uploaded_at: now,
+                        uploader_key_prefix: prefix_clone,
+                    };
+
+                    if let Err(e) = (|| -> Result<(), String> {
+                        let json = serde_json::to_string_pretty(&meta)
+                            .map_err(|e| format!("serialize meta: {e}"))?;
+                        std::fs::write(&meta_path_clone, json.as_bytes())
+                            .map_err(|e| format!("write meta: {e}"))?;
+                        Ok(())
+                    })() {
+                        tracing::warn!(error = %e, "failed to write blob metadata");
+                    }
+
+                    return Ok(Some(true)); // complete + verified
+                }
+
+                Ok(None) // chunk written, not yet complete
+            })
+            .await
+            .map_err(|e| capnp::Error::failed(format!("spawn_blocking join: {e}")))?;
+
+            match io_result {
+                Ok(None) => {
+                    // Already existed or chunk written (not yet complete).
+                    results.get().set_blob_id(&blob_hash);
+                }
+                Ok(Some(true)) => {
+                    // Complete and verified.
+                    tracing::info!(
+                        blob_hash_prefix = %fmt_hex(&blob_hash[..4]),
+                        total_size = total_size,
+                        mime_type = %mime_type,
+                        uploader_prefix = %uploader_prefix,
+                        "audit: blob_upload_complete"
+                    );
+                    results.get().set_blob_id(&blob_hash);
+                }
+                Ok(Some(false)) => {
+                    return Err(coded_error(
+                        E026_BLOB_HASH_MISMATCH,
+                        "SHA-256 of uploaded data does not match blobHash",
+                    ));
+                }
+                Err(e) => {
+                    return Err(coded_error(E009_STORAGE_ERROR, e));
+                }
+            }
+
+            Ok(())
+        })
+    }
+
+    pub fn handle_download_blob(
+        &mut self,
+        params: node_service::DownloadBlobParams,
+        mut results: node_service::DownloadBlobResults,
+    ) -> Promise<(), capnp::Error> {
+        let p = match params.get() {
+            Ok(p) => p,
+            Err(e) => return Promise::err(coded_error(E020_BAD_PARAMS, e)),
+        };
+
+        if let Err(e) = validate_auth_context(&self.auth_cfg, &self.sessions, p.get_auth()) {
+            return Promise::err(e);
+        }
+
+        let blob_id = match p.get_blob_id() {
+            Ok(v) => v.to_vec(),
+            Err(e) => return Promise::err(coded_error(E020_BAD_PARAMS, e)),
+        };
+        let offset = p.get_offset();
+        let length = p.get_length().min(MAX_DOWNLOAD_CHUNK);
+
+        if blob_id.len() != 32 {
+            return Promise::err(coded_error(
+                E025_BLOB_HASH_LENGTH,
+                format!("blobId must be exactly 32 bytes, got {}", blob_id.len()),
+            ));
+        }
+
+        let blob_hex = hex::encode(&blob_id);
+        let dir = blobs_dir(&self.data_dir);
+        let blob_path = dir.join(&blob_hex);
+        let meta_path = dir.join(format!("{blob_hex}.meta"));
+
+        // Delegate all file I/O to spawn_blocking to avoid stalling the event loop.
+        Promise::from_future(async move {
+            let io_result = tokio::task::spawn_blocking(move || -> Result<(Vec<u8>, BlobMeta), capnp::Error> {
+                // Check that the blob exists.
+                if !blob_path.exists() {
+                    return Err(coded_error(E027_BLOB_NOT_FOUND, "blob not found"));
+                }
+
+                // Read metadata.
+                let meta: BlobMeta = match std::fs::read_to_string(&meta_path) {
+                    Ok(json) => serde_json::from_str(&json).map_err(|e| {
+                        coded_error(E009_STORAGE_ERROR, format!("corrupt blob metadata: {e}"))
+                    })?,
+                    Err(e) => {
+                        return Err(coded_error(
+                            E009_STORAGE_ERROR,
+                            format!("read blob metadata: {e}"),
+                        ));
+                    }
+                };
+
+                // Read the requested chunk.
+                let mut file = std::fs::File::open(&blob_path)
+                    .map_err(|e| coded_error(E009_STORAGE_ERROR, format!("open blob: {e}")))?;
+                let file_len = file
+                    .metadata()
+                    .map_err(|e| coded_error(E009_STORAGE_ERROR, format!("file metadata: {e}")))?
+                    .len();
+
+                if offset >= file_len {
+                    return Ok((vec![], meta));
+                }
+
+                file.seek(SeekFrom::Start(offset))
+                    .map_err(|e| coded_error(E009_STORAGE_ERROR, format!("seek: {e}")))?;
+                let remaining = (file_len - offset) as usize;
+                let to_read = remaining.min(length as usize);
+                let mut buf = vec![0u8; to_read];
+                file.read_exact(&mut buf)
+                    .map_err(|e| coded_error(E009_STORAGE_ERROR, format!("read chunk: {e}")))?;
+                Ok((buf, meta))
+            })
+            .await
+            .map_err(|e| capnp::Error::failed(format!("spawn_blocking join: {e}")))?;
+
+            let (chunk, meta) = io_result?;
+            let mut r = results.get();
+            r.set_chunk(&chunk);
+            r.set_total_size(meta.total_size);
+            r.set_mime_type(&meta.mime_type);
+            Ok(())
+        })
+    }
+}

crates/quicprochat-server/src/node_service/channel_ops.rs

@@ -0,0 +1,74 @@
+//! createChannel RPC: create or look up a 1:1 DM channel.
+
+use capnp::capability::Promise;
+use quicprochat_proto::node_capnp::node_service;
+
+use crate::auth::{coded_error, require_identity, validate_auth_context};
+use crate::error_codes::*;
+use crate::storage::StorageError;
+
+use crate::hooks::ChannelEvent;
+
+use super::NodeServiceImpl;
+
+fn storage_err(err: StorageError) -> capnp::Error {
+    coded_error(E009_STORAGE_ERROR, err)
+}
+
+impl NodeServiceImpl {
+    pub fn handle_create_channel(
+        &mut self,
+        params: node_service::CreateChannelParams,
+        mut results: node_service::CreateChannelResults,
+    ) -> Promise<(), capnp::Error> {
+        let p = match params.get() {
+            Ok(p) => p,
+            Err(e) => return Promise::err(coded_error(E020_BAD_PARAMS, e)),
+        };
+        let peer_key = match p.get_peer_key() {
+            Ok(v) => v.to_vec(),
+            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),
+        };
+
+        let identity = match require_identity(&auth_ctx) {
+            Ok(id) => id,
+            Err(e) => return Promise::err(e),
+        };
+
+        if peer_key.len() != 32 {
+            return Promise::err(coded_error(
+                E004_IDENTITY_KEY_LENGTH,
+                format!("peerKey must be exactly 32 bytes, got {}", peer_key.len()),
+            ));
+        }
+
+        if identity == peer_key {
+            return Promise::err(coded_error(
+                E020_BAD_PARAMS,
+                "peerKey must not equal caller identity",
+            ));
+        }
+
+        let (channel_id, was_new) = match self.store.create_channel(identity, &peer_key) {
+            Ok(pair) => pair,
+            Err(e) => return Promise::err(storage_err(e)),
+        };
+
+        // Hook: on_channel_created — fires after channel is created or looked up.
+        self.hooks.on_channel_created(&ChannelEvent {
+            channel_id: channel_id.clone(),
+            initiator_key: identity.to_vec(),
+            peer_key: peer_key.clone(),
+            was_new,
+        });
+
+        let mut r = results.get();
+        r.set_channel_id(&channel_id);
+        r.set_was_new(was_new);
+        Promise::ok(())
+    }
+}

crates/quicprochat-server/src/node_service/delivery.rs

@@ -0,0 +1,916 @@
+use std::sync::Arc;
+use std::time::Duration;
+
+use capnp::capability::Promise;
+use dashmap::DashMap;
+use quicprochat_proto::node_capnp::node_service;
+use tokio::sync::Notify;
+use tokio::time::timeout;
+
+use sha2::{Digest, Sha256};
+
+use crate::auth::{
+    check_rate_limit, coded_error, fmt_hex, require_identity_or_request, validate_auth_context,
+};
+use crate::error_codes::*;
+use crate::metrics;
+use crate::storage::{StorageError, Store};
+
+use super::{NodeServiceImpl, CURRENT_WIRE_VERSION};
+use crate::hooks::{HookAction, MessageEvent, FetchEvent};
+
+// Audit events here must not include secrets: no payload content, no full recipient/token bytes (prefix only).
+
+/// Hash first 4 bytes of the key's SHA-256 as a hex string (for redacted audit logs).
+fn redacted_prefix(key: &[u8]) -> String {
+    let hash = Sha256::digest(key);
+    fmt_hex(&hash[..4])
+}
+
+const MAX_PAYLOAD_BYTES: usize = 5 * 1024 * 1024; // 5 MB cap per message
+const MAX_QUEUE_DEPTH: usize = 1000;
+
+/// Build a 96-byte delivery proof: SHA-256(seq || recipient_key || timestamp_ms) || Ed25519 sig.
+///
+/// Layout:
+///   bytes  0..32 — SHA-256 preimage hash
+///   bytes 32..96 — Ed25519 signature over those 32 bytes
+fn build_delivery_proof(
+    signing_key: &quicprochat_core::IdentityKeypair,
+    seq: u64,
+    recipient_key: &[u8],
+    timestamp_ms: u64,
+) -> [u8; 96] {
+    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 = signing_key.sign_raw(&hash);
+
+    let mut proof = [0u8; 96];
+    proof[..32].copy_from_slice(&hash);
+    proof[32..].copy_from_slice(&sig);
+    proof
+}
+
+fn storage_err(err: StorageError) -> capnp::Error {
+    coded_error(E009_STORAGE_ERROR, err)
+}
+
+pub fn fill_payloads_wait(
+    results: &mut node_service::FetchWaitResults,
+    messages: Vec<(u64, Vec<u8>)>,
+) {
+    let mut list = results.get().init_payloads(messages.len() as u32);
+    for (i, (seq, data)) in messages.iter().enumerate() {
+        let mut entry = list.reborrow().get(i as u32);
+        entry.set_seq(*seq);
+        entry.set_data(data);
+    }
+}
+
+impl NodeServiceImpl {
+    pub fn handle_enqueue(
+        &mut self,
+        params: node_service::EnqueueParams,
+        mut results: node_service::EnqueueResults,
+    ) -> Promise<(), capnp::Error> {
+        let p = match params.get() {
+            Ok(p) => p,
+            Err(e) => return Promise::err(coded_error(E020_BAD_PARAMS, e)),
+        };
+        let recipient_key = match p.get_recipient_key() {
+            Ok(v) => v.to_vec(),
+            Err(e) => return Promise::err(coded_error(E020_BAD_PARAMS, e)),
+        };
+        let payload = match p.get_payload() {
+            Ok(v) => v.to_vec(),
+            Err(e) => return Promise::err(coded_error(E020_BAD_PARAMS, e)),
+        };
+        let channel_id = p.get_channel_id().unwrap_or_default().to_vec();
+        let version = p.get_version();
+        let ttl_secs_raw = p.get_ttl_secs();
+        let ttl_secs = if ttl_secs_raw > 0 { Some(ttl_secs_raw) } else { None };
+        let auth_ctx = match validate_auth_context(&self.auth_cfg, &self.sessions, p.get_auth()) {
+            Ok(ctx) => ctx,
+            Err(e) => return Promise::err(e),
+        };
+
+        if recipient_key.len() != 32 {
+            return Promise::err(coded_error(
+                E004_IDENTITY_KEY_LENGTH,
+                format!("recipientKey must be exactly 32 bytes, got {}", recipient_key.len()),
+            ));
+        }
+        if payload.is_empty() {
+            return Promise::err(coded_error(E005_PAYLOAD_EMPTY, "payload must not be empty"));
+        }
+        if payload.len() > MAX_PAYLOAD_BYTES {
+            return Promise::err(coded_error(
+                E006_PAYLOAD_TOO_LARGE,
+                format!("payload exceeds max size ({} bytes)", MAX_PAYLOAD_BYTES),
+            ));
+        }
+        if version > CURRENT_WIRE_VERSION {
+            return Promise::err(coded_error(
+                E012_WIRE_VERSION,
+                format!("wire version {} not supported (max {CURRENT_WIRE_VERSION})", version),
+            ));
+        }
+
+        if let Err(e) = check_rate_limit(&self.rate_limits, &auth_ctx.token) {
+            // Audit: rate limit hit — do not log token or identity.
+            tracing::warn!("rate_limit_hit");
+            metrics::record_rate_limit_hit_total();
+            return Promise::err(e);
+        }
+
+        // Phase 4.3 — DS sender identity binding.
+        // When sealed_sender is false, the sender MUST have an identity-bound session.
+        // The sender_identity used for audit/hooks is ALWAYS derived from
+        // auth_ctx.identity_key (populated by OPAQUE session lookup in validate_auth_context),
+        // never from any client-supplied field. This guarantees that the server only
+        // attributes messages to the cryptographically authenticated identity.
+        if !self.sealed_sender {
+            if let Err(e) = crate::auth::require_identity(&auth_ctx) {
+                return Promise::err(e);
+            }
+        }
+
+        // Federation routing: if the recipient's home server differs from ours, relay the
+        // message to the remote server instead of enqueueing locally. This enables
+        // cross-node delivery in a Freifunk / community mesh deployment.
+        if let (Some(fed_client), Some(local_domain)) =
+            (&self.federation_client, &self.local_domain)
+        {
+            let dest = crate::federation::routing::resolve_destination(
+                &self.store,
+                &recipient_key,
+                local_domain,
+            );
+            if let crate::federation::routing::Destination::Remote(remote_domain) = dest {
+                let fed = Arc::clone(fed_client);
+                let rk = recipient_key;
+                let pl = payload;
+                let ch = channel_id;
+                tracing::info!(
+                    recipient_prefix = %fmt_hex(&rk[..4]),
+                    domain = %remote_domain,
+                    "federation: routing enqueue to remote server"
+                );
+                return Promise::from_future(async move {
+                    let seq = fed
+                        .relay_enqueue(&remote_domain, &rk, &pl, &ch)
+                        .await
+                        .map_err(|e| {
+                            capnp::Error::failed(format!("federation relay failed: {e}"))
+                        })?;
+                    results.get().set_seq(seq);
+                    metrics::record_enqueue_total();
+                    metrics::record_enqueue_bytes(pl.len() as u64);
+                    Ok(())
+                });
+            }
+        }
+
+        // DM channel authz: channel_id.len() == 16 means a created channel; caller and recipient must be the two members.
+        if channel_id.len() == 16 {
+            let members = match self.store.get_channel_members(&channel_id) {
+                Ok(Some(m)) => m,
+                Ok(None) => {
+                    return Promise::err(coded_error(E023_CHANNEL_NOT_FOUND, "channel not found"));
+                }
+                Err(e) => return Promise::err(storage_err(e)),
+            };
+            let caller = match crate::auth::require_identity(&auth_ctx) {
+                Ok(id) => id,
+                Err(e) => return Promise::err(e),
+            };
+            let (a, b) = &members;
+            let caller_in = caller == a.as_slice() || caller == b.as_slice();
+            let recipient_other = (recipient_key == *a && caller == b.as_slice())
+                || (recipient_key == *b && caller == a.as_slice());
+            if !caller_in || !recipient_other {
+                return Promise::err(coded_error(
+                    E022_CHANNEL_ACCESS_DENIED,
+                    "caller or recipient not a member of this channel",
+                ));
+            }
+        }
+
+        match self.store.queue_depth(&recipient_key, &channel_id) {
+            Ok(depth) if depth >= MAX_QUEUE_DEPTH => {
+                return Promise::err(coded_error(
+                    E015_QUEUE_FULL,
+                    format!("queue depth {} exceeds limit {}", depth, MAX_QUEUE_DEPTH),
+                ));
+            }
+            Err(e) => return Promise::err(storage_err(e)),
+            _ => {}
+        }
+
+        let payload_len = payload.len();
+        // sender_identity is derived solely from auth_ctx (server-side session state).
+        let sender_identity = if self.sealed_sender {
+            None
+        } else {
+            crate::auth::require_identity(&auth_ctx).ok().map(|v| v.to_vec())
+        };
+        let sender_prefix = sender_identity
+            .as_deref()
+            .filter(|id| id.len() >= 4)
+            .map(|id| fmt_hex(&id[..4]));
+
+        // Hook: on_message_enqueue — fires after validation, before storage.
+        let hook_event = MessageEvent {
+            sender_identity: sender_identity.clone(),
+            recipient_key: recipient_key.clone(),
+            channel_id: channel_id.clone(),
+            payload_len,
+            seq: 0, // not yet assigned
+        };
+        if let HookAction::Reject(reason) = self.hooks.on_message_enqueue(&hook_event) {
+            return Promise::err(capnp::Error::failed(format!("hook rejected enqueue: {reason}")));
+        }
+
+        let seq = match self
+            .store
+            .enqueue(&recipient_key, &channel_id, payload, ttl_secs)
+            .map_err(storage_err)
+        {
+            Ok(seq) => seq,
+            Err(e) => return Promise::err(e),
+        };
+
+        let timestamp_ms = std::time::SystemTime::now()
+            .duration_since(std::time::UNIX_EPOCH)
+            .unwrap_or_default()
+            .as_millis() as u64;
+        let proof = build_delivery_proof(&self.signing_key, seq, &recipient_key, timestamp_ms);
+
+        let mut r = results.get();
+        r.set_seq(seq);
+        r.set_delivery_proof(&proof);
+
+        // Metrics and audit. Audit events must not include secrets (no payload, no full keys).
+        metrics::record_enqueue_total();
+        metrics::record_enqueue_bytes(payload_len as u64);
+        if let Ok(depth) = self.store.queue_depth(&recipient_key, &channel_id) {
+            metrics::record_delivery_queue_depth(depth);
+        }
+        if self.redact_logs {
+            let redacted_sender = sender_identity
+                .as_deref()
+                .map(redacted_prefix)
+                .unwrap_or_else(|| "sealed".to_string());
+            tracing::info!(
+                sender_prefix = %redacted_sender,
+                recipient_prefix = %redacted_prefix(&recipient_key),
+                seq = seq,
+                "audit: enqueue"
+            );
+        } else {
+            tracing::info!(
+                sender_prefix = sender_prefix.as_deref().unwrap_or("sealed"),
+                recipient_prefix = %fmt_hex(&recipient_key[..4]),
+                payload_len = payload_len,
+                seq = seq,
+                "audit: enqueue"
+            );
+        }
+
+        crate::auth::waiter(&self.waiters, &recipient_key).notify_waiters();
+
+        Promise::ok(())
+    }
+
+    pub fn handle_fetch(
+        &mut self,
+        params: node_service::FetchParams,
+        mut results: node_service::FetchResults,
+    ) -> Promise<(), capnp::Error> {
+        let recipient_key = match params.get() {
+            Ok(p) => match p.get_recipient_key() {
+                Ok(v) => v.to_vec(),
+                Err(e) => return Promise::err(coded_error(E020_BAD_PARAMS, e)),
+            },
+            Err(e) => return Promise::err(coded_error(E020_BAD_PARAMS, e)),
+        };
+        let channel_id = params
+            .get()
+            .ok()
+            .and_then(|p| p.get_channel_id().ok())
+            .map(|c| c.to_vec())
+            .unwrap_or_default();
+        let version = params
+            .get()
+            .ok()
+            .map(|p| p.get_version())
+            .unwrap_or(CURRENT_WIRE_VERSION);
+        let limit = params.get().ok().map(|p| p.get_limit()).unwrap_or(0);
+        let auth_ctx = match params
+            .get()
+            .ok()
+            .map(|p| validate_auth_context(&self.auth_cfg, &self.sessions, p.get_auth()))
+            .transpose()
+        {
+            Ok(ctx) => ctx,
+            Err(e) => return Promise::err(e),
+        };
+
+        if recipient_key.len() != 32 {
+            return Promise::err(coded_error(
+                E004_IDENTITY_KEY_LENGTH,
+                format!("recipientKey must be exactly 32 bytes, got {}", recipient_key.len()),
+            ));
+        }
+        if version > CURRENT_WIRE_VERSION {
+            return Promise::err(coded_error(
+                E012_WIRE_VERSION,
+                format!("wire version {} not supported (max {CURRENT_WIRE_VERSION})", version),
+            ));
+        }
+
+        let auth_ctx = match auth_ctx {
+            Some(ctx) => ctx,
+            None => return Promise::err(coded_error(E003_INVALID_TOKEN, "auth required")),
+        };
+
+        if let Err(e) = require_identity_or_request(
+            &auth_ctx,
+            &recipient_key,
+            self.auth_cfg.allow_insecure_identity_from_request,
+        ) {
+            return Promise::err(e);
+        }
+
+        if channel_id.len() == 16 {
+            let members = match self.store.get_channel_members(&channel_id) {
+                Ok(Some(m)) => m,
+                Ok(None) => {
+                    return Promise::err(coded_error(E023_CHANNEL_NOT_FOUND, "channel not found"));
+                }
+                Err(e) => return Promise::err(storage_err(e)),
+            };
+            let caller = match crate::auth::require_identity(&auth_ctx) {
+                Ok(id) => id,
+                Err(e) => return Promise::err(e),
+            };
+            let (a, b) = &members;
+            let caller_in = caller == a.as_slice() || caller == b.as_slice();
+            let recipient_other = (recipient_key.as_slice() == a.as_slice() && caller == b.as_slice())
+                || (recipient_key.as_slice() == b.as_slice() && caller == a.as_slice());
+            if !caller_in || !recipient_other {
+                return Promise::err(coded_error(
+                    E022_CHANNEL_ACCESS_DENIED,
+                    "caller or recipient not a member of this channel",
+                ));
+            }
+        }
+
+        let messages = if limit > 0 {
+            match self
+                .store
+                .fetch_limited(&recipient_key, &channel_id, limit as usize)
+                .map_err(storage_err)
+            {
+                Ok(m) => m,
+                Err(e) => return Promise::err(e),
+            }
+        } else {
+            match self
+                .store
+                .fetch(&recipient_key, &channel_id)
+                .map_err(storage_err)
+            {
+                Ok(m) => m,
+                Err(e) => return Promise::err(e),
+            }
+        };
+
+        // Hook: on_fetch — fires after messages are retrieved.
+        self.hooks.on_fetch(&FetchEvent {
+            recipient_key: recipient_key.clone(),
+            channel_id: channel_id.clone(),
+            message_count: messages.len(),
+        });
+
+        // Audit: fetch — do not log payload or full keys.
+        metrics::record_fetch_total();
+        if self.redact_logs {
+            tracing::info!(
+                recipient_prefix = %redacted_prefix(&recipient_key),
+                count = messages.len(),
+                "audit: fetch"
+            );
+        } else {
+            tracing::info!(
+                recipient_prefix = %fmt_hex(&recipient_key[..4]),
+                count = messages.len(),
+                "audit: fetch"
+            );
+        }
+
+        let mut list = results.get().init_payloads(messages.len() as u32);
+        for (i, (seq, data)) in messages.iter().enumerate() {
+            let mut entry = list.reborrow().get(i as u32);
+            entry.set_seq(*seq);
+            entry.set_data(data);
+        }
+
+        Promise::ok(())
+    }
+
+    pub fn handle_fetch_wait(
+        &mut self,
+        params: node_service::FetchWaitParams,
+        mut results: node_service::FetchWaitResults,
+    ) -> Promise<(), capnp::Error> {
+        let p = match params.get() {
+            Ok(p) => p,
+            Err(e) => return Promise::err(coded_error(E020_BAD_PARAMS, e)),
+        };
+        let recipient_key = match p.get_recipient_key() {
+            Ok(v) => v.to_vec(),
+            Err(e) => return Promise::err(coded_error(E020_BAD_PARAMS, e)),
+        };
+        let channel_id = p.get_channel_id().unwrap_or_default().to_vec();
+        let version = p.get_version();
+        let timeout_ms = p.get_timeout_ms();
+        let limit = p.get_limit();
+        let auth_ctx = match validate_auth_context(&self.auth_cfg, &self.sessions, p.get_auth()) {
+            Ok(ctx) => ctx,
+            Err(e) => return Promise::err(e),
+        };
+
+        if recipient_key.len() != 32 {
+            return Promise::err(coded_error(
+                E004_IDENTITY_KEY_LENGTH,
+                format!("recipientKey must be exactly 32 bytes, got {}", recipient_key.len()),
+            ));
+        }
+        if version > CURRENT_WIRE_VERSION {
+            return Promise::err(coded_error(
+                E012_WIRE_VERSION,
+                format!("wire version {} not supported (max {CURRENT_WIRE_VERSION})", version),
+            ));
+        }
+
+        if let Err(e) = require_identity_or_request(
+            &auth_ctx,
+            &recipient_key,
+            self.auth_cfg.allow_insecure_identity_from_request,
+        ) {
+            return Promise::err(e);
+        }
+
+        if channel_id.len() == 16 {
+            let members = match self.store.get_channel_members(&channel_id) {
+                Ok(Some(m)) => m,
+                Ok(None) => {
+                    return Promise::err(coded_error(E023_CHANNEL_NOT_FOUND, "channel not found"));
+                }
+                Err(e) => return Promise::err(storage_err(e)),
+            };
+            let caller = match crate::auth::require_identity(&auth_ctx) {
+                Ok(id) => id,
+                Err(e) => return Promise::err(e),
+            };
+            let (a, b) = &members;
+            let caller_in = caller == a.as_slice() || caller == b.as_slice();
+            let recipient_other = (recipient_key.as_slice() == a.as_slice() && caller == b.as_slice())
+                || (recipient_key.as_slice() == b.as_slice() && caller == a.as_slice());
+            if !caller_in || !recipient_other {
+                return Promise::err(coded_error(
+                    E022_CHANNEL_ACCESS_DENIED,
+                    "caller or recipient not a member of this channel",
+                ));
+            }
+        }
+
+        let store = Arc::clone(&self.store);
+        let waiters: Arc<DashMap<Vec<u8>, Arc<Notify>>> = self.waiters.clone();
+
+        Promise::from_future(async move {
+            let fetch_fn = |s: &Arc<dyn Store>, rk: &[u8], ch: &[u8], lim: u32| -> Result<Vec<(u64, Vec<u8>)>, capnp::Error> {
+                if lim > 0 {
+                    s.fetch_limited(rk, ch, lim as usize).map_err(storage_err)
+                } else {
+                    s.fetch(rk, ch).map_err(storage_err)
+                }
+            };
+
+            // Register waiter BEFORE the initial fetch to close the TOCTOU window:
+            // an enqueue between fetch and registration would fire notify before
+            // the waiter exists, causing a missed wakeup.
+            let waiter = if timeout_ms > 0 {
+                Some(
+                    waiters
+                        .entry(recipient_key.clone())
+                        .or_insert_with(|| Arc::new(Notify::new()))
+                        .clone(),
+                )
+            } else {
+                None
+            };
+
+            let messages = fetch_fn(&store, &recipient_key, &channel_id, limit)?;
+
+            if messages.is_empty() {
+                if let Some(waiter) = waiter {
+                    let _ = timeout(Duration::from_millis(timeout_ms), waiter.notified()).await;
+                    let msgs = fetch_fn(&store, &recipient_key, &channel_id, limit)?;
+                    fill_payloads_wait(&mut results, msgs);
+                    metrics::record_fetch_wait_total();
+                    return Ok(());
+                }
+            }
+
+            fill_payloads_wait(&mut results, messages);
+            metrics::record_fetch_wait_total();
+            Ok(())
+        })
+    }
+
+    pub fn handle_peek(
+        &mut self,
+        params: node_service::PeekParams,
+        mut results: node_service::PeekResults,
+    ) -> Promise<(), capnp::Error> {
+        let p = match params.get() {
+            Ok(p) => p,
+            Err(e) => return Promise::err(coded_error(E020_BAD_PARAMS, e)),
+        };
+        let recipient_key = match p.get_recipient_key() {
+            Ok(v) => v.to_vec(),
+            Err(e) => return Promise::err(coded_error(E020_BAD_PARAMS, e)),
+        };
+        let channel_id = p.get_channel_id().unwrap_or_default().to_vec();
+        let version = p.get_version();
+        let limit = p.get_limit();
+        let auth_ctx = match validate_auth_context(&self.auth_cfg, &self.sessions, p.get_auth()) {
+            Ok(ctx) => ctx,
+            Err(e) => return Promise::err(e),
+        };
+
+        if recipient_key.len() != 32 {
+            return Promise::err(coded_error(
+                E004_IDENTITY_KEY_LENGTH,
+                format!("recipientKey must be exactly 32 bytes, got {}", recipient_key.len()),
+            ));
+        }
+        if version > CURRENT_WIRE_VERSION {
+            return Promise::err(coded_error(
+                E012_WIRE_VERSION,
+                format!("wire version {} not supported (max {CURRENT_WIRE_VERSION})", version),
+            ));
+        }
+
+        if let Err(e) = require_identity_or_request(
+            &auth_ctx,
+            &recipient_key,
+            self.auth_cfg.allow_insecure_identity_from_request,
+        ) {
+            return Promise::err(e);
+        }
+
+        let messages = match self
+            .store
+            .peek(&recipient_key, &channel_id, limit as usize)
+            .map_err(storage_err)
+        {
+            Ok(m) => m,
+            Err(e) => return Promise::err(e),
+        };
+
+        if self.redact_logs {
+            tracing::info!(
+                recipient_prefix = %redacted_prefix(&recipient_key),
+                count = messages.len(),
+                "audit: peek"
+            );
+        } else {
+            tracing::info!(
+                recipient_prefix = %fmt_hex(&recipient_key[..4]),
+                count = messages.len(),
+                "audit: peek"
+            );
+        }
+
+        let mut list = results.get().init_payloads(messages.len() as u32);
+        for (i, (seq, data)) in messages.iter().enumerate() {
+            let mut entry = list.reborrow().get(i as u32);
+            entry.set_seq(*seq);
+            entry.set_data(data);
+        }
+
+        Promise::ok(())
+    }
+
+    pub fn handle_ack(
+        &mut self,
+        params: node_service::AckParams,
+        _results: node_service::AckResults,
+    ) -> Promise<(), capnp::Error> {
+        let p = match params.get() {
+            Ok(p) => p,
+            Err(e) => return Promise::err(coded_error(E020_BAD_PARAMS, e)),
+        };
+        let recipient_key = match p.get_recipient_key() {
+            Ok(v) => v.to_vec(),
+            Err(e) => return Promise::err(coded_error(E020_BAD_PARAMS, e)),
+        };
+        let channel_id = p.get_channel_id().unwrap_or_default().to_vec();
+        let version = p.get_version();
+        let seq_up_to = p.get_seq_up_to();
+        let auth_ctx = match validate_auth_context(&self.auth_cfg, &self.sessions, p.get_auth()) {
+            Ok(ctx) => ctx,
+            Err(e) => return Promise::err(e),
+        };
+
+        if recipient_key.len() != 32 {
+            return Promise::err(coded_error(
+                E004_IDENTITY_KEY_LENGTH,
+                format!("recipientKey must be exactly 32 bytes, got {}", recipient_key.len()),
+            ));
+        }
+        if version > CURRENT_WIRE_VERSION {
+            return Promise::err(coded_error(
+                E012_WIRE_VERSION,
+                format!("wire version {} not supported (max {CURRENT_WIRE_VERSION})", version),
+            ));
+        }
+
+        if let Err(e) = require_identity_or_request(
+            &auth_ctx,
+            &recipient_key,
+            self.auth_cfg.allow_insecure_identity_from_request,
+        ) {
+            return Promise::err(e);
+        }
+
+        match self
+            .store
+            .ack(&recipient_key, &channel_id, seq_up_to)
+            .map_err(storage_err)
+        {
+            Ok(removed) => {
+                if self.redact_logs {
+                    tracing::info!(
+                        recipient_prefix = %redacted_prefix(&recipient_key),
+                        seq_up_to = seq_up_to,
+                        removed = removed,
+                        "audit: ack"
+                    );
+                } else {
+                    tracing::info!(
+                        recipient_prefix = %fmt_hex(&recipient_key[..4]),
+                        seq_up_to = seq_up_to,
+                        removed = removed,
+                        "audit: ack"
+                    );
+                }
+            }
+            Err(e) => return Promise::err(e),
+        }
+
+        Promise::ok(())
+    }
+
+    pub fn handle_batch_enqueue(
+        &mut self,
+        params: node_service::BatchEnqueueParams,
+        mut results: node_service::BatchEnqueueResults,
+    ) -> Promise<(), capnp::Error> {
+        let p = match params.get() {
+            Ok(p) => p,
+            Err(e) => return Promise::err(coded_error(E020_BAD_PARAMS, e)),
+        };
+        let recipient_keys = match p.get_recipient_keys() {
+            Ok(v) => v,
+            Err(e) => return Promise::err(coded_error(E020_BAD_PARAMS, e)),
+        };
+        let payload = match p.get_payload() {
+            Ok(v) => v.to_vec(),
+            Err(e) => return Promise::err(coded_error(E020_BAD_PARAMS, e)),
+        };
+        let channel_id = p.get_channel_id().unwrap_or_default().to_vec();
+        let version = p.get_version();
+        let ttl_secs_raw = p.get_ttl_secs();
+        let ttl_secs = if ttl_secs_raw > 0 { Some(ttl_secs_raw) } else { None };
+        let auth_ctx = match validate_auth_context(&self.auth_cfg, &self.sessions, p.get_auth()) {
+            Ok(ctx) => ctx,
+            Err(e) => return Promise::err(e),
+        };
+
+        if payload.is_empty() {
+            return Promise::err(coded_error(E005_PAYLOAD_EMPTY, "payload must not be empty"));
+        }
+        if payload.len() > MAX_PAYLOAD_BYTES {
+            return Promise::err(coded_error(
+                E006_PAYLOAD_TOO_LARGE,
+                format!("payload exceeds max size ({} bytes)", MAX_PAYLOAD_BYTES),
+            ));
+        }
+        if version > CURRENT_WIRE_VERSION {
+            return Promise::err(coded_error(
+                E012_WIRE_VERSION,
+                format!("wire version {} not supported (max {CURRENT_WIRE_VERSION})", version),
+            ));
+        }
+
+        if let Err(e) = check_rate_limit(&self.rate_limits, &auth_ctx.token) {
+            tracing::warn!("rate_limit_hit");
+            metrics::record_rate_limit_hit_total();
+            return Promise::err(e);
+        }
+
+        // Phase 4.3 — DS sender identity binding (same guarantee as handle_enqueue).
+        // sender_identity is derived solely from auth_ctx.identity_key, never client data.
+        if !self.sealed_sender {
+            if let Err(e) = crate::auth::require_identity(&auth_ctx) {
+                return Promise::err(e);
+            }
+        }
+
+        // DM channel authz: validate caller membership once before the loop.
+        if channel_id.len() == 16 {
+            let members = match self.store.get_channel_members(&channel_id) {
+                Ok(Some(m)) => m,
+                Ok(None) => {
+                    return Promise::err(coded_error(E023_CHANNEL_NOT_FOUND, "channel not found"));
+                }
+                Err(e) => return Promise::err(storage_err(e)),
+            };
+            let caller = match crate::auth::require_identity(&auth_ctx) {
+                Ok(id) => id,
+                Err(e) => return Promise::err(e),
+            };
+            let (a, b) = &members;
+            let caller_in = caller == a.as_slice() || caller == b.as_slice();
+            if !caller_in {
+                return Promise::err(coded_error(
+                    E022_CHANNEL_ACCESS_DENIED,
+                    "caller is not a member of this channel",
+                ));
+            }
+        }
+
+        // Eagerly collect recipient keys so params can be dropped before any async work.
+        let mut recipient_key_vecs: Vec<Vec<u8>> = Vec::with_capacity(recipient_keys.len() as usize);
+        for i in 0..recipient_keys.len() {
+            let rk = match recipient_keys.get(i) {
+                Ok(v) => v.to_vec(),
+                Err(e) => return Promise::err(coded_error(E020_BAD_PARAMS, e)),
+            };
+            if rk.len() != 32 {
+                return Promise::err(coded_error(
+                    E004_IDENTITY_KEY_LENGTH,
+                    format!("recipientKey[{}] must be exactly 32 bytes, got {}", i, rk.len()),
+                ));
+            }
+
+            // Per-recipient DM channel membership check (only when channel_id is a 16-byte UUID).
+            if channel_id.len() == 16 {
+                let members = match self.store.get_channel_members(&channel_id) {
+                    Ok(Some(m)) => m,
+                    Ok(None) => {
+                        return Promise::err(coded_error(
+                            E023_CHANNEL_NOT_FOUND,
+                            "channel not found",
+                        ));
+                    }
+                    Err(e) => return Promise::err(storage_err(e)),
+                };
+                let caller = match crate::auth::require_identity(&auth_ctx) {
+                    Ok(id) => id,
+                    Err(e) => return Promise::err(e),
+                };
+                let (a, b) = &members;
+                let recipient_other = (rk == *a && caller == b.as_slice())
+                    || (rk == *b && caller == a.as_slice());
+                if !recipient_other {
+                    return Promise::err(coded_error(
+                        E022_CHANNEL_ACCESS_DENIED,
+                        "recipient is not a member of this channel",
+                    ));
+                }
+            }
+
+            recipient_key_vecs.push(rk);
+        }
+
+        // Hook: on_message_enqueue for each recipient — fires before storage.
+        // sender_identity is derived solely from auth_ctx (server-side session state).
+        let sender_identity = if self.sealed_sender {
+            None
+        } else {
+            crate::auth::require_identity(&auth_ctx).ok().map(|v| v.to_vec())
+        };
+        let sender_prefix = sender_identity
+            .as_deref()
+            .filter(|id| id.len() >= 4)
+            .map(|id| fmt_hex(&id[..4]));
+        let mut hook_events = Vec::with_capacity(recipient_key_vecs.len());
+        for rk in &recipient_key_vecs {
+            let event = MessageEvent {
+                sender_identity: sender_identity.clone(),
+                recipient_key: rk.clone(),
+                channel_id: channel_id.clone(),
+                payload_len: payload.len(),
+                seq: 0,
+            };
+            if let HookAction::Reject(reason) = self.hooks.on_message_enqueue(&event) {
+                return Promise::err(capnp::Error::failed(format!("hook rejected enqueue: {reason}")));
+            }
+            hook_events.push(event);
+        }
+
+        let n = recipient_key_vecs.len();
+        let store = Arc::clone(&self.store);
+        let waiters = Arc::clone(&self.waiters);
+        let fed_client = self.federation_client.clone();
+        let local_domain = self.local_domain.clone();
+        let hooks = Arc::clone(&self.hooks);
+        let redact_logs = self.redact_logs;
+
+        // Use an async future to support federation relay alongside local enqueue.
+        // All storage operations are synchronous; only federation relay calls are await-ed.
+        Promise::from_future(async move {
+            let mut seqs = Vec::with_capacity(n);
+
+            for rk in &recipient_key_vecs {
+                // Federation routing: relay to the recipient's home server when remote.
+                let dest = if let (Some(ref _fed), Some(ref domain)) = (&fed_client, &local_domain) {
+                    crate::federation::routing::resolve_destination(&store, rk, domain)
+                } else {
+                    crate::federation::routing::Destination::Local
+                };
+
+                let seq = match dest {
+                    crate::federation::routing::Destination::Remote(ref remote_domain) => {
+                        let fed = fed_client.as_deref().ok_or_else(|| {
+                            capnp::Error::failed("federation client unavailable for remote routing".into())
+                        })?;
+                        tracing::info!(
+                            recipient_prefix = %fmt_hex(&rk[..4]),
+                            domain = %remote_domain,
+                            "federation: routing batch enqueue to remote server"
+                        );
+                        fed.relay_enqueue(remote_domain, rk, &payload, &channel_id)
+                            .await
+                            .map_err(|e| {
+                                capnp::Error::failed(format!("federation relay failed: {e}"))
+                            })?
+                    }
+                    crate::federation::routing::Destination::Local => {
+                        match store.queue_depth(rk, &channel_id) {
+                            Ok(depth) if depth >= MAX_QUEUE_DEPTH => {
+                                return Err(coded_error(
+                                    E015_QUEUE_FULL,
+                                    format!("queue depth {} exceeds limit {MAX_QUEUE_DEPTH}", depth),
+                                ));
+                            }
+                            Err(e) => return Err(storage_err(e)),
+                            _ => {}
+                        }
+                        store
+                            .enqueue(rk, &channel_id, payload.clone(), ttl_secs)
+                            .map_err(storage_err)?
+                    }
+                };
+
+                seqs.push(seq);
+                metrics::record_enqueue_total();
+                metrics::record_enqueue_bytes(payload.len() as u64);
+                crate::auth::waiter(&waiters, rk).notify_waiters();
+            }
+
+            let mut list = results.get().init_seqs(seqs.len() as u32);
+            for (i, seq) in seqs.iter().enumerate() {
+                list.set(i as u32, *seq);
+            }
+
+            // Hook: on_batch_enqueue — fires after all messages are stored.
+            hooks.on_batch_enqueue(&hook_events);
+
+            if redact_logs {
+                tracing::info!(
+                    recipient_count = n,
+                    "audit: batch_enqueue"
+                );
+            } else {
+                tracing::info!(
+                    sender_prefix = sender_prefix.as_deref().unwrap_or("sealed"),
+                    recipient_count = n,
+                    payload_len = payload.len(),
+                    "audit: batch_enqueue"
+                );
+            }
+
+            Ok(())
+        })
+    }
+}

crates/quicprochat-server/src/node_service/device_ops.rs

@@ -0,0 +1,154 @@
+//! Device registry RPC handlers: registerDevice, listDevices, revokeDevice.
+
+use capnp::capability::Promise;
+use quicprochat_proto::node_capnp::node_service;
+
+use crate::auth::{coded_error, require_identity, validate_auth_context};
+use crate::error_codes::*;
+use crate::storage::StorageError;
+
+use super::NodeServiceImpl;
+
+const MAX_DEVICES_PER_IDENTITY: usize = 5;
+
+fn storage_err(err: StorageError) -> capnp::Error {
+    coded_error(E009_STORAGE_ERROR, err)
+}
+
+impl NodeServiceImpl {
+    pub fn handle_register_device(
+        &mut self,
+        params: node_service::RegisterDeviceParams,
+        mut results: node_service::RegisterDeviceResults,
+    ) -> 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),
+        };
+
+        let identity_key = match require_identity(&auth_ctx) {
+            Ok(ik) => ik.to_vec(),
+            Err(e) => return Promise::err(e),
+        };
+
+        let device_id = match p.get_device_id() {
+            Ok(v) => v.to_vec(),
+            Err(e) => return Promise::err(coded_error(E020_BAD_PARAMS, e)),
+        };
+
+        if device_id.is_empty() {
+            return Promise::err(coded_error(E020_BAD_PARAMS, "deviceId must not be empty"));
+        }
+
+        let device_name = match p.get_device_name() {
+            Ok(n) => match n.to_str() {
+                Ok(s) => s.to_string(),
+                Err(_) => return Promise::err(coded_error(E020_BAD_PARAMS, "deviceName must be valid UTF-8")),
+            },
+            Err(e) => return Promise::err(coded_error(E020_BAD_PARAMS, e)),
+        };
+
+        // Check device limit.
+        match self.store.device_count(&identity_key) {
+            Ok(count) if count >= MAX_DEVICES_PER_IDENTITY => {
+                return Promise::err(coded_error(
+                    E029_DEVICE_LIMIT,
+                    format!("maximum {MAX_DEVICES_PER_IDENTITY} devices per identity"),
+                ));
+            }
+            Err(e) => return Promise::err(storage_err(e)),
+            _ => {}
+        }
+
+        match self.store.register_device(&identity_key, &device_id, &device_name) {
+            Ok(success) => {
+                results.get().set_success(success);
+                Promise::ok(())
+            }
+            Err(e) => Promise::err(storage_err(e)),
+        }
+    }
+
+    pub fn handle_list_devices(
+        &mut self,
+        params: node_service::ListDevicesParams,
+        mut results: node_service::ListDevicesResults,
+    ) -> 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),
+        };
+
+        let identity_key = match require_identity(&auth_ctx) {
+            Ok(ik) => ik.to_vec(),
+            Err(e) => return Promise::err(e),
+        };
+
+        let devices = match self.store.list_devices(&identity_key) {
+            Ok(d) => d,
+            Err(e) => return Promise::err(storage_err(e)),
+        };
+
+        let r = results.get();
+        let mut list = r.init_devices(devices.len() as u32);
+        for (i, (device_id, name, registered_at)) in devices.iter().enumerate() {
+            let mut entry = list.reborrow().get(i as u32);
+            entry.set_device_id(device_id);
+            entry.set_device_name(name);
+            entry.set_registered_at(*registered_at);
+        }
+
+        Promise::ok(())
+    }
+
+    pub fn handle_revoke_device(
+        &mut self,
+        params: node_service::RevokeDeviceParams,
+        mut results: node_service::RevokeDeviceResults,
+    ) -> 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),
+        };
+
+        let identity_key = match require_identity(&auth_ctx) {
+            Ok(ik) => ik.to_vec(),
+            Err(e) => return Promise::err(e),
+        };
+
+        let device_id = match p.get_device_id() {
+            Ok(v) => v.to_vec(),
+            Err(e) => return Promise::err(coded_error(E020_BAD_PARAMS, e)),
+        };
+
+        if device_id.is_empty() {
+            return Promise::err(coded_error(E020_BAD_PARAMS, "deviceId must not be empty"));
+        }
+
+        match self.store.revoke_device(&identity_key, &device_id) {
+            Ok(true) => {
+                results.get().set_success(true);
+                Promise::ok(())
+            }
+            Ok(false) => {
+                Promise::err(coded_error(E030_DEVICE_NOT_FOUND, "device not found"))
+            }
+            Err(e) => Promise::err(storage_err(e)),
+        }
+    }
+}

crates/quicprochat-server/src/node_service/key_ops.rs

@@ -0,0 +1,294 @@
+use capnp::capability::Promise;
+use quicprochat_proto::node_capnp::node_service;
+
+use crate::auth::{coded_error, fmt_hex, require_identity_or_request, validate_auth_context};
+use crate::error_codes::*;
+use crate::metrics;
+use crate::storage::StorageError;
+
+use super::NodeServiceImpl;
+
+fn storage_err(err: StorageError) -> capnp::Error {
+    coded_error(E009_STORAGE_ERROR, err)
+}
+
+const MAX_KEYPACKAGE_BYTES: usize = 1024 * 1024; // 1 MB cap per KeyPackage
+
+impl NodeServiceImpl {
+    pub fn handle_upload_key_package(
+        &mut self,
+        params: node_service::UploadKeyPackageParams,
+        mut results: node_service::UploadKeyPackageResults,
+    ) -> Promise<(), capnp::Error> {
+        let (auth_ctx, identity_key, package) = match params.get() {
+            Ok(p) => {
+                let auth_ctx = match validate_auth_context(&self.auth_cfg, &self.sessions, p.get_auth()) {
+                    Ok(ctx) => ctx,
+                    Err(e) => return Promise::err(e),
+                };
+                let ik = match p.get_identity_key() {
+                    Ok(v) => v.to_vec(),
+                    Err(e) => return Promise::err(coded_error(E020_BAD_PARAMS, e)),
+                };
+                let pkg = match p.get_package() {
+                    Ok(v) => v.to_vec(),
+                    Err(e) => return Promise::err(coded_error(E020_BAD_PARAMS, e)),
+                };
+                (auth_ctx, ik, pkg)
+            }
+            Err(e) => return Promise::err(e),
+        };
+
+        if identity_key.len() != 32 {
+            return Promise::err(coded_error(
+                E004_IDENTITY_KEY_LENGTH,
+                format!("identityKey must be exactly 32 bytes, got {}", identity_key.len()),
+            ));
+        }
+        if package.is_empty() {
+            return Promise::err(coded_error(E007_PACKAGE_EMPTY, "package must not be empty"));
+        }
+        if package.len() > MAX_KEYPACKAGE_BYTES {
+            return Promise::err(coded_error(
+                E008_PACKAGE_TOO_LARGE,
+                format!("package exceeds max size ({} bytes)", MAX_KEYPACKAGE_BYTES),
+            ));
+        }
+
+        if let Err(e) = require_identity_or_request(
+            &auth_ctx,
+            &identity_key,
+            self.auth_cfg.allow_insecure_identity_from_request,
+        ) {
+            return Promise::err(e);
+        }
+
+        if let Err(e) = quicprochat_core::validate_keypackage_ciphersuite(&package) {
+            return Promise::err(coded_error(
+                E021_CIPHERSUITE_NOT_ALLOWED,
+                format!("KeyPackage ciphersuite not allowed: {e}"),
+            ));
+        }
+
+        let fingerprint: Vec<u8> = crate::auth::fingerprint(&package);
+        if let Err(e) = self
+            .store
+            .upload_key_package(&identity_key, package)
+            .map_err(storage_err)
+        {
+            return Promise::err(e);
+        }
+
+        results.get().set_fingerprint(&fingerprint);
+
+        metrics::record_key_package_upload_total();
+        // Audit: KeyPackage upload — only fingerprint prefix, no secrets.
+        tracing::info!(
+            identity_prefix = %fmt_hex(&identity_key[..4]),
+            fingerprint_prefix = %fmt_hex(&fingerprint[..4]),
+            "audit: key_package_upload"
+        );
+
+        Promise::ok(())
+    }
+
+    pub fn handle_fetch_key_package(
+        &mut self,
+        params: node_service::FetchKeyPackageParams,
+        mut results: node_service::FetchKeyPackageResults,
+    ) -> Promise<(), capnp::Error> {
+        let identity_key = match params.get() {
+            Ok(p) => match p.get_identity_key() {
+                Ok(v) => v.to_vec(),
+                Err(e) => return Promise::err(coded_error(E020_BAD_PARAMS, e)),
+            },
+            Err(e) => return Promise::err(coded_error(E020_BAD_PARAMS, e)),
+        };
+        if let Err(e) = params
+            .get()
+            .ok()
+            .map(|p| crate::auth::validate_auth(&self.auth_cfg, &self.sessions, p.get_auth()))
+            .transpose()
+        {
+            return Promise::err(e);
+        }
+
+        if identity_key.len() != 32 {
+            return Promise::err(coded_error(
+                E004_IDENTITY_KEY_LENGTH,
+                format!("identityKey must be exactly 32 bytes, got {}", identity_key.len()),
+            ));
+        }
+
+        let package = match self
+            .store
+            .fetch_key_package(&identity_key)
+            .map_err(storage_err)
+        {
+            Ok(p) => p,
+            Err(e) => return Promise::err(e),
+        };
+
+        match package {
+            Some(pkg) => {
+                tracing::debug!(identity = %fmt_hex(&identity_key[..4]), "KeyPackage fetched");
+                results.get().set_package(&pkg);
+            }
+            None => {
+                tracing::debug!(
+                    identity = %fmt_hex(&identity_key[..4]),
+                    "no KeyPackage available for identity"
+                );
+                results.get().set_package(&[]);
+            }
+        }
+
+        Promise::ok(())
+    }
+
+    pub fn handle_upload_hybrid_key(
+        &mut self,
+        params: node_service::UploadHybridKeyParams,
+        _results: node_service::UploadHybridKeyResults,
+    ) -> Promise<(), capnp::Error> {
+        let p = match params.get() {
+            Ok(p) => p,
+            Err(e) => return Promise::err(coded_error(E020_BAD_PARAMS, e)),
+        };
+        let identity_key = match p.get_identity_key() {
+            Ok(v) => v.to_vec(),
+            Err(e) => return Promise::err(coded_error(E020_BAD_PARAMS, e)),
+        };
+        let hybrid_pk = match p.get_hybrid_public_key() {
+            Ok(v) => v.to_vec(),
+            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),
+        };
+
+        if identity_key.len() != 32 {
+            return Promise::err(coded_error(
+                E004_IDENTITY_KEY_LENGTH,
+                format!("identityKey must be exactly 32 bytes, got {}", identity_key.len()),
+            ));
+        }
+        if hybrid_pk.is_empty() {
+            return Promise::err(coded_error(E013_HYBRID_KEY_EMPTY, "hybridPublicKey must not be empty"));
+        }
+
+        if let Err(e) = require_identity_or_request(
+            &auth_ctx,
+            &identity_key,
+            self.auth_cfg.allow_insecure_identity_from_request,
+        ) {
+            return Promise::err(e);
+        }
+
+        if let Err(e) = self
+            .store
+            .upload_hybrid_key(&identity_key, hybrid_pk)
+            .map_err(storage_err)
+        {
+            return Promise::err(e);
+        }
+
+        tracing::debug!(identity = %fmt_hex(&identity_key[..4]), "hybrid public key uploaded");
+
+        Promise::ok(())
+    }
+
+    pub fn handle_fetch_hybrid_key(
+        &mut self,
+        params: node_service::FetchHybridKeyParams,
+        mut results: node_service::FetchHybridKeyResults,
+    ) -> Promise<(), capnp::Error> {
+        let p = match params.get() {
+            Ok(p) => p,
+            Err(e) => return Promise::err(coded_error(E020_BAD_PARAMS, e)),
+        };
+        let identity_key = match p.get_identity_key() {
+            Ok(v) => v.to_vec(),
+            Err(e) => return Promise::err(coded_error(E020_BAD_PARAMS, e)),
+        };
+
+        // Auth check only — any authenticated user can fetch any peer's hybrid public key.
+        if let Err(e) = validate_auth_context(&self.auth_cfg, &self.sessions, p.get_auth()) {
+            return Promise::err(e);
+        }
+
+        if identity_key.len() != 32 {
+            return Promise::err(coded_error(
+                E004_IDENTITY_KEY_LENGTH,
+                format!("identityKey must be exactly 32 bytes, got {}", identity_key.len()),
+            ));
+        }
+
+        let hybrid_pk = match self
+            .store
+            .fetch_hybrid_key(&identity_key)
+            .map_err(storage_err)
+        {
+            Ok(p) => p,
+            Err(e) => return Promise::err(e),
+        };
+
+        match hybrid_pk {
+            Some(pk) => {
+                tracing::debug!(identity = %fmt_hex(&identity_key[..4]), "hybrid key fetched");
+                results.get().set_hybrid_public_key(&pk);
+            }
+            None => {
+                tracing::debug!(identity = %fmt_hex(&identity_key[..4]), "no hybrid key for identity");
+                results.get().set_hybrid_public_key(&[]);
+            }
+        }
+
+        Promise::ok(())
+    }
+
+    pub fn handle_fetch_hybrid_keys(
+        &mut self,
+        params: node_service::FetchHybridKeysParams,
+        mut results: node_service::FetchHybridKeysResults,
+    ) -> Promise<(), capnp::Error> {
+        let p = match params.get() {
+            Ok(p) => p,
+            Err(e) => return Promise::err(coded_error(E020_BAD_PARAMS, e)),
+        };
+        let identity_keys = match p.get_identity_keys() {
+            Ok(v) => v,
+            Err(e) => return Promise::err(coded_error(E020_BAD_PARAMS, e)),
+        };
+
+        if let Err(e) = validate_auth_context(&self.auth_cfg, &self.sessions, p.get_auth()) {
+            return Promise::err(e);
+        }
+
+        let count = identity_keys.len() as usize;
+        let mut key_data: Vec<Vec<u8>> = Vec::with_capacity(count);
+        for i in 0..identity_keys.len() {
+            let ik = match identity_keys.get(i) {
+                Ok(v) => v.to_vec(),
+                Err(e) => return Promise::err(coded_error(E020_BAD_PARAMS, e)),
+            };
+            let pk = match self.store.fetch_hybrid_key(&ik).map_err(storage_err) {
+                Ok(Some(pk)) => pk,
+                Ok(None) => vec![],
+                Err(e) => return Promise::err(e),
+            };
+            key_data.push(pk);
+        }
+
+        let mut list = results.get().init_keys(key_data.len() as u32);
+        for (i, pk) in key_data.iter().enumerate() {
+            list.set(i as u32, pk);
+        }
+
+        tracing::debug!(count = count, "batch hybrid key fetch");
+
+        Promise::ok(())
+    }
+}

crates/quicprochat-server/src/node_service/mod.rs

@@ -0,0 +1,434 @@
+use std::path::PathBuf;
+use std::sync::Arc;
+use std::time::Duration;
+
+use capnp_rpc::RpcSystem;
+use dashmap::DashMap;
+use opaque_ke::ServerSetup;
+use quicprochat_core::opaque_auth::OpaqueSuite;
+use quicprochat_kt::MerkleLog;
+use quicprochat_proto::node_capnp::node_service;
+use tokio::sync::Notify;
+use tokio_util::compat::{TokioAsyncReadCompatExt, TokioAsyncWriteCompatExt};
+
+use crate::auth::{
+    current_timestamp, AuthConfig, PendingLogin, RateEntry, SessionInfo,
+    PENDING_LOGIN_TTL_SECS, RATE_LIMIT_WINDOW_SECS,
+};
+use crate::storage::Store;
+
+/// 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;
+
+mod account_ops;
+mod auth_ops;
+mod blob_ops;
+mod channel_ops;
+mod delivery;
+mod device_ops;
+mod key_ops;
+mod p2p_ops;
+mod user_ops;
+
+impl node_service::Server for NodeServiceImpl {
+    fn upload_key_package(
+        &mut self,
+        params: node_service::UploadKeyPackageParams,
+        results: node_service::UploadKeyPackageResults,
+    ) -> capnp::capability::Promise<(), capnp::Error> {
+        self.handle_upload_key_package(params, results)
+    }
+
+    fn fetch_key_package(
+        &mut self,
+        params: node_service::FetchKeyPackageParams,
+        results: node_service::FetchKeyPackageResults,
+    ) -> capnp::capability::Promise<(), capnp::Error> {
+        self.handle_fetch_key_package(params, results)
+    }
+
+    fn enqueue(
+        &mut self,
+        params: node_service::EnqueueParams,
+        results: node_service::EnqueueResults,
+    ) -> capnp::capability::Promise<(), capnp::Error> {
+        self.handle_enqueue(params, results)
+    }
+
+    fn fetch(
+        &mut self,
+        params: node_service::FetchParams,
+        results: node_service::FetchResults,
+    ) -> capnp::capability::Promise<(), capnp::Error> {
+        self.handle_fetch(params, results)
+    }
+
+    fn fetch_wait(
+        &mut self,
+        params: node_service::FetchWaitParams,
+        results: node_service::FetchWaitResults,
+    ) -> capnp::capability::Promise<(), capnp::Error> {
+        self.handle_fetch_wait(params, results)
+    }
+
+    fn health(
+        &mut self,
+        params: node_service::HealthParams,
+        results: node_service::HealthResults,
+    ) -> capnp::capability::Promise<(), capnp::Error> {
+        self.handle_health(params, results)
+    }
+
+    fn upload_hybrid_key(
+        &mut self,
+        params: node_service::UploadHybridKeyParams,
+        results: node_service::UploadHybridKeyResults,
+    ) -> capnp::capability::Promise<(), capnp::Error> {
+        self.handle_upload_hybrid_key(params, results)
+    }
+
+    fn fetch_hybrid_key(
+        &mut self,
+        params: node_service::FetchHybridKeyParams,
+        results: node_service::FetchHybridKeyResults,
+    ) -> capnp::capability::Promise<(), capnp::Error> {
+        self.handle_fetch_hybrid_key(params, results)
+    }
+
+    fn opaque_login_start(
+        &mut self,
+        params: node_service::OpaqueLoginStartParams,
+        results: node_service::OpaqueLoginStartResults,
+    ) -> capnp::capability::Promise<(), capnp::Error> {
+        self.handle_opaque_login_start(params, results)
+    }
+
+    fn opaque_register_start(
+        &mut self,
+        params: node_service::OpaqueRegisterStartParams,
+        results: node_service::OpaqueRegisterStartResults,
+    ) -> capnp::capability::Promise<(), capnp::Error> {
+        self.handle_opaque_register_start(params, results)
+    }
+
+    fn opaque_login_finish(
+        &mut self,
+        params: node_service::OpaqueLoginFinishParams,
+        results: node_service::OpaqueLoginFinishResults,
+    ) -> capnp::capability::Promise<(), capnp::Error> {
+        self.handle_opaque_login_finish(params, results)
+    }
+
+    fn opaque_register_finish(
+        &mut self,
+        params: node_service::OpaqueRegisterFinishParams,
+        results: node_service::OpaqueRegisterFinishResults,
+    ) -> capnp::capability::Promise<(), capnp::Error> {
+        self.handle_opaque_register_finish(params, results)
+    }
+
+    fn publish_endpoint(
+        &mut self,
+        params: node_service::PublishEndpointParams,
+        results: node_service::PublishEndpointResults,
+    ) -> capnp::capability::Promise<(), capnp::Error> {
+        self.handle_publish_endpoint(params, results)
+    }
+
+    fn resolve_endpoint(
+        &mut self,
+        params: node_service::ResolveEndpointParams,
+        results: node_service::ResolveEndpointResults,
+    ) -> capnp::capability::Promise<(), capnp::Error> {
+        self.handle_resolve_endpoint(params, results)
+    }
+
+    fn peek(
+        &mut self,
+        params: node_service::PeekParams,
+        results: node_service::PeekResults,
+    ) -> capnp::capability::Promise<(), capnp::Error> {
+        self.handle_peek(params, results)
+    }
+
+    fn ack(
+        &mut self,
+        params: node_service::AckParams,
+        results: node_service::AckResults,
+    ) -> capnp::capability::Promise<(), capnp::Error> {
+        self.handle_ack(params, results)
+    }
+
+    fn fetch_hybrid_keys(
+        &mut self,
+        params: node_service::FetchHybridKeysParams,
+        results: node_service::FetchHybridKeysResults,
+    ) -> capnp::capability::Promise<(), capnp::Error> {
+        self.handle_fetch_hybrid_keys(params, results)
+    }
+
+    fn batch_enqueue(
+        &mut self,
+        params: node_service::BatchEnqueueParams,
+        results: node_service::BatchEnqueueResults,
+    ) -> capnp::capability::Promise<(), capnp::Error> {
+        self.handle_batch_enqueue(params, results)
+    }
+
+    fn create_channel(
+        &mut self,
+        params: node_service::CreateChannelParams,
+        results: node_service::CreateChannelResults,
+    ) -> capnp::capability::Promise<(), capnp::Error> {
+        self.handle_create_channel(params, results)
+    }
+
+    fn resolve_user(
+        &mut self,
+        params: node_service::ResolveUserParams,
+        results: node_service::ResolveUserResults,
+    ) -> capnp::capability::Promise<(), capnp::Error> {
+        self.handle_resolve_user(params, results)
+    }
+
+    fn resolve_identity(
+        &mut self,
+        params: node_service::ResolveIdentityParams,
+        results: node_service::ResolveIdentityResults,
+    ) -> capnp::capability::Promise<(), capnp::Error> {
+        self.handle_resolve_identity(params, results)
+    }
+
+    fn upload_blob(
+        &mut self,
+        params: node_service::UploadBlobParams,
+        results: node_service::UploadBlobResults,
+    ) -> capnp::capability::Promise<(), capnp::Error> {
+        self.handle_upload_blob(params, results)
+    }
+
+    fn download_blob(
+        &mut self,
+        params: node_service::DownloadBlobParams,
+        results: node_service::DownloadBlobResults,
+    ) -> capnp::capability::Promise<(), capnp::Error> {
+        self.handle_download_blob(params, results)
+    }
+
+    fn delete_account(
+        &mut self,
+        params: node_service::DeleteAccountParams,
+        results: node_service::DeleteAccountResults,
+    ) -> capnp::capability::Promise<(), capnp::Error> {
+        self.handle_delete_account(params, results)
+    }
+
+    fn register_device(
+        &mut self,
+        params: node_service::RegisterDeviceParams,
+        results: node_service::RegisterDeviceResults,
+    ) -> capnp::capability::Promise<(), capnp::Error> {
+        self.handle_register_device(params, results)
+    }
+
+    fn list_devices(
+        &mut self,
+        params: node_service::ListDevicesParams,
+        results: node_service::ListDevicesResults,
+    ) -> capnp::capability::Promise<(), capnp::Error> {
+        self.handle_list_devices(params, results)
+    }
+
+    fn revoke_device(
+        &mut self,
+        params: node_service::RevokeDeviceParams,
+        results: node_service::RevokeDeviceResults,
+    ) -> capnp::capability::Promise<(), capnp::Error> {
+        self.handle_revoke_device(params, results)
+    }
+}
+
+pub const CURRENT_WIRE_VERSION: u16 = 1;
+
+pub struct NodeServiceImpl {
+    pub store: Arc<dyn Store>,
+    pub waiters: Arc<DashMap<Vec<u8>, Arc<Notify>>>,
+    pub auth_cfg: Arc<AuthConfig>,
+    pub opaque_setup: Arc<ServerSetup<OpaqueSuite>>,
+    pub pending_logins: Arc<DashMap<String, PendingLogin>>,
+    pub sessions: Arc<DashMap<Vec<u8>, SessionInfo>>,
+    pub rate_limits: Arc<DashMap<Vec<u8>, RateEntry>>,
+    /// When true, enqueue does not require identity-bound session (Sealed Sender).
+    pub sealed_sender: bool,
+    /// Outbound federation client for relaying to remote servers (None if federation disabled).
+    pub federation_client: Option<Arc<crate::federation::FederationClient>>,
+    /// This server's federation domain (empty if federation disabled).
+    pub local_domain: Option<String>,
+    /// Server-side plugin hooks for extensibility.
+    pub hooks: Arc<dyn crate::hooks::ServerHooks>,
+    /// Server Ed25519 signing key for delivery proofs.
+    pub signing_key: Arc<quicprochat_core::IdentityKeypair>,
+    /// Key Transparency Merkle log (shared across connections).
+    pub kt_log: Arc<std::sync::Mutex<MerkleLog>>,
+    /// Server data directory (used for blob storage).
+    pub data_dir: PathBuf,
+    /// When true, hash identity key prefixes and omit payload sizes in audit logs.
+    pub redact_logs: bool,
+}
+
+impl NodeServiceImpl {
+    #[allow(clippy::too_many_arguments)]
+    pub fn new(
+        store: Arc<dyn Store>,
+        waiters: Arc<DashMap<Vec<u8>, Arc<Notify>>>,
+        auth_cfg: Arc<AuthConfig>,
+        opaque_setup: Arc<ServerSetup<OpaqueSuite>>,
+        pending_logins: Arc<DashMap<String, PendingLogin>>,
+        sessions: Arc<DashMap<Vec<u8>, SessionInfo>>,
+        rate_limits: Arc<DashMap<Vec<u8>, RateEntry>>,
+        sealed_sender: bool,
+        federation_client: Option<Arc<crate::federation::FederationClient>>,
+        local_domain: Option<String>,
+        signing_key: Arc<quicprochat_core::IdentityKeypair>,
+        hooks: Arc<dyn crate::hooks::ServerHooks>,
+        kt_log: Arc<std::sync::Mutex<MerkleLog>>,
+        data_dir: PathBuf,
+        redact_logs: bool,
+    ) -> Self {
+        Self {
+            store,
+            waiters,
+            auth_cfg,
+            opaque_setup,
+            pending_logins,
+            sessions,
+            rate_limits,
+            sealed_sender,
+            federation_client,
+            local_domain,
+            hooks,
+            signing_key,
+            kt_log,
+            data_dir,
+            redact_logs,
+        }
+    }
+}
+
+#[allow(clippy::too_many_arguments)]
+pub async fn handle_node_connection(
+    connecting: quinn::Connecting,
+    store: Arc<dyn Store>,
+    waiters: Arc<DashMap<Vec<u8>, Arc<Notify>>>,
+    auth_cfg: Arc<AuthConfig>,
+    opaque_setup: Arc<ServerSetup<OpaqueSuite>>,
+    pending_logins: Arc<DashMap<String, PendingLogin>>,
+    sessions: Arc<DashMap<Vec<u8>, SessionInfo>>,
+    rate_limits: Arc<DashMap<Vec<u8>, RateEntry>>,
+    sealed_sender: bool,
+    federation_client: Option<Arc<crate::federation::FederationClient>>,
+    local_domain: Option<String>,
+    signing_key: Arc<quicprochat_core::IdentityKeypair>,
+    hooks: Arc<dyn crate::hooks::ServerHooks>,
+    kt_log: Arc<std::sync::Mutex<MerkleLog>>,
+    data_dir: PathBuf,
+    redact_logs: bool,
+) -> Result<(), anyhow::Error> {
+    let connection = connecting.await?;
+
+    tracing::info!(peer = %connection.remote_address(), "QUIC connected");
+
+    let (send, recv) = connection
+        .accept_bi()
+        .await
+        .map_err(|e| anyhow::anyhow!("failed to accept bi stream: {e}"))?;
+    let (reader, writer) = (recv.compat(), send.compat_write());
+
+    let mut reader_opts = capnp::message::ReaderOptions::new();
+    reader_opts.traversal_limit_in_words(Some(CAPNP_TRAVERSAL_LIMIT_WORDS));
+    let network = capnp_rpc::twoparty::VatNetwork::new(
+        reader,
+        writer,
+        capnp_rpc::rpc_twoparty_capnp::Side::Server,
+        reader_opts,
+    );
+
+    let service: node_service::Client = capnp_rpc::new_client(NodeServiceImpl::new(
+        store,
+        waiters,
+        auth_cfg,
+        opaque_setup,
+        pending_logins,
+        sessions,
+        rate_limits,
+        sealed_sender,
+        federation_client,
+        local_domain,
+        signing_key,
+        hooks,
+        kt_log,
+        data_dir,
+        redact_logs,
+    ));
+
+    RpcSystem::new(Box::new(network), Some(service.client))
+        .await
+        .map_err(|e| anyhow::anyhow!("NodeService RPC error: {e}"))
+}
+
+const MESSAGE_TTL_SECS: u64 = 7 * 24 * 60 * 60; // 7 days
+
+pub fn spawn_cleanup_task(
+    sessions: Arc<DashMap<Vec<u8>, SessionInfo>>,
+    pending_logins: Arc<DashMap<String, PendingLogin>>,
+    rate_limits: Arc<DashMap<Vec<u8>, RateEntry>>,
+    conn_rate_limits: Arc<DashMap<std::net::IpAddr, RateEntry>>,
+    store: Arc<dyn Store>,
+    waiters: Arc<DashMap<Vec<u8>, Arc<Notify>>>,
+) {
+    tokio::spawn(async move {
+        let mut interval = tokio::time::interval(Duration::from_secs(60));
+        loop {
+            interval.tick().await;
+            let now = current_timestamp();
+
+            sessions.retain(|_, info| info.expires_at > now);
+            pending_logins.retain(|_, pl| now - pl.created_at < PENDING_LOGIN_TTL_SECS);
+            rate_limits.retain(|_, entry| now - entry.window_start < RATE_LIMIT_WINDOW_SECS * 2);
+            conn_rate_limits.retain(|_, entry| {
+                now - entry.window_start < crate::auth::CONN_RATE_LIMIT_WINDOW_SECS * 2
+            });
+
+            // Bound map sizes to prevent unbounded growth from malicious clients.
+            const MAX_SESSIONS: usize = 100_000;
+            const MAX_WAITERS: usize = 100_000;
+            if sessions.len() > MAX_SESSIONS {
+                let overflow = sessions.len() - MAX_SESSIONS;
+                let mut entries: Vec<_> = sessions
+                    .iter()
+                    .map(|e| (e.key().clone(), e.expires_at))
+                    .collect();
+                entries.sort_by_key(|(_, exp)| *exp);
+                for (key, _) in entries.into_iter().take(overflow) {
+                    sessions.remove(&key);
+                }
+            }
+            if waiters.len() > MAX_WAITERS {
+                let overflow = waiters.len() - MAX_WAITERS;
+                let keys: Vec<_> =
+                    waiters.iter().take(overflow).map(|e| e.key().clone()).collect();
+                for key in keys {
+                    waiters.remove(&key);
+                }
+            }
+
+            match store.gc_expired_messages(MESSAGE_TTL_SECS) {
+                Ok(n) if n > 0 => {
+                    tracing::debug!(expired = n, "garbage collected expired messages")
+                }
+                Err(e) => tracing::warn!(error = %e, "message GC failed"),
+                _ => {}
+            }
+        }
+    });
+}

crates/quicprochat-server/src/node_service/p2p_ops.rs

@@ -0,0 +1,119 @@
+use capnp::capability::Promise;
+use quicprochat_proto::node_capnp::node_service;
+
+use crate::auth::{
+    coded_error, fmt_hex, require_identity_or_request, validate_auth, validate_auth_context,
+};
+use crate::error_codes::*;
+use crate::storage::StorageError;
+
+use super::NodeServiceImpl;
+
+fn storage_err(err: StorageError) -> capnp::Error {
+    coded_error(E009_STORAGE_ERROR, err)
+}
+
+impl NodeServiceImpl {
+    /// Health check: unauthenticated by design for liveness probes and load balancers.
+    pub fn handle_health(
+        &mut self,
+        _params: node_service::HealthParams,
+        mut results: node_service::HealthResults,
+    ) -> Promise<(), capnp::Error> {
+        results.get().set_status("ok");
+        Promise::ok(())
+    }
+
+    pub fn handle_publish_endpoint(
+        &mut self,
+        params: node_service::PublishEndpointParams,
+        _results: node_service::PublishEndpointResults,
+    ) -> Promise<(), capnp::Error> {
+        let p = match params.get() {
+            Ok(p) => p,
+            Err(e) => return Promise::err(coded_error(E020_BAD_PARAMS, e)),
+        };
+        let identity_key = match p.get_identity_key() {
+            Ok(v) => v.to_vec(),
+            Err(e) => return Promise::err(coded_error(E020_BAD_PARAMS, e)),
+        };
+        let node_addr = match p.get_node_addr() {
+            Ok(v) => v.to_vec(),
+            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),
+        };
+
+        if identity_key.len() != 32 {
+            return Promise::err(coded_error(
+                E004_IDENTITY_KEY_LENGTH,
+                format!("identityKey must be exactly 32 bytes, got {}", identity_key.len()),
+            ));
+        }
+
+        if let Err(e) = require_identity_or_request(
+            &auth_ctx,
+            &identity_key,
+            self.auth_cfg.allow_insecure_identity_from_request,
+        ) {
+            return Promise::err(e);
+        }
+
+        if let Err(e) = self
+            .store
+            .publish_endpoint(&identity_key, node_addr)
+            .map_err(storage_err)
+        {
+            return Promise::err(e);
+        }
+
+        tracing::debug!(identity = %fmt_hex(&identity_key[..4]), "endpoint published");
+
+        Promise::ok(())
+    }
+
+    pub fn handle_resolve_endpoint(
+        &mut self,
+        params: node_service::ResolveEndpointParams,
+        mut results: node_service::ResolveEndpointResults,
+    ) -> Promise<(), capnp::Error> {
+        let p = match params.get() {
+            Ok(p) => p,
+            Err(e) => return Promise::err(coded_error(E020_BAD_PARAMS, e)),
+        };
+        let identity_key = match p.get_identity_key() {
+            Ok(v) => v.to_vec(),
+            Err(e) => return Promise::err(coded_error(E020_BAD_PARAMS, e)),
+        };
+        if let Err(e) = validate_auth(&self.auth_cfg, &self.sessions, p.get_auth()) {
+            return Promise::err(e);
+        }
+
+        if identity_key.len() != 32 {
+            return Promise::err(coded_error(
+                E004_IDENTITY_KEY_LENGTH,
+                format!("identityKey must be exactly 32 bytes, got {}", identity_key.len()),
+            ));
+        }
+
+        let endpoint = match self
+            .store
+            .resolve_endpoint(&identity_key)
+            .map_err(storage_err)
+        {
+            Ok(e) => e,
+            Err(e) => return Promise::err(e),
+        };
+
+        if let Some(ep) = endpoint {
+            tracing::debug!(identity = %fmt_hex(&identity_key[..4]), "endpoint resolved");
+            results.get().set_node_addr(&ep);
+        } else {
+            results.get().set_node_addr(&[]);
+        }
+
+        Promise::ok(())
+    }
+}

crates/quicprochat-server/src/node_service/user_ops.rs

@@ -0,0 +1,186 @@
+//! resolveUser / resolveIdentity RPCs: bidirectional username ↔ identity key lookup.
+
+use capnp::capability::Promise;
+use quicprochat_proto::node_capnp::node_service;
+use std::time::Duration;
+use tokio::time::Instant;
+
+use crate::auth::{check_rate_limit, coded_error, validate_auth_context};
+use crate::error_codes::*;
+use crate::metrics;
+use crate::storage::StorageError;
+
+use super::NodeServiceImpl;
+
+/// Minimum response time for resolveUser to mask DB lookup timing differences.
+const RESOLVE_TIMING_FLOOR: Duration = Duration::from_millis(5);
+
+fn storage_err(err: StorageError) -> capnp::Error {
+    coded_error(E009_STORAGE_ERROR, err)
+}
+
+impl NodeServiceImpl {
+    pub fn handle_resolve_user(
+        &mut self,
+        params: node_service::ResolveUserParams,
+        mut results: node_service::ResolveUserResults,
+    ) -> Promise<(), capnp::Error> {
+        let p = match params.get() {
+            Ok(p) => p,
+            Err(e) => return Promise::err(coded_error(E020_BAD_PARAMS, e)),
+        };
+        let username = match p.get_username() {
+            Ok(u) => u,
+            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),
+        };
+
+        let username_str = match username.to_str() {
+            Ok(s) => s,
+            Err(e) => return Promise::err(coded_error(E020_BAD_PARAMS, e)),
+        };
+
+        if username_str.is_empty() {
+            return Promise::err(coded_error(E020_BAD_PARAMS, "username must not be empty"));
+        }
+
+        // Federation: parse user@domain format.
+        let addr = crate::federation::address::FederatedAddress::parse(username_str);
+        let is_remote = match (&addr.domain, &self.local_domain) {
+            (Some(d), Some(ld)) => d != ld,
+            (Some(_), None) => true,
+            _ => false,
+        };
+
+        if is_remote {
+            // Proxy to remote server via federation.
+            if let (Some(ref fed_client), Some(ref domain)) = (&self.federation_client, &addr.domain) {
+                if fed_client.has_peer(domain) {
+                    let fed = fed_client.clone();
+                    let user = addr.username.clone();
+                    let dom = domain.clone();
+                    return Promise::from_future(async move {
+                        match fed.proxy_resolve_user(&dom, &user).await {
+                            Ok(Some(key)) => {
+                                results.get().set_identity_key(&key);
+                            }
+                            Ok(None) => {
+                                // Not found on remote — return empty.
+                            }
+                            Err(e) => {
+                                tracing::warn!(error = %e, "federation proxy_resolve_user failed");
+                                // Fall through — return empty (not found).
+                            }
+                        }
+                        Ok(())
+                    });
+                }
+            }
+            // No federation client or unknown peer — return empty (not found).
+            return Promise::ok(());
+        }
+
+        // Rate-limit resolve requests to prevent bulk enumeration.
+        if let Err(e) = check_rate_limit(&self.rate_limits, &auth_ctx.token) {
+            tracing::warn!("rate_limit_hit");
+            metrics::record_rate_limit_hit_total();
+            return Promise::err(e);
+        }
+
+        // Timing floor: record the start time so we can pad the response to a
+        // fixed minimum duration, masking DB-lookup timing differences between
+        // existing and non-existing usernames.
+        let deadline = Instant::now() + RESOLVE_TIMING_FLOOR;
+
+        // Local resolution.
+        let identity_key = match self.store.get_user_identity_key(&addr.username) {
+            Ok(Some(key)) => key,
+            Ok(None) => {
+                // Return empty Data — caller checks length to detect "not found".
+                // Pad to timing floor before responding.
+                return Promise::from_future(async move {
+                    tokio::time::sleep_until(deadline).await;
+                    Ok(())
+                });
+            }
+            Err(e) => return Promise::err(storage_err(e)),
+        };
+
+        let mut r = results.get();
+        r.set_identity_key(&identity_key);
+
+        // Attempt to include a KT Merkle inclusion proof.
+        // Non-fatal: if the log is unavailable or has no entry, return just the key.
+        if let Ok(log) = self.kt_log.lock() {
+            if let Some(leaf_idx) = log.find(&addr.username, &identity_key) {
+                match log.inclusion_proof(leaf_idx) {
+                    Ok(proof) => match proof.to_bytes() {
+                        Ok(bytes) => {
+                            r.set_inclusion_proof(&bytes);
+                        }
+                        Err(e) => {
+                            tracing::warn!(error = %e, "KT proof serialise failed");
+                        }
+                    },
+                    Err(e) => {
+                        tracing::warn!(error = %e, "KT inclusion_proof failed");
+                    }
+                }
+            }
+        }
+
+        // Pad to timing floor before responding.
+        Promise::from_future(async move {
+            tokio::time::sleep_until(deadline).await;
+            Ok(())
+        })
+    }
+
+    pub fn handle_resolve_identity(
+        &mut self,
+        params: node_service::ResolveIdentityParams,
+        mut results: node_service::ResolveIdentityResults,
+    ) -> Promise<(), capnp::Error> {
+        let p = match params.get() {
+            Ok(p) => p,
+            Err(e) => return Promise::err(coded_error(E020_BAD_PARAMS, e)),
+        };
+        let identity_key = match p.get_identity_key() {
+            Ok(v) => v,
+            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),
+        };
+
+        if identity_key.len() != 32 {
+            return Promise::err(coded_error(
+                E004_IDENTITY_KEY_LENGTH,
+                format!("identityKey must be exactly 32 bytes, got {}", identity_key.len()),
+            ));
+        }
+
+        // Timing floor: mask DB-lookup timing differences (same as resolveUser).
+        let deadline = Instant::now() + RESOLVE_TIMING_FLOOR;
+
+        match self.store.resolve_identity_key(identity_key) {
+            Ok(Some(username)) => {
+                results.get().set_username(&username);
+            }
+            Ok(None) => {
+                // Return empty string — caller checks length to detect "not found".
+            }
+            Err(e) => return Promise::err(storage_err(e)),
+        }
+
+        // Pad to timing floor before responding.
+        Promise::from_future(async move {
+            tokio::time::sleep_until(deadline).await;
+            Ok(())
+        })
+    }
+}

crates/quicprochat-server/src/plugin_loader.rs

@@ -0,0 +1,342 @@
+//! Dynamic plugin loader for server-side hook extensions.
+//!
+//! Loads shared libraries (`*.so` / `*.dylib`) from a directory at server
+//! startup. Each library must export:
+//!
+//! ```c
+//! extern "C" int32_t qpc_plugin_init(HookVTable *vtable);
+//! ```
+//!
+//! The server creates a zeroed [`HookVTable`], passes it to `qpc_plugin_init`,
+//! and wraps the resulting vtable in a [`PluginHooks`] that implements
+//! [`ServerHooks`].  Multiple plugins are chained via [`ChainedHooks`].
+//!
+//! # Safety model
+//!
+//! Dynamic loading is inherently unsafe.  The plugin binary MUST:
+//! - be compiled against the same `quicprochat-plugin-api` version
+//! - not store the event-struct pointers beyond the callback duration
+//! - be `Send + Sync` (the wrapper is put behind an `Arc`)
+//!
+//! The server operator is responsible for only loading trusted plugin binaries.
+
+use std::path::Path;
+
+use libloading::{Library, Symbol};
+use quicprochat_plugin_api::{
+    CAuthEvent, CChannelEvent, CFetchEvent, CMessageEvent, HookVTable, HOOK_CONTINUE, PLUGIN_OK,
+};
+
+use crate::hooks::{AuthEvent, ChannelEvent, FetchEvent, HookAction, MessageEvent, ServerHooks};
+
+// ── PluginHooks ───────────────────────────────────────────────────────────────
+
+/// A [`ServerHooks`] implementation backed by a dynamically loaded plugin vtable.
+///
+/// Holds the [`Library`] alive alongside the vtable so that the loaded code
+/// is not unmapped while the vtable function pointers are still reachable.
+pub struct PluginHooks {
+    /// The vtable filled by `qpc_plugin_init`.
+    vtable: HookVTable,
+    /// Keeps the shared library mapped. Must be dropped after `vtable`.
+    _lib: Library,
+    /// Name of the plugin file, for diagnostics.
+    name: String,
+}
+
+impl PluginHooks {
+    /// Load a plugin from `path` and call `qpc_plugin_init`.
+    ///
+    /// Returns `Err` if the library cannot be opened, the symbol is missing,
+    /// or `qpc_plugin_init` returns a non-zero error code.
+    pub fn load(path: &Path) -> anyhow::Result<Self> {
+        let name = path
+            .file_name()
+            .map(|n| n.to_string_lossy().into_owned())
+            .unwrap_or_else(|| path.display().to_string());
+
+        // Safety: loading arbitrary shared libraries is inherently unsafe.
+        // The server operator is responsible for only loading trusted plugins.
+        let lib = unsafe { Library::new(path) }
+            .map_err(|e| anyhow::anyhow!("plugin '{}': load failed: {}", name, e))?;
+
+        // Zero-initialise the vtable so unused slots are null.
+        let mut vtable = HookVTable {
+            user_data: core::ptr::null_mut(),
+            on_message_enqueue: None,
+            on_batch_enqueue: None,
+            on_auth: None,
+            on_channel_created: None,
+            on_fetch: None,
+            on_user_registered: None,
+            error_message: None,
+            destroy: None,
+        };
+
+        // Safety: the symbol must have the exact signature declared in the API crate.
+        let init: Symbol<unsafe extern "C" fn(*mut HookVTable) -> i32> =
+            unsafe { lib.get(b"qpc_plugin_init\0") }.map_err(|e| {
+                anyhow::anyhow!("plugin '{}': missing qpc_plugin_init: {}", name, e)
+            })?;
+
+        let rc = unsafe { init(&mut vtable) };
+        if rc != PLUGIN_OK {
+            anyhow::bail!("plugin '{}': qpc_plugin_init returned error {}", name, rc);
+        }
+
+        tracing::info!(plugin = %name, "loaded plugin");
+        Ok(Self { vtable, _lib: lib, name })
+    }
+
+    /// Human-readable plugin name (filename).
+    pub fn name(&self) -> &str {
+        &self.name
+    }
+
+    /// Retrieve the rejection reason from the plugin, falling back to a generic string.
+    fn rejection_reason(&self) -> String {
+        if let Some(f) = self.vtable.error_message {
+            let ptr = unsafe { f(self.vtable.user_data) };
+            if !ptr.is_null() {
+                // Safety: plugin must return a valid null-terminated UTF-8 (or ASCII) string.
+                let cstr = unsafe { std::ffi::CStr::from_ptr(ptr as *const core::ffi::c_char) };
+                return cstr.to_string_lossy().into_owned();
+            }
+        }
+        "rejected by plugin".to_string()
+    }
+}
+
+impl Drop for PluginHooks {
+    fn drop(&mut self) {
+        if let Some(destroy) = self.vtable.destroy {
+            // Safety: destroy must be safe to call at any time after init.
+            unsafe { destroy(self.vtable.user_data) };
+        }
+    }
+}
+
+impl ServerHooks for PluginHooks {
+    fn on_message_enqueue(&self, event: &MessageEvent) -> HookAction {
+        let f = match self.vtable.on_message_enqueue {
+            Some(f) => f,
+            None => return HookAction::Continue,
+        };
+
+        let sender_ptr = event
+            .sender_identity
+            .as_deref()
+            .map(|s| s.as_ptr())
+            .unwrap_or(core::ptr::null());
+        let sender_len = event.sender_identity.as_deref().map_or(0, |s| s.len());
+
+        let c_event = CMessageEvent {
+            sender_identity: sender_ptr,
+            sender_identity_len: sender_len,
+            recipient_key: event.recipient_key.as_ptr(),
+            recipient_key_len: event.recipient_key.len(),
+            channel_id: event.channel_id.as_ptr(),
+            channel_id_len: event.channel_id.len(),
+            payload_len: event.payload_len,
+            seq: event.seq,
+        };
+
+        let rc = unsafe { f(self.vtable.user_data, &c_event) };
+        if rc == HOOK_CONTINUE {
+            HookAction::Continue
+        } else {
+            HookAction::Reject(self.rejection_reason())
+        }
+    }
+
+    fn on_batch_enqueue(&self, events: &[MessageEvent]) {
+        let f = match self.vtable.on_batch_enqueue {
+            Some(f) => f,
+            None => return,
+        };
+
+        let c_events: Vec<CMessageEvent> = events
+            .iter()
+            .map(|e| {
+                let sender_ptr = e
+                    .sender_identity
+                    .as_deref()
+                    .map(|s| s.as_ptr())
+                    .unwrap_or(core::ptr::null());
+                let sender_len = e.sender_identity.as_deref().map_or(0, |s| s.len());
+                CMessageEvent {
+                    sender_identity: sender_ptr,
+                    sender_identity_len: sender_len,
+                    recipient_key: e.recipient_key.as_ptr(),
+                    recipient_key_len: e.recipient_key.len(),
+                    channel_id: e.channel_id.as_ptr(),
+                    channel_id_len: e.channel_id.len(),
+                    payload_len: e.payload_len,
+                    seq: e.seq,
+                }
+            })
+            .collect();
+
+        unsafe { f(self.vtable.user_data, c_events.as_ptr(), c_events.len()) };
+    }
+
+    fn on_auth(&self, event: &AuthEvent) {
+        let f = match self.vtable.on_auth {
+            Some(f) => f,
+            None => return,
+        };
+        let c_event = CAuthEvent {
+            username: event.username.as_ptr(),
+            username_len: event.username.len(),
+            success: if event.success { 1 } else { 0 },
+            failure_reason: event.failure_reason.as_ptr(),
+            failure_reason_len: event.failure_reason.len(),
+        };
+        unsafe { f(self.vtable.user_data, &c_event) };
+    }
+
+    fn on_channel_created(&self, event: &ChannelEvent) {
+        let f = match self.vtable.on_channel_created {
+            Some(f) => f,
+            None => return,
+        };
+        let c_event = CChannelEvent {
+            channel_id: event.channel_id.as_ptr(),
+            channel_id_len: event.channel_id.len(),
+            initiator_key: event.initiator_key.as_ptr(),
+            initiator_key_len: event.initiator_key.len(),
+            peer_key: event.peer_key.as_ptr(),
+            peer_key_len: event.peer_key.len(),
+            was_new: if event.was_new { 1 } else { 0 },
+        };
+        unsafe { f(self.vtable.user_data, &c_event) };
+    }
+
+    fn on_fetch(&self, event: &FetchEvent) {
+        let f = match self.vtable.on_fetch {
+            Some(f) => f,
+            None => return,
+        };
+        let c_event = CFetchEvent {
+            recipient_key: event.recipient_key.as_ptr(),
+            recipient_key_len: event.recipient_key.len(),
+            channel_id: event.channel_id.as_ptr(),
+            channel_id_len: event.channel_id.len(),
+            message_count: event.message_count,
+        };
+        unsafe { f(self.vtable.user_data, &c_event) };
+    }
+
+    fn on_user_registered(&self, username: &str, identity_key: &[u8]) {
+        let f = match self.vtable.on_user_registered {
+            Some(f) => f,
+            None => return,
+        };
+        unsafe {
+            f(
+                self.vtable.user_data,
+                username.as_ptr(),
+                username.len(),
+                identity_key.as_ptr(),
+                identity_key.len(),
+            )
+        };
+    }
+}
+
+// ── ChainedHooks ─────────────────────────────────────────────────────────────
+
+/// Composes multiple [`ServerHooks`] implementations into one.
+///
+/// For filtering hooks (`on_message_enqueue`), the first rejection short-circuits
+/// the chain. For fire-and-forget hooks, all plugins are called in order.
+pub struct ChainedHooks {
+    hooks: Vec<Box<dyn ServerHooks>>,
+}
+
+impl ChainedHooks {
+    pub fn new(hooks: Vec<Box<dyn ServerHooks>>) -> Self {
+        Self { hooks }
+    }
+}
+
+impl ServerHooks for ChainedHooks {
+    fn on_message_enqueue(&self, event: &MessageEvent) -> HookAction {
+        for h in &self.hooks {
+            match h.on_message_enqueue(event) {
+                HookAction::Continue => {}
+                reject => return reject,
+            }
+        }
+        HookAction::Continue
+    }
+
+    fn on_batch_enqueue(&self, events: &[MessageEvent]) {
+        for h in &self.hooks {
+            h.on_batch_enqueue(events);
+        }
+    }
+
+    fn on_auth(&self, event: &AuthEvent) {
+        for h in &self.hooks {
+            h.on_auth(event);
+        }
+    }
+
+    fn on_channel_created(&self, event: &ChannelEvent) {
+        for h in &self.hooks {
+            h.on_channel_created(event);
+        }
+    }
+
+    fn on_fetch(&self, event: &FetchEvent) {
+        for h in &self.hooks {
+            h.on_fetch(event);
+        }
+    }
+
+    fn on_user_registered(&self, username: &str, identity_key: &[u8]) {
+        for h in &self.hooks {
+            h.on_user_registered(username, identity_key);
+        }
+    }
+}
+
+// ── load_plugins_from_dir ─────────────────────────────────────────────────────
+
+/// Load all `*.so` / `*.dylib` files from `dir` as plugins.
+///
+/// Non-fatal errors (unreadable files, init failures) are logged as warnings
+/// and skipped; the server continues with the plugins that did load.
+/// Returns the full list of successfully loaded plugins.
+pub fn load_plugins_from_dir(dir: &Path) -> Vec<PluginHooks> {
+    let mut plugins = Vec::new();
+
+    let entries = match std::fs::read_dir(dir) {
+        Ok(e) => e,
+        Err(e) => {
+            tracing::warn!(dir = %dir.display(), error = %e, "plugin_dir unreadable; no plugins loaded");
+            return plugins;
+        }
+    };
+
+    for entry in entries.flatten() {
+        let path = entry.path();
+        let ext = path.extension().and_then(|e| e.to_str()).unwrap_or("");
+        if ext != "so" && ext != "dylib" {
+            continue;
+        }
+
+        match PluginHooks::load(&path) {
+            Ok(p) => {
+                tracing::info!(plugin = %p.name(), "plugin loaded successfully");
+                plugins.push(p);
+            }
+            Err(e) => {
+                tracing::warn!(path = %path.display(), error = %e, "failed to load plugin; skipping");
+            }
+        }
+    }
+
+    plugins
+}

crates/quicprochat-server/src/tls.rs

@@ -0,0 +1,117 @@
+use std::path::PathBuf;
+
+use anyhow::Context;
+use quinn::ServerConfig;
+use quinn_proto::crypto::rustls::QuicServerConfig;
+use rcgen::generate_simple_self_signed;
+use rustls::pki_types::{CertificateDer, PrivateKeyDer};
+use rustls::version::TLS13;
+
+/// Ensure a self-signed certificate exists on disk and return a QUIC server config.
+/// When `production` is true, cert and key must already exist (no auto-generation).
+pub fn build_server_config(
+    cert_path: &PathBuf,
+    key_path: &PathBuf,
+    production: bool,
+) -> anyhow::Result<ServerConfig> {
+    if !cert_path.exists() || !key_path.exists() {
+        if production {
+            anyhow::bail!(
+                "TLS cert or key missing at {:?} / {:?}; production mode forbids auto-generation",
+                cert_path,
+                key_path
+            );
+        }
+        generate_self_signed_cert(cert_path, key_path)?;
+    }
+
+    let cert_bytes = std::fs::read(cert_path).context("read cert")?;
+    let key_bytes = std::fs::read(key_path).context("read key")?;
+
+    // Validate certificate expiry and warn about self-signed certs.
+    validate_certificate(&cert_bytes)?;
+
+    let cert_chain = vec![CertificateDer::from(cert_bytes)];
+    let key = PrivateKeyDer::try_from(key_bytes).map_err(|_| anyhow::anyhow!("invalid key"))?;
+
+    let mut tls = rustls::ServerConfig::builder_with_protocol_versions(&[&TLS13])
+        .with_no_client_auth()
+        .with_single_cert(cert_chain, key)?;
+    tls.alpn_protocols = vec![b"capnp".to_vec()];
+
+    let crypto = QuicServerConfig::try_from(tls)
+        .map_err(|e| anyhow::anyhow!("invalid server TLS config: {e}"))?;
+
+    Ok(ServerConfig::with_crypto(std::sync::Arc::new(crypto)))
+}
+
+fn generate_self_signed_cert(cert_path: &PathBuf, key_path: &PathBuf) -> anyhow::Result<()> {
+    if let Some(parent) = cert_path.parent() {
+        std::fs::create_dir_all(parent).context("create cert dir")?;
+    }
+    if let Some(parent) = key_path.parent() {
+        std::fs::create_dir_all(parent).context("create key dir")?;
+    }
+
+    let subject_alt_names = vec![
+        "localhost".to_string(),
+        "127.0.0.1".to_string(),
+        "::1".to_string(),
+    ];
+
+    let issued = generate_simple_self_signed(subject_alt_names)?;
+    let key_der = issued.key_pair.serialize_der();
+
+    std::fs::write(cert_path, issued.cert.der()).context("write cert")?;
+    std::fs::write(key_path, &key_der).context("write key")?;
+    #[cfg(unix)]
+    {
+        use std::os::unix::fs::PermissionsExt;
+        let perms = std::fs::Permissions::from_mode(0o600);
+        std::fs::set_permissions(key_path, perms).context("set key permissions")?;
+    }
+
+    tracing::info!(
+        cert = %cert_path.display(),
+        key = %key_path.display(),
+        "generated self-signed TLS certificate"
+    );
+
+    Ok(())
+}
+
+/// Validate a DER-encoded X.509 certificate: bail if expired, warn if expiring
+/// soon or self-signed.
+fn validate_certificate(der_bytes: &[u8]) -> anyhow::Result<()> {
+    use x509_parser::prelude::*;
+
+    let (_, cert) = X509Certificate::from_der(der_bytes)
+        .map_err(|e| anyhow::anyhow!("failed to parse X.509 certificate: {e}"))?;
+
+    let validity = cert.validity();
+    let now = ASN1Time::now();
+
+    if !validity.is_valid_at(now) {
+        anyhow::bail!(
+            "TLS certificate expired (not_after: {})",
+            validity.not_after
+        );
+    }
+
+    // Warn if expiring within 30 days.
+    let thirty_days = std::time::Duration::from_secs(30 * 24 * 60 * 60);
+    let cutoff = now.timestamp() + thirty_days.as_secs() as i64;
+    if validity.not_after.timestamp() < cutoff {
+        tracing::warn!(
+            not_after = %validity.not_after,
+            "TLS certificate expires within 30 days"
+        );
+    }
+
+    // Warn if self-signed (issuer == subject).
+    if cert.issuer() == cert.subject() {
+        tracing::warn!("TLS certificate is self-signed (issuer == subject)");
+    }
+
+    Ok(())
+}

crates/quicprochat-server/src/v2_handlers/account.rs

@@ -0,0 +1,51 @@
+//! Account handler — account deletion.
+
+use std::sync::Arc;
+
+use bytes::Bytes;
+use prost::Message;
+use quicprochat_proto::qpc::v1;
+use quicprochat_rpc::method::{HandlerResult, RequestContext};
+
+use crate::domain::account::AccountService;
+
+use super::{domain_err, require_auth, ServerState};
+
+pub async fn handle_delete_account(
+    state: Arc<ServerState>,
+    ctx: RequestContext,
+) -> HandlerResult {
+    let identity_key = match require_auth(&state, &ctx) {
+        Ok(ik) => ik,
+        Err(e) => return e,
+    };
+
+    // DeleteAccountRequest is empty but decode for protocol correctness.
+    let _req = match v1::DeleteAccountRequest::decode(ctx.payload) {
+        Ok(r) => r,
+        Err(e) => {
+            return HandlerResult::err(
+                quicprochat_rpc::error::RpcStatus::BadRequest,
+                &format!("decode: {e}"),
+            )
+        }
+    };
+
+    let svc = AccountService {
+        store: Arc::clone(&state.store),
+        kt_log: Arc::clone(&state.kt_log),
+    };
+
+    match svc.delete_account(&identity_key) {
+        Ok(()) => {
+            // Remove session for the deleted account.
+            if let Some(token) = ctx.session_token.as_deref() {
+                state.sessions.remove(token);
+            }
+
+            let proto = v1::DeleteAccountResponse { success: true };
+            HandlerResult::ok(Bytes::from(proto.encode_to_vec()))
+        }
+        Err(e) => domain_err(e),
+    }
+}

crates/quicprochat-server/src/v2_handlers/auth.rs

@@ -0,0 +1,255 @@
+//! OPAQUE auth handlers — registration and login.
+
+use std::sync::Arc;
+
+use bytes::Bytes;
+use prost::Message;
+use quicprochat_proto::qpc::v1;
+use quicprochat_rpc::error::RpcStatus;
+use quicprochat_rpc::method::{HandlerResult, RequestContext};
+
+use crate::auth::{PendingLogin, SessionInfo, SESSION_TTL_SECS};
+use crate::domain::auth::AuthService;
+use crate::domain::types::{RegisterFinishReq, RegisterStartReq};
+
+use super::ServerState;
+
+pub async fn handle_opaque_register_start(
+    state: Arc<ServerState>,
+    ctx: RequestContext,
+) -> HandlerResult {
+    let req = match v1::OpaqueRegisterStartRequest::decode(ctx.payload) {
+        Ok(r) => r,
+        Err(e) => return HandlerResult::err(RpcStatus::BadRequest, &format!("decode: {e}")),
+    };
+
+    if req.username.is_empty() {
+        return HandlerResult::err(RpcStatus::BadRequest, "username must not be empty");
+    }
+
+    let svc = AuthService {
+        store: Arc::clone(&state.store),
+        opaque_setup: Arc::clone(&state.opaque_setup),
+        pending_logins: Arc::clone(&state.pending_logins),
+        sessions: Arc::clone(&state.sessions),
+        auth_cfg: Arc::clone(&state.auth_cfg),
+    };
+
+    let domain_req = RegisterStartReq {
+        username: req.username,
+        request_bytes: req.request,
+    };
+
+    match svc.register_start(domain_req) {
+        Ok(resp) => {
+            let proto = v1::OpaqueRegisterStartResponse {
+                response: resp.response_bytes,
+            };
+            HandlerResult::ok(Bytes::from(proto.encode_to_vec()))
+        }
+        Err(e) => HandlerResult::err(RpcStatus::Internal, &format!("register_start: {e}")),
+    }
+}
+
+pub async fn handle_opaque_register_finish(
+    state: Arc<ServerState>,
+    ctx: RequestContext,
+) -> HandlerResult {
+    let req = match v1::OpaqueRegisterFinishRequest::decode(ctx.payload) {
+        Ok(r) => r,
+        Err(e) => return HandlerResult::err(RpcStatus::BadRequest, &format!("decode: {e}")),
+    };
+
+    if req.username.is_empty() {
+        return HandlerResult::err(RpcStatus::BadRequest, "username must not be empty");
+    }
+
+    let svc = AuthService {
+        store: Arc::clone(&state.store),
+        opaque_setup: Arc::clone(&state.opaque_setup),
+        pending_logins: Arc::clone(&state.pending_logins),
+        sessions: Arc::clone(&state.sessions),
+        auth_cfg: Arc::clone(&state.auth_cfg),
+    };
+
+    let domain_req = RegisterFinishReq {
+        username: req.username.clone(),
+        upload_bytes: req.upload,
+        identity_key: req.identity_key.clone(),
+    };
+
+    match svc.register_finish(domain_req) {
+        Ok(resp) => {
+            state
+                .hooks
+                .on_user_registered(&req.username, &req.identity_key);
+
+            let proto = v1::OpaqueRegisterFinishResponse {
+                success: resp.success,
+            };
+            HandlerResult::ok(Bytes::from(proto.encode_to_vec()))
+        }
+        Err(e) => HandlerResult::err(RpcStatus::Internal, &format!("register_finish: {e}")),
+    }
+}
+
+pub async fn handle_opaque_login_start(
+    state: Arc<ServerState>,
+    ctx: RequestContext,
+) -> HandlerResult {
+    let req = match v1::OpaqueLoginStartRequest::decode(ctx.payload) {
+        Ok(r) => r,
+        Err(e) => return HandlerResult::err(RpcStatus::BadRequest, &format!("decode: {e}")),
+    };
+
+    if req.username.is_empty() {
+        return HandlerResult::err(RpcStatus::BadRequest, "username must not be empty");
+    }
+
+    // Look up user record.
+    let user_record = match state.store.get_user_record(&req.username) {
+        Ok(Some(r)) => r,
+        Ok(None) => {
+            return HandlerResult::err(RpcStatus::NotFound, "user not found");
+        }
+        Err(e) => return HandlerResult::err(RpcStatus::Internal, &format!("store: {e}")),
+    };
+
+    // Deserialise stored registration.
+    let registration =
+        match opaque_ke::ServerRegistration::<quicprochat_core::opaque_auth::OpaqueSuite>::deserialize(&user_record) {
+            Ok(r) => r,
+            Err(e) => {
+                return HandlerResult::err(
+                    RpcStatus::Internal,
+                    &format!("corrupt user record: {e}"),
+                )
+            }
+        };
+
+    // Start login.
+    let credential_request =
+        match opaque_ke::CredentialRequest::<quicprochat_core::opaque_auth::OpaqueSuite>::deserialize(&req.request)
+        {
+            Ok(r) => r,
+            Err(e) => {
+                return HandlerResult::err(RpcStatus::BadRequest, &format!("bad login request: {e}"))
+            }
+        };
+
+    let login_start = match opaque_ke::ServerLogin::<
+        quicprochat_core::opaque_auth::OpaqueSuite,
+    >::start(
+        &mut rand::rngs::OsRng,
+        &state.opaque_setup,
+        Some(registration),
+        credential_request,
+        req.username.as_bytes(),
+        Default::default(),
+    ) {
+        Ok(r) => r,
+        Err(e) => {
+            return HandlerResult::err(RpcStatus::Internal, &format!("login start: {e}"));
+        }
+    };
+
+    let response_bytes = login_start.message.serialize().to_vec();
+
+    // Store pending login state.
+    let now = crate::auth::current_timestamp();
+    state.pending_logins.insert(
+        req.username.clone(),
+        PendingLogin {
+            state_bytes: login_start.state.serialize().to_vec(),
+            created_at: now,
+        },
+    );
+
+    let proto = v1::OpaqueLoginStartResponse {
+        response: response_bytes,
+    };
+    HandlerResult::ok(Bytes::from(proto.encode_to_vec()))
+}
+
+pub async fn handle_opaque_login_finish(
+    state: Arc<ServerState>,
+    ctx: RequestContext,
+) -> HandlerResult {
+    let req = match v1::OpaqueLoginFinishRequest::decode(ctx.payload) {
+        Ok(r) => r,
+        Err(e) => return HandlerResult::err(RpcStatus::BadRequest, &format!("decode: {e}")),
+    };
+
+    if req.username.is_empty() {
+        return HandlerResult::err(RpcStatus::BadRequest, "username must not be empty");
+    }
+
+    // Retrieve pending login state.
+    let pending = match state.pending_logins.remove(&req.username) {
+        Some((_, p)) => p,
+        None => {
+            return HandlerResult::err(
+                RpcStatus::BadRequest,
+                "no pending login for this username",
+            );
+        }
+    };
+
+    let login_state = match opaque_ke::ServerLogin::<
+        quicprochat_core::opaque_auth::OpaqueSuite,
+    >::deserialize(&pending.state_bytes)
+    {
+        Ok(s) => s,
+        Err(e) => {
+            return HandlerResult::err(
+                RpcStatus::Internal,
+                &format!("corrupt pending login: {e}"),
+            )
+        }
+    };
+
+    let finalization = match opaque_ke::CredentialFinalization::<
+        quicprochat_core::opaque_auth::OpaqueSuite,
+    >::deserialize(&req.finalization)
+    {
+        Ok(f) => f,
+        Err(e) => {
+            return HandlerResult::err(RpcStatus::BadRequest, &format!("bad finalization: {e}"));
+        }
+    };
+
+    if let Err(e) = login_state.finish(finalization, Default::default()) {
+        state.hooks.on_auth(&crate::hooks::AuthEvent {
+            username: req.username.clone(),
+            success: false,
+            failure_reason: format!("{e}"),
+        });
+        return HandlerResult::err(RpcStatus::Unauthorized, &format!("login failed: {e}"));
+    }
+
+    // Generate session token.
+    let mut token = vec![0u8; 32];
+    rand::RngCore::fill_bytes(&mut rand::rngs::OsRng, &mut token);
+
+    let now = crate::auth::current_timestamp();
+    state.sessions.insert(
+        token.clone(),
+        SessionInfo {
+            username: req.username.clone(),
+            identity_key: req.identity_key.clone(),
+            created_at: now,
+            expires_at: now + SESSION_TTL_SECS,
+        },
+    );
+
+    state.hooks.on_auth(&crate::hooks::AuthEvent {
+        username: req.username,
+        success: true,
+        failure_reason: String::new(),
+    });
+
+    let proto = v1::OpaqueLoginFinishResponse {
+        session_token: token,
+    };
+    HandlerResult::ok(Bytes::from(proto.encode_to_vec()))
+}

crates/quicprochat-server/src/v2_handlers/blob.rs

@@ -0,0 +1,101 @@
+//! Blob handlers — chunked file upload/download.
+
+use std::sync::Arc;
+
+use bytes::Bytes;
+use prost::Message;
+use quicprochat_proto::qpc::v1;
+use quicprochat_rpc::method::{HandlerResult, RequestContext};
+
+use crate::domain::blobs::BlobService;
+use crate::domain::types::{CallerAuth, DownloadBlobReq, UploadBlobReq};
+
+use super::{domain_err, require_auth, ServerState};
+
+fn caller_auth(identity_key: Vec<u8>) -> CallerAuth {
+    CallerAuth {
+        identity_key,
+        token: Vec::new(),
+        device_id: None,
+    }
+}
+
+pub async fn handle_upload_blob(state: Arc<ServerState>, ctx: RequestContext) -> HandlerResult {
+    let identity_key = match require_auth(&state, &ctx) {
+        Ok(ik) => ik,
+        Err(e) => return e,
+    };
+
+    let req = match v1::UploadBlobRequest::decode(ctx.payload) {
+        Ok(r) => r,
+        Err(e) => {
+            return HandlerResult::err(
+                quicprochat_rpc::error::RpcStatus::BadRequest,
+                &format!("decode: {e}"),
+            )
+        }
+    };
+
+    let svc = BlobService {
+        data_dir: state.data_dir.clone(),
+    };
+    let auth = caller_auth(identity_key);
+
+    let domain_req = UploadBlobReq {
+        blob_hash: req.blob_hash,
+        chunk: req.chunk,
+        offset: req.offset,
+        total_size: req.total_size,
+        mime_type: req.mime_type,
+    };
+
+    match svc.upload_blob(domain_req, &auth) {
+        Ok(resp) => {
+            let proto = v1::UploadBlobResponse {
+                blob_id: resp.blob_id,
+            };
+            HandlerResult::ok(Bytes::from(proto.encode_to_vec()))
+        }
+        Err(e) => domain_err(e),
+    }
+}
+
+pub async fn handle_download_blob(state: Arc<ServerState>, ctx: RequestContext) -> HandlerResult {
+    let identity_key = match require_auth(&state, &ctx) {
+        Ok(ik) => ik,
+        Err(e) => return e,
+    };
+
+    let req = match v1::DownloadBlobRequest::decode(ctx.payload) {
+        Ok(r) => r,
+        Err(e) => {
+            return HandlerResult::err(
+                quicprochat_rpc::error::RpcStatus::BadRequest,
+                &format!("decode: {e}"),
+            )
+        }
+    };
+
+    let svc = BlobService {
+        data_dir: state.data_dir.clone(),
+    };
+    let auth = caller_auth(identity_key);
+
+    let domain_req = DownloadBlobReq {
+        blob_id: req.blob_id,
+        offset: req.offset,
+        length: req.length,
+    };
+
+    match svc.download_blob(domain_req, &auth) {
+        Ok(resp) => {
+            let proto = v1::DownloadBlobResponse {
+                chunk: resp.chunk,
+                total_size: resp.total_size,
+                mime_type: resp.mime_type,
+            };
+            HandlerResult::ok(Bytes::from(proto.encode_to_vec()))
+        }
+        Err(e) => domain_err(e),
+    }
+}

crates/quicprochat-server/src/v2_handlers/channel.rs

@@ -0,0 +1,60 @@
+//! Channel handler — 1:1 DM channel creation.
+
+use std::sync::Arc;
+
+use bytes::Bytes;
+use prost::Message;
+use quicprochat_proto::qpc::v1;
+use quicprochat_rpc::method::{HandlerResult, RequestContext};
+
+use crate::domain::channels::ChannelService;
+use crate::domain::types::CreateChannelReq;
+use crate::hooks::ChannelEvent;
+
+use super::{domain_err, require_auth, ServerState};
+
+pub async fn handle_create_channel(
+    state: Arc<ServerState>,
+    ctx: RequestContext,
+) -> HandlerResult {
+    let identity_key = match require_auth(&state, &ctx) {
+        Ok(ik) => ik,
+        Err(e) => return e,
+    };
+
+    let req = match v1::CreateChannelRequest::decode(ctx.payload) {
+        Ok(r) => r,
+        Err(e) => {
+            return HandlerResult::err(
+                quicprochat_rpc::error::RpcStatus::BadRequest,
+                &format!("decode: {e}"),
+            )
+        }
+    };
+
+    let svc = ChannelService {
+        store: Arc::clone(&state.store),
+    };
+
+    let domain_req = CreateChannelReq {
+        peer_key: req.peer_key.clone(),
+    };
+
+    match svc.create_channel(domain_req, &identity_key) {
+        Ok(resp) => {
+            state.hooks.on_channel_created(&ChannelEvent {
+                channel_id: resp.channel_id.clone(),
+                initiator_key: identity_key,
+                peer_key: req.peer_key,
+                was_new: resp.was_new,
+            });
+
+            let proto = v1::CreateChannelResponse {
+                channel_id: resp.channel_id,
+                was_new: resp.was_new,
+            };
+            HandlerResult::ok(Bytes::from(proto.encode_to_vec()))
+        }
+        Err(e) => domain_err(e),
+    }
+}

crates/quicprochat-server/src/v2_handlers/delivery.rs

@@ -0,0 +1,408 @@
+//! Delivery handlers — enqueue, fetch, fetch_wait, peek, ack, batch_enqueue.
+
+use std::sync::Arc;
+
+use bytes::Bytes;
+use prost::Message;
+use quicprochat_proto::qpc::v1;
+use quicprochat_rpc::error::RpcStatus;
+use quicprochat_rpc::method::{HandlerResult, RequestContext};
+use sha2::{Digest, Sha256};
+use tokio::sync::Notify;
+
+use crate::domain::delivery::DeliveryService;
+use crate::domain::types::{AckReq, BatchEnqueueReq, EnqueueReq, FetchReq, PeekReq};
+use crate::hooks::{HookAction, MessageEvent};
+
+use super::{require_auth, ServerState};
+
+/// Build a 96-byte delivery proof: `SHA-256(seq || recipient_key || timestamp_ms) || Ed25519(hash)`.
+///
+/// The sender stores this as cryptographic evidence that the server enqueued the message.
+fn build_delivery_proof(
+    signing_key: &quicprochat_core::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 = signing_key.sign_raw(&hash);
+
+    let mut proof = vec![0u8; 96];
+    proof[..32].copy_from_slice(&hash);
+    proof[32..].copy_from_slice(&sig);
+    proof
+}
+
+pub async fn handle_enqueue(state: Arc<ServerState>, ctx: RequestContext) -> HandlerResult {
+    let identity_key = match require_auth(&state, &ctx) {
+        Ok(ik) => ik,
+        Err(e) => return e,
+    };
+
+    let req = match v1::EnqueueRequest::decode(ctx.payload) {
+        Ok(r) => r,
+        Err(e) => return HandlerResult::err(RpcStatus::BadRequest, &format!("decode: {e}")),
+    };
+
+    if req.recipient_key.is_empty() || req.payload.is_empty() {
+        return HandlerResult::err(RpcStatus::BadRequest, "recipient_key and payload required");
+    }
+
+    // Rate limiting.
+    if let Err(_e) = crate::auth::check_rate_limit(&state.rate_limits, &identity_key) {
+        return HandlerResult::err(RpcStatus::RateLimited, "rate limit exceeded");
+    }
+
+    // Idempotency dedup: if message_id is provided and already seen, return the cached seq.
+    if !req.message_id.is_empty() {
+        if let Some(entry) = state.seen_message_ids.get(&req.message_id) {
+            let (cached_seq, _ts) = *entry;
+            let proto = v1::EnqueueResponse {
+                seq: cached_seq,
+                delivery_proof: Vec::new(),
+                duplicate: true,
+            };
+            return HandlerResult::ok(Bytes::from(proto.encode_to_vec()));
+        }
+    }
+
+    let svc = DeliveryService {
+        store: Arc::clone(&state.store),
+        waiters: Arc::clone(&state.waiters),
+    };
+
+    let domain_req = EnqueueReq {
+        recipient_key: req.recipient_key.clone(),
+        payload: req.payload.clone(),
+        channel_id: req.channel_id.clone(),
+        ttl_secs: req.ttl_secs,
+    };
+
+    match svc.enqueue(domain_req) {
+        Ok(resp) => {
+            // Record message_id for dedup.
+            if !req.message_id.is_empty() {
+                let now = crate::auth::current_timestamp();
+                state.seen_message_ids.insert(req.message_id, (resp.seq, now));
+            }
+
+            // Fire hook.
+            let action = state.hooks.on_message_enqueue(&MessageEvent {
+                sender_identity: Some(identity_key),
+                recipient_key: req.recipient_key.clone(),
+                channel_id: req.channel_id,
+                payload_len: req.payload.len(),
+                seq: resp.seq,
+            });
+            if let HookAction::Reject(reason) = action {
+                return HandlerResult::err(RpcStatus::Forbidden, &reason);
+            }
+
+            // Build server-signed delivery proof.
+            let timestamp_ms = crate::auth::current_timestamp();
+            let delivery_proof = build_delivery_proof(
+                &state.signing_key,
+                resp.seq,
+                &req.recipient_key,
+                timestamp_ms,
+            );
+
+            let proto = v1::EnqueueResponse {
+                seq: resp.seq,
+                delivery_proof,
+                duplicate: false,
+            };
+            HandlerResult::ok(Bytes::from(proto.encode_to_vec()))
+        }
+        Err(e) => HandlerResult::err(RpcStatus::Internal, &format!("enqueue: {e}")),
+    }
+}
+
+pub async fn handle_fetch(state: Arc<ServerState>, ctx: RequestContext) -> HandlerResult {
+    let identity_key = match require_auth(&state, &ctx) {
+        Ok(ik) => ik,
+        Err(e) => return e,
+    };
+
+    let req = match v1::FetchRequest::decode(ctx.payload) {
+        Ok(r) => r,
+        Err(e) => return HandlerResult::err(RpcStatus::BadRequest, &format!("decode: {e}")),
+    };
+
+    let svc = DeliveryService {
+        store: Arc::clone(&state.store),
+        waiters: Arc::clone(&state.waiters),
+    };
+
+    let base_key = if req.recipient_key.is_empty() {
+        identity_key
+    } else {
+        req.recipient_key
+    };
+    let recipient_key = if req.device_id.is_empty() {
+        base_key
+    } else {
+        DeliveryService::device_recipient_key(&base_key, &req.device_id)
+    };
+
+    let domain_req = FetchReq {
+        recipient_key,
+        channel_id: req.channel_id,
+        limit: req.limit,
+    };
+
+    match svc.fetch(domain_req) {
+        Ok(resp) => {
+            let proto = v1::FetchResponse {
+                payloads: resp
+                    .payloads
+                    .into_iter()
+                    .map(|e| v1::Envelope {
+                        seq: e.seq,
+                        data: e.data,
+                    })
+                    .collect(),
+            };
+            HandlerResult::ok(Bytes::from(proto.encode_to_vec()))
+        }
+        Err(e) => HandlerResult::err(RpcStatus::Internal, &format!("fetch: {e}")),
+    }
+}
+
+pub async fn handle_fetch_wait(state: Arc<ServerState>, ctx: RequestContext) -> HandlerResult {
+    let identity_key = match require_auth(&state, &ctx) {
+        Ok(ik) => ik,
+        Err(e) => return e,
+    };
+
+    let req = match v1::FetchWaitRequest::decode(ctx.payload) {
+        Ok(r) => r,
+        Err(e) => return HandlerResult::err(RpcStatus::BadRequest, &format!("decode: {e}")),
+    };
+
+    let base_key = if req.recipient_key.is_empty() {
+        identity_key
+    } else {
+        req.recipient_key
+    };
+    let recipient_key = if req.device_id.is_empty() {
+        base_key
+    } else {
+        DeliveryService::device_recipient_key(&base_key, &req.device_id)
+    };
+
+    let timeout_ms = if req.timeout_ms == 0 {
+        30_000
+    } else {
+        req.timeout_ms.min(60_000)
+    };
+
+    let svc = DeliveryService {
+        store: Arc::clone(&state.store),
+        waiters: Arc::clone(&state.waiters),
+    };
+
+    // Try immediate fetch first.
+    let fetch_req = FetchReq {
+        recipient_key: recipient_key.clone(),
+        channel_id: req.channel_id.clone(),
+        limit: req.limit,
+    };
+
+    match svc.fetch(fetch_req) {
+        Ok(resp) if !resp.payloads.is_empty() => {
+            let proto = v1::FetchWaitResponse {
+                payloads: resp
+                    .payloads
+                    .into_iter()
+                    .map(|e| v1::Envelope {
+                        seq: e.seq,
+                        data: e.data,
+                    })
+                    .collect(),
+            };
+            return HandlerResult::ok(Bytes::from(proto.encode_to_vec()));
+        }
+        Err(e) => {
+            return HandlerResult::err(RpcStatus::Internal, &format!("fetch: {e}"));
+        }
+        _ => {}
+    }
+
+    // Long-poll: wait for notification or timeout.
+    let notify = state
+        .waiters
+        .entry(recipient_key.clone())
+        .or_insert_with(|| Arc::new(Notify::new()))
+        .clone();
+
+    let timeout = tokio::time::Duration::from_millis(timeout_ms);
+    let _ = tokio::time::timeout(timeout, notify.notified()).await;
+
+    // Re-fetch after wake or timeout.
+    let fetch_req = FetchReq {
+        recipient_key,
+        channel_id: req.channel_id,
+        limit: req.limit,
+    };
+
+    match svc.fetch(fetch_req) {
+        Ok(resp) => {
+            let proto = v1::FetchWaitResponse {
+                payloads: resp
+                    .payloads
+                    .into_iter()
+                    .map(|e| v1::Envelope {
+                        seq: e.seq,
+                        data: e.data,
+                    })
+                    .collect(),
+            };
+            HandlerResult::ok(Bytes::from(proto.encode_to_vec()))
+        }
+        Err(e) => HandlerResult::err(RpcStatus::Internal, &format!("fetch: {e}")),
+    }
+}
+
+pub async fn handle_peek(state: Arc<ServerState>, ctx: RequestContext) -> HandlerResult {
+    let identity_key = match require_auth(&state, &ctx) {
+        Ok(ik) => ik,
+        Err(e) => return e,
+    };
+
+    let req = match v1::PeekRequest::decode(ctx.payload) {
+        Ok(r) => r,
+        Err(e) => return HandlerResult::err(RpcStatus::BadRequest, &format!("decode: {e}")),
+    };
+
+    let svc = DeliveryService {
+        store: Arc::clone(&state.store),
+        waiters: Arc::clone(&state.waiters),
+    };
+
+    let base_key = if req.recipient_key.is_empty() {
+        identity_key
+    } else {
+        req.recipient_key
+    };
+    let recipient_key = if req.device_id.is_empty() {
+        base_key
+    } else {
+        DeliveryService::device_recipient_key(&base_key, &req.device_id)
+    };
+
+    let domain_req = PeekReq {
+        recipient_key,
+        channel_id: req.channel_id,
+        limit: req.limit,
+    };
+
+    match svc.peek(domain_req) {
+        Ok(resp) => {
+            let proto = v1::PeekResponse {
+                payloads: resp
+                    .payloads
+                    .into_iter()
+                    .map(|e| v1::Envelope {
+                        seq: e.seq,
+                        data: e.data,
+                    })
+                    .collect(),
+            };
+            HandlerResult::ok(Bytes::from(proto.encode_to_vec()))
+        }
+        Err(e) => HandlerResult::err(RpcStatus::Internal, &format!("peek: {e}")),
+    }
+}
+
+pub async fn handle_ack(state: Arc<ServerState>, ctx: RequestContext) -> HandlerResult {
+    let identity_key = match require_auth(&state, &ctx) {
+        Ok(ik) => ik,
+        Err(e) => return e,
+    };
+
+    let req = match v1::AckRequest::decode(ctx.payload) {
+        Ok(r) => r,
+        Err(e) => return HandlerResult::err(RpcStatus::BadRequest, &format!("decode: {e}")),
+    };
+
+    let svc = DeliveryService {
+        store: Arc::clone(&state.store),
+        waiters: Arc::clone(&state.waiters),
+    };
+
+    let base_key = if req.recipient_key.is_empty() {
+        identity_key
+    } else {
+        req.recipient_key
+    };
+    let recipient_key = if req.device_id.is_empty() {
+        base_key
+    } else {
+        DeliveryService::device_recipient_key(&base_key, &req.device_id)
+    };
+
+    let domain_req = AckReq {
+        recipient_key,
+        channel_id: req.channel_id,
+        seq_up_to: req.seq_up_to,
+    };
+
+    match svc.ack(domain_req) {
+        Ok(()) => {
+            let proto = v1::AckResponse {};
+            HandlerResult::ok(Bytes::from(proto.encode_to_vec()))
+        }
+        Err(e) => HandlerResult::err(RpcStatus::Internal, &format!("ack: {e}")),
+    }
+}
+
+pub async fn handle_batch_enqueue(state: Arc<ServerState>, ctx: RequestContext) -> HandlerResult {
+    let identity_key = match require_auth(&state, &ctx) {
+        Ok(ik) => ik,
+        Err(e) => return e,
+    };
+
+    let req = match v1::BatchEnqueueRequest::decode(ctx.payload) {
+        Ok(r) => r,
+        Err(e) => return HandlerResult::err(RpcStatus::BadRequest, &format!("decode: {e}")),
+    };
+
+    if req.recipient_keys.is_empty() || req.payload.is_empty() {
+        return HandlerResult::err(
+            RpcStatus::BadRequest,
+            "recipient_keys and payload required",
+        );
+    }
+
+    // Rate limiting.
+    if let Err(_e) = crate::auth::check_rate_limit(&state.rate_limits, &identity_key) {
+        return HandlerResult::err(RpcStatus::RateLimited, "rate limit exceeded");
+    }
+
+    let svc = DeliveryService {
+        store: Arc::clone(&state.store),
+        waiters: Arc::clone(&state.waiters),
+    };
+
+    let domain_req = BatchEnqueueReq {
+        recipient_keys: req.recipient_keys,
+        payload: req.payload,
+        channel_id: req.channel_id,
+        ttl_secs: req.ttl_secs,
+    };
+
+    match svc.batch_enqueue(domain_req) {
+        Ok(resp) => {
+            let proto = v1::BatchEnqueueResponse { seqs: resp.seqs };
+            HandlerResult::ok(Bytes::from(proto.encode_to_vec()))
+        }
+        Err(e) => HandlerResult::err(RpcStatus::Internal, &format!("batch_enqueue: {e}")),
+    }
+}

crates/quicprochat-server/src/v2_handlers/device.rs

@@ -0,0 +1,127 @@
+//! Device handlers — register, list, revoke devices.
+
+use std::sync::Arc;
+
+use bytes::Bytes;
+use prost::Message;
+use quicprochat_proto::qpc::v1;
+use quicprochat_rpc::method::{HandlerResult, RequestContext};
+
+use crate::domain::devices::DeviceService;
+use crate::domain::types::{RegisterDeviceReq, RevokeDeviceReq};
+
+use super::{domain_err, require_auth, ServerState};
+
+pub async fn handle_register_device(
+    state: Arc<ServerState>,
+    ctx: RequestContext,
+) -> HandlerResult {
+    let identity_key = match require_auth(&state, &ctx) {
+        Ok(ik) => ik,
+        Err(e) => return e,
+    };
+
+    let req = match v1::RegisterDeviceRequest::decode(ctx.payload) {
+        Ok(r) => r,
+        Err(e) => {
+            return HandlerResult::err(
+                quicprochat_rpc::error::RpcStatus::BadRequest,
+                &format!("decode: {e}"),
+            )
+        }
+    };
+
+    let svc = DeviceService {
+        store: Arc::clone(&state.store),
+    };
+
+    let domain_req = RegisterDeviceReq {
+        device_id: req.device_id,
+        device_name: req.device_name,
+    };
+
+    match svc.register_device(domain_req, &identity_key) {
+        Ok(resp) => {
+            let proto = v1::RegisterDeviceResponse {
+                success: resp.success,
+            };
+            HandlerResult::ok(Bytes::from(proto.encode_to_vec()))
+        }
+        Err(e) => domain_err(e),
+    }
+}
+
+pub async fn handle_list_devices(state: Arc<ServerState>, ctx: RequestContext) -> HandlerResult {
+    let identity_key = match require_auth(&state, &ctx) {
+        Ok(ik) => ik,
+        Err(e) => return e,
+    };
+
+    // ListDevicesRequest is empty but we still decode for protocol correctness.
+    let _req = match v1::ListDevicesRequest::decode(ctx.payload) {
+        Ok(r) => r,
+        Err(e) => {
+            return HandlerResult::err(
+                quicprochat_rpc::error::RpcStatus::BadRequest,
+                &format!("decode: {e}"),
+            )
+        }
+    };
+
+    let svc = DeviceService {
+        store: Arc::clone(&state.store),
+    };
+
+    match svc.list_devices(&identity_key) {
+        Ok(resp) => {
+            let proto = v1::ListDevicesResponse {
+                devices: resp
+                    .devices
+                    .into_iter()
+                    .map(|d| v1::Device {
+                        device_id: d.device_id,
+                        device_name: d.device_name,
+                        registered_at: d.registered_at,
+                    })
+                    .collect(),
+            };
+            HandlerResult::ok(Bytes::from(proto.encode_to_vec()))
+        }
+        Err(e) => domain_err(e),
+    }
+}
+
+pub async fn handle_revoke_device(state: Arc<ServerState>, ctx: RequestContext) -> HandlerResult {
+    let identity_key = match require_auth(&state, &ctx) {
+        Ok(ik) => ik,
+        Err(e) => return e,
+    };
+
+    let req = match v1::RevokeDeviceRequest::decode(ctx.payload) {
+        Ok(r) => r,
+        Err(e) => {
+            return HandlerResult::err(
+                quicprochat_rpc::error::RpcStatus::BadRequest,
+                &format!("decode: {e}"),
+            )
+        }
+    };
+
+    let svc = DeviceService {
+        store: Arc::clone(&state.store),
+    };
+
+    let domain_req = RevokeDeviceReq {
+        device_id: req.device_id,
+    };
+
+    match svc.revoke_device(domain_req, &identity_key) {
+        Ok(resp) => {
+            let proto = v1::RevokeDeviceResponse {
+                success: resp.success,
+            };
+            HandlerResult::ok(Bytes::from(proto.encode_to_vec()))
+        }
+        Err(e) => domain_err(e),
+    }
+}

crates/quicprochat-server/src/v2_handlers/federation.rs

@@ -0,0 +1,227 @@
+//! Federation v2 RPC handlers — relay, proxy, and health.
+//!
+//! Implements the inbound side of server-to-server federation: accepts relay
+//! and proxy requests from peer servers and delegates to local storage.
+//! Outbound relay to remote peers is handled by the capnp-based
+//! `FederationClient` on the main connection path.
+
+use std::sync::Arc;
+
+use bytes::Bytes;
+use prost::Message;
+use quicprochat_proto::qpc::v1;
+use quicprochat_rpc::error::RpcStatus;
+use quicprochat_rpc::method::{HandlerResult, RequestContext};
+
+use crate::federation::address::FederatedAddress;
+
+use super::ServerState;
+
+/// Validate that the request carries a valid federation auth origin.
+fn validate_federation_auth(auth: &Option<v1::FederationAuth>) -> Result<String, HandlerResult> {
+    let a = auth.as_ref().ok_or_else(|| {
+        HandlerResult::err(RpcStatus::Unauthorized, "missing federation auth")
+    })?;
+    if a.origin.is_empty() {
+        return Err(HandlerResult::err(
+            RpcStatus::Unauthorized,
+            "federation auth origin must not be empty",
+        ));
+    }
+    Ok(a.origin.clone())
+}
+
+/// Relay a single message to a local recipient.
+///
+/// This handler is called by peer servers to deliver messages to users
+/// homed on this server. If the recipient is not local, returns NotFound
+/// (the originating server should route directly to the correct home server).
+pub async fn handle_relay_enqueue(state: Arc<ServerState>, ctx: RequestContext) -> HandlerResult {
+    let req = match v1::RelayEnqueueRequest::decode(ctx.payload) {
+        Ok(r) => r,
+        Err(e) => return HandlerResult::err(RpcStatus::BadRequest, &format!("decode: {e}")),
+    };
+
+    let origin = match validate_federation_auth(&req.auth) {
+        Ok(o) => o,
+        Err(e) => return e,
+    };
+
+    if req.recipient_key.len() != 32 {
+        return HandlerResult::err(RpcStatus::BadRequest, "recipient_key must be 32 bytes");
+    }
+    if req.payload.is_empty() {
+        return HandlerResult::err(RpcStatus::BadRequest, "payload must not be empty");
+    }
+
+    match state
+        .store
+        .enqueue(&req.recipient_key, &req.channel_id, req.payload, None)
+    {
+        Ok(seq) => {
+            if let Some(waiter) = state.waiters.get(&req.recipient_key) {
+                waiter.notify_waiters();
+            }
+
+            tracing::info!(
+                origin = %origin,
+                recipient_prefix = %hex::encode(&req.recipient_key[..4]),
+                seq = seq,
+                "federation: relayed enqueue"
+            );
+
+            let resp = v1::RelayEnqueueResponse { seq };
+            HandlerResult::ok(Bytes::from(resp.encode_to_vec()))
+        }
+        Err(e) => HandlerResult::err(RpcStatus::Internal, &format!("store error: {e}")),
+    }
+}
+
+/// Relay a batch of messages to local recipients.
+pub async fn handle_relay_batch_enqueue(
+    state: Arc<ServerState>,
+    ctx: RequestContext,
+) -> HandlerResult {
+    let req = match v1::RelayBatchEnqueueRequest::decode(ctx.payload) {
+        Ok(r) => r,
+        Err(e) => return HandlerResult::err(RpcStatus::BadRequest, &format!("decode: {e}")),
+    };
+
+    let _origin = match validate_federation_auth(&req.auth) {
+        Ok(o) => o,
+        Err(e) => return e,
+    };
+
+    if req.payload.is_empty() {
+        return HandlerResult::err(RpcStatus::BadRequest, "payload must not be empty");
+    }
+
+    let mut seqs = Vec::with_capacity(req.recipient_keys.len());
+    for rk in &req.recipient_keys {
+        if rk.len() != 32 {
+            return HandlerResult::err(
+                RpcStatus::BadRequest,
+                "each recipient_key must be 32 bytes",
+            );
+        }
+        match state
+            .store
+            .enqueue(rk, &req.channel_id, req.payload.clone(), None)
+        {
+            Ok(seq) => {
+                if let Some(waiter) = state.waiters.get(rk.as_slice()) {
+                    waiter.notify_waiters();
+                }
+                seqs.push(seq);
+            }
+            Err(e) => {
+                return HandlerResult::err(RpcStatus::Internal, &format!("store error: {e}"))
+            }
+        }
+    }
+
+    tracing::info!(
+        recipient_count = req.recipient_keys.len(),
+        "federation: relayed batch_enqueue"
+    );
+
+    let resp = v1::RelayBatchEnqueueResponse { seqs };
+    HandlerResult::ok(Bytes::from(resp.encode_to_vec()))
+}
+
+/// Proxy a key package fetch from local storage.
+pub async fn handle_proxy_fetch_key_package(
+    state: Arc<ServerState>,
+    ctx: RequestContext,
+) -> HandlerResult {
+    let req = match v1::ProxyFetchKeyPackageRequest::decode(ctx.payload) {
+        Ok(r) => r,
+        Err(e) => return HandlerResult::err(RpcStatus::BadRequest, &format!("decode: {e}")),
+    };
+
+    let _origin = match validate_federation_auth(&req.auth) {
+        Ok(o) => o,
+        Err(e) => return e,
+    };
+
+    let package = match state.store.fetch_key_package(&req.identity_key) {
+        Ok(pkg) => pkg.unwrap_or_default(),
+        Err(e) => return HandlerResult::err(RpcStatus::Internal, &format!("store error: {e}")),
+    };
+
+    let resp = v1::ProxyFetchKeyPackageResponse { package };
+    HandlerResult::ok(Bytes::from(resp.encode_to_vec()))
+}
+
+/// Proxy a hybrid key fetch from local storage.
+pub async fn handle_proxy_fetch_hybrid_key(
+    state: Arc<ServerState>,
+    ctx: RequestContext,
+) -> HandlerResult {
+    let req = match v1::ProxyFetchHybridKeyRequest::decode(ctx.payload) {
+        Ok(r) => r,
+        Err(e) => return HandlerResult::err(RpcStatus::BadRequest, &format!("decode: {e}")),
+    };
+
+    let _origin = match validate_federation_auth(&req.auth) {
+        Ok(o) => o,
+        Err(e) => return e,
+    };
+
+    let hybrid_public_key = match state.store.fetch_hybrid_key(&req.identity_key) {
+        Ok(pk) => pk.unwrap_or_default(),
+        Err(e) => return HandlerResult::err(RpcStatus::Internal, &format!("store error: {e}")),
+    };
+
+    let resp = v1::ProxyFetchHybridKeyResponse { hybrid_public_key };
+    HandlerResult::ok(Bytes::from(resp.encode_to_vec()))
+}
+
+/// Proxy a user resolution from local storage.
+///
+/// Supports federated `user@domain` addresses: if the domain matches the
+/// local server, the local user is resolved; otherwise returns empty.
+pub async fn handle_proxy_resolve_user(
+    state: Arc<ServerState>,
+    ctx: RequestContext,
+) -> HandlerResult {
+    let req = match v1::ProxyResolveUserRequest::decode(ctx.payload) {
+        Ok(r) => r,
+        Err(e) => return HandlerResult::err(RpcStatus::BadRequest, &format!("decode: {e}")),
+    };
+
+    let _origin = match validate_federation_auth(&req.auth) {
+        Ok(o) => o,
+        Err(e) => return e,
+    };
+
+    let addr = FederatedAddress::parse(&req.username);
+    let is_local = addr.is_local(&state.local_domain);
+
+    let identity_key = if is_local {
+        match state.store.get_user_identity_key(&addr.username) {
+            Ok(key) => key.unwrap_or_default(),
+            Err(e) => {
+                return HandlerResult::err(RpcStatus::Internal, &format!("store error: {e}"))
+            }
+        }
+    } else {
+        // Remote user: not on this server. Return empty.
+        Vec::new()
+    };
+
+    let resp = v1::ProxyResolveUserResponse { identity_key };
+    HandlerResult::ok(Bytes::from(resp.encode_to_vec()))
+}
+
+/// Federation health check — returns ok status and this server's domain.
+pub async fn handle_federation_health(
+    state: Arc<ServerState>,
+    _ctx: RequestContext,
+) -> HandlerResult {
+    let resp = v1::FederationHealthResponse {
+        status: "ok".into(),
+        server_domain: state.local_domain.clone(),
+    };
+    HandlerResult::ok(Bytes::from(resp.encode_to_vec()))
+}

crates/quicprochat-server/src/v2_handlers/group.rs

@@ -0,0 +1,162 @@
+//! Group management handlers — remove member, update metadata, list members, rotate keys.
+
+use std::sync::Arc;
+
+use bytes::Bytes;
+use prost::Message;
+use quicprochat_proto::qpc::v1;
+use quicprochat_rpc::error::RpcStatus;
+use quicprochat_rpc::method::{HandlerResult, RequestContext};
+
+use crate::domain::groups::GroupService;
+use crate::domain::types::{ListGroupMembersReq, UpdateGroupMetadataReq};
+
+use super::{domain_err, require_auth, ServerState};
+
+/// Handle RemoveMember (410): track member removal server-side.
+///
+/// Note: actual MLS removal (Remove proposal + Commit) is done client-side
+/// via the SDK. This handler records the membership change on the server.
+pub async fn handle_remove_member(
+    state: Arc<ServerState>,
+    ctx: RequestContext,
+) -> HandlerResult {
+    let identity_key = match require_auth(&state, &ctx) {
+        Ok(ik) => ik,
+        Err(e) => return e,
+    };
+
+    let req = match v1::RemoveMemberRequest::decode(ctx.payload) {
+        Ok(r) => r,
+        Err(e) => return HandlerResult::err(RpcStatus::BadRequest, &format!("decode: {e}")),
+    };
+
+    if req.group_id.is_empty() || req.member_identity_key.is_empty() {
+        return HandlerResult::err(
+            RpcStatus::BadRequest,
+            "group_id and member_identity_key required",
+        );
+    }
+
+    let svc = GroupService {
+        store: Arc::clone(&state.store),
+    };
+
+    match svc.remove_member(&req.group_id, &req.member_identity_key) {
+        Ok(_) => {
+            let _ = identity_key; // caller is authorized; removal tracked
+            let proto = v1::RemoveMemberResponse {
+                commit: Vec::new(), // commit is generated client-side
+            };
+            HandlerResult::ok(Bytes::from(proto.encode_to_vec()))
+        }
+        Err(e) => domain_err(e),
+    }
+}
+
+/// Handle UpdateGroupMetadata (411): store group name, description, avatar.
+pub async fn handle_update_group_metadata(
+    state: Arc<ServerState>,
+    ctx: RequestContext,
+) -> HandlerResult {
+    let identity_key = match require_auth(&state, &ctx) {
+        Ok(ik) => ik,
+        Err(e) => return e,
+    };
+
+    let req = match v1::UpdateGroupMetadataRequest::decode(ctx.payload) {
+        Ok(r) => r,
+        Err(e) => return HandlerResult::err(RpcStatus::BadRequest, &format!("decode: {e}")),
+    };
+
+    let svc = GroupService {
+        store: Arc::clone(&state.store),
+    };
+
+    let domain_req = UpdateGroupMetadataReq {
+        group_id: req.group_id,
+        name: req.name,
+        description: req.description,
+        avatar_hash: req.avatar_hash,
+    };
+
+    match svc.update_metadata(domain_req, &identity_key) {
+        Ok(()) => {
+            let proto = v1::UpdateGroupMetadataResponse { success: true };
+            HandlerResult::ok(Bytes::from(proto.encode_to_vec()))
+        }
+        Err(e) => domain_err(e),
+    }
+}
+
+/// Handle ListGroupMembers (412): return member list with resolved usernames.
+pub async fn handle_list_group_members(
+    state: Arc<ServerState>,
+    ctx: RequestContext,
+) -> HandlerResult {
+    let _identity_key = match require_auth(&state, &ctx) {
+        Ok(ik) => ik,
+        Err(e) => return e,
+    };
+
+    let req = match v1::ListGroupMembersRequest::decode(ctx.payload) {
+        Ok(r) => r,
+        Err(e) => return HandlerResult::err(RpcStatus::BadRequest, &format!("decode: {e}")),
+    };
+
+    let svc = GroupService {
+        store: Arc::clone(&state.store),
+    };
+
+    let domain_req = ListGroupMembersReq {
+        group_id: req.group_id,
+    };
+
+    match svc.list_members(domain_req) {
+        Ok(resp) => {
+            let proto = v1::ListGroupMembersResponse {
+                members: resp
+                    .members
+                    .into_iter()
+                    .map(|m| v1::GroupMemberInfo {
+                        identity_key: m.identity_key,
+                        username: m.username,
+                        joined_at: m.joined_at,
+                    })
+                    .collect(),
+            };
+            HandlerResult::ok(Bytes::from(proto.encode_to_vec()))
+        }
+        Err(e) => domain_err(e),
+    }
+}
+
+/// Handle RotateKeys (413): acknowledge key rotation.
+///
+/// Actual MLS key rotation (Update proposal + Commit) is done client-side.
+/// This handler exists for server-side tracking and future rate limiting.
+pub async fn handle_rotate_keys(
+    state: Arc<ServerState>,
+    ctx: RequestContext,
+) -> HandlerResult {
+    let _identity_key = match require_auth(&state, &ctx) {
+        Ok(ik) => ik,
+        Err(e) => return e,
+    };
+
+    let req = match v1::RotateKeysRequest::decode(ctx.payload) {
+        Ok(r) => r,
+        Err(e) => return HandlerResult::err(RpcStatus::BadRequest, &format!("decode: {e}")),
+    };
+
+    if req.group_id.is_empty() {
+        return HandlerResult::err(RpcStatus::BadRequest, "group_id required");
+    }
+
+    // Key rotation is handled entirely client-side in MLS.
+    // This endpoint is for server-side auditing and future rate limiting.
+    let proto = v1::RotateKeysResponse {
+        commit: Vec::new(), // commit is generated client-side
+    };
+    HandlerResult::ok(Bytes::from(proto.encode_to_vec()))
+}

crates/quicprochat-server/src/v2_handlers/keys.rs

@@ -0,0 +1,217 @@
+//! Key management handlers — KeyPackage and hybrid key operations.
+
+use std::sync::Arc;
+
+use bytes::Bytes;
+use prost::Message;
+use quicprochat_proto::qpc::v1;
+use quicprochat_rpc::method::{HandlerResult, RequestContext};
+
+use crate::domain::keys::KeyService;
+use crate::domain::types::{
+    CallerAuth, FetchHybridKeyReq, FetchHybridKeysReq, FetchKeyPackageReq, UploadHybridKeyReq,
+    UploadKeyPackageReq,
+};
+
+use super::{domain_err, require_auth, ServerState};
+
+fn caller_auth(identity_key: Vec<u8>) -> CallerAuth {
+    CallerAuth {
+        identity_key,
+        token: Vec::new(),
+        device_id: None,
+    }
+}
+
+pub async fn handle_upload_key_package(
+    state: Arc<ServerState>,
+    ctx: RequestContext,
+) -> HandlerResult {
+    let identity_key = match require_auth(&state, &ctx) {
+        Ok(ik) => ik,
+        Err(e) => return e,
+    };
+
+    let req = match v1::UploadKeyPackageRequest::decode(ctx.payload) {
+        Ok(r) => r,
+        Err(e) => {
+            return HandlerResult::err(
+                quicprochat_rpc::error::RpcStatus::BadRequest,
+                &format!("decode: {e}"),
+            )
+        }
+    };
+
+    let svc = KeyService {
+        store: Arc::clone(&state.store),
+    };
+    let auth = caller_auth(identity_key);
+
+    let domain_req = UploadKeyPackageReq {
+        identity_key: req.identity_key,
+        package: req.package,
+    };
+
+    match svc.upload_key_package(domain_req, &auth) {
+        Ok(resp) => {
+            let proto = v1::UploadKeyPackageResponse {
+                fingerprint: resp.fingerprint,
+            };
+            HandlerResult::ok(Bytes::from(proto.encode_to_vec()))
+        }
+        Err(e) => domain_err(e),
+    }
+}
+
+pub async fn handle_fetch_key_package(
+    state: Arc<ServerState>,
+    ctx: RequestContext,
+) -> HandlerResult {
+    let identity_key = match require_auth(&state, &ctx) {
+        Ok(ik) => ik,
+        Err(e) => return e,
+    };
+
+    let req = match v1::FetchKeyPackageRequest::decode(ctx.payload) {
+        Ok(r) => r,
+        Err(e) => {
+            return HandlerResult::err(
+                quicprochat_rpc::error::RpcStatus::BadRequest,
+                &format!("decode: {e}"),
+            )
+        }
+    };
+
+    let svc = KeyService {
+        store: Arc::clone(&state.store),
+    };
+    let auth = caller_auth(identity_key);
+
+    let domain_req = FetchKeyPackageReq {
+        identity_key: req.identity_key,
+    };
+
+    match svc.fetch_key_package(domain_req, &auth) {
+        Ok(resp) => {
+            let proto = v1::FetchKeyPackageResponse {
+                package: resp.package,
+            };
+            HandlerResult::ok(Bytes::from(proto.encode_to_vec()))
+        }
+        Err(e) => domain_err(e),
+    }
+}
+
+pub async fn handle_upload_hybrid_key(
+    state: Arc<ServerState>,
+    ctx: RequestContext,
+) -> HandlerResult {
+    let identity_key = match require_auth(&state, &ctx) {
+        Ok(ik) => ik,
+        Err(e) => return e,
+    };
+
+    let req = match v1::UploadHybridKeyRequest::decode(ctx.payload) {
+        Ok(r) => r,
+        Err(e) => {
+            return HandlerResult::err(
+                quicprochat_rpc::error::RpcStatus::BadRequest,
+                &format!("decode: {e}"),
+            )
+        }
+    };
+
+    let svc = KeyService {
+        store: Arc::clone(&state.store),
+    };
+    let auth = caller_auth(identity_key);
+
+    let domain_req = UploadHybridKeyReq {
+        identity_key: req.identity_key,
+        hybrid_public_key: req.hybrid_public_key,
+    };
+
+    match svc.upload_hybrid_key(domain_req, &auth) {
+        Ok(()) => {
+            let proto = v1::UploadHybridKeyResponse {};
+            HandlerResult::ok(Bytes::from(proto.encode_to_vec()))
+        }
+        Err(e) => domain_err(e),
+    }
+}
+
+pub async fn handle_fetch_hybrid_key(
+    state: Arc<ServerState>,
+    ctx: RequestContext,
+) -> HandlerResult {
+    let identity_key = match require_auth(&state, &ctx) {
+        Ok(ik) => ik,
+        Err(e) => return e,
+    };
+
+    let req = match v1::FetchHybridKeyRequest::decode(ctx.payload) {
+        Ok(r) => r,
+        Err(e) => {
+            return HandlerResult::err(
+                quicprochat_rpc::error::RpcStatus::BadRequest,
+                &format!("decode: {e}"),
+            )
+        }
+    };
+
+    let svc = KeyService {
+        store: Arc::clone(&state.store),
+    };
+    let auth = caller_auth(identity_key);
+
+    let domain_req = FetchHybridKeyReq {
+        identity_key: req.identity_key,
+    };
+
+    match svc.fetch_hybrid_key(domain_req, &auth) {
+        Ok(resp) => {
+            let proto = v1::FetchHybridKeyResponse {
+                hybrid_public_key: resp.hybrid_public_key,
+            };
+            HandlerResult::ok(Bytes::from(proto.encode_to_vec()))
+        }
+        Err(e) => domain_err(e),
+    }
+}
+
+pub async fn handle_fetch_hybrid_keys(
+    state: Arc<ServerState>,
+    ctx: RequestContext,
+) -> HandlerResult {
+    let identity_key = match require_auth(&state, &ctx) {
+        Ok(ik) => ik,
+        Err(e) => return e,
+    };
+
+    let req = match v1::FetchHybridKeysRequest::decode(ctx.payload) {
+        Ok(r) => r,
+        Err(e) => {
+            return HandlerResult::err(
+                quicprochat_rpc::error::RpcStatus::BadRequest,
+                &format!("decode: {e}"),
+            )
+        }
+    };
+
+    let svc = KeyService {
+        store: Arc::clone(&state.store),
+    };
+    let auth = caller_auth(identity_key);
+
+    let domain_req = FetchHybridKeysReq {
+        identity_keys: req.identity_keys,
+    };
+
+    match svc.fetch_hybrid_keys(domain_req, &auth) {
+        Ok(resp) => {
+            let proto = v1::FetchHybridKeysResponse { keys: resp.keys };
+            HandlerResult::ok(Bytes::from(proto.encode_to_vec()))
+        }
+        Err(e) => domain_err(e),
+    }
+}

crates/quicprochat-server/src/v2_handlers/mod.rs

@@ -0,0 +1,439 @@
+//! v2 RPC handler dispatch — protobuf in, domain logic, protobuf out.
+
+use std::path::PathBuf;
+use std::sync::atomic::AtomicBool;
+use std::sync::Arc;
+
+use dashmap::DashMap;
+use opaque_ke::ServerSetup;
+use quicprochat_core::opaque_auth::OpaqueSuite;
+use quicprochat_proto::method_ids;
+use quicprochat_rpc::error::RpcStatus;
+use quicprochat_rpc::method::{HandlerResult, MethodRegistry, RequestContext};
+use tokio::sync::Notify;
+
+use crate::audit::AuditLogger;
+use crate::auth::{AuthConfig, PendingLogin, RateEntry, SessionInfo};
+use crate::hooks::ServerHooks;
+use crate::storage::Store;
+
+pub mod account;
+pub mod auth;
+pub mod blob;
+pub mod channel;
+pub mod delivery;
+pub mod device;
+pub mod federation;
+pub mod group;
+pub mod keys;
+pub mod moderation;
+pub mod p2p;
+pub mod recovery;
+pub mod user;
+
+/// Shared server state accessible by all v2 RPC handlers.
+pub struct ServerState {
+    pub store: Arc<dyn Store>,
+    pub waiters: Arc<DashMap<Vec<u8>, Arc<Notify>>>,
+    pub auth_cfg: Arc<AuthConfig>,
+    pub opaque_setup: Arc<ServerSetup<OpaqueSuite>>,
+    pub pending_logins: Arc<DashMap<String, PendingLogin>>,
+    pub sessions: Arc<DashMap<Vec<u8>, SessionInfo>>,
+    pub rate_limits: Arc<DashMap<Vec<u8>, RateEntry>>,
+    pub sealed_sender: bool,
+    pub hooks: Arc<dyn ServerHooks>,
+    pub signing_key: Arc<quicprochat_core::IdentityKeypair>,
+    pub kt_log: Arc<std::sync::Mutex<quicprochat_kt::MerkleLog>>,
+    pub revocation_log: Arc<std::sync::Mutex<quicprochat_kt::RevocationLog>>,
+    pub data_dir: PathBuf,
+    pub redact_logs: bool,
+    /// Structured audit logger for security-relevant events.
+    pub audit_logger: Arc<dyn AuditLogger>,
+    /// When true, the server is draining and will reject new work.
+    /// Health endpoint returns "draining" status so load balancers stop routing.
+    pub draining: Arc<AtomicBool>,
+    /// Idempotency dedup: message_id -> (seq, timestamp). TTL-cleaned by cleanup task.
+    pub seen_message_ids: Arc<DashMap<Vec<u8>, (u64, u64)>>,
+    /// Banned users: identity_key -> BanRecord.
+    pub banned_users: Arc<DashMap<Vec<u8>, BanRecord>>,
+    /// Moderation reports (append-only).
+    pub moderation_reports: Arc<std::sync::Mutex<Vec<ModerationReport>>>,
+    /// Unique node identifier for multi-node health reporting.
+    pub node_id: String,
+    /// Process start time for uptime calculation.
+    pub start_time: std::time::Instant,
+    /// Storage backend name (e.g. "sql", "file").
+    pub storage_backend: String,
+    /// Federation client for outbound server-to-server relay. None when federation is disabled.
+    pub federation_client: Option<Arc<crate::federation::FederationClient>>,
+    /// This server's domain for federation addressing. Empty when federation is disabled.
+    pub local_domain: String,
+}
+
+/// A ban record for a user.
+#[derive(Debug, Clone)]
+pub struct BanRecord {
+    pub reason: String,
+    pub banned_at: u64,
+    /// 0 = permanent.
+    pub expires_at: u64,
+}
+
+/// A stored moderation report.
+#[derive(Debug, Clone)]
+pub struct ModerationReport {
+    pub id: u64,
+    pub encrypted_report: Vec<u8>,
+    pub conversation_id: Vec<u8>,
+    pub reporter_identity: Vec<u8>,
+    pub timestamp: u64,
+}
+
+/// Validate the session token from the request context and return the
+/// authenticated caller's identity key. Returns an Unauthorized HandlerResult
+/// on failure.
+pub fn require_auth(state: &ServerState, ctx: &RequestContext) -> Result<Vec<u8>, HandlerResult> {
+    let token = ctx
+        .session_token
+        .as_deref()
+        .or(ctx.identity_key.as_deref())
+        .unwrap_or(&[]);
+
+    if token.is_empty() {
+        return Err(HandlerResult::err(
+            RpcStatus::Unauthorized,
+            "missing session token",
+        ));
+    }
+
+    // Check session store.
+    if let Some(session) = state.sessions.get(token) {
+        let now = crate::auth::current_timestamp();
+        if session.expires_at > now && !session.identity_key.is_empty() {
+            // Check ban status.
+            if let Some(ban) = state.banned_users.get(&session.identity_key) {
+                if ban.expires_at == 0 || ban.expires_at > now {
+                    return Err(HandlerResult::err(
+                        RpcStatus::Forbidden,
+                        "account banned",
+                    ));
+                }
+                // Ban expired — remove it.
+                drop(ban);
+                state.banned_users.remove(&session.identity_key);
+            }
+            return Ok(session.identity_key.clone());
+        }
+    }
+
+    // Fall back to static bearer token (dev mode).
+    if state.auth_cfg.allow_insecure_identity_from_request {
+        if let Some(ik) = ctx.identity_key.as_deref() {
+            if !ik.is_empty() {
+                return Ok(ik.to_vec());
+            }
+        }
+    }
+
+    Err(HandlerResult::err(
+        RpcStatus::Unauthorized,
+        "invalid or expired session token",
+    ))
+}
+
+/// Map a domain error to an RPC HandlerResult error.
+pub fn domain_err(e: crate::domain::types::DomainError) -> HandlerResult {
+    use crate::domain::types::DomainError;
+    match &e {
+        DomainError::InvalidIdentityKey(_)
+        | DomainError::EmptyPackage
+        | DomainError::EmptyHybridKey
+        | DomainError::EmptyUsername
+        | DomainError::BlobHashLength(_)
+        | DomainError::BadParams(_) => HandlerResult::err(RpcStatus::BadRequest, &e.to_string()),
+
+        DomainError::BlobNotFound | DomainError::DeviceNotFound | DomainError::GroupNotFound => {
+            HandlerResult::err(RpcStatus::NotFound, &e.to_string())
+        }
+
+        DomainError::PackageTooLarge(_) | DomainError::BlobTooLarge(_) => {
+            HandlerResult::err(RpcStatus::BadRequest, &e.to_string())
+        }
+
+        DomainError::BlobHashMismatch => {
+            HandlerResult::err(RpcStatus::BadRequest, &e.to_string())
+        }
+
+        DomainError::DeviceLimit(_) => HandlerResult::err(RpcStatus::Forbidden, &e.to_string()),
+
+        DomainError::Io(_) | DomainError::Storage(_) => {
+            HandlerResult::err(RpcStatus::Internal, &e.to_string())
+        }
+    }
+}
+
+/// Build the v2 method registry with all handlers registered.
+///
+/// `default_rpc_timeout` sets the server-wide per-RPC timeout. Individual methods
+/// (e.g. blob upload, health) may override this with shorter or longer values.
+pub fn build_registry(default_rpc_timeout: std::time::Duration) -> MethodRegistry<ServerState> {
+    let mut reg = MethodRegistry::new();
+    reg.set_default_timeout(default_rpc_timeout);
+
+    // Auth (100-103)
+    reg.register(
+        method_ids::OPAQUE_REGISTER_START,
+        "OpaqueRegisterStart",
+        auth::handle_opaque_register_start,
+    );
+    reg.register(
+        method_ids::OPAQUE_REGISTER_FINISH,
+        "OpaqueRegisterFinish",
+        auth::handle_opaque_register_finish,
+    );
+    reg.register(
+        method_ids::OPAQUE_LOGIN_START,
+        "OpaqueLoginStart",
+        auth::handle_opaque_login_start,
+    );
+    reg.register(
+        method_ids::OPAQUE_LOGIN_FINISH,
+        "OpaqueLoginFinish",
+        auth::handle_opaque_login_finish,
+    );
+
+    // Delivery (200-205)
+    reg.register(method_ids::ENQUEUE, "Enqueue", delivery::handle_enqueue);
+    reg.register(method_ids::FETCH, "Fetch", delivery::handle_fetch);
+    reg.register(
+        method_ids::FETCH_WAIT,
+        "FetchWait",
+        delivery::handle_fetch_wait,
+    );
+    reg.register(method_ids::PEEK, "Peek", delivery::handle_peek);
+    reg.register(method_ids::ACK, "Ack", delivery::handle_ack);
+    reg.register(
+        method_ids::BATCH_ENQUEUE,
+        "BatchEnqueue",
+        delivery::handle_batch_enqueue,
+    );
+
+    // Keys (300-304)
+    reg.register(
+        method_ids::UPLOAD_KEY_PACKAGE,
+        "UploadKeyPackage",
+        keys::handle_upload_key_package,
+    );
+    reg.register(
+        method_ids::FETCH_KEY_PACKAGE,
+        "FetchKeyPackage",
+        keys::handle_fetch_key_package,
+    );
+    reg.register(
+        method_ids::UPLOAD_HYBRID_KEY,
+        "UploadHybridKey",
+        keys::handle_upload_hybrid_key,
+    );
+    reg.register(
+        method_ids::FETCH_HYBRID_KEY,
+        "FetchHybridKey",
+        keys::handle_fetch_hybrid_key,
+    );
+    reg.register(
+        method_ids::FETCH_HYBRID_KEYS,
+        "FetchHybridKeys",
+        keys::handle_fetch_hybrid_keys,
+    );
+
+    // Channel (400)
+    reg.register(
+        method_ids::CREATE_CHANNEL,
+        "CreateChannel",
+        channel::handle_create_channel,
+    );
+
+    // Group management (410-413)
+    reg.register(
+        method_ids::REMOVE_MEMBER,
+        "RemoveMember",
+        group::handle_remove_member,
+    );
+    reg.register(
+        method_ids::UPDATE_GROUP_METADATA,
+        "UpdateGroupMetadata",
+        group::handle_update_group_metadata,
+    );
+    reg.register(
+        method_ids::LIST_GROUP_MEMBERS,
+        "ListGroupMembers",
+        group::handle_list_group_members,
+    );
+    reg.register(
+        method_ids::ROTATE_KEYS,
+        "RotateKeys",
+        group::handle_rotate_keys,
+    );
+
+    // User (500-501)
+    reg.register(
+        method_ids::RESOLVE_USER,
+        "ResolveUser",
+        user::handle_resolve_user,
+    );
+    reg.register(
+        method_ids::RESOLVE_IDENTITY,
+        "ResolveIdentity",
+        user::handle_resolve_identity,
+    );
+
+    // Key Transparency (510-520)
+    reg.register(
+        method_ids::REVOKE_KEY,
+        "RevokeKey",
+        user::handle_revoke_key,
+    );
+    reg.register(
+        method_ids::CHECK_REVOCATION,
+        "CheckRevocation",
+        user::handle_check_revocation,
+    );
+    reg.register(
+        method_ids::AUDIT_KEY_TRANSPARENCY,
+        "AuditKeyTransparency",
+        user::handle_audit_key_transparency,
+    );
+
+    // Blob (600-601) — longer timeout for file transfers.
+    reg.register_with_timeout(
+        method_ids::UPLOAD_BLOB,
+        "UploadBlob",
+        std::time::Duration::from_secs(120),
+        blob::handle_upload_blob,
+    );
+    reg.register_with_timeout(
+        method_ids::DOWNLOAD_BLOB,
+        "DownloadBlob",
+        std::time::Duration::from_secs(120),
+        blob::handle_download_blob,
+    );
+
+    // Device (700-702)
+    reg.register(
+        method_ids::REGISTER_DEVICE,
+        "RegisterDevice",
+        device::handle_register_device,
+    );
+    reg.register(
+        method_ids::LIST_DEVICES,
+        "ListDevices",
+        device::handle_list_devices,
+    );
+    reg.register(
+        method_ids::REVOKE_DEVICE,
+        "RevokeDevice",
+        device::handle_revoke_device,
+    );
+
+    // P2P (800-802)
+    reg.register(
+        method_ids::PUBLISH_ENDPOINT,
+        "PublishEndpoint",
+        p2p::handle_publish_endpoint,
+    );
+    reg.register(
+        method_ids::RESOLVE_ENDPOINT,
+        "ResolveEndpoint",
+        p2p::handle_resolve_endpoint,
+    );
+    reg.register_with_timeout(
+        method_ids::HEALTH,
+        "Health",
+        std::time::Duration::from_secs(5),
+        p2p::handle_health,
+    );
+
+    // Federation (900-905)
+    reg.register(
+        method_ids::RELAY_ENQUEUE,
+        "RelayEnqueue",
+        federation::handle_relay_enqueue,
+    );
+    reg.register(
+        method_ids::RELAY_BATCH_ENQUEUE,
+        "RelayBatchEnqueue",
+        federation::handle_relay_batch_enqueue,
+    );
+    reg.register(
+        method_ids::PROXY_FETCH_KEY_PACKAGE,
+        "ProxyFetchKeyPackage",
+        federation::handle_proxy_fetch_key_package,
+    );
+    reg.register(
+        method_ids::PROXY_FETCH_HYBRID_KEY,
+        "ProxyFetchHybridKey",
+        federation::handle_proxy_fetch_hybrid_key,
+    );
+    reg.register(
+        method_ids::PROXY_RESOLVE_USER,
+        "ProxyResolveUser",
+        federation::handle_proxy_resolve_user,
+    );
+    reg.register(
+        method_ids::FEDERATION_HEALTH,
+        "FederationHealth",
+        federation::handle_federation_health,
+    );
+
+    // Moderation (420-424)
+    reg.register(
+        method_ids::REPORT_MESSAGE,
+        "ReportMessage",
+        moderation::handle_report_message,
+    );
+    reg.register(
+        method_ids::BAN_USER,
+        "BanUser",
+        moderation::handle_ban_user,
+    );
+    reg.register(
+        method_ids::UNBAN_USER,
+        "UnbanUser",
+        moderation::handle_unban_user,
+    );
+    reg.register(
+        method_ids::LIST_REPORTS,
+        "ListReports",
+        moderation::handle_list_reports,
+    );
+    reg.register(
+        method_ids::LIST_BANNED,
+        "ListBanned",
+        moderation::handle_list_banned,
+    );
+
+    // Recovery (750-752)
+    reg.register(
+        method_ids::STORE_RECOVERY_BUNDLE,
+        "StoreRecoveryBundle",
+        recovery::handle_store_recovery_bundle,
+    );
+    reg.register(
+        method_ids::FETCH_RECOVERY_BUNDLE,
+        "FetchRecoveryBundle",
+        recovery::handle_fetch_recovery_bundle,
+    );
+    reg.register(
+        method_ids::DELETE_RECOVERY_BUNDLE,
+        "DeleteRecoveryBundle",
+        recovery::handle_delete_recovery_bundle,
+    );
+
+    // Account (950)
+    reg.register(
+        method_ids::DELETE_ACCOUNT,
+        "DeleteAccount",
+        account::handle_delete_account,
+    );
+
+    reg
+}

crates/quicprochat-server/src/v2_handlers/moderation.rs

@@ -0,0 +1,199 @@
+//! Moderation handlers — report, ban, unban, list reports, list banned.
+
+use std::sync::Arc;
+
+use bytes::Bytes;
+use prost::Message;
+use quicprochat_proto::qpc::v1;
+use quicprochat_rpc::error::RpcStatus;
+use quicprochat_rpc::method::{HandlerResult, RequestContext};
+use tracing::{info, warn};
+
+use super::{require_auth, BanRecord, ModerationReport, ServerState};
+
+/// Submit an encrypted report. Any authenticated user can report.
+pub async fn handle_report_message(state: Arc<ServerState>, ctx: RequestContext) -> HandlerResult {
+    let identity_key = match require_auth(&state, &ctx) {
+        Ok(ik) => ik,
+        Err(e) => return e,
+    };
+
+    let req = match v1::ReportMessageRequest::decode(ctx.payload) {
+        Ok(r) => r,
+        Err(e) => return HandlerResult::err(RpcStatus::BadRequest, &format!("decode: {e}")),
+    };
+
+    if req.encrypted_report.is_empty() {
+        return HandlerResult::err(RpcStatus::BadRequest, "encrypted_report required");
+    }
+
+    let now = crate::auth::current_timestamp();
+    let report = {
+        let mut reports = match state.moderation_reports.lock() {
+            Ok(r) => r,
+            Err(e) => {
+                warn!("moderation_reports lock poisoned: {e}");
+                return HandlerResult::err(RpcStatus::Internal, "internal error");
+            }
+        };
+        let id = reports.len() as u64;
+        let report = ModerationReport {
+            id,
+            encrypted_report: req.encrypted_report,
+            conversation_id: req.conversation_id,
+            reporter_identity: identity_key.clone(),
+            timestamp: now,
+        };
+        reports.push(report.clone());
+        report
+    };
+
+    info!(
+        report_id = report.id,
+        reporter = hex::encode(&identity_key[..4.min(identity_key.len())]),
+        "moderation report submitted"
+    );
+
+    let proto = v1::ReportMessageResponse { accepted: true };
+    HandlerResult::ok(Bytes::from(proto.encode_to_vec()))
+}
+
+/// Ban a user. Requires admin role (currently: any authenticated user for MVP).
+pub async fn handle_ban_user(state: Arc<ServerState>, ctx: RequestContext) -> HandlerResult {
+    let admin_key = match require_auth(&state, &ctx) {
+        Ok(ik) => ik,
+        Err(e) => return e,
+    };
+
+    let req = match v1::BanUserRequest::decode(ctx.payload) {
+        Ok(r) => r,
+        Err(e) => return HandlerResult::err(RpcStatus::BadRequest, &format!("decode: {e}")),
+    };
+
+    if req.identity_key.is_empty() || req.identity_key.len() != 32 {
+        return HandlerResult::err(RpcStatus::BadRequest, "identity_key must be 32 bytes");
+    }
+
+    let now = crate::auth::current_timestamp();
+    let expires_at = if req.duration_secs == 0 {
+        0 // permanent
+    } else {
+        now + req.duration_secs
+    };
+
+    let record = BanRecord {
+        reason: req.reason.clone(),
+        banned_at: now,
+        expires_at,
+    };
+    state.banned_users.insert(req.identity_key.clone(), record);
+
+    info!(
+        target_key = hex::encode(&req.identity_key[..4]),
+        admin_key = hex::encode(&admin_key[..4.min(admin_key.len())]),
+        reason = %req.reason,
+        duration_secs = req.duration_secs,
+        "user banned"
+    );
+
+    let proto = v1::BanUserResponse { success: true };
+    HandlerResult::ok(Bytes::from(proto.encode_to_vec()))
+}
+
+/// Unban a user. Requires admin role.
+pub async fn handle_unban_user(state: Arc<ServerState>, ctx: RequestContext) -> HandlerResult {
+    let admin_key = match require_auth(&state, &ctx) {
+        Ok(ik) => ik,
+        Err(e) => return e,
+    };
+
+    let req = match v1::UnbanUserRequest::decode(ctx.payload) {
+        Ok(r) => r,
+        Err(e) => return HandlerResult::err(RpcStatus::BadRequest, &format!("decode: {e}")),
+    };
+
+    if req.identity_key.is_empty() {
+        return HandlerResult::err(RpcStatus::BadRequest, "identity_key required");
+    }
+
+    let removed = state.banned_users.remove(&req.identity_key).is_some();
+
+    info!(
+        target_key = hex::encode(&req.identity_key[..4.min(req.identity_key.len())]),
+        admin_key = hex::encode(&admin_key[..4.min(admin_key.len())]),
+        removed,
+        "user unbanned"
+    );
+
+    let proto = v1::UnbanUserResponse { success: removed };
+    HandlerResult::ok(Bytes::from(proto.encode_to_vec()))
+}
+
+/// List moderation reports. Requires admin role.
+pub async fn handle_list_reports(state: Arc<ServerState>, ctx: RequestContext) -> HandlerResult {
+    let _admin_key = match require_auth(&state, &ctx) {
+        Ok(ik) => ik,
+        Err(e) => return e,
+    };
+
+    let req = match v1::ListReportsRequest::decode(ctx.payload) {
+        Ok(r) => r,
+        Err(e) => return HandlerResult::err(RpcStatus::BadRequest, &format!("decode: {e}")),
+    };
+
+    let reports = match state.moderation_reports.lock() {
+        Ok(r) => r,
+        Err(e) => {
+            warn!("moderation_reports lock poisoned: {e}");
+            return HandlerResult::err(RpcStatus::Internal, "internal error");
+        }
+    };
+
+    let offset = req.offset as usize;
+    let limit = if req.limit == 0 { 50 } else { req.limit as usize };
+
+    let entries: Vec<v1::ReportEntry> = reports
+        .iter()
+        .skip(offset)
+        .take(limit)
+        .map(|r| v1::ReportEntry {
+            id: r.id,
+            encrypted_report: r.encrypted_report.clone(),
+            conversation_id: r.conversation_id.clone(),
+            reporter_identity: r.reporter_identity.clone(),
+            timestamp: r.timestamp,
+        })
+        .collect();
+
+    let proto = v1::ListReportsResponse { reports: entries };
+    HandlerResult::ok(Bytes::from(proto.encode_to_vec()))
+}
+
+/// List banned users.
+pub async fn handle_list_banned(state: Arc<ServerState>, ctx: RequestContext) -> HandlerResult {
+    let _admin_key = match require_auth(&state, &ctx) {
+        Ok(ik) => ik,
+        Err(e) => return e,
+    };
+
+    let _req = match v1::ListBannedRequest::decode(ctx.payload) {
+        Ok(r) => r,
+        Err(e) => return HandlerResult::err(RpcStatus::BadRequest, &format!("decode: {e}")),
+    };
+
+    let now = crate::auth::current_timestamp();
+    let entries: Vec<v1::BannedUserEntry> = state
+        .banned_users
+        .iter()
+        .filter(|entry| entry.expires_at == 0 || entry.expires_at > now)
+        .map(|entry| v1::BannedUserEntry {
+            identity_key: entry.key().clone(),
+            reason: entry.reason.clone(),
+            banned_at: entry.banned_at,
+            expires_at: entry.expires_at,
+        })
+        .collect();
+
+    let proto = v1::ListBannedResponse { users: entries };
+    HandlerResult::ok(Bytes::from(proto.encode_to_vec()))
+}

crates/quicprochat-server/src/v2_handlers/p2p.rs

@@ -0,0 +1,118 @@
+//! P2P handlers — publish/resolve endpoints and health check.
+
+use std::sync::Arc;
+
+use bytes::Bytes;
+use prost::Message;
+use quicprochat_proto::qpc::v1;
+use quicprochat_rpc::method::{HandlerResult, RequestContext};
+
+use crate::domain::p2p::P2pService;
+use crate::domain::types::{CallerAuth, PublishEndpointReq, ResolveEndpointReq};
+
+use super::{domain_err, require_auth, ServerState};
+
+fn caller_auth(identity_key: Vec<u8>) -> CallerAuth {
+    CallerAuth {
+        identity_key,
+        token: Vec::new(),
+        device_id: None,
+    }
+}
+
+pub async fn handle_publish_endpoint(
+    state: Arc<ServerState>,
+    ctx: RequestContext,
+) -> HandlerResult {
+    let identity_key = match require_auth(&state, &ctx) {
+        Ok(ik) => ik,
+        Err(e) => return e,
+    };
+
+    let req = match v1::PublishEndpointRequest::decode(ctx.payload) {
+        Ok(r) => r,
+        Err(e) => {
+            return HandlerResult::err(
+                quicprochat_rpc::error::RpcStatus::BadRequest,
+                &format!("decode: {e}"),
+            )
+        }
+    };
+
+    let svc = P2pService {
+        store: Arc::clone(&state.store),
+    };
+    let auth = caller_auth(identity_key);
+
+    let domain_req = PublishEndpointReq {
+        identity_key: req.identity_key,
+        node_addr: req.node_addr,
+    };
+
+    match svc.publish_endpoint(domain_req, &auth) {
+        Ok(()) => {
+            let proto = v1::PublishEndpointResponse {};
+            HandlerResult::ok(Bytes::from(proto.encode_to_vec()))
+        }
+        Err(e) => domain_err(e),
+    }
+}
+
+pub async fn handle_resolve_endpoint(
+    state: Arc<ServerState>,
+    ctx: RequestContext,
+) -> HandlerResult {
+    let identity_key = match require_auth(&state, &ctx) {
+        Ok(ik) => ik,
+        Err(e) => return e,
+    };
+
+    let req = match v1::ResolveEndpointRequest::decode(ctx.payload) {
+        Ok(r) => r,
+        Err(e) => {
+            return HandlerResult::err(
+                quicprochat_rpc::error::RpcStatus::BadRequest,
+                &format!("decode: {e}"),
+            )
+        }
+    };
+
+    let svc = P2pService {
+        store: Arc::clone(&state.store),
+    };
+    let auth = caller_auth(identity_key);
+
+    let domain_req = ResolveEndpointReq {
+        identity_key: req.identity_key,
+    };
+
+    match svc.resolve_endpoint(domain_req, &auth) {
+        Ok(resp) => {
+            let proto = v1::ResolveEndpointResponse {
+                node_addr: resp.node_addr,
+            };
+            HandlerResult::ok(Bytes::from(proto.encode_to_vec()))
+        }
+        Err(e) => domain_err(e),
+    }
+}
+
+pub async fn handle_health(
+    state: Arc<ServerState>,
+    _ctx: RequestContext,
+) -> HandlerResult {
+    let status = if state.draining.load(std::sync::atomic::Ordering::Relaxed) {
+        "draining"
+    } else {
+        "ok"
+    };
+    let uptime = state.start_time.elapsed().as_secs();
+    let resp = v1::HealthResponse {
+        status: status.into(),
+        node_id: state.node_id.clone(),
+        version: env!("CARGO_PKG_VERSION").to_string(),
+        uptime_secs: uptime,
+        storage_backend: state.storage_backend.clone(),
+    };
+    HandlerResult::ok(Bytes::from(resp.encode_to_vec()))
+}

crates/quicprochat-server/src/v2_handlers/recovery.rs

@@ -0,0 +1,99 @@
+//! Recovery handlers — store/fetch/delete encrypted recovery bundles.
+
+use std::sync::Arc;
+
+use bytes::Bytes;
+use prost::Message;
+use quicprochat_proto::qpc::v1;
+use quicprochat_rpc::method::{HandlerResult, RequestContext};
+
+use crate::domain::recovery::RecoveryService;
+
+use super::{domain_err, ServerState};
+
+/// Store an encrypted recovery bundle (no auth required — recovery is pre-login).
+pub async fn handle_store_recovery_bundle(
+    state: Arc<ServerState>,
+    ctx: RequestContext,
+) -> HandlerResult {
+    let req = match v1::StoreRecoveryBundleRequest::decode(ctx.payload) {
+        Ok(r) => r,
+        Err(e) => {
+            return HandlerResult::err(
+                quicprochat_rpc::error::RpcStatus::BadRequest,
+                &format!("decode: {e}"),
+            )
+        }
+    };
+
+    let svc = RecoveryService {
+        store: Arc::clone(&state.store),
+    };
+
+    match svc.store_bundle(&req.token_hash, req.bundle, req.ttl_secs) {
+        Ok(()) => {
+            let proto = v1::StoreRecoveryBundleResponse { success: true };
+            HandlerResult::ok(Bytes::from(proto.encode_to_vec()))
+        }
+        Err(e) => domain_err(e),
+    }
+}
+
+/// Fetch an encrypted recovery bundle (no auth required — recovery is pre-login).
+pub async fn handle_fetch_recovery_bundle(
+    state: Arc<ServerState>,
+    ctx: RequestContext,
+) -> HandlerResult {
+    let req = match v1::FetchRecoveryBundleRequest::decode(ctx.payload) {
+        Ok(r) => r,
+        Err(e) => {
+            return HandlerResult::err(
+                quicprochat_rpc::error::RpcStatus::BadRequest,
+                &format!("decode: {e}"),
+            )
+        }
+    };
+
+    let svc = RecoveryService {
+        store: Arc::clone(&state.store),
+    };
+
+    match svc.fetch_bundle(&req.token_hash) {
+        Ok(bundle_opt) => {
+            let proto = v1::FetchRecoveryBundleResponse {
+                bundle: bundle_opt.unwrap_or_default(),
+            };
+            HandlerResult::ok(Bytes::from(proto.encode_to_vec()))
+        }
+        Err(e) => domain_err(e),
+    }
+}
+
+/// Delete an encrypted recovery bundle (no auth required — caller proves
+/// knowledge of the token_hash).
+pub async fn handle_delete_recovery_bundle(
+    state: Arc<ServerState>,
+    ctx: RequestContext,
+) -> HandlerResult {
+    let req = match v1::DeleteRecoveryBundleRequest::decode(ctx.payload) {
+        Ok(r) => r,
+        Err(e) => {
+            return HandlerResult::err(
+                quicprochat_rpc::error::RpcStatus::BadRequest,
+                &format!("decode: {e}"),
+            )
+        }
+    };
+
+    let svc = RecoveryService {
+        store: Arc::clone(&state.store),
+    };
+
+    match svc.delete_bundle(&req.token_hash) {
+        Ok(deleted) => {
+            let proto = v1::DeleteRecoveryBundleResponse { success: deleted };
+            HandlerResult::ok(Bytes::from(proto.encode_to_vec()))
+        }
+        Err(e) => domain_err(e),
+    }
+}

crates/quicprochat-server/src/v2_handlers/user.rs

@@ -0,0 +1,213 @@
+//! User resolution handlers — username <-> identity key lookups,
+//! key revocation, and KT audit.
+
+use std::sync::Arc;
+
+use bytes::Bytes;
+use prost::Message;
+use quicprochat_proto::qpc::v1;
+use quicprochat_rpc::method::{HandlerResult, RequestContext};
+
+use crate::domain::types::{
+    AuditKeyTransparencyReq, CheckRevocationReq, ResolveIdentityReq, ResolveUserReq, RevokeKeyReq,
+};
+use crate::domain::users::UserService;
+
+use super::{domain_err, require_auth, ServerState};
+
+fn user_svc(state: &Arc<ServerState>) -> UserService {
+    UserService {
+        store: Arc::clone(&state.store),
+        kt_log: Arc::clone(&state.kt_log),
+        revocation_log: Arc::clone(&state.revocation_log),
+    }
+}
+
+pub async fn handle_resolve_user(state: Arc<ServerState>, ctx: RequestContext) -> HandlerResult {
+    let _identity_key = match require_auth(&state, &ctx) {
+        Ok(ik) => ik,
+        Err(e) => return e,
+    };
+
+    let req = match v1::ResolveUserRequest::decode(ctx.payload) {
+        Ok(r) => r,
+        Err(e) => {
+            return HandlerResult::err(
+                quicprochat_rpc::error::RpcStatus::BadRequest,
+                &format!("decode: {e}"),
+            )
+        }
+    };
+
+    let svc = user_svc(&state);
+
+    let domain_req = ResolveUserReq {
+        username: req.username,
+    };
+
+    match svc.resolve_user(domain_req) {
+        Ok(resp) => {
+            let proto = v1::ResolveUserResponse {
+                identity_key: resp.identity_key,
+                inclusion_proof: resp.inclusion_proof,
+            };
+            HandlerResult::ok(Bytes::from(proto.encode_to_vec()))
+        }
+        Err(e) => domain_err(e),
+    }
+}
+
+pub async fn handle_resolve_identity(
+    state: Arc<ServerState>,
+    ctx: RequestContext,
+) -> HandlerResult {
+    let _identity_key = match require_auth(&state, &ctx) {
+        Ok(ik) => ik,
+        Err(e) => return e,
+    };
+
+    let req = match v1::ResolveIdentityRequest::decode(ctx.payload) {
+        Ok(r) => r,
+        Err(e) => {
+            return HandlerResult::err(
+                quicprochat_rpc::error::RpcStatus::BadRequest,
+                &format!("decode: {e}"),
+            )
+        }
+    };
+
+    let svc = user_svc(&state);
+
+    let domain_req = ResolveIdentityReq {
+        identity_key: req.identity_key,
+    };
+
+    match svc.resolve_identity(domain_req) {
+        Ok(resp) => {
+            let proto = v1::ResolveIdentityResponse {
+                username: resp.username,
+            };
+            HandlerResult::ok(Bytes::from(proto.encode_to_vec()))
+        }
+        Err(e) => domain_err(e),
+    }
+}
+
+pub async fn handle_revoke_key(state: Arc<ServerState>, ctx: RequestContext) -> HandlerResult {
+    let _identity_key = match require_auth(&state, &ctx) {
+        Ok(ik) => ik,
+        Err(e) => return e,
+    };
+
+    let req = match v1::RevokeKeyRequest::decode(ctx.payload) {
+        Ok(r) => r,
+        Err(e) => {
+            return HandlerResult::err(
+                quicprochat_rpc::error::RpcStatus::BadRequest,
+                &format!("decode: {e}"),
+            )
+        }
+    };
+
+    let svc = user_svc(&state);
+
+    let domain_req = RevokeKeyReq {
+        identity_key: req.identity_key,
+        reason: req.reason,
+    };
+
+    match svc.revoke_key(domain_req) {
+        Ok(resp) => {
+            let proto = v1::RevokeKeyResponse {
+                success: resp.success,
+                leaf_index: resp.leaf_index,
+            };
+            HandlerResult::ok(Bytes::from(proto.encode_to_vec()))
+        }
+        Err(e) => domain_err(e),
+    }
+}
+
+pub async fn handle_check_revocation(
+    state: Arc<ServerState>,
+    ctx: RequestContext,
+) -> HandlerResult {
+    let _identity_key = match require_auth(&state, &ctx) {
+        Ok(ik) => ik,
+        Err(e) => return e,
+    };
+
+    let req = match v1::CheckRevocationRequest::decode(ctx.payload) {
+        Ok(r) => r,
+        Err(e) => {
+            return HandlerResult::err(
+                quicprochat_rpc::error::RpcStatus::BadRequest,
+                &format!("decode: {e}"),
+            )
+        }
+    };
+
+    let svc = user_svc(&state);
+
+    let domain_req = CheckRevocationReq {
+        identity_key: req.identity_key,
+    };
+
+    match svc.check_revocation(domain_req) {
+        Ok(resp) => {
+            let proto = v1::CheckRevocationResponse {
+                revoked: resp.revoked,
+                reason: resp.reason,
+                timestamp_ms: resp.timestamp_ms,
+            };
+            HandlerResult::ok(Bytes::from(proto.encode_to_vec()))
+        }
+        Err(e) => domain_err(e),
+    }
+}
+
+pub async fn handle_audit_key_transparency(
+    state: Arc<ServerState>,
+    ctx: RequestContext,
+) -> HandlerResult {
+    let _identity_key = match require_auth(&state, &ctx) {
+        Ok(ik) => ik,
+        Err(e) => return e,
+    };
+
+    let req = match v1::AuditKeyTransparencyRequest::decode(ctx.payload) {
+        Ok(r) => r,
+        Err(e) => {
+            return HandlerResult::err(
+                quicprochat_rpc::error::RpcStatus::BadRequest,
+                &format!("decode: {e}"),
+            )
+        }
+    };
+
+    let svc = user_svc(&state);
+
+    let domain_req = AuditKeyTransparencyReq {
+        start: req.start,
+        end: req.end,
+    };
+
+    match svc.audit_key_transparency(domain_req) {
+        Ok(resp) => {
+            let proto = v1::AuditKeyTransparencyResponse {
+                entries: resp
+                    .entries
+                    .into_iter()
+                    .map(|e| v1::LogEntry {
+                        index: e.index,
+                        leaf_hash: e.leaf_hash,
+                    })
+                    .collect(),
+                tree_size: resp.tree_size,
+                root: resp.root,
+            };
+            HandlerResult::ok(Bytes::from(proto.encode_to_vec()))
+        }
+        Err(e) => domain_err(e),
+    }
+}

crates/quicprochat-server/src/webtransport.rs

@@ -0,0 +1,420 @@
+//! WebTransport server endpoint for browser clients.
+//!
+//! Accepts HTTP/3 WebTransport sessions and dispatches RPC requests through the
+//! same v2 handler registry as the native QUIC endpoint. Browsers connect via:
+//!
+//! ```js
+//! const wt = new WebTransport("https://server:7443");
+//! ```
+//!
+//! Each WebTransport bidirectional stream carries a single RPC request/response
+//! using the same wire format as the native QUIC transport:
+//!
+//! ```text
+//! [method_id: u16][request_id: u32][payload_len: u32][protobuf bytes]
+//! ```
+
+use std::sync::Arc;
+
+use bytes::BytesMut;
+use h3_quinn::quinn;
+use h3_webtransport::server::AcceptedBi;
+use tokio::io::{AsyncReadExt, AsyncWriteExt};
+use tracing::{debug, info, warn};
+
+use crate::v2_handlers::ServerState;
+use quicprochat_rpc::error::RpcStatus;
+use quicprochat_rpc::framing::{RequestFrame, ResponseFrame};
+use quicprochat_rpc::method::{HandlerResult, MethodRegistry, RequestContext};
+
+/// Concrete H3 connection type.
+type H3Conn = h3::server::Connection<h3_quinn::Connection, bytes::Bytes>;
+
+/// Concrete request resolver type.
+type H3Resolver = h3::server::RequestResolver<h3_quinn::Connection, bytes::Bytes>;
+
+/// Type alias for the concrete WebTransport session type used by this server.
+type WtSession =
+    h3_webtransport::server::WebTransportSession<h3_quinn::Connection, bytes::Bytes>;
+
+/// Type alias for the concrete WebTransport bidi stream.
+type WtBidiStream = h3_webtransport::stream::BidiStream<
+    h3_quinn::BidiStream<bytes::Bytes>,
+    bytes::Bytes,
+>;
+
+/// Start the WebTransport listener in a background task.
+///
+/// The endpoint uses the provided quinn `ServerConfig` (with "h3" ALPN) and
+/// binds to `listen_addr`. Incoming HTTP/3 CONNECT requests are upgraded to
+/// WebTransport sessions.
+pub fn spawn_webtransport_listener(
+    listen_addr: std::net::SocketAddr,
+    server_config: quinn::ServerConfig,
+    state: Arc<ServerState>,
+    registry: Arc<MethodRegistry<ServerState>>,
+) -> anyhow::Result<()> {
+    let endpoint = quinn::Endpoint::server(server_config, listen_addr)
+        .map_err(|e| anyhow::anyhow!("bind WebTransport endpoint {listen_addr}: {e}"))?;
+
+    info!(addr = %listen_addr, "WebTransport endpoint listening");
+
+    tokio::spawn(async move {
+        accept_loop(endpoint, state, registry).await;
+    });
+
+    Ok(())
+}
+
+/// Accept QUIC connections and upgrade them to HTTP/3 + WebTransport.
+async fn accept_loop(
+    endpoint: quinn::Endpoint,
+    state: Arc<ServerState>,
+    registry: Arc<MethodRegistry<ServerState>>,
+) {
+    while let Some(incoming) = endpoint.accept().await {
+        let state = Arc::clone(&state);
+        let registry = Arc::clone(&registry);
+
+        tokio::spawn(async move {
+            let connection = match incoming.await {
+                Ok(c) => c,
+                Err(e) => {
+                    warn!(error = %e, "WebTransport: QUIC accept failed");
+                    return;
+                }
+            };
+
+            let remote = connection.remote_address();
+            debug!(remote = %remote, "WebTransport: new QUIC connection");
+            metrics::counter!("webtransport_connections_total").increment(1);
+            metrics::gauge!("webtransport_active_connections").increment(1.0);
+
+            if let Err(e) = handle_h3_connection(connection, state, registry).await {
+                debug!(remote = %remote, error = %e, "WebTransport: session error");
+            }
+
+            metrics::gauge!("webtransport_active_connections").decrement(1.0);
+        });
+    }
+}
+
+/// Handle an HTTP/3 connection: accept the WebTransport CONNECT request and
+/// process bidirectional streams as RPC calls.
+async fn handle_h3_connection(
+    connection: quinn::Connection,
+    state: Arc<ServerState>,
+    registry: Arc<MethodRegistry<ServerState>>,
+) -> anyhow::Result<()> {
+    let h3_quinn_conn = h3_quinn::Connection::new(connection);
+    let mut h3_conn: H3Conn = h3::server::builder()
+        .enable_webtransport(true)
+        .enable_extended_connect(true)
+        .enable_datagram(true)
+        .build::<h3_quinn::Connection, bytes::Bytes>(h3_quinn_conn)
+        .await
+        .map_err(|e| anyhow::anyhow!("H3 connection setup: {e}"))?;
+
+    // Accept HTTP/3 requests until we get a CONNECT for WebTransport.
+    loop {
+        let resolver: H3Resolver = match h3_conn.accept().await {
+            Ok(Some(r)) => r,
+            Ok(None) => {
+                debug!("WebTransport: H3 connection closed");
+                return Ok(());
+            }
+            Err(e) => {
+                return Err(anyhow::anyhow!("WebTransport: H3 accept error: {e}"));
+            }
+        };
+
+        let (request, stream) = resolver
+            .resolve_request()
+            .await
+            .map_err(|e| anyhow::anyhow!("resolve request: {e}"))?;
+
+        let method = request.method().clone();
+        let uri = request.uri().clone();
+
+        if method == http::Method::CONNECT {
+            debug!(uri = %uri, "WebTransport: CONNECT request");
+
+            let wt_session = h3_webtransport::server::WebTransportSession::accept(
+                request, stream, h3_conn,
+            )
+            .await
+            .map_err(|e| anyhow::anyhow!("WebTransport session accept: {e}"))?;
+
+            info!("WebTransport: session established");
+            metrics::counter!("webtransport_sessions_total").increment(1);
+
+            serve_wt_streams(wt_session, state, registry).await;
+            return Ok(());
+        }
+
+        debug!(method = %method, uri = %uri, "WebTransport: non-CONNECT request ignored");
+    }
+}
+
+/// Per-connection state from the WebTransport auth handshake.
+#[derive(Debug, Clone, Default)]
+struct ConnectionState {
+    session_token: Option<Vec<u8>>,
+    identity_key: Option<Vec<u8>>,
+}
+
+/// Accept bidirectional streams from a WebTransport session and dispatch
+/// each as an RPC request.
+async fn serve_wt_streams(
+    session: WtSession,
+    state: Arc<ServerState>,
+    registry: Arc<MethodRegistry<ServerState>>,
+) {
+    // Auth handshake: the first bidi stream carries the session token.
+    let conn_state: Arc<ConnectionState> = match accept_auth_stream(&session).await {
+        Ok(cs) => Arc::new(cs),
+        Err(e) => {
+            warn!(error = %e, "WebTransport: auth handshake failed");
+            return;
+        }
+    };
+
+    loop {
+        match session.accept_bi().await {
+            Ok(Some(AcceptedBi::BidiStream(_session_id, stream))) => {
+                let state = Arc::clone(&state);
+                let registry = Arc::clone(&registry);
+                let conn_state = Arc::clone(&conn_state);
+                tokio::spawn(async move {
+                    if let Err(e) =
+                        handle_wt_bidi_stream(stream, state, registry, &conn_state).await
+                    {
+                        debug!(error = %e, "WebTransport: stream error");
+                    }
+                });
+            }
+            Ok(Some(AcceptedBi::Request(_req, _stream))) => {
+                debug!("WebTransport: ignoring nested HTTP/3 request");
+            }
+            Ok(None) => {
+                debug!("WebTransport: no more bidi streams");
+                break;
+            }
+            Err(e) => {
+                debug!(error = %e, "WebTransport: accept_bi error");
+                break;
+            }
+        }
+    }
+}
+
+/// Accept the first bidirectional stream as an auth init handshake.
+///
+/// The client sends a raw session token (length-prefixed: `u32 BE + token bytes`).
+/// The server reads it and sends a 1-byte ack (0x00).
+async fn accept_auth_stream(session: &WtSession) -> anyhow::Result<ConnectionState> {
+    let accepted = session
+        .accept_bi()
+        .await
+        .map_err(|e| anyhow::anyhow!("auth stream accept: {e}"))?
+        .ok_or_else(|| anyhow::anyhow!("session closed before auth handshake"))?;
+
+    let mut stream: WtBidiStream = match accepted {
+        AcceptedBi::BidiStream(_session_id, stream) => stream,
+        AcceptedBi::Request(_, _) => {
+            anyhow::bail!("expected bidi stream for auth, got HTTP/3 request")
+        }
+    };
+
+    // Read the token: [len: u32 BE][token bytes]
+    let mut header = [0u8; 4];
+    AsyncReadExt::read_exact(&mut stream, &mut header)
+        .await
+        .map_err(|e| anyhow::anyhow!("auth read header: {e}"))?;
+    let len = u32::from_be_bytes(header) as usize;
+
+    if len > 4096 {
+        anyhow::bail!("auth token too large: {len} bytes");
+    }
+
+    let mut token = vec![0u8; len];
+    if len > 0 {
+        AsyncReadExt::read_exact(&mut stream, &mut token)
+            .await
+            .map_err(|e| anyhow::anyhow!("auth read token: {e}"))?;
+    }
+
+    // Send ack: single zero byte.
+    AsyncWriteExt::write_all(&mut stream, &[0u8])
+        .await
+        .map_err(|e| anyhow::anyhow!("auth ack send: {e}"))?;
+
+    debug!(token_len = token.len(), "WebTransport: auth init received");
+
+    Ok(ConnectionState {
+        session_token: Some(token),
+        identity_key: None,
+    })
+}
+
+/// Handle a single WebTransport bidirectional stream: read request, dispatch,
+/// write response. Uses the same framing as native QUIC.
+async fn handle_wt_bidi_stream(
+    mut stream: WtBidiStream,
+    state: Arc<ServerState>,
+    registry: Arc<MethodRegistry<ServerState>>,
+    conn_state: &ConnectionState,
+) -> anyhow::Result<()> {
+    // Read the complete request from the stream.
+    let max_size =
+        quicprochat_rpc::framing::MAX_PAYLOAD_SIZE + quicprochat_rpc::framing::REQUEST_HEADER_SIZE;
+
+    let mut buf = Vec::with_capacity(1024);
+    let mut tmp = [0u8; 8192];
+    loop {
+        let n = AsyncReadExt::read(&mut stream, &mut tmp)
+            .await
+            .map_err(|e| anyhow::anyhow!("recv: {e}"))?;
+
+        if n == 0 {
+            break;
+        }
+
+        buf.extend_from_slice(&tmp[..n]);
+
+        if buf.len() > max_size {
+            anyhow::bail!("payload too large");
+        }
+    }
+
+    let mut bytes = BytesMut::from(buf.as_slice());
+
+    let frame = match RequestFrame::decode(&mut bytes)
+        .map_err(|e| anyhow::anyhow!("decode: {e}"))?
+    {
+        Some(f) => f,
+        None => anyhow::bail!("incomplete request frame"),
+    };
+
+    let trace_id = format!(
+        "wt-{:016x}",
+        std::time::SystemTime::now()
+            .duration_since(std::time::UNIX_EPOCH)
+            .unwrap_or_default()
+            .as_nanos() as u64
+    );
+
+    let result = match registry.get(frame.method_id) {
+        Some((handler, name, timeout)) => {
+            let span = tracing::info_span!(
+                "wt_rpc",
+                trace_id = %trace_id,
+                method_id = frame.method_id,
+                method = name,
+                req_id = frame.request_id,
+            );
+            let _guard = span.enter();
+            debug!("dispatching");
+
+            let deadline = timeout.map(|d| tokio::time::Instant::now() + d);
+            let start = std::time::Instant::now();
+
+            let ctx = RequestContext {
+                identity_key: conn_state.identity_key.clone(),
+                session_token: conn_state.session_token.clone(),
+                payload: frame.payload,
+                trace_id: trace_id.clone(),
+                deadline,
+            };
+
+            let result = if let Some(dur) = timeout {
+                match tokio::time::timeout(dur, handler(Arc::clone(&state), ctx)).await {
+                    Ok(r) => r,
+                    Err(_) => {
+                        warn!(method = name, "WebTransport: request deadline exceeded");
+                        HandlerResult::err(RpcStatus::DeadlineExceeded, "request deadline exceeded")
+                    }
+                }
+            } else {
+                handler(Arc::clone(&state), ctx).await
+            };
+
+            let elapsed = start.elapsed();
+            metrics::histogram!("webtransport_request_duration_seconds", "method" => name)
+                .record(elapsed.as_secs_f64());
+            metrics::counter!("webtransport_requests_total", "method" => name).increment(1);
+
+            result
+        }
+        None => {
+            warn!(method_id = frame.method_id, "WebTransport: unknown method");
+            HandlerResult::err(RpcStatus::UnknownMethod, "unknown method")
+        }
+    };
+
+    let response = ResponseFrame {
+        status: result.status as u8,
+        request_id: frame.request_id,
+        payload: result.payload,
+    };
+
+    let encoded = response.encode();
+    AsyncWriteExt::write_all(&mut stream, &encoded)
+        .await
+        .map_err(|e| anyhow::anyhow!("send response: {e}"))?;
+    AsyncWriteExt::shutdown(&mut stream)
+        .await
+        .map_err(|e| anyhow::anyhow!("shutdown: {e}"))?;
+
+    Ok(())
+}
+
+/// Build a quinn `ServerConfig` for the WebTransport endpoint.
+///
+/// Uses the same TLS cert/key as the main server but with "h3" ALPN.
+pub fn build_webtransport_server_config(
+    cert_path: &std::path::Path,
+    key_path: &std::path::Path,
+) -> anyhow::Result<quinn::ServerConfig> {
+    use anyhow::Context;
+    use rustls::pki_types::{CertificateDer, PrivateKeyDer};
+    use rustls::version::TLS13;
+
+    let cert_bytes = std::fs::read(cert_path).context("read WebTransport cert")?;
+    let key_bytes = std::fs::read(key_path).context("read WebTransport key")?;
+
+    let cert_chain = vec![CertificateDer::from(cert_bytes)];
+    let key = PrivateKeyDer::try_from(key_bytes)
+        .map_err(|_| anyhow::anyhow!("invalid WebTransport private key"))?;
+
+    let mut tls = rustls::ServerConfig::builder_with_protocol_versions(&[&TLS13])
+        .with_no_client_auth()
+        .with_single_cert(cert_chain, key)?;
+    tls.alpn_protocols = vec![b"h3".to_vec()];
+
+    let crypto = quinn_proto::crypto::rustls::QuicServerConfig::try_from(tls)
+        .map_err(|e| anyhow::anyhow!("invalid WebTransport TLS config: {e}"))?;
+
+    let mut transport = quinn::TransportConfig::default();
+    transport.max_idle_timeout(Some(
+        std::time::Duration::from_secs(300)
+            .try_into()
+            .map_err(|e| anyhow::anyhow!("idle timeout: {e}"))?,
+    ));
+    // WebTransport sessions may have multiple simultaneous streams.
+    transport.max_concurrent_bidi_streams(64u32.into());
+    transport.max_concurrent_uni_streams(16u32.into());
+
+    let mut server_config = quinn::ServerConfig::with_crypto(Arc::new(crypto));
+    server_config.transport_config(Arc::new(transport));
+
+    Ok(server_config)
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn webtransport_module_compiles() {
+        assert!(true);
+    }
+}

crates/quicprochat-server/src/ws_bridge.rs

@@ -0,0 +1,645 @@
+//! WebSocket JSON-RPC bridge for browser clients.
+//!
+//! Provides a lightweight JSON-RPC interface over WebSocket so that browsers
+//! can interact with the server without a Cap'n Proto / QUIC stack.
+//!
+//! Security parity with the Cap'n Proto path:
+//! - Rate limiting via `check_rate_limit()` on all mutating handlers
+//! - DM channel membership verification on `send`
+//! - Payload size limits (5 MB)
+//! - Timing floor on `resolveUser` to mask lookup timing
+
+use std::net::SocketAddr;
+use std::sync::Arc;
+use std::time::Duration;
+
+use base64::Engine;
+use dashmap::DashMap;
+use futures::stream::StreamExt;
+use futures::SinkExt;
+use serde::{Deserialize, Serialize};
+use tokio::net::TcpListener;
+use tokio::sync::Notify;
+use tokio::time::Instant;
+use tokio_tungstenite::tungstenite::Message;
+
+use crate::auth::{check_rate_limit, validate_token_raw, AuthConfig, AuthContext, RateEntry, SessionInfo};
+use crate::storage::Store;
+
+const B64: base64::engine::general_purpose::GeneralPurpose =
+    base64::engine::general_purpose::STANDARD;
+
+/// Maximum payload size for WS bridge (same as Cap'n Proto path).
+const MAX_PAYLOAD_BYTES: usize = 5 * 1024 * 1024;
+
+/// Minimum response time for resolveUser to mask DB lookup timing differences.
+const RESOLVE_TIMING_FLOOR: Duration = Duration::from_millis(5);
+
+// ── Shared state ────────────────────────────────────────────────────────────
+
+/// Subset of server state needed by the WS bridge (all `Send + Sync`).
+#[allow(dead_code)] // sealed_sender plumbed for future use
+pub struct WsBridgeState {
+    pub store: Arc<dyn Store>,
+    pub waiters: Arc<DashMap<Vec<u8>, Arc<Notify>>>,
+    pub auth_cfg: Arc<AuthConfig>,
+    pub sessions: Arc<DashMap<Vec<u8>, SessionInfo>>,
+    pub rate_limits: Arc<DashMap<Vec<u8>, RateEntry>>,
+    pub sealed_sender: bool,
+    pub allow_insecure_auth: bool,
+}
+
+// ── JSON-RPC types ──────────────────────────────────────────────────────────
+
+#[derive(Deserialize)]
+struct RpcRequest {
+    id: serde_json::Value,
+    method: String,
+    #[serde(default)]
+    params: serde_json::Value,
+}
+
+#[derive(Serialize)]
+struct RpcResponse {
+    id: serde_json::Value,
+    ok: bool,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    result: Option<serde_json::Value>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    error: Option<String>,
+}
+
+impl RpcResponse {
+    fn success(id: serde_json::Value, result: serde_json::Value) -> Self {
+        Self {
+            id,
+            ok: true,
+            result: Some(result),
+            error: None,
+        }
+    }
+
+    fn error(id: serde_json::Value, msg: impl Into<String>) -> Self {
+        Self {
+            id,
+            ok: false,
+            result: None,
+            error: Some(msg.into()),
+        }
+    }
+}
+
+// ── Auth helper ─────────────────────────────────────────────────────────────
+
+/// Extract and validate the "token" field from params. In insecure-auth mode
+/// with no token configured, an empty token is accepted as the bearer.
+fn extract_auth(
+    state: &WsBridgeState,
+    params: &serde_json::Value,
+) -> Result<AuthContext, String> {
+    let token_str = params
+        .get("token")
+        .and_then(|v| v.as_str())
+        .unwrap_or("");
+
+    let token_bytes = token_str.as_bytes().to_vec();
+
+    // In insecure-auth mode with no configured token, accept any (including empty)
+    // token as the bearer token. This mirrors the Cap'n Proto path behaviour.
+    if state.allow_insecure_auth && state.auth_cfg.required_token.is_none() {
+        // Treat the request identity from params as the identity.
+        return Ok(AuthContext {
+            token: token_bytes,
+            identity_key: None,
+        });
+    }
+
+    validate_token_raw(&state.auth_cfg, &state.sessions, &token_bytes)
+}
+
+/// Resolve identity key: either from auth context (session-bound) or from
+/// request params (insecure-auth mode). Returns the 32-byte identity key.
+fn resolve_identity(
+    state: &WsBridgeState,
+    auth_ctx: &AuthContext,
+    params: &serde_json::Value,
+) -> Result<Vec<u8>, String> {
+    // If auth context has an identity-bound session, use that.
+    if let Some(ref ik) = auth_ctx.identity_key {
+        return Ok(ik.clone());
+    }
+
+    // In insecure-auth mode, accept identity from params.
+    if state.allow_insecure_auth {
+        // Try base64-encoded identityKey first.
+        if let Some(b64) = params.get("identityKey").and_then(|v| v.as_str()) {
+            return B64
+                .decode(b64)
+                .map_err(|e| format!("bad base64 identityKey: {e}"));
+        }
+        // Try username lookup.
+        if let Some(username) = params.get("username").and_then(|v| v.as_str()) {
+            if let Ok(Some(ik)) = state.store.get_user_identity_key(username) {
+                return Ok(ik);
+            }
+            return Err(format!("user not found: {username}"));
+        }
+    }
+
+    Err("no identity: login required or pass identityKey/username in insecure mode".to_string())
+}
+
+/// Apply rate limiting using the auth token. Returns an error string on limit exceeded.
+fn ws_check_rate_limit(state: &WsBridgeState, auth_ctx: &AuthContext) -> Result<(), String> {
+    check_rate_limit(&state.rate_limits, &auth_ctx.token)
+        .map_err(|e| format!("rate limit exceeded: {e}"))
+}
+
+// ── Dispatch ────────────────────────────────────────────────────────────────
+
+async fn dispatch(state: &WsBridgeState, req: RpcRequest) -> RpcResponse {
+    match req.method.as_str() {
+        "health" => handle_health(req.id),
+        "resolveUser" => handle_resolve_user(state, req.id, &req.params).await,
+        "createChannel" => handle_create_channel(state, req.id, &req.params),
+        "send" => handle_send(state, req.id, &req.params),
+        "receive" => handle_receive(state, req.id, &req.params),
+        "deleteAccount" => handle_delete_account(state, req.id, &req.params),
+        "register" => handle_register(state, req.id, &req.params),
+        _ => RpcResponse::error(req.id, format!("unknown method: {}", req.method)),
+    }
+}
+
+// ── Handlers ────────────────────────────────────────────────────────────────
+
+fn handle_health(id: serde_json::Value) -> RpcResponse {
+    RpcResponse::success(id, serde_json::json!("ok"))
+}
+
+fn handle_register(
+    state: &WsBridgeState,
+    id: serde_json::Value,
+    params: &serde_json::Value,
+) -> RpcResponse {
+    // Only allow in insecure-auth mode (development/demo).
+    if !state.allow_insecure_auth {
+        return RpcResponse::error(id, "register is only available in --allow-insecure-auth mode");
+    }
+
+    // Rate limit.
+    let auth_ctx = match extract_auth(state, params) {
+        Ok(ctx) => ctx,
+        Err(e) => return RpcResponse::error(id, e),
+    };
+    if let Err(e) = ws_check_rate_limit(state, &auth_ctx) {
+        return RpcResponse::error(id, e);
+    }
+
+    // Validate username.
+    let username = match params.get("username").and_then(|v| v.as_str()) {
+        Some(u) if !u.is_empty() => u,
+        _ => return RpcResponse::error(id, "missing or empty 'username' param"),
+    };
+    if username.len() > 32 {
+        return RpcResponse::error(id, "username must be at most 32 characters");
+    }
+    if !username.chars().all(|c| c.is_ascii_alphanumeric() || c == '_') {
+        return RpcResponse::error(id, "username must be alphanumeric or underscore only");
+    }
+
+    // Validate identity key.
+    let ik_b64 = match params.get("identityKey").and_then(|v| v.as_str()) {
+        Some(s) if !s.is_empty() => s,
+        _ => return RpcResponse::error(id, "missing or empty 'identityKey' param"),
+    };
+    let identity_key = match B64.decode(ik_b64) {
+        Ok(k) => k,
+        Err(e) => return RpcResponse::error(id, format!("bad base64 identityKey: {e}")),
+    };
+    if identity_key.len() != 32 {
+        return RpcResponse::error(id, "identityKey must be 32 bytes");
+    }
+
+    // Check if username is already taken by a different key.
+    match state.store.get_user_identity_key(username) {
+        Ok(Some(existing)) if existing == identity_key => {
+            // Idempotent: same key, return success.
+            return RpcResponse::success(
+                id,
+                serde_json::json!({
+                    "username": username,
+                    "identityKey": B64.encode(&identity_key),
+                }),
+            );
+        }
+        Ok(Some(_)) => {
+            return RpcResponse::error(id, "username already taken");
+        }
+        Ok(None) => {} // Available, proceed.
+        Err(e) => return RpcResponse::error(id, format!("storage error: {e}")),
+    }
+
+    // Store the mapping.
+    if let Err(e) = state.store.store_user_identity_key(username, identity_key.clone()) {
+        return RpcResponse::error(id, format!("storage error: {e}"));
+    }
+
+    tracing::info!(
+        username = %username,
+        key_prefix = %hex::encode(&identity_key[..4]),
+        "audit: ws_bridge register"
+    );
+
+    RpcResponse::success(
+        id,
+        serde_json::json!({
+            "username": username,
+            "identityKey": B64.encode(&identity_key),
+        }),
+    )
+}
+
+async fn handle_resolve_user(
+    state: &WsBridgeState,
+    id: serde_json::Value,
+    params: &serde_json::Value,
+) -> RpcResponse {
+    let auth_ctx = match extract_auth(state, params) {
+        Ok(ctx) => ctx,
+        Err(e) => return RpcResponse::error(id, e),
+    };
+
+    // Rate limit resolve requests to prevent bulk enumeration.
+    if let Err(e) = ws_check_rate_limit(state, &auth_ctx) {
+        return RpcResponse::error(id, e);
+    }
+
+    let username = match params.get("username").and_then(|v| v.as_str()) {
+        Some(u) if !u.is_empty() => u,
+        _ => return RpcResponse::error(id, "missing or empty 'username' param"),
+    };
+
+    // Timing floor: mask DB-lookup timing differences between existing and
+    // non-existing usernames (same as Cap'n Proto resolveUser handler).
+    let deadline = Instant::now() + RESOLVE_TIMING_FLOOR;
+
+    let response = match state.store.get_user_identity_key(username) {
+        Ok(Some(key)) => {
+            RpcResponse::success(id, serde_json::json!({ "identityKey": B64.encode(&key) }))
+        }
+        Ok(None) => RpcResponse::success(id, serde_json::json!({ "identityKey": null })),
+        Err(e) => RpcResponse::error(id, format!("storage error: {e}")),
+    };
+
+    // Pad to timing floor before responding.
+    tokio::time::sleep_until(deadline).await;
+
+    response
+}
+
+fn handle_create_channel(
+    state: &WsBridgeState,
+    id: serde_json::Value,
+    params: &serde_json::Value,
+) -> RpcResponse {
+    let auth_ctx = match extract_auth(state, params) {
+        Ok(ctx) => ctx,
+        Err(e) => return RpcResponse::error(id, e),
+    };
+
+    // Rate limit.
+    if let Err(e) = ws_check_rate_limit(state, &auth_ctx) {
+        return RpcResponse::error(id, e);
+    }
+
+    let my_key = match resolve_identity(state, &auth_ctx, params) {
+        Ok(k) => k,
+        Err(e) => return RpcResponse::error(id, e),
+    };
+
+    // Accept peer key as base64 or resolve from username.
+    let peer_key = if let Some(b64) = params.get("peerKey").and_then(|v| v.as_str()) {
+        match B64.decode(b64) {
+            Ok(k) => k,
+            Err(e) => return RpcResponse::error(id, format!("bad base64 peerKey: {e}")),
+        }
+    } else if let Some(username) = params.get("peerUsername").and_then(|v| v.as_str()) {
+        match state.store.get_user_identity_key(username) {
+            Ok(Some(k)) => k,
+            Ok(None) => return RpcResponse::error(id, format!("peer user not found: {username}")),
+            Err(e) => return RpcResponse::error(id, format!("storage error: {e}")),
+        }
+    } else {
+        return RpcResponse::error(id, "missing 'peerKey' (base64) or 'peerUsername'");
+    };
+
+    if peer_key.len() != 32 {
+        return RpcResponse::error(id, "peerKey must be 32 bytes");
+    }
+
+    match state.store.create_channel(&my_key, &peer_key) {
+        Ok((channel_id, was_new)) => RpcResponse::success(
+            id,
+            serde_json::json!({
+                "channelId": B64.encode(&channel_id),
+                "wasNew": was_new,
+            }),
+        ),
+        Err(e) => RpcResponse::error(id, format!("storage error: {e}")),
+    }
+}
+
+fn handle_send(
+    state: &WsBridgeState,
+    id: serde_json::Value,
+    params: &serde_json::Value,
+) -> RpcResponse {
+    let auth_ctx = match extract_auth(state, params) {
+        Ok(ctx) => ctx,
+        Err(e) => return RpcResponse::error(id, e),
+    };
+
+    // Rate limit (parity with Cap'n Proto enqueue path).
+    if let Err(e) = ws_check_rate_limit(state, &auth_ctx) {
+        return RpcResponse::error(id, e);
+    }
+
+    let sender_key = match resolve_identity(state, &auth_ctx, params) {
+        Ok(k) => k,
+        Err(e) => return RpcResponse::error(id, e),
+    };
+
+    // Resolve recipient: base64 key or username.
+    let recipient_key =
+        if let Some(b64) = params.get("recipientKey").and_then(|v| v.as_str()) {
+            match B64.decode(b64) {
+                Ok(k) => k,
+                Err(e) => {
+                    return RpcResponse::error(id, format!("bad base64 recipientKey: {e}"))
+                }
+            }
+        } else if let Some(username) = params.get("recipient").and_then(|v| v.as_str()) {
+            match state.store.get_user_identity_key(username) {
+                Ok(Some(k)) => k,
+                Ok(None) => {
+                    return RpcResponse::error(id, format!("recipient not found: {username}"))
+                }
+                Err(e) => return RpcResponse::error(id, format!("storage error: {e}")),
+            }
+        } else {
+            return RpcResponse::error(id, "missing 'recipientKey' (base64) or 'recipient' (username)");
+        };
+
+    if recipient_key.len() != 32 {
+        return RpcResponse::error(id, "recipientKey must be 32 bytes");
+    }
+
+    // Payload: base64-encoded binary or plain text message.
+    let payload = if let Some(b64) = params.get("payload").and_then(|v| v.as_str()) {
+        match B64.decode(b64) {
+            Ok(p) => p,
+            Err(e) => return RpcResponse::error(id, format!("bad base64 payload: {e}")),
+        }
+    } else if let Some(msg) = params.get("message").and_then(|v| v.as_str()) {
+        msg.as_bytes().to_vec()
+    } else {
+        return RpcResponse::error(id, "missing 'payload' (base64) or 'message' (text)");
+    };
+
+    if payload.is_empty() {
+        return RpcResponse::error(id, "payload must not be empty");
+    }
+
+    // Payload size limit (same as Cap'n Proto path: 5 MB).
+    if payload.len() > MAX_PAYLOAD_BYTES {
+        return RpcResponse::error(
+            id,
+            format!("payload exceeds max size ({MAX_PAYLOAD_BYTES} bytes)"),
+        );
+    }
+
+    // Create or look up the DM channel between sender and recipient.
+    let channel_id = match state.store.create_channel(&sender_key, &recipient_key) {
+        Ok((ch, _)) => ch,
+        Err(e) => return RpcResponse::error(id, format!("channel error: {e}")),
+    };
+
+    // DM channel membership verification (parity with Cap'n Proto enqueue path).
+    if channel_id.len() == 16 {
+        let members = match state.store.get_channel_members(&channel_id) {
+            Ok(Some(m)) => m,
+            Ok(None) => return RpcResponse::error(id, "channel not found"),
+            Err(e) => return RpcResponse::error(id, format!("storage error: {e}")),
+        };
+        let (a, b) = &members;
+        let caller_in = sender_key == *a || sender_key == *b;
+        let recipient_other = (recipient_key == *a && sender_key == *b)
+            || (recipient_key == *b && sender_key == *a);
+        if !caller_in || !recipient_other {
+            return RpcResponse::error(id, "caller or recipient not a member of this channel");
+        }
+    }
+
+    match state
+        .store
+        .enqueue(&recipient_key, &channel_id, payload, None)
+    {
+        Ok(seq) => {
+            // Notify any waiting long-poll fetchers.
+            if let Some(notify) = state.waiters.get(&recipient_key) {
+                notify.notify_waiters();
+            }
+
+            // Audit logging (no secrets: no payload, no full keys).
+            tracing::info!(
+                recipient_prefix = %hex::encode(&recipient_key[..std::cmp::min(4, recipient_key.len())]),
+                seq = seq,
+                "audit: ws_bridge enqueue"
+            );
+
+            RpcResponse::success(id, serde_json::json!({ "seq": seq }))
+        }
+        Err(e) => RpcResponse::error(id, format!("enqueue error: {e}")),
+    }
+}
+
+fn handle_receive(
+    state: &WsBridgeState,
+    id: serde_json::Value,
+    params: &serde_json::Value,
+) -> RpcResponse {
+    let auth_ctx = match extract_auth(state, params) {
+        Ok(ctx) => ctx,
+        Err(e) => return RpcResponse::error(id, e),
+    };
+
+    // Rate limit.
+    if let Err(e) = ws_check_rate_limit(state, &auth_ctx) {
+        return RpcResponse::error(id, e);
+    }
+
+    let my_key = match resolve_identity(state, &auth_ctx, params) {
+        Ok(k) => k,
+        Err(e) => return RpcResponse::error(id, e),
+    };
+
+    // Resolve sender/peer: base64 key or username (needed to find the channel).
+    let peer_key = if let Some(b64) = params.get("recipientKey").and_then(|v| v.as_str()) {
+        match B64.decode(b64) {
+            Ok(k) => k,
+            Err(e) => return RpcResponse::error(id, format!("bad base64 recipientKey: {e}")),
+        }
+    } else if let Some(username) = params.get("recipient").and_then(|v| v.as_str()) {
+        match state.store.get_user_identity_key(username) {
+            Ok(Some(k)) => k,
+            Ok(None) => return RpcResponse::error(id, format!("user not found: {username}")),
+            Err(e) => return RpcResponse::error(id, format!("storage error: {e}")),
+        }
+    } else {
+        return RpcResponse::error(id, "missing 'recipientKey' (base64) or 'recipient' (username)");
+    };
+
+    // Find the channel between me and the peer.
+    let channel_id = match state.store.create_channel(&my_key, &peer_key) {
+        Ok((ch, _)) => ch,
+        Err(e) => return RpcResponse::error(id, format!("channel error: {e}")),
+    };
+
+    // Fetch (drain) all messages for me in this channel.
+    match state.store.fetch(&my_key, &channel_id) {
+        Ok(messages) => {
+            let items: Vec<serde_json::Value> = messages
+                .into_iter()
+                .map(|(seq, data)| {
+                    // Try to decode as UTF-8 text; fall back to base64.
+                    let text = String::from_utf8(data.clone()).ok();
+                    serde_json::json!({
+                        "seq": seq,
+                        "data": B64.encode(&data),
+                        "text": text,
+                    })
+                })
+                .collect();
+            RpcResponse::success(id, serde_json::json!(items))
+        }
+        Err(e) => RpcResponse::error(id, format!("fetch error: {e}")),
+    }
+}
+
+fn handle_delete_account(
+    state: &WsBridgeState,
+    id: serde_json::Value,
+    params: &serde_json::Value,
+) -> RpcResponse {
+    let auth_ctx = match extract_auth(state, params) {
+        Ok(ctx) => ctx,
+        Err(e) => return RpcResponse::error(id, e),
+    };
+
+    // Rate limit.
+    if let Err(e) = ws_check_rate_limit(state, &auth_ctx) {
+        return RpcResponse::error(id, e);
+    }
+
+    let identity_key = match resolve_identity(state, &auth_ctx, params) {
+        Ok(k) => k,
+        Err(e) => return RpcResponse::error(id, e),
+    };
+
+    match state.store.delete_account(&identity_key) {
+        Ok(()) => {
+            // Invalidate sessions for this identity.
+            let tokens_to_remove: Vec<Vec<u8>> = state
+                .sessions
+                .iter()
+                .filter(|entry| entry.value().identity_key == identity_key)
+                .map(|entry| entry.key().clone())
+                .collect();
+            for token in &tokens_to_remove {
+                state.sessions.remove(token);
+            }
+            RpcResponse::success(id, serde_json::json!({ "deleted": true }))
+        }
+        Err(e) => RpcResponse::error(id, format!("delete failed: {e}")),
+    }
+}
+
+// ── WebSocket listener ──────────────────────────────────────────────────────
+
+/// Spawn the WebSocket JSON-RPC bridge as a background tokio task.
+pub fn spawn_ws_bridge(addr: SocketAddr, state: Arc<WsBridgeState>) {
+    tokio::spawn(async move {
+        let listener = match TcpListener::bind(addr).await {
+            Ok(l) => l,
+            Err(e) => {
+                tracing::error!(addr = %addr, error = %e, "ws_bridge: failed to bind");
+                return;
+            }
+        };
+        tracing::info!(addr = %addr, "ws_bridge: accepting WebSocket connections");
+
+        loop {
+            let (stream, peer) = match listener.accept().await {
+                Ok(pair) => pair,
+                Err(e) => {
+                    tracing::warn!(error = %e, "ws_bridge: accept error");
+                    continue;
+                }
+            };
+
+            let state = Arc::clone(&state);
+            tokio::spawn(async move {
+                let ws = match tokio_tungstenite::accept_async(stream).await {
+                    Ok(ws) => ws,
+                    Err(e) => {
+                        tracing::debug!(peer = %peer, error = %e, "ws_bridge: handshake failed");
+                        return;
+                    }
+                };
+                tracing::debug!(peer = %peer, "ws_bridge: client connected");
+
+                let (mut sink, mut stream) = ws.split();
+
+                while let Some(msg) = stream.next().await {
+                    let msg = match msg {
+                        Ok(m) => m,
+                        Err(e) => {
+                            tracing::debug!(peer = %peer, error = %e, "ws_bridge: read error");
+                            break;
+                        }
+                    };
+
+                    let text = match msg {
+                        Message::Text(t) => t,
+                        Message::Close(_) => break,
+                        Message::Ping(_) | Message::Pong(_) => continue,
+                        _ => continue,
+                    };
+
+                    let req: RpcRequest = match serde_json::from_str(&text) {
+                        Ok(r) => r,
+                        Err(e) => {
+                            let resp = RpcResponse::error(
+                                serde_json::Value::Null,
+                                format!("invalid JSON: {e}"),
+                            );
+                            let json = serde_json::to_string(&resp).unwrap_or_default();
+                            if sink.send(Message::Text(json.into())).await.is_err() {
+                                break;
+                            }
+                            continue;
+                        }
+                    };
+
+                    let resp = dispatch(&state, req).await;
+                    let json = serde_json::to_string(&resp).unwrap_or_default();
+                    if sink.send(Message::Text(json.into())).await.is_err() {
+                        break;
+                    }
+                }
+
+                tracing::debug!(peer = %peer, "ws_bridge: client disconnected");
+            });
+        }
+    });
+}