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Christian Nennemann ff795c72e6 Implement peer review feedback for draft-nennemann-wimse-ect-00 
Address 11 items from peer review:
- Fix area designation from Security to ART (WIMSE is in ART area)
- Switch inp_hash/out_hash to fixed SHA-256 without algorithm prefix,
  matching DPoP (RFC 9449) and WIMSE WPT tth claim patterns
- Add partial DAG verification guidance for unavailable parents
- Add DAG integrity attacks subsection (false parents, pruning, shadow DAGs)
- Add privilege escalation subsection (ECTs are not authorization)
- Add revocation propagation semantics through the DAG
- Add W3C PROV Data Model to Related Work
- Strengthen Txn-Token differentiation with fan-in/convergence bullet
- Add explicit token binding paragraph to replay prevention
- Switch verification step 3 to algorithm allowlist model
- Add par/ext claim naming justification notes

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
2026-02-25 21:59:16 +01:00

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WIMSE C. Nennemann
Internet-Draft Independent Researcher
Intended status: Standards Track 25 February 2026
Expires: 29 August 2026
Execution Context Tokens for Distributed Agentic Workflows
draft-nennemann-wimse-ect-00
Abstract
This document defines Execution Context Tokens (ECTs), an extension
to the Workload Identity in Multi System Environments (WIMSE)
architecture for distributed agentic workflows. ECTs provide signed,
structured records of task execution order across agent-to-agent
communication. By extending WIMSE Workload Identity Tokens with
execution context claims in JSON Web Token (JWT) format, this
specification enables systems to maintain structured audit trails of
agent execution. ECTs use a directed acyclic graph (DAG) structure
to represent task dependencies and integrate with WIMSE Workload
Identity Tokens (WIT) using the same signing model and cryptographic
primitives. A new HTTP header field, Execution-Context, is defined
for transporting ECTs alongside existing WIMSE headers.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 29 August 2026.
Copyright Notice
Copyright (c) 2026 IETF Trust and the persons identified as the
document authors. All rights reserved.
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This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
extracted from this document must include Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Motivation . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Problem Statement . . . . . . . . . . . . . . . . . . . . 4
1.3. Scope and Applicability . . . . . . . . . . . . . . . . . 4
2. Conventions and Definitions . . . . . . . . . . . . . . . . . 5
3. WIMSE Architecture Integration . . . . . . . . . . . . . . . 5
3.1. WIMSE Foundation . . . . . . . . . . . . . . . . . . . . 5
3.2. Extension Model . . . . . . . . . . . . . . . . . . . . . 6
3.3. Integration Points . . . . . . . . . . . . . . . . . . . 7
4. Execution Context Token Format . . . . . . . . . . . . . . . 8
4.1. JOSE Header . . . . . . . . . . . . . . . . . . . . . . . 8
4.2. JWT Claims . . . . . . . . . . . . . . . . . . . . . . . 8
4.2.1. Standard JWT Claims . . . . . . . . . . . . . . . . . 8
4.2.2. Execution Context . . . . . . . . . . . . . . . . . . 10
4.2.3. Data Integrity . . . . . . . . . . . . . . . . . . . 10
4.2.4. Extensions . . . . . . . . . . . . . . . . . . . . . 11
4.3. Complete ECT Example . . . . . . . . . . . . . . . . . . 11
5. HTTP Header Transport . . . . . . . . . . . . . . . . . . . . 12
5.1. Execution-Context Header Field . . . . . . . . . . . . . 12
6. DAG Validation . . . . . . . . . . . . . . . . . . . . . . . 12
6.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 12
6.2. Validation Rules . . . . . . . . . . . . . . . . . . . . 13
6.3. Handling Unavailable Parent ECTs . . . . . . . . . . . . 13
7. Signature and Token Verification . . . . . . . . . . . . . . 14
7.1. Verification Procedure . . . . . . . . . . . . . . . . . 14
8. Audit Ledger Interface . . . . . . . . . . . . . . . . . . . 15
9. Security Considerations . . . . . . . . . . . . . . . . . . . 16
9.1. Threat Model . . . . . . . . . . . . . . . . . . . . . . 16
9.2. Self-Assertion Limitation . . . . . . . . . . . . . . . . 16
9.3. Organizational Prerequisites . . . . . . . . . . . . . . 17
9.4. Signature Verification . . . . . . . . . . . . . . . . . 17
9.5. Replay Attack Prevention . . . . . . . . . . . . . . . . 17
9.6. Man-in-the-Middle Protection . . . . . . . . . . . . . . 18
9.7. Key Compromise . . . . . . . . . . . . . . . . . . . . . 18
9.8. Collusion and False Claims . . . . . . . . . . . . . . . 19
9.9. DAG Integrity Attacks . . . . . . . . . . . . . . . . . . 19
9.10. Privilege Escalation via ECTs . . . . . . . . . . . . . . 20
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9.11. Denial of Service . . . . . . . . . . . . . . . . . . . . 20
9.12. Timestamp Accuracy . . . . . . . . . . . . . . . . . . . 20
9.13. ECT Size Constraints . . . . . . . . . . . . . . . . . . 21
10. Privacy Considerations . . . . . . . . . . . . . . . . . . . 21
10.1. Data Exposure in ECTs . . . . . . . . . . . . . . . . . 21
10.2. Data Minimization . . . . . . . . . . . . . . . . . . . 22
10.3. Storage and Access Control . . . . . . . . . . . . . . . 22
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22
11.1. Media Type Registration . . . . . . . . . . . . . . . . 22
11.2. HTTP Header Field Registration . . . . . . . . . . . . . 23
11.3. JWT Claims Registration . . . . . . . . . . . . . . . . 23
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 24
12.1. Normative References . . . . . . . . . . . . . . . . . . 24
12.2. Informative References . . . . . . . . . . . . . . . . . 25
Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Cross-Organization Financial Trading . . . . . . . . . . . . . 27
Related Work . . . . . . . . . . . . . . . . . . . . . . . . . . 28
WIMSE Workload Identity . . . . . . . . . . . . . . . . . . . . 28
OAuth 2.0 Token Exchange and the "act" Claim . . . . . . . . . 28
Transaction Tokens . . . . . . . . . . . . . . . . . . . . . . 29
Distributed Tracing (OpenTelemetry) . . . . . . . . . . . . . . 30
W3C Provenance Data Model (PROV) . . . . . . . . . . . . . . . 30
SCITT (Supply Chain Integrity, Transparency, and Trust) . . . . 30
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 30
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 30
1. Introduction
1.1. Motivation
The Workload Identity in Multi System Environments (WIMSE) framework
[I-D.ietf-wimse-arch] provides robust workload authentication through
Workload Identity Tokens (WIT) and Workload Proof Tokens (WPT). The
WIMSE service-to-service protocol [I-D.ietf-wimse-s2s-protocol]
defines how workloads authenticate each other across call chains
using the Workload-Identity and Workload-Proof-Token HTTP headers.
However, workload identity alone does not address execution
accountability. Knowing who performed an action does not record what
was done or in what order.
Regulated environments increasingly deploy autonomous agents that
coordinate across organizational boundaries. Domains such as
healthcare, finance, and logistics require structured, auditable
records of automated decision-making and execution.
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This document defines an extension to the WIMSE architecture that
addresses the gap between workload identity and execution
accountability. WIMSE authenticates agents; this extension records
what they did and in what order.
As identified in [I-D.ni-wimse-ai-agent-identity], call context in
agentic workflows needs to be visible and preserved. ECTs provide a
mechanism to address this requirement with cryptographic assurances.
1.2. Problem Statement
Three core gaps exist in current approaches to regulated agentic
systems:
1. WIMSE authenticates agents but does not record what they actually
did. A WIT proves "Agent A is authorized" but not "Agent A
executed Task X, producing Output Z."
2. No standard mechanism exists to cryptographically order and link
task execution across a multi-agent workflow.
3. No mechanism exists to reconstruct the complete execution history
of a distributed workflow for audit purposes.
Existing observability tools such as distributed tracing
[OPENTELEMETRY] provide visibility for debugging and monitoring but
do not provide cryptographic assurances. Tracing data is not
cryptographically signed, not tamper-evident, and not designed for
regulatory audit scenarios.
1.3. Scope and Applicability
This document defines:
* The Execution Context Token (ECT) format (Section 4)
* DAG structure for task dependency ordering (Section 6)
* Integration with the WIMSE identity framework (Section 3)
* An HTTP header for ECT transport (Section 5)
* Audit ledger interface requirements (Section 8)
The following are out of scope and are handled by WIMSE:
* Workload authentication and identity provisioning
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* Key distribution and management
* Trust domain establishment and management
* Credential lifecycle management
2. Conventions and Definitions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
The following terms are used in this document:
Agent: An autonomous workload, as defined by WIMSE
[I-D.ietf-wimse-arch], that executes tasks within a workflow.
Task: A discrete unit of agent work that consumes inputs and
produces outputs.
Directed Acyclic Graph (DAG): A graph structure representing task
dependency ordering where edges are directed and no cycles exist.
Execution Context Token (ECT): A JSON Web Token [RFC7519] defined by
this specification that records task execution details.
Audit Ledger: An append-only, immutable log of all ECTs within a
workflow or set of workflows, used for audit and verification.
Workload Identity Token (WIT): A WIMSE credential proving a
workload's identity within a trust domain.
Workload Proof Token (WPT): A WIMSE proof-of-possession token used
for request-level authentication.
Trust Domain: A WIMSE concept representing an organizational
boundary with a shared identity issuer, corresponding to a SPIFFE
[SPIFFE] trust domain.
3. WIMSE Architecture Integration
3.1. WIMSE Foundation
The WIMSE architecture [I-D.ietf-wimse-arch] defines:
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* Workload Identity Tokens (WIT) that prove a workload's identity
within a trust domain ("I am Agent X in trust domain Y")
* Workload Proof Tokens (WPT) that prove possession of the private
key associated with a WIT ("I control the key for Agent X")
* Multi-hop authentication via the service-to-service protocol
[I-D.ietf-wimse-s2s-protocol]
The following execution accountability needs are complementary to the
WIMSE scope and are not addressed by workload identity alone:
* Recording what agents actually do with their authenticated
identity
* Maintaining structured execution records
* Linking actions to their predecessors with cryptographic assurance
3.2. Extension Model
ECTs extend WIMSE by adding an execution accountability layer between
the identity layer and the application layer:
+--------------------------------------------------+
| WIMSE Layer (Identity) |
| WIT: "I am Agent X (spiffe://td/agent/x)" |
| WPT: "I prove I control the key for Agent X" |
+--------------------------------------------------+
|
v
+--------------------------------------------------+
| ECT Layer (Execution Accountability) [This Spec]|
| ECT: "Task executed, dependencies met, |
| inputs/outputs hashed" |
+--------------------------------------------------+
|
v
+--------------------------------------------------+
| Optional: Audit Ledger (Immutable Record) |
| "ECTs MAY be appended to an audit ledger" |
+--------------------------------------------------+
Figure 1: WIMSE Extension Architecture Layers
This extension reuses the WIMSE signing model, extends JWT claims
using standard JWT extensibility [RFC7519], and maintains WIMSE
concepts including trust domains and workload identifiers.
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3.3. Integration Points
An ECT integrates with the WIMSE identity framework through the
following mechanisms:
* The ECT JOSE header "kid" parameter MUST reference the public key
identifier from the agent's WIT.
* In WIMSE deployments, the ECT "iss" claim SHOULD use the WIMSE
workload identifier format (a SPIFFE ID [SPIFFE]).
* The ECT MUST be signed with the same private key associated with
the agent's WIT.
* The ECT signing algorithm (JOSE header "alg" parameter) MUST match
the algorithm used in the corresponding WIT.
When an agent makes an HTTP request to another agent, the Execution-
Context header is carried alongside WIMSE identity headers:
HTTP Request from Agent A to Agent B:
Workload-Identity: <WIT for Agent A>
Execution-Context: <ECT recording what A did>
Figure 2: HTTP Header Stacking
When a Workload Proof Token (WPT) is available per
[I-D.ietf-wimse-s2s-protocol], agents SHOULD include it alongside the
WIT and ECT. ECT verification does not depend on the presence of a
WPT; the ECT is independently verifiable via the WIT public key.
The receiving agent (Agent B) verifies in order:
1. WIT (WIMSE layer): Verifies Agent A's identity within the trust
domain. WPT verification, if present, per
[I-D.ietf-wimse-s2s-protocol].
2. ECT (this extension): Records what Agent A did and what precedent
tasks exist.
3. Ledger (if deployed): Appends the verified ECT to the audit
ledger.
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4. Execution Context Token Format
An Execution Context Token is a JSON Web Token (JWT) [RFC7519] signed
as a JSON Web Signature (JWS) [RFC7515]. ECTs MUST use JWS Compact
Serialization (the base64url-encoded header.payload.signature format)
so that they can be carried in a single HTTP header value.
4.1. JOSE Header
The ECT JOSE header MUST contain the following parameters:
{
"alg": "ES256",
"typ": "wimse-exec+jwt",
"kid": "agent-a-key-id-123"
}
Figure 3: ECT JOSE Header Example
alg: REQUIRED. The digital signature algorithm used to sign the
ECT. MUST match the algorithm in the corresponding WIT.
Implementations MUST support ES256 [RFC7518]. The "alg" value
MUST NOT be "none". Symmetric algorithms (e.g., HS256, HS384,
HS512) MUST NOT be used, as ECTs require asymmetric signatures for
non-repudiation.
typ: REQUIRED. MUST be set to "wimse-exec+jwt" to distinguish ECTs
from other JWT types, consistent with the WIMSE convention for
type parameter values.
kid: REQUIRED. The key identifier referencing the public key from
the agent's WIT [RFC7517]. Used by verifiers to look up the
correct public key for signature verification.
4.2. JWT Claims
The ECT payload contains both WIMSE-compatible standard JWT claims
and execution context claims defined by this specification.
4.2.1. Standard JWT Claims
The following standard JWT claims [RFC7519] MUST be present in every
ECT:
iss: REQUIRED. StringOrURI. A URI identifying the issuer of the
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ECT. In WIMSE deployments, this SHOULD be the workload's SPIFFE
ID in the format spiffe://<trust-domain>/<path>, matching the
"sub" claim of the agent's WIT. Non-WIMSE deployments MAY use
other URI schemes (e.g., HTTPS URLs or URN:UUID identifiers).
aud: REQUIRED. StringOrURI or array of StringOrURI. The intended
recipient(s) of the ECT. Because ECTs serve as both inter-agent
messages and audit records, the "aud" claim SHOULD contain the
identifiers of all entities that will verify the ECT. In practice
this means:
* *Point-to-point delivery*: when an ECT is sent from one agent
to a single next agent, "aud" contains that agent's workload
identity. The receiving agent verifies the ECT and forwards it
to the ledger on behalf of the issuer.
* *Direct-to-ledger submission*: when an ECT is submitted
directly to the audit ledger (e.g., after a join or at workflow
completion), "aud" contains the ledger's identity.
* *Multi-audience*: when an ECT must be verified by both the next
agent and the ledger independently, "aud" MUST be an array
containing both identifiers (e.g.,
["spiffe://example.com/agent/next",
"spiffe://example.com/system/ledger"]). Each verifier checks
that its own identity appears in the array.
In multi-parent (join) scenarios where a task depends on ECTs from
multiple parent agents, the joining agent creates a new ECT with
the parent task IDs in "par". The "aud" of this new ECT is set
according to the rules above based on where the ECT will be
delivered — it is independent of the "aud" values in the parent
ECTs.
iat: REQUIRED. NumericDate. The time at which the ECT was issued.
The ECT records a completed action, so the "iat" value reflects
when the record was created, not when task execution began.
exp: REQUIRED. NumericDate. The expiration time of the ECT.
Implementations SHOULD set this to 5 to 15 minutes after "iat" to
limit the replay window while allowing for reasonable clock skew
and processing time.
The standard JWT "nbf" (Not Before) claim is not used in ECTs because
ECTs record completed actions and are valid immediately upon
issuance.
jti: REQUIRED. String. A globally unique identifier for both the
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ECT and the task it records, in UUID format [RFC9562]. Since each
ECT represents exactly one task, "jti" serves as both the token
identifier (for replay detection) and the task identifier (for DAG
parent references in "par"). Receivers MUST reject ECTs whose
"jti" has already been seen within the expiration window. When
"wid" is present, uniqueness is scoped to the workflow; when "wid"
is absent, uniqueness MUST be enforced globally across the ECT
store.
4.2.2. Execution Context
The following claims are defined by this specification:
wid: OPTIONAL. String. A workflow identifier that groups related
ECTs into a single workflow. When present, MUST be a UUID
[RFC9562].
exec_act: REQUIRED. String. The action or task type identifier
describing what the agent performed (e.g., "process_payment",
"validate_safety", "calculate_dosage"). Note: this claim is
intentionally named "exec_act" rather than "act" to avoid
collision with the "act" (Actor) claim registered by [RFC8693].
par: REQUIRED. Array of strings. Parent task identifiers
representing DAG dependencies. Each element MUST be the "jti"
value of a previously verified ECT. An empty array indicates a
root task with no dependencies. A workflow MAY contain multiple
root tasks. Parent ECTs may have passed their own "exp" time; ECT
expiration applies to the verification window of the ECT itself,
not to its validity as a parent reference in the ECT store. Note:
"par" is not a registered JWT claim and does not conflict with
OAuth Pushed Authorization Requests (RFC 9126), which defines an
endpoint, not a token claim.
4.2.3. Data Integrity
The following claims provide integrity verification for task inputs
and outputs without revealing the data itself:
inp_hash: OPTIONAL. String. The base64url encoding (without
padding) of the SHA-256 hash of the input data, computed over the
raw octets of the input. This follows the same fixed-algorithm
pattern used by the DPoP "ath" claim [RFC9449] and the WIMSE WPT
"tth" claim [I-D.ietf-wimse-s2s-protocol]: SHA-256 is the
mandatory algorithm with no algorithm prefix in the value.
out_hash: OPTIONAL. String. The base64url encoding (without
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padding) of the SHA-256 hash of the output data, using the same
format as "inp_hash".
4.2.4. Extensions
ext: OPTIONAL. Object. A general-purpose extension object for
domain-specific claims not defined by this specification. The
short name "ext" follows the JWT convention of concise claim names
and is chosen over alternatives like "extensions" for compactness.
Implementations that do not understand extension claims MUST
ignore them.
To avoid key collisions between different domains, extension key
names SHOULD use reverse domain notation (e.g.,
"com.example.custom_field") to avoid collisions between independently
developed extensions. To prevent abuse and excessive token size, the
serialized JSON representation of the "ext" object SHOULD NOT exceed
4096 bytes, and the JSON nesting depth within the "ext" object SHOULD
NOT exceed 5 levels. Implementations SHOULD reject ECTs whose "ext"
claim exceeds these limits.
Extension keys for domain-specific use cases MAY be defined in future
documents.
4.3. Complete ECT Example
The following is a complete ECT payload example:
{
"iss": "spiffe://example.com/agent/clinical",
"aud": "spiffe://example.com/agent/safety",
"iat": 1772064150,
"exp": 1772064750,
"jti": "550e8400-e29b-41d4-a716-446655440001",
"wid": "a0b1c2d3-e4f5-6789-abcd-ef0123456789",
"exec_act": "recommend_treatment",
"par": [],
"inp_hash": "n4bQgYhMfWWaL-qgxVrQFaO_TxsrC4Is0V1sFbDwCgg",
"out_hash": "LCa0a2j_xo_5m0U8HTBBNBNCLXBkg7-g-YpeiGJm564",
"ext": {
"com.example.trace_id": "abc123"
}
}
Figure 4: Complete ECT Payload Example
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5. HTTP Header Transport
5.1. Execution-Context Header Field
This specification defines the Execution-Context HTTP header field
[RFC9110] for transporting ECTs between agents.
The header field value is the ECT in JWS Compact Serialization format
[RFC7515]. The value consists of three Base64url-encoded parts
separated by period (".") characters.
An agent sending a request to another agent includes the Execution-
Context header alongside the WIMSE Workload-Identity header:
GET /api/safety-check HTTP/1.1
Host: safety-agent.example.com
Workload-Identity: eyJhbGci...WIT...
Execution-Context: eyJhbGci...ECT...
Figure 5: HTTP Request with ECT Header
When multiple parent tasks contribute context to a single request,
multiple Execution-Context header field lines MAY be included, each
carrying a separate ECT in JWS Compact Serialization format.
When a receiver processes multiple Execution-Context headers, it MUST
individually verify each ECT per the procedure in Section 7. If any
single ECT fails verification, the receiver MUST reject the entire
request. The set of verified parent task IDs across all received
ECTs represents the complete set of parent dependencies available for
the receiving agent's subsequent ECT.
6. DAG Validation
6.1. Overview
ECTs form a Directed Acyclic Graph (DAG) where each task references
its parent tasks via the "par" claim. This structure provides a
cryptographically signed record of execution ordering, enabling
auditors to reconstruct the complete workflow and verify that
required predecessor tasks were recorded before dependent tasks.
DAG validation is performed against the ECT store — either an audit
ledger or the set of parent ECTs received inline.
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6.2. Validation Rules
When receiving and verifying an ECT, implementations MUST perform the
following DAG validation steps:
1. Task ID Uniqueness: The "jti" claim MUST be unique within the
applicable scope (the workflow identified by "wid", or the entire
ECT store if "wid" is absent). If an ECT with the same "jti"
already exists, the ECT MUST be rejected.
2. Parent Existence: Every task identifier listed in the "par" array
MUST correspond to a task that is available in the ECT store
(either previously recorded in the ledger or received inline as a
verified parent ECT). If any parent task is not found, the ECT
MUST be rejected.
3. Temporal Ordering: The "iat" value of every parent task MUST NOT
be greater than the "iat" value of the current task plus a
configurable clock skew tolerance (RECOMMENDED: 30 seconds).
That is, for each parent: parent.iat < child.iat +
clock_skew_tolerance. The tolerance accounts for clock skew
between agents; it does not guarantee strict causal ordering from
timestamps alone. Causal ordering is primarily enforced by the
DAG structure (parent existence in the ECT store), not by
timestamps. If any parent task violates this constraint, the ECT
MUST be rejected.
4. Acyclicity: Following the chain of parent references MUST NOT
lead back to the current ECT's "jti". If a cycle is detected,
the ECT MUST be rejected.
5. Trust Domain Consistency: Parent tasks SHOULD belong to the same
trust domain or to a trust domain with which a federation
relationship has been established.
To prevent denial-of-service via extremely deep or wide DAGs,
implementations SHOULD enforce a maximum ancestor traversal limit
(RECOMMENDED: 10000 nodes). If the limit is reached before cycle
detection completes, the ECT SHOULD be rejected.
6.3. Handling Unavailable Parent ECTs
In distributed deployments, a parent ECT referenced in the "par"
array may not yet be available in the local ECT store at the time of
validation — for example, due to replication lag in a distributed
ledger or out-of-order message delivery.
Implementations MUST distinguish between two cases:
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1. Parent not found and definitively absent: The parent "jti" does
not exist in any accessible ECT store. The ECT MUST be rejected.
2. Parent not yet available: The parent "jti" is not present locally
but may arrive due to known replication delays. Implementations
MAY defer validation for a bounded period (RECOMMENDED: no more
than 60 seconds).
Deferred ECTs MUST NOT be treated as verified until all parent
references are resolved. If any parent reference remains unresolved
after the deferral period or after the ECT's own "exp" time
(whichever comes first), the ECT MUST be rejected.
7. Signature and Token Verification
7.1. Verification Procedure
When an agent receives an ECT, it MUST perform the following
verification steps in order:
1. Parse the JWS Compact Serialization to extract the JOSE header,
payload, and signature components per [RFC7515].
2. Verify that the "typ" header parameter is "wimse-exec+jwt".
3. Verify that the "alg" header parameter appears in the verifier's
configured allowlist of accepted signing algorithms. The
allowlist MUST NOT include "none" or any symmetric algorithm
(e.g., HS256, HS384, HS512). Implementations MUST include ES256
in the allowlist; additional asymmetric algorithms MAY be
included per deployment policy.
4. Verify the "kid" header parameter references a known, valid
public key from a WIT within the trust domain.
5. Retrieve the public key identified by "kid" and verify the JWS
signature per [RFC7515] Section 5.2.
6. Verify that the signing key identified by "kid" has not been
revoked within the trust domain. Implementations MUST check the
key's revocation status using the trust domain's key lifecycle
mechanism (e.g., certificate revocation list, OCSP, or SPIFFE
trust bundle updates).
7. Verify the "alg" header parameter matches the algorithm in the
corresponding WIT.
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8. Verify the "iss" claim matches the "sub" claim of the WIT
associated with the "kid" public key.
9. Verify the "aud" claim contains the verifier's own workload
identity. When "aud" is an array, it is sufficient that the
verifier's identity appears as one element; the presence of
other audience values does not cause verification failure. When
the verifier is the audit ledger, the ledger's own identity MUST
appear in "aud".
10. Verify the "exp" claim indicates the ECT has not expired.
11. Verify the "iat" claim is not unreasonably far in the past
(implementation-specific threshold, RECOMMENDED maximum of 15
minutes) and is not unreasonably far in the future (RECOMMENDED:
no more than 30 seconds ahead of the verifier's current time, to
account for clock skew).
12. Verify all required claims ("jti", "exec_act", "par") are
present and well-formed.
13. Perform DAG validation per Section 6.
14. If all checks pass and an audit ledger is deployed, the ECT
SHOULD be appended to the ledger.
If any verification step fails, the ECT MUST be rejected and the
failure MUST be logged for audit purposes. Error messages SHOULD NOT
reveal whether specific parent task IDs exist in the ECT store, to
prevent information disclosure.
When ECT verification fails during HTTP request processing, the
receiving agent SHOULD respond with HTTP 403 (Forbidden) if the WIT
is valid but the ECT is invalid, and HTTP 401 (Unauthorized) if the
ECT signature verification fails. The response body SHOULD include a
generic error indicator without revealing which specific verification
step failed. The receiving agent MUST NOT process the requested
action when ECT verification fails.
8. Audit Ledger Interface
ECTs MAY be recorded in an immutable audit ledger for compliance
verification and post-hoc analysis. A ledger is RECOMMENDED for
regulated environments but is not required for point-to-point
operation. This specification does not mandate a specific storage
technology. Implementations MAY use append-only logs, databases with
cryptographic commitment schemes, distributed ledgers, or any storage
mechanism that provides the required properties.
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When an audit ledger is deployed, the implementation MUST provide:
1. Append-only semantics: Once an ECT is recorded, it MUST NOT be
modified or deleted.
2. Ordering: The ledger MUST maintain a total ordering of ECT
entries via a monotonically increasing sequence number.
3. Lookup by ECT ID: The ledger MUST support efficient retrieval of
ECT entries by "jti" value.
4. Integrity verification: The ledger SHOULD provide a mechanism to
verify that no entries have been tampered with (e.g., hash chains
or Merkle trees).
The ledger SHOULD be maintained by an entity independent of the
workflow agents to reduce the risk of collusion.
9. Security Considerations
This section addresses security considerations following the guidance
in [RFC3552].
9.1. Threat Model
The following threat actors are considered:
* Malicious agent (insider threat): An agent within the trust domain
that intentionally creates false ECT claims.
* Compromised agent (external attacker): An agent whose private key
has been obtained by an external attacker.
* Ledger tamperer: An entity attempting to modify or delete ledger
entries after they have been recorded.
* Time manipulator: An entity attempting to manipulate timestamps to
alter perceived execution ordering.
9.2. Self-Assertion Limitation
ECTs are self-asserted by the executing agent. The agent claims what
it did, and this claim is signed with its private key. A compromised
or malicious agent could create ECTs with false claims (e.g.,
claiming an action was performed when it was not).
ECTs do not independently verify that:
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* The claimed execution actually occurred as described
* The input/output hashes correspond to the actual data processed
* The agent faithfully performed the stated action
The trustworthiness of ECT claims depends on the trustworthiness of
the signing agent and the integrity of the broader deployment
environment.
9.3. Organizational Prerequisites
ECTs operate within a broader trust framework. The guarantees
provided by ECTs are only meaningful when the following
organizational controls are in place:
* Key management governance: Controls over who provisions agent keys
and how keys are protected.
* Ledger integrity governance: The ledger is maintained by an entity
independent of the workflow agents.
* Agent deployment governance: Agents are deployed and maintained in
a manner that preserves their integrity.
9.4. Signature Verification
ECTs MUST be signed with the agent's private key using JWS [RFC7515].
The signature algorithm MUST match the algorithm specified in the
agent's WIT. Receivers MUST verify the ECT signature against the WIT
public key before processing any claims. Receivers MUST verify that
the signing key has not been revoked within the trust domain (see
step 6 in Section 7).
If signature verification fails or if the signing key has been
revoked, the ECT MUST be rejected entirely and the failure MUST be
logged.
Implementations MUST use established JWS libraries and MUST NOT
implement custom signature verification.
9.5. Replay Attack Prevention
ECTs include short expiration times (RECOMMENDED: 5-15 minutes) to
limit the window for replay attacks. The "aud" claim restricts
replay to unintended recipients: an ECT intended for Agent B will be
rejected by Agent C. The "iat" claim enables receivers to reject
ECTs that are too old, even if not yet expired.
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The DAG structure provides additional replay protection: an ECT
referencing parent tasks that already have a recorded child task with
the same action can be flagged as a potential replay.
Implementations MUST maintain a cache of recently-seen "jti" values
to detect replayed ECTs within the expiration window. An ECT with a
duplicate "jti" value MUST be rejected.
Additionally, each ECT is cryptographically bound to the issuing
agent via the JOSE "kid" parameter, which references the agent's WIT
public key. Verifiers MUST confirm that the "kid" resolves to the
"iss" agent's key (step 8 in Section 7), preventing one agent from
replaying another agent's ECT as its own.
9.6. Man-in-the-Middle Protection
ECTs do not replace transport-layer security. ECTs MUST be
transmitted over TLS or mTLS connections. When used with the WIMSE
service-to-service protocol [I-D.ietf-wimse-s2s-protocol], transport
security is already established. HTTP Message Signatures [RFC9421]
provide an alternative channel binding mechanism.
The defense-in-depth model provides:
* TLS/mTLS (transport layer): Prevents network-level tampering.
* WIT/WPT (WIMSE identity layer): Proves agent identity and request
authorization.
* ECT (execution accountability layer): Records what the agent did.
9.7. Key Compromise
If an agent's private key is compromised, an attacker can forge ECTs
that appear to originate from that agent. To mitigate this risk:
* Implementations SHOULD use short-lived keys and rotate them
frequently (hours to days, not months).
* Private keys SHOULD be stored in Hardware Security Modules (HSMs)
or equivalent secure key storage.
* Trust domains MUST support rapid key revocation.
* Upon suspected compromise, the trust domain MUST revoke the
compromised key and issue a new WIT with a fresh key pair.
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ECTs signed with a compromised key that were recorded in the ledger
before revocation remain valid historical records but SHOULD be
flagged in the ledger as "signed with subsequently revoked key" for
audit purposes.
ECT revocation does not propagate through the DAG. If a parent ECT's
signing key is later revoked, child ECTs that were verified and
recorded before that revocation remain valid — they captured a
legitimate execution record at the time of issuance. However,
auditors reviewing a workflow SHOULD flag any ECT in the DAG whose
signing key was subsequently revoked, so that the scope of a
potential compromise can be assessed. New ECTs MUST NOT be created
with a "par" reference to an ECT whose signing key is known to be
revoked at creation time.
9.8. Collusion and False Claims
A single malicious agent cannot forge parent task references because
DAG validation requires parent tasks to exist in the ledger.
However, multiple colluding agents could potentially create a false
execution history if they control the ledger.
Mitigations include:
* Independent ledger maintenance: The ledger SHOULD be maintained by
an entity independent of the workflow agents.
* Cross-verification: Multiple independent ledger replicas can be
compared for consistency.
* Out-of-band audit: External auditors periodically verify ledger
contents against expected workflow patterns.
9.9. DAG Integrity Attacks
Because the DAG structure is the primary mechanism for establishing
execution ordering, attackers may attempt to manipulate it:
* False parent references: A malicious agent creates an ECT that
references parent tasks from an unrelated workflow, inserting
itself into a legitimate execution history. DAG validation
(Section 6) mitigates this by requiring parent existence in the
ECT store, and the "wid" claim scopes parent references to a
single workflow when present.
* Parent omission (pruning): An agent deliberately omits one or more
actual parent dependencies from the "par" array to hide that
certain tasks influenced its output. Because ECTs are self-
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asserted (Section 9.2), no mechanism can force an agent to declare
all dependencies. External auditors can detect omission by
comparing the declared DAG against expected workflow patterns.
* Shadow DAGs: Multiple colluding agents fabricate an entire
execution history by creating a sequence of ECTs with mutual
parent references. Independent ledger maintenance and cross-
verification (see Section 9.8 above) are the primary mitigations.
Verifiers SHOULD validate that the declared "wid" of parent ECTs
matches the "wid" of the child ECT, rejecting cross-workflow parent
references unless explicitly permitted by deployment policy.
9.10. Privilege Escalation via ECTs
ECTs record execution history; they do not convey authorization.
Verifiers MUST NOT interpret the presence of an ECT, or a particular
set of parent references in "par", as an authorization grant. The
"par" claim demonstrates that predecessor tasks were recorded, not
that the current agent is authorized to act on their outputs.
Authorization decisions MUST remain with the identity and
authorization layer (WIT, WPT, and deployment policy). As noted in
[I-D.ni-wimse-ai-agent-identity], AI intermediaries introduce novel
escalation vectors; ECTs MUST NOT be used to circumvent authorization
boundaries.
9.11. Denial of Service
ECT signature verification is computationally inexpensive
(approximately 1ms per ECT on modern hardware for ES256). DAG
validation complexity is O(V) where V is the number of ancestor nodes
reachable from the parent references; for typical shallow DAGs this
is efficient.
Implementations SHOULD apply rate limiting at the API layer to
prevent excessive ECT submissions. DAG validation SHOULD be
performed after signature verification to avoid wasting resources on
unsigned or incorrectly signed tokens.
9.12. Timestamp Accuracy
ECTs rely on timestamps ("iat", "exp") for temporal ordering. Clock
skew between agents can lead to incorrect ordering judgments.
Implementations SHOULD use synchronized time sources (e.g., NTP) and
SHOULD allow a configurable clock skew tolerance (RECOMMENDED: 30
seconds).
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Cross-organizational deployments where agents span multiple trust
domains with independent time sources MAY require a higher clock skew
tolerance. Deployments using trust domain federation SHOULD document
their configured clock skew tolerance value and SHOULD ensure all
participating trust domains agree on a common tolerance.
The temporal ordering check in DAG validation incorporates the clock
skew tolerance to account for minor clock differences between agents.
9.13. ECT Size Constraints
ECTs with many parent tasks or large extension objects can increase
HTTP header size. Implementations SHOULD limit the "par" array to a
maximum of 256 entries. Workflows requiring more parent references
SHOULD introduce intermediate aggregation tasks. The "ext" object
SHOULD NOT exceed 4096 bytes when serialized as JSON and SHOULD NOT
exceed a nesting depth of 5 levels (see also Section 4.2.4).
10. Privacy Considerations
10.1. Data Exposure in ECTs
ECTs necessarily reveal:
* Agent identities ("iss", "aud") for accountability purposes
* Action descriptions ("exec_act") for audit trail completeness
* Timestamps ("iat", "exp") for temporal ordering
ECTs are designed to NOT reveal:
* Actual input or output data values (replaced with cryptographic
hashes via "inp_hash" and "out_hash")
* Internal computation details or intermediate steps
* Proprietary algorithms or intellectual property
* Personally identifiable information (PII)
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10.2. Data Minimization
Implementations SHOULD minimize the information included in ECTs.
The "exec_act" claim SHOULD use structured identifiers (e.g.,
"process_payment") rather than natural language descriptions.
Extension keys in "ext" (Section 4.2.4) deserve particular attention:
human-readable values risk exposing sensitive operational details.
See Section 4.2.4 for guidance on using structured identifiers.
10.3. Storage and Access Control
ECTs stored in audit ledgers SHOULD be access-controlled so that only
authorized auditors can read them. Implementations SHOULD consider
encryption at rest for ledger storage. ECTs provide structural
records of execution ordering; they are not intended for public
disclosure.
Full input and output data (corresponding to the hashes in ECTs)
SHOULD be stored separately from the ledger with additional access
controls, since auditors may need to verify hash correctness but
general access to the data values is not needed.
11. IANA Considerations
11.1. Media Type Registration
This document requests registration of the following media type in
the "Media Types" registry maintained by IANA:
Type name: application
Subtype name: wimse-exec+jwt
Required parameters: none
Optional parameters: none
Encoding considerations: 8bit; an ECT is a JWT that is a JWS using
the Compact Serialization, which is a sequence of Base64url-
encoded values separated by period characters.
Security considerations: See the Security Considerations section of
this document.
Interoperability considerations: none
Published specification: This document
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Applications that use this media type: Applications that implement
agentic workflows requiring execution context tracing and audit
trails.
Additional information: Magic number(s): none File extension(s):
none Macintosh file type code(s): none
Person and email address to contact for further information: Christi
an Nennemann, ietf@nennemann.de
Intended usage: COMMON
Restrictions on usage: none
Author: Christian Nennemann
Change controller: IETF
11.2. HTTP Header Field Registration
This document requests registration of the following header field in
the "Hypertext Transfer Protocol (HTTP) Field Name Registry"
maintained by IANA:
Field name: Execution-Context
Status: permanent
Specification document: This document, Section 5
11.3. JWT Claims Registration
This document requests registration of the following claims in the
"JSON Web Token Claims" registry maintained by IANA:
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+============+=====================+===================+===========+
| Claim Name | Claim Description | Change Controller | Reference |
+============+=====================+===================+===========+
| wid | Workflow Identifier | IETF | Section |
| | | | 4.2.2 |
+------------+---------------------+-------------------+-----------+
| exec_act | Action/Task Type | IETF | Section |
| | | | 4.2.2 |
+------------+---------------------+-------------------+-----------+
| par | Parent Task | IETF | Section |
| | Identifiers | | 4.2.2 |
+------------+---------------------+-------------------+-----------+
| inp_hash | Input Data Hash | IETF | Section |
| | | | 4.2.3 |
+------------+---------------------+-------------------+-----------+
| out_hash | Output Data Hash | IETF | Section |
| | | | 4.2.3 |
+------------+---------------------+-------------------+-----------+
| ext | Extension Object | IETF | Section |
| | | | 4.2.4 |
+------------+---------------------+-------------------+-----------+
Table 1: JWT Claims Registrations
12. References
12.1. Normative References
[I-D.ietf-wimse-arch]
Salowey, J. A., Rosomakho, Y., and H. Tschofenig,
"Workload Identity in a Multi System Environment (WIMSE)
Architecture", Work in Progress, Internet-Draft, draft-
ietf-wimse-arch-06, 30 September 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-wimse-
arch-06>.
[I-D.ietf-wimse-s2s-protocol]
Campbell, B., Salowey, J. A., Schwenkschuster, A., and Y.
Sheffer, "WIMSE Workload-to-Workload Authentication", Work
in Progress, Internet-Draft, draft-ietf-wimse-s2s-
protocol-07, 16 October 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-wimse-
s2s-protocol-07>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/rfc/rfc2119>.
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[RFC7515] Jones, M., Bradley, J., and N. Sakimura, "JSON Web
Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May
2015, <https://www.rfc-editor.org/rfc/rfc7515>.
[RFC7517] Jones, M., "JSON Web Key (JWK)", RFC 7517,
DOI 10.17487/RFC7517, May 2015,
<https://www.rfc-editor.org/rfc/rfc7517>.
[RFC7518] Jones, M., "JSON Web Algorithms (JWA)", RFC 7518,
DOI 10.17487/RFC7518, May 2015,
<https://www.rfc-editor.org/rfc/rfc7518>.
[RFC7519] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
(JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015,
<https://www.rfc-editor.org/rfc/rfc7519>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.
[RFC9110] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
Ed., "HTTP Semantics", STD 97, RFC 9110,
DOI 10.17487/RFC9110, June 2022,
<https://www.rfc-editor.org/rfc/rfc9110>.
[RFC9562] Davis, K., Peabody, B., and P. Leach, "Universally Unique
IDentifiers (UUIDs)", RFC 9562, DOI 10.17487/RFC9562, May
2024, <https://www.rfc-editor.org/rfc/rfc9562>.
12.2. Informative References
[I-D.ietf-oauth-transaction-tokens]
Tulshibagwale, A., Fletcher, G., and P. Kasselman,
"Transaction Tokens", Work in Progress, Internet-Draft,
draft-ietf-oauth-transaction-tokens-07, 24 January 2026,
<https://datatracker.ietf.org/doc/html/draft-ietf-oauth-
transaction-tokens-07>.
[I-D.ietf-scitt-architecture]
Birkholz, H., Delignat-Lavaud, A., Fournet, C., Deshpande,
Y., and S. Lasker, "An Architecture for Trustworthy and
Transparent Digital Supply Chains", Work in Progress,
Internet-Draft, draft-ietf-scitt-architecture-22, 10
October 2025, <https://datatracker.ietf.org/doc/html/
draft-ietf-scitt-architecture-22>.
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[I-D.ni-wimse-ai-agent-identity]
Yuan, N. and P. C. Liu, "WIMSE Applicability for AI
Agents", Work in Progress, Internet-Draft, draft-ni-wimse-
ai-agent-identity-01, 20 October 2025,
<https://datatracker.ietf.org/doc/html/draft-ni-wimse-ai-
agent-identity-01>.
[I-D.oauth-transaction-tokens-for-agents]
Raut, A., "Transaction Tokens For Agents", Work in
Progress, Internet-Draft, draft-oauth-transaction-tokens-
for-agents-04, 10 February 2026,
<https://datatracker.ietf.org/doc/html/draft-oauth-
transaction-tokens-for-agents-04>.
[OPENTELEMETRY]
Cloud Native Computing Foundation, "OpenTelemetry
Specification",
<https://opentelemetry.io/docs/specs/otel/>.
[RFC3552] Rescorla, E. and B. Korver, "Guidelines for Writing RFC
Text on Security Considerations", BCP 72, RFC 3552,
DOI 10.17487/RFC3552, July 2003,
<https://www.rfc-editor.org/rfc/rfc3552>.
[RFC8693] Jones, M., Nadalin, A., Campbell, B., Ed., Bradley, J.,
and C. Mortimore, "OAuth 2.0 Token Exchange", RFC 8693,
DOI 10.17487/RFC8693, January 2020,
<https://www.rfc-editor.org/rfc/rfc8693>.
[RFC9421] Backman, A., Ed., Richer, J., Ed., and M. Sporny, "HTTP
Message Signatures", RFC 9421, DOI 10.17487/RFC9421,
February 2024, <https://www.rfc-editor.org/rfc/rfc9421>.
[RFC9449] Fett, D., Campbell, B., Bradley, J., Lodderstedt, T.,
Jones, M., and D. Waite, "OAuth 2.0 Demonstrating Proof of
Possession (DPoP)", RFC 9449, DOI 10.17487/RFC9449,
September 2023, <https://www.rfc-editor.org/rfc/rfc9449>.
[SPIFFE] "Secure Production Identity Framework for Everyone
(SPIFFE)",
<https://spiffe.io/docs/latest/spiffe-about/overview/>.
Use Cases
This section describes a representative use case demonstrating how
ECTs provide structured execution records.
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Note: task identifiers in this section are abbreviated for
readability. In production, all "jti" values are required to be
UUIDs per Section 4.2.2.
Cross-Organization Financial Trading
In a cross-organization trading workflow, an investment bank's agents
coordinate with an external credit rating agency. The agents operate
in separate trust domains with a federation relationship. The DAG
records that independent assessments from both organizations were
completed before trade execution.
Trust Domain: bank.example
Agent A1 (Portfolio Risk):
jti: task-001 par: []
iss: spiffe://bank.example/agent/risk
exec_act: analyze_portfolio_risk
Trust Domain: ratings.example (external)
Agent B1 (Credit Rating):
jti: task-002 par: []
iss: spiffe://ratings.example/agent/credit
exec_act: assess_credit_rating
Trust Domain: bank.example
Agent A2 (Compliance):
jti: task-003 par: [task-001, task-002]
iss: spiffe://bank.example/agent/compliance
exec_act: verify_trade_compliance
Agent A3 (Execution):
jti: task-004 par: [task-003]
iss: spiffe://bank.example/agent/execution
exec_act: execute_trade
Figure 6: Cross-Organization Trading Workflow
The resulting DAG:
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task-001 (analyze_portfolio_risk) task-002 (assess_credit_rating)
[bank.example] [ratings.example]
\ /
v v
task-003 (verify_trade_compliance)
[bank.example]
|
v
task-004 (execute_trade)
[bank.example]
Figure 7: Cross-Organization DAG
Task 003 has two parents from different trust domains, demonstrating
cross-organizational fan-in. The compliance agent verifies both
parent ECTs — one signed by a local key and one by a federated key
from the rating agency's trust domain.
Related Work
WIMSE Workload Identity
The WIMSE architecture [I-D.ietf-wimse-arch] and service-to- service
protocol [I-D.ietf-wimse-s2s-protocol] provide the identity
foundation upon which ECTs are built. WIT/WPT answer "who is this
agent?" and "does it control the claimed key?" while ECTs record
"what did this agent do?" Together they form an identity-plus-
accountability framework for regulated agentic systems.
OAuth 2.0 Token Exchange and the "act" Claim
[RFC8693] defines the OAuth 2.0 Token Exchange protocol and registers
the "act" (Actor) claim in the JWT Claims registry. The "act" claim
creates nested JSON objects representing a delegation chain: "who is
acting on behalf of whom." While the nesting superficially resembles
a chain, it is strictly linear (each "act" object contains at most
one nested "act"), represents authorization delegation rather than
task execution, and carries no task identifiers or input/output
integrity data. The "act" chain cannot represent branching (fan-out)
or convergence (fan-in) and therefore cannot form a DAG.
ECTs intentionally use the distinct claim name "exec_act" for the
action/task type to avoid collision with the "act" claim. The two
concepts are orthogonal: "act" records "who authorized whom," ECTs
record "what was done, in what order."
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Transaction Tokens
OAuth Transaction Tokens [I-D.ietf-oauth-transaction-tokens]
propagate authorization context across workload call chains. The
Txn-Token "req_wl" claim accumulates a comma-separated list of
workloads that requested replacement tokens, which is the closest
existing mechanism to call-chain recording.
However, "req_wl" cannot form a DAG because:
* It is linear: a comma-separated string with no branching or
merging representation. When a workload fans out to multiple
downstream services, each receives the same "req_wl" value and the
branching is invisible.
* It is incomplete: only workloads that request a replacement token
from the Transaction Token Service appear in "req_wl"; workloads
that forward the token unchanged are not recorded.
* It carries no task-level granularity, no parent references, and no
execution content.
* It cannot represent convergence (fan-in): when two independent
paths must both complete before a dependent task proceeds, a
linear "req_wl" string cannot express that relationship.
Extensions for agentic use cases
([I-D.oauth-transaction-tokens-for-agents]) add agent identity and
constraints ("agentic_ctx") but no execution ordering or DAG
structure.
ECTs and Transaction Tokens are complementary: a Txn-Token propagates
authorization context ("this request is authorized for scope X on
behalf of user Y"), while an ECT records execution accountability
("task T was performed, depending on tasks P1 and P2"). An agent
request could carry both a Txn-Token for authorization and an ECT for
execution recording. The WPT "tth" claim defined in
[I-D.ietf-wimse-s2s-protocol] can hash-bind a WPT to a co-present
Txn-Token; a similar binding mechanism for ECTs is a potential future
extension.
Nennemann Expires 29 August 2026 [Page 29]
Internet-Draft WIMSE Execution Context February 2026
Distributed Tracing (OpenTelemetry)
OpenTelemetry [OPENTELEMETRY] and similar distributed tracing systems
provide observability for debugging and monitoring. ECTs differ in
several important ways: ECTs are cryptographically signed per-task
with the agent's private key; ECTs are tamper-evident through JWS
signatures; ECTs enforce DAG validation rules; and ECTs are designed
for regulatory audit rather than operational monitoring.
OpenTelemetry data is typically controlled by the platform operator
and can be modified or deleted without detection. ECTs and
distributed traces are complementary: traces provide observability
while ECTs provide signed execution records. ECTs may reference
OpenTelemetry trace identifiers in the "ext" claim for correlation.
W3C Provenance Data Model (PROV)
The W3C PROV Data Model defines an Entity-Activity-Agent ontology for
representing provenance information. PROV's concepts map closely to
ECT structures: PROV Activities correspond to ECT tasks, PROV Agents
correspond to WIMSE workloads, and PROV's "wasInformedBy" relation
corresponds to ECT "par" references. However, PROV uses RDF/OWL
ontologies designed for post-hoc documentation, while ECTs are
runtime-embeddable JWT tokens with cryptographic signatures. ECT
audit data could be exported to PROV format for interoperability with
provenance-aware systems.
SCITT (Supply Chain Integrity, Transparency, and Trust)
The SCITT architecture [I-D.ietf-scitt-architecture] defines a
framework for transparent and auditable supply chain records. ECTs
and SCITT are complementary: the ECT "wid" claim can serve as a
correlation identifier in SCITT Signed Statements, linking an ECT
audit trail to a supply chain transparency record.
Acknowledgments
The author thanks the WIMSE working group for their foundational work
on workload identity in multi-system environments. The concepts of
Workload Identity Tokens and Workload Proof Tokens provide the
identity foundation upon which execution context tracing is built.
Author's Address
Christian Nennemann
Independent Researcher
Email: ietf@nennemann.de
Nennemann Expires 29 August 2026 [Page 30]
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