ietf-wimse-ect/draft-nennemann-wimse-execution-context-00.md

---
title: "Execution Context Tokens for Distributed Agentic Workflows"
abbrev: "WIMSE Execution Context"
category: std
docname: draft-nennemann-wimse-execution-context-00
submissiontype: IETF
number:
date:
v: 3
area: "Security"
keyword:
  - execution context
  - workload identity
  - agentic workflows
  - audit trail
  - compliance
  - regulated systems

author:
  -
    fullname: Christian Nennemann
    organization: Independent Researcher
    email: ietf@nennemann.de

normative:
  RFC2119:
  RFC8174:
  RFC3339:
  RFC7515:
  RFC7519:
  RFC7518:
  RFC9562:
  RFC9110:
  I-D.ietf-wimse-arch:
  I-D.ietf-wimse-s2s-protocol:

informative:
  RFC3552:
  RFC7517:
  RFC8693:
  RFC9421:
  I-D.ni-wimse-ai-agent-identity:
  SPIFFE:
    title: "Secure Production Identity Framework for Everyone (SPIFFE)"
    target: https://spiffe.io/docs/latest/spiffe-about/overview/
    date: false
  EU-AI-ACT:
    title: "Regulation (EU) 2024/1689 of the European Parliament and of the Council laying down harmonised rules on artificial intelligence (Artificial Intelligence Act)"
    target: https://eur-lex.europa.eu/eli/reg/2024/1689
    date: 2024-06-13
    author:
      - org: European Parliament and Council of the European Union
  FDA-21CFR11:
    title: "Title 21, Code of Federal Regulations, Part 11: Electronic Records; Electronic Signatures"
    target: https://www.ecfr.gov/current/title-21/chapter-I/subchapter-A/part-11
    date: false
    author:
      - org: U.S. Food and Drug Administration
  MIFID-II:
    title: "Directive 2014/65/EU of the European Parliament and of the Council on markets in financial instruments (MiFID II)"
    target: https://eur-lex.europa.eu/eli/dir/2014/65
    date: 2014-05-15
    author:
      - org: European Parliament and Council of the European Union
  DORA:
    title: "Regulation (EU) 2022/2554 on digital operational resilience for the financial sector (DORA)"
    target: https://eur-lex.europa.eu/eli/reg/2022/2554
    date: 2022-12-14
    author:
      - org: European Parliament and Council of the European Union
  EU-MDR:
    title: "Regulation (EU) 2017/745 on medical devices (MDR)"
    target: https://eur-lex.europa.eu/eli/reg/2017/745
    date: 2017-04-05
    author:
      - org: European Parliament and Council of the European Union
  OPENTELEMETRY:
    title: "OpenTelemetry Specification"
    target: https://opentelemetry.io/docs/specs/otel/
    date: false
    author:
      - org: Cloud Native Computing Foundation
  I-D.ietf-scitt-architecture:

--- abstract

This document defines Execution Context Tokens (ECTs), an extension
to the Workload Identity in Multi System Environments (WIMSE)
architecture for distributed agentic workflows in regulated
environments.  ECTs provide cryptographic proof of task execution
order, policy enforcement decisions, and compliance state across
agent-to-agent communication.  By extending WIMSE Workload Identity
Tokens with execution context claims in JSON Web Token (JWT)
format, this specification enables regulated systems to maintain
structured audit trails that support compliance verification.
ECTs use a directed acyclic graph (DAG) structure to represent task
dependencies, record policy evaluation outcomes at each decision
point, and integrate with WIMSE Workload Identity Tokens (WIT) and
Workload Proof Tokens (WPT) using the same signing model and
cryptographic primitives.  A new HTTP header field,
Execution-Context, is defined for transporting ECTs alongside
existing WIMSE headers.  ECTs are a technical building block that
supports, but does not by itself constitute, compliance with
regulatory frameworks.

--- middle

# Introduction

## 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 prove
what was done, what policy was applied, or whether compliance
requirements were satisfied at each decision point.

Regulated environments increasingly deploy autonomous agents that
coordinate across organizational boundaries.  Multiple regulatory
frameworks motivate the need for structured execution records:

- The EU Artificial Intelligence Act {{EU-AI-ACT}} Article 12
  requires high-risk AI systems to be designed with capabilities
  enabling automatic recording of events ("logs") while the
  system is operating.

- The U.S. FDA 21 CFR Part 11 {{FDA-21CFR11}} requires
  computer-generated, timestamped audit trails that independently
  record the date, time, operator identity, and actions taken
  (Section 11.10(e)).

- The Markets in Financial Instruments Directive (MiFID II)
  {{MIFID-II}} requires firms to maintain records of transactions
  and orders that are sufficient to enable supervisory authorities
  to monitor compliance.

- The Digital Operational Resilience Act (DORA) {{DORA}} Article 12
  requires financial entities to have logging policies that record
  ICT activities and anomalies.

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, in what order, and what policy was evaluated.

As identified in {{I-D.ni-wimse-ai-agent-identity}}, call context
in agentic workflows must always be visible and preserved.  ECTs
provide a mechanism to address this requirement with cryptographic
assurances.

## 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, under Policy Y, producing Output Z."

2.  No standard mechanism exists to record policy evaluation
    outcomes at each decision point in a multi-agent workflow.

3.  No mechanism exists to cryptographically link compensation and
    rollback decisions to original actions.

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.

## Scope and Applicability

This document defines:

- The Execution Context Token (ECT) format ({{ect-format}})
- DAG structure for task dependency ordering ({{dag-validation}})
- Policy checkpoint recording ({{policy-claims}})
- Integration with the WIMSE identity framework
  ({{wimse-integration}})
- An HTTP header for ECT transport ({{http-header}})
- Audit ledger interface requirements ({{ledger-interface}})

The following are out of scope and are handled by WIMSE:

- Workload authentication and identity provisioning
- Key distribution and management
- Trust domain establishment and management
- Credential lifecycle management

## Relationship to Regulatory Compliance

ECTs are a technical mechanism that can support compliance programs
by providing structured, cryptographically signed execution
records.  ECTs do not by themselves constitute compliance with any
regulatory framework referenced in this document.

Compliance with each referenced regulation requires organizational
controls, policies, procedures, validation, and governance measures
beyond the scope of this specification.  The regulatory references
in this document are intended to motivate the design requirements,
not to claim that implementing ECTs satisfies these regulations.

ECTs provide evidence of claimed execution ordering and policy
evaluation.  They do not independently verify that the claimed
execution actually occurred as described, that the policy
evaluation was correct, or that 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.

# Conventions and Definitions

{::boilerplate bcp14-tagged}

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 and policy evaluation outcomes.

Audit Ledger:
: An append-only, immutable log of all ECTs within a workflow or
  set of workflows, used for regulatory audit and compliance
  verification.

Policy Checkpoint:
: A point in a workflow where a policy evaluation outcome is
  recorded within an ECT.

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.

Witness:
: A third-party entity that observes and attests to the execution
  of a task, providing additional accountability.

# WIMSE Architecture Integration {#wimse-integration}

## WIMSE Foundation

The WIMSE architecture {{I-D.ietf-wimse-arch}} defines:

- 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
- Recording policy evaluation outcomes at each hop
- Maintaining structured execution records
- Linking compensation or rollback actions to original tasks

## Extension Model

ECTs extend WIMSE by adding an execution accountability layer
between the identity layer and the application layer:

~~~ ascii-art
+--------------------------------------------------+
|  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,        |
|          policy evaluated, outcome recorded"      |
+--------------------------------------------------+
                       |
                       v
+--------------------------------------------------+
|  Ledger Layer (Immutable Record)                 |
|    "All ECTs appended to audit ledger"           |
+--------------------------------------------------+
~~~
{: #fig-layers title="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.

## Integration Points {#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.

- The ECT "iss" claim MUST use the WIMSE workload identifier
  format (a SPIFFE ID {{SPIFFE}}).

- The ECT MUST be signed with the same private key used to
  generate the agent's WPT.

- 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 three
tokens are carried in their respective HTTP header fields:

~~~ ascii-art
HTTP Request from Agent A to Agent B:
  Workload-Identity:    <WIT for Agent A>
  Workload-Proof-Token: <WPT proving A controls key>
  Execution-Context:    <ECT recording what A did>
~~~
{: #fig-http-headers title="HTTP Header Stacking"}

The receiving agent (Agent B) verifies in order:

1.  WIT and WPT (WIMSE layer): Proves who Agent A is and that the
    request is authentic.

2.  ECT (this extension): Records what Agent A did, what policy was
    evaluated, and what precedent tasks exist.

3.  Ledger: Appends the verified ECT to the audit ledger.

# Execution Context Token Format {#ect-format}

An Execution Context Token is a JSON Web Token (JWT) {{RFC7519}}
signed as a JSON Web Signature (JWS) {{RFC7515}} using the Compact
Serialization.  JWS JSON Serialization MUST NOT be used for ECTs.

## JOSE Header {#jose-header}

The ECT JOSE header MUST contain the following parameters:

~~~json
{
  "alg": "ES256",
  "typ": "wimse-exec+jwt",
  "kid": "agent-a-key-id-123"
}
~~~
{: #fig-header title="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.

## JWT Claims {#jwt-claims}

The ECT payload contains both WIMSE-compatible standard JWT claims
and execution context claims defined by this specification.

### WIMSE-Compatible Claims

The following standard JWT claims {{RFC7519}} MUST be present in
every ECT:

iss:
: REQUIRED.  StringOrURI.  The issuer of the ECT, which MUST be
  the workload's SPIFFE ID in the format
  `spiffe://<trust-domain>/<path>`.  This MUST match the "sub"
  claim of the agent's WIT.

sub:
: OPTIONAL.  StringOrURI.  The subject of the ECT.  When present,
  MUST equal the "iss" claim.

aud:
: REQUIRED.  StringOrURI or array of StringOrURI.  The intended
  recipient(s) of the ECT.  Typically the next agent in the
  workflow or the ledger endpoint.

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.

jti:
: OPTIONAL.  String.  A unique identifier for the ECT, useful for
  additional replay detection.

### Execution Context Claims {#exec-claims}

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}}.  When absent, the "tid" uniqueness requirement
  applies globally across the entire ledger.

tid:
: REQUIRED.  String.  A globally unique task identifier in UUID
  format {{RFC9562}}.  Each task MUST have a unique "tid" value.
  When "wid" is present, uniqueness is scoped to the workflow;
  when "wid" is absent, uniqueness MUST be enforced globally
  across the ledger.

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 a valid
  "tid" from a previously executed task.  An empty array indicates
  a root task with no dependencies.  A workflow MAY contain
  multiple root tasks.

### Policy Claims {#policy-claims}

The following claims record policy evaluation outcomes:

pol:
: REQUIRED.  String.  The identifier of the policy rule that was
  evaluated for this task (e.g.,
  "clinical_data_access_policy_v1").

pol_decision:
: REQUIRED.  String.  The result of the policy evaluation.  MUST
  be one of: "approved", "rejected", or "pending_human_review".

pol_enforcer:
: OPTIONAL.  StringOrURI.  The identity of the entity (system or
  person) that evaluated the policy decision.  When present,
  SHOULD use SPIFFE ID format.

pol_timestamp:
: OPTIONAL.  NumericDate.  The time at which the policy decision
  was made.  When present, MUST be equal to or earlier than the
  "iat" claim.

### Data Integrity Claims {#data-integrity-claims}

The following claims provide integrity verification for task
inputs and outputs without revealing the data itself:

inp_hash:
: OPTIONAL.  String.  A cryptographic hash of the input data,
  formatted as "hash-algorithm:base64url-encoded-hash" (e.g.,
  "sha-256:n4bQgYhMfWWaL-qgxVrQFaO\_TxsrC4Is0V1sFbDwCgg").  The
  hash algorithm identifier SHOULD be "sha-256".  The hash MUST be
  computed over the raw octets of the input data.

out_hash:
: OPTIONAL.  String.  A cryptographic hash of the output data,
  using the same format as "inp_hash".

inp_classification:
: OPTIONAL.  String.  The data sensitivity classification of the
  input (e.g., "public", "confidential", "restricted").

### Operational Claims {#operational-claims}

The following claims provide additional operational context:

exec_time_ms:
: OPTIONAL.  Integer.  The execution duration of the task in
  milliseconds.  MUST be a non-negative integer.

regulated_domain:
: OPTIONAL.  String.  The regulatory domain applicable to this
  task.  Values are drawn from an extensible set; initial values
  include "medtech", "finance", and "military".

model_version:
: OPTIONAL.  String.  The version identifier of the AI or ML model
  used to perform the task, if applicable.

### Witness Claims {#witness-claims}

witnessed_by:
: OPTIONAL.  Array of StringOrURI.  Identifiers of third-party
  entities that observed or attested to the execution of this
  task.  When present, each element SHOULD use SPIFFE ID format.
  In regulated environments, implementations SHOULD use witness
  attestation for critical decision points to mitigate the risk
  of single-agent false claims.

### Compensation Claims {#compensation-claims}

compensation_required:
: OPTIONAL.  Boolean.  Indicates whether this task is a
  compensation or rollback action for a previous task.

compensation_reason:
: OPTIONAL.  String.  A human-readable reason for the compensation
  action.  MUST be present if "compensation_required" is true.

Note: compensation ECTs reference historical parent tasks via the
"par" claim.  The referenced 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
ledger.

### Extension Claims {#extension-claims}

ext:
: OPTIONAL.  Object.  An extension object for domain-specific
  claims not defined by this specification.  Implementations
  that do not understand extension claims SHOULD ignore them.
  To avoid key collisions between different domains, extension
  key names SHOULD use reverse domain notation (e.g.,
  "com.example.custom_field").

The "ext" claim is a generic extension mechanism; it is not
registered in the IANA JWT Claims registry because its semantics
depend on the domain-specific claims within it.

## Complete ECT Example

The following is a complete ECT payload example:

~~~json
{
  "iss": "spiffe://example.com/agent/clinical",
  "sub": "spiffe://example.com/agent/clinical",
  "aud": "spiffe://example.com/agent/safety",
  "iat": 1772064150,
  "exp": 1772064750,

  "wid": "a0b1c2d3-e4f5-6789-abcd-ef0123456789",
  "tid": "550e8400-e29b-41d4-a716-446655440001",
  "exec_act": "recommend_treatment",
  "par": [],

  "pol": "clinical_reasoning_policy_v2",
  "pol_decision": "approved",
  "pol_enforcer": "spiffe://example.com/policy/clinical-engine",
  "pol_timestamp": 1772064145,

  "inp_hash": "sha-256:n4bQgYhMfWWaL-qgxVrQFaO_TxsrC4Is0V1sFbDwCgg",
  "out_hash": "sha-256:LCa0a2j_xo_5m0U8HTBBNBNCLXBkg7-g-YpeiGJm564",
  "inp_classification": "confidential",
  "exec_time_ms": 245,
  "regulated_domain": "medtech",
  "model_version": "clinical-reasoning-v4.2",

  "witnessed_by": [
    "spiffe://example.com/audit/observer-1"
  ]
}
~~~
{: #fig-full-ect title="Complete ECT Payload Example"}

# HTTP Header Transport {#http-header}

## 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
and Workload-Proof-Token headers:

~~~
GET /api/safety-check HTTP/1.1
Host: safety-agent.example.com
Workload-Identity: eyJhbGci...WIT...
Workload-Proof-Token: eyJhbGci...WPT...
Execution-Context: eyJhbGci...ECT...
~~~
{: #fig-http-example title="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.

# DAG Validation {#dag-validation}

## 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.

## Validation Rules

When receiving and verifying an ECT, implementations MUST perform
the following DAG validation steps:

1.  Task ID Uniqueness: The "tid" claim MUST be unique within the
    applicable scope (the workflow identified by "wid", or the
    entire ledger if "wid" is absent).  If a task with the same
    "tid" already exists, the ECT MUST be rejected.

2.  Parent Existence: Every task identifier listed in the "par"
    array MUST correspond to a task that has been previously
    recorded in the ledger.  If any parent task is not found, the
    ECT MUST be rejected.

3.  Temporal Ordering: The "iat" value of every parent task MUST be
    less than the "iat" value of the current task plus a
    configurable clock skew tolerance (RECOMMENDED: 30 seconds).
    If any parent task has an "iat" that violates this constraint,
    the ECT MUST be rejected.

4.  Acyclicity: Following the chain of parent references MUST NOT
    lead back to the current task's "tid".  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.

## DAG Validation Algorithm

The following pseudocode describes the DAG validation procedure:

~~~ pseudocode
function validate_dag(ect, ledger, clock_skew_tolerance):
  // Step 1: Uniqueness check
  if ledger.contains(ect.tid, ect.wid):
    return error("Task ID already exists in ledger")

  // Step 2: Parent existence and temporal ordering
  for parent_id in ect.par:
    parent = ledger.get(parent_id)
    if parent is null:
      return error("Parent task not found: " + parent_id)
    if parent.iat >= ect.iat + clock_skew_tolerance:
      return error("Parent task not earlier than current")

  // Step 3: Cycle detection
  visited = set()
  if has_cycle(ect.tid, ect.par, ledger, visited):
    return error("Circular dependency detected")

  return success

function has_cycle(target_tid, parent_ids, ledger, visited):
  for parent_id in parent_ids:
    if parent_id == target_tid:
      return true
    if parent_id in visited:
      continue
    visited.add(parent_id)
    parent = ledger.get(parent_id)
    if parent is not null:
      if has_cycle(target_tid, parent.par, ledger, visited):
        return true
  return false
~~~
{: #fig-dag-validation title="DAG Validation Pseudocode"}

The cycle detection traverses the ancestor graph rooted at the
current task's parents.  The complexity is O(V) where V is the
number of ancestor nodes reachable from the current task's parent
references.  For typical workflows with shallow DAGs, this is
efficient.  Implementations SHOULD cache cycle detection results
for previously verified tasks to avoid redundant traversals.

# Signature and Token Verification {#verification}

## 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 is not "none" and is
    not a symmetric algorithm.

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 the "alg" header parameter matches the algorithm in the
    corresponding WIT.

7.  Verify the "iss" claim matches the "sub" claim of the WIT
    associated with the "kid" public key.

8.  Verify the "aud" claim contains the verifier's own workload
    identity or an expected recipient identifier.

9.  Verify the "exp" claim indicates the ECT has not expired.

10. Verify the "iat" claim is not unreasonably far in the past
    (implementation-specific threshold, RECOMMENDED maximum of
    15 minutes).

11. Verify all required claims ("tid", "exec_act", "par", "pol",
    "pol_decision") are present and well-formed.

12. Verify "pol_decision" is one of "approved", "rejected", or
    "pending_human_review".

13. Perform DAG validation per {{dag-validation}}.

14. If all checks pass, the ECT MUST be appended to the audit
    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
ledger, to prevent information disclosure.

## Verification Pseudocode

~~~ pseudocode
function verify_ect(ect_jws, verifier_id,
                     trust_domain_keys, ledger):
  // Parse JWS
  (header, payload, signature) = parse_jws(ect_jws)

  // Verify header
  if header.typ != "wimse-exec+jwt":
    return reject("Invalid typ parameter")

  if header.alg == "none" or is_symmetric(header.alg):
    return reject("Prohibited algorithm")

  // Look up public key
  public_key = trust_domain_keys.get(header.kid)
  if public_key is null:
    return reject("Unknown key identifier")

  // Verify signature
  if not verify_jws_signature(header, payload,
                               signature, public_key):
    return reject("Invalid signature")

  // Verify algorithm alignment
  wit = get_wit_for_key(header.kid)
  if header.alg != wit.alg:
    return reject("Algorithm mismatch with WIT")

  // Verify issuer matches WIT subject
  if payload.iss != wit.sub:
    return reject("Issuer does not match WIT subject")

  // Verify audience
  if verifier_id not in payload.aud:
    return reject("ECT not intended for this recipient")

  // Verify not expired
  if payload.exp < current_time():
    return reject("ECT has expired")

  // Verify iat freshness
  if payload.iat < current_time() - max_age_threshold:
    return reject("ECT issued too long ago")

  // Verify required claims
  for claim in ["tid", "exec_act", "par",
                 "pol", "pol_decision"]:
    if claim not in payload:
      return reject("Missing required claim: " + claim)

  // Validate pol_decision value
  if payload.pol_decision not in
     ["approved", "rejected", "pending_human_review"]:
    return reject("Invalid pol_decision value")

  // Validate DAG
  result = validate_dag(payload, ledger,
                         clock_skew_tolerance)
  if result is error:
    return reject("DAG validation failed")

  // All checks passed; append to ledger
  ledger.append(payload)
  return accept
~~~
{: #fig-verification title="ECT Verification Pseudocode"}

# Audit Ledger Interface {#ledger-interface}

## Overview

ECTs are designed to be recorded in an immutable audit ledger for
compliance verification and post-hoc analysis.  This specification
defines the logical interface for the ledger but 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.

## Required Properties

An audit ledger 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 task ID: The ledger MUST support efficient retrieval
    of ECT entries by "tid" 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.

## Ledger Entry Structure

Each ledger entry is a logical record containing:

~~~json
{
  "ledger_sequence": 42,
  "task_id": "550e8400-e29b-41d4-a716-446655440001",
  "agent_id": "spiffe://example.com/agent/clinical",
  "action": "recommend_treatment",
  "parents": [],
  "ect_jws": "eyJhbGciOiJFUzI1NiIs...<complete JWS>",
  "signature_verified": true,
  "verification_timestamp": "2026-02-24T15:42:31.000Z",
  "stored_timestamp": "2026-02-24T15:42:31.050Z"
}
~~~
{: #fig-ledger-entry title="Ledger Entry Example"}

The "ect_jws" field contains the full JWS Compact Serialization
and is the authoritative record.  The other fields ("agent_id",
"action", "parents") are convenience indexes derived from the
ECT payload; if they disagree with the JWS payload, the JWS
payload takes precedence.

# Use Cases {#use-cases}

This section describes representative use cases demonstrating how
ECTs provide execution records in regulated environments.  These
examples demonstrate ECT mechanics; production deployments would
include additional domain-specific requirements beyond the scope
of this specification.

Note: task identifiers in this section are abbreviated for
readability.  In production, all "tid" values MUST be UUIDs per
{{RFC9562}}.

## Medical Device SDLC Workflow

In a medical device software development lifecycle (SDLC),
AI agents assist across multiple phases from requirements
analysis through release approval.  Regulatory frameworks
including {{FDA-21CFR11}} Section 11.10(e) and {{EU-MDR}} require
audit trails documenting the complete development process for
software used in medical devices.

~~~
Agent A (Spec Reviewer):
  tid: task-001    par: []
  exec_act: review_requirements_spec
  pol: spec_review_policy_v2     pol_decision: approved

Agent B (Code Generator):
  tid: task-002    par: [task-001]
  exec_act: implement_module
  pol: coding_standards_v3       pol_decision: approved

Agent C (Test Agent):
  tid: task-003    par: [task-002]
  exec_act: execute_test_suite
  pol: test_coverage_policy_v1   pol_decision: approved

Agent D (Build Agent):
  tid: task-004    par: [task-003]
  exec_act: build_release_artifact
  pol: build_validation_v2       pol_decision: approved

Human Release Manager:
  tid: task-005    par: [task-004]
  exec_act: approve_release
  pol: release_approval_policy   pol_decision: approved
  pol_enforcer: spiffe://meddev.example/human/release-mgr-42
  witnessed_by: [spiffe://meddev.example/audit/qa-observer-1]
~~~
{: #fig-medtech-sdlc title="Medical Device SDLC Workflow"}

ECTs record that requirements were reviewed before implementation
began, that tests were executed against the implemented code, that
the build artifact was validated, and that a human release manager
explicitly approved the release.  The DAG structure ensures no
phase was skipped or reordered.

### FDA Audit with DAG Reconstruction

During a regulatory audit, an FDA reviewer requests evidence of
the development process for a specific software release.  The
auditing authority retrieves all ECTs sharing the same workflow
identifier ("wid") from the audit ledger and reconstructs the
complete DAG:

~~~
task-001 (review_requirements_spec)
  |
  v
task-002 (implement_module)
  |
  v
task-003 (execute_test_suite)
  |
  v
task-004 (build_release_artifact)
  |
  v
task-005 (approve_release) [human, witnessed]
~~~
{: #fig-fda-audit title="Reconstructed DAG for FDA Audit"}

The reconstructed DAG provides cryptographic evidence that:

- Each phase was executed by an identified and authenticated agent.
- Policy checkpoints were evaluated at every phase transition.
- The execution sequence was maintained (no step was bypassed).
- A human-in-the-loop approved the final release, with independent
  witness attestation.
- Timestamps and execution durations are recorded for each step.

This can contribute to compliance with:

- {{FDA-21CFR11}} Section 11.10(e): Computer-generated audit trails
  that record the date, time, and identity of the operator.
- {{EU-MDR}} Annex II: Technical documentation traceability for the
  software development lifecycle.
- {{EU-AI-ACT}} Article 12: Automatic logging capabilities for
  high-risk AI systems involved in the development process.
- {{EU-AI-ACT}} Article 14: ECTs can record evidence that human
  oversight events occurred during the release process.

## Financial Trading Workflow

In a financial trading workflow, agents perform risk assessment,
compliance verification, and trade execution.  The DAG structure
records that compliance checks were evaluated before trade
execution.

~~~
Agent A (Risk Assessment):
  tid: task-001    par: []
  exec_act: calculate_risk_exposure
  pol: risk_limits_policy_v2  pol_decision: approved

Agent B (Compliance):
  tid: task-002    par: [task-001]
  exec_act: verify_compliance
  pol: compliance_check_v1    pol_decision: approved

Agent C (Execution):
  tid: task-003    par: [task-002]
  exec_act: execute_trade
  pol: execution_policy_v3    pol_decision: approved
~~~
{: #fig-finance title="Financial Trading Workflow"}

This can contribute to compliance with:

- {{MIFID-II}}: ECTs provide cryptographic records of the execution
  sequence that can support transaction audit requirements.
- {{DORA}} Article 12: ECTs contribute to ICT activity logging.
- {{EU-AI-ACT}} Article 12: Logging of decisions made by AI-driven
  systems.

## Compensation and Rollback

When a compliance violation is discovered after execution, ECTs
provide a mechanism to record authorized compensation actions with
a cryptographic link to the original task:

~~~json
{
  "iss": "spiffe://bank.com/agent/operations",
  "sub": "spiffe://bank.com/agent/operations",
  "aud": "spiffe://bank.com/system/ledger",
  "iat": 1772150550,
  "exp": 1772151150,
  "wid": "d3e4f5a6-b7c8-9012-def0-123456789012",
  "tid": "550e8400-e29b-41d4-a716-446655440099",
  "exec_act": "initiate_trade_rollback",
  "par": ["550e8400-e29b-41d4-a716-446655440003"],
  "pol": "compensation_policy_v1",
  "pol_decision": "approved",
  "pol_enforcer": "spiffe://bank.com/human/compliance-officer",
  "compensation_required": true,
  "compensation_reason": "policy_violation_in_parent_trade"
}
~~~
{: #fig-compensation title="Compensation ECT Example"}

The "par" claim links the compensation action to the original
trade, creating an auditable chain from execution through
violation discovery to remediation.

## Autonomous Logistics Coordination

In a logistics workflow, multiple compliance checks must complete
before shipment commitment.  The DAG structure records that all
required checks were completed:

~~~
Agent A (Route Planning):
  tid: task-001    par: []
  exec_act: plan_route
  pol: route_policy_v1        pol_decision: approved

Agent B (Customs):
  tid: task-002    par: [task-001]
  exec_act: validate_customs
  pol: customs_policy_v2      pol_decision: approved

Agent C (Safety):
  tid: task-003    par: [task-001]
  exec_act: verify_cargo_safety
  pol: safety_policy_v1       pol_decision: approved

Agent D (Payment):
  tid: task-004    par: [task-002, task-003]
  exec_act: authorize_payment
  pol: payment_policy_v3      pol_decision: approved

System (Commitment):
  tid: task-005    par: [task-004]
  exec_act: commit_shipment
  pol: commitment_policy_v1   pol_decision: approved
~~~
{: #fig-logistics title="Logistics Workflow with Parallel Tasks"}

Note that tasks 002 and 003 both depend only on task-001 and can
execute in parallel.  Task 004 depends on both, demonstrating the
DAG's ability to represent parallel execution with a join point.

# Security Considerations

This section addresses security considerations following the
guidance in {{RFC3552}}.

## 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.

## 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., setting "pol_decision" to "approved" without actually
evaluating the policy).

ECTs do not independently verify that:

- The claimed execution actually occurred as described
- The policy evaluation was correctly performed
- 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.  To mitigate single-agent false claims,
regulated environments SHOULD use the "witnessed_by" mechanism
to include independent third-party observers at critical decision
points.

## 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.
- Policy lifecycle management: Policy identifiers in ECTs map to
  actual, validated policy rules.
- Agent deployment governance: Agents are deployed and maintained
  in a manner that preserves their integrity.

## 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.

If signature verification fails, 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.

## 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.

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 SHOULD maintain a cache of recently-seen "jti"
values (when present) to detect replayed ECTs within the
expiration window.

## 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
  and under what policy.

## 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.

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.

## 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.
- Witness attestation: Using the "witnessed_by" claim to include
  independent third-party observers.
- 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.

## 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.

## 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).

The temporal ordering check in DAG validation incorporates the
clock skew tolerance to account for minor clock differences
between agents.

## 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 reasonable size and SHOULD set maximum size limits for
the "ext" object to prevent abuse.

# Privacy Considerations

## Data Exposure in ECTs

ECTs necessarily reveal:

- Agent identities ("iss", "aud") for accountability purposes
- Action descriptions ("exec_act") for audit trail completeness
- Policy evaluation outcomes ("pol", "pol_decision") for
  compliance verification
- 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)

## 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.
The "pol" claim SHOULD reference policy identifiers rather than
embedding policy content.

## Storage and Access Control

ECTs stored in audit ledgers SHOULD be access-controlled so that
only authorized auditors and regulators can read them.
Implementations SHOULD consider encryption at rest for ledger
storage containing sensitive regulatory data.

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.

## Regulatory Access

ECTs are designed for interpretation by qualified human auditors
and regulators.  ECTs provide structural records of execution
ordering and policy evaluation; they are not intended for public
disclosure.

# IANA Considerations

## 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

Applications that use this media type:
: Applications that implement regulated 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:
: Christian Nennemann, ietf@nennemann.de

Intended usage:
: COMMON

Restrictions on usage:
: none

Author:
: Christian Nennemann

Change controller:
: IETF

## HTTP Header Field Registration {#header-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, {{http-header}}

## JWT Claims Registration {#claims-registration}

This document requests registration of the following claims in
the "JSON Web Token Claims" registry maintained by IANA:

| Claim Name | Claim Description | Change Controller | Reference |
|:---:|:---|:---:|:---:|
| wid | Workflow Identifier | IETF | {{exec-claims}} |
| tid | Task Identifier | IETF | {{exec-claims}} |
| exec_act | Action/Task Type | IETF | {{exec-claims}} |
| par | Parent Task Identifiers | IETF | {{exec-claims}} |
| pol | Policy Rule Identifier | IETF | {{policy-claims}} |
| pol_decision | Policy Decision Result | IETF | {{policy-claims}} |
| pol_enforcer | Policy Enforcer Identity | IETF | {{policy-claims}} |
| pol_timestamp | Policy Decision Timestamp | IETF | {{policy-claims}} |
| inp_hash | Input Data Hash | IETF | {{data-integrity-claims}} |
| out_hash | Output Data Hash | IETF | {{data-integrity-claims}} |
| inp_classification | Input Data Classification | IETF | {{data-integrity-claims}} |
| exec_time_ms | Execution Time (ms) | IETF | {{operational-claims}} |
| witnessed_by | Witness Identities | IETF | {{witness-claims}} |
| regulated_domain | Regulatory Domain | IETF | {{operational-claims}} |
| model_version | AI/ML Model Version | IETF | {{operational-claims}} |
| compensation_required | Compensation Flag | IETF | {{compensation-claims}} |
| compensation_reason | Compensation Reason | IETF | {{compensation-claims}} |
{: #table-claims title="JWT Claims Registrations"}

--- back

# Related Work
{:numbered="false"}

## WIMSE Workload Identity
{:numbered="false"}

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?" and "what policy was
evaluated?"  Together they form an identity-plus-accountability
framework for regulated agentic systems.

## OAuth 2.0 Token Exchange
{:numbered="false"}

{{RFC8693}} defines the OAuth 2.0 Token Exchange protocol and
registers the "act" (Actor) claim in the JWT Claims registry.
ECTs intentionally use the distinct claim name "exec_act" for the
action/task type to avoid collision with the "act" claim.
Transaction tokens in OAuth establish API authorization context;
ECTs serve the complementary purpose of recording execution
accountability across multi-step workflows.

## Distributed Tracing (OpenTelemetry)
{:numbered="false"}

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.

## Blockchain and Distributed Ledgers
{:numbered="false"}

Both ECTs and blockchain systems provide immutable records.  This
specification intentionally defines only the ECT token format and
is agnostic to the storage mechanism.  ECTs can be stored in
append-only logs, databases with cryptographic commitments,
blockchain networks, or any storage providing the required
properties defined in {{ledger-interface}}.

## SCITT (Supply Chain Integrity, Transparency, and Trust)
{:numbered="false"}

The SCITT architecture {{I-D.ietf-scitt-architecture}} defines a
framework for creating transparent and auditable supply chain
records through Transparency Services, Signed Statements, and
Receipts.  ECTs and SCITT are naturally complementary: the ECT
"wid" (Workflow Identifier) claim can serve as a correlation
identifier referenced in SCITT Signed Statements, linking a
complete ECT audit trail to a supply chain transparency record.
For example, in a regulated manufacturing workflow, each agent
step produces an ECT (recording what was done, by whom, under
what policy), while the overall workflow identified by "wid" is
registered as a SCITT Signed Statement on a Transparency Service.
This enables auditors to verify both the individual execution
steps (via ECT DAG validation) and the end-to-end supply chain
integrity (via SCITT Receipts) using the "wid" as the shared
correlation point.  The "ext" claim in ECTs ({{exec-claims}})
can carry SCITT-specific metadata such as Transparency Service
identifiers or Receipt references for tighter integration.

## W3C Verifiable Credentials
{:numbered="false"}

W3C Verifiable Credentials represent claims about subjects (e.g.,
identity, qualifications).  ECTs represent execution records of
actions (what happened, in what order, under what policy).  While
both use JWT/JWS as a serialization format, their semantics and
use cases are distinct.

# Implementation Guidance
{:numbered="false"}

## Minimal Implementation
{:numbered="false"}

A minimal conforming implementation should:

1.  Create JWTs with all required claims ("iss", "aud", "iat",
    "exp", "tid", "exec_act", "par", "pol", "pol_decision").
2.  Sign ECTs with the agent's private key using an algorithm
    matching the WIT (ES256 recommended).
3.  Verify ECT signatures against WIT public keys.
4.  Perform DAG validation (parent existence, temporal ordering,
    cycle detection).
5.  Append verified ECTs to an audit ledger.

## Storage Recommendations
{:numbered="false"}

- Append-only log: Simplest approach; immutability by design.
- Database with hash chains: Periodic cryptographic commitments
  over batches of entries.
- Distributed ledger: Maximum immutability guarantees for
  cross-organizational audit.
- Hybrid: Hot storage in a database, cold archive in immutable
  storage.

## Performance Considerations
{:numbered="false"}

- ES256 signature verification: approximately 1ms per ECT on
  modern hardware.
- DAG validation: O(V) where V is the number of reachable ancestor
  nodes (typically small for shallow workflows).
- JSON serialization: sub-millisecond per ECT.
- Total per-request overhead: approximately 5-10ms, acceptable
  for regulated workflows where correctness is prioritized over
  latency.

## Interoperability
{:numbered="false"}

Implementations should use established JWT/JWS libraries (JOSE)
for token creation and verification.  Custom cryptographic
implementations should not be used.  Implementations should be
tested against multiple JWT libraries to ensure interoperability.

# Regulatory Compliance Mapping
{:numbered="false"}

The following table summarizes how ECTs can contribute to
compliance with various regulatory frameworks.  ECTs are a
technical building block; achieving compliance requires
additional organizational measures beyond this specification.

| Regulation | Requirement | ECT Contribution |
|:---|:---|:---|
| FDA 21 CFR Part 11 | Audit trails recording date, time, operator, actions (11.10(e)) | Cryptographic signatures and append-only ledger contribute to audit trail requirements |
| EU MDR | Technical documentation traceability (Annex II) | ECTs provide signed records of AI-assisted decision sequences |
| EU AI Act Art. 12 | Automatic logging capabilities for high-risk AI | ECTs contribute cryptographic activity logging |
| EU AI Act Art. 14 | Human oversight capability | ECTs can record evidence that human oversight events occurred |
| MiFID II | Transaction records for supervisory authorities | ECTs provide cryptographic execution sequence records |
| DORA Art. 12 | ICT activity logging policies | ECT ledger contributes to ICT activity audit trail |
{: #table-regulatory title="Regulatory Compliance Mapping"}

# Examples
{:numbered="false"}

## Example 1: Simple Two-Agent Workflow
{:numbered="false"}

Agent A executes a data retrieval task and sends the ECT to
Agent B:

ECT JOSE Header:

~~~json
{
  "alg": "ES256",
  "typ": "wimse-exec+jwt",
  "kid": "agent-a-key-2026-02"
}
~~~

ECT Payload:

~~~json
{
  "iss": "spiffe://example.com/agent/data-retrieval",
  "sub": "spiffe://example.com/agent/data-retrieval",
  "aud": "spiffe://example.com/agent/validator",
  "iat": 1772064150,
  "exp": 1772064750,
  "wid": "b1c2d3e4-f5a6-7890-bcde-f01234567890",
  "tid": "550e8400-e29b-41d4-a716-446655440001",
  "exec_act": "fetch_patient_data",
  "par": [],
  "pol": "clinical_data_access_policy_v1",
  "pol_decision": "approved",
  "inp_hash": "sha-256:n4bQgYhMfWWaL-qgxVrQFaO_TxsrC4Is0V1sFbDwCgg",
  "out_hash": "sha-256:LCa0a2j_xo_5m0U8HTBBNBNCLXBkg7-g-YpeiGJm564",
  "exec_time_ms": 142,
  "regulated_domain": "medtech"
}
~~~

Agent B receives the ECT, verifies it, executes a validation
task, and creates its own ECT:

~~~json
{
  "iss": "spiffe://example.com/agent/validator",
  "sub": "spiffe://example.com/agent/validator",
  "aud": "spiffe://example.com/system/ledger",
  "iat": 1772064160,
  "exp": 1772064760,
  "wid": "b1c2d3e4-f5a6-7890-bcde-f01234567890",
  "tid": "550e8400-e29b-41d4-a716-446655440002",
  "exec_act": "validate_safety",
  "par": ["550e8400-e29b-41d4-a716-446655440001"],
  "pol": "safety_validation_policy_v2",
  "pol_decision": "approved",
  "exec_time_ms": 89,
  "regulated_domain": "medtech"
}
~~~

The resulting DAG:

~~~
task-...-0001 (fetch_patient_data)
  |
  v
task-...-0002 (validate_safety)
~~~

## Example 2: Medical Device SDLC with Release Approval
{:numbered="false"}

A multi-step medical device software lifecycle workflow with
autonomous agents and human release approval:

Task 1 (Spec Review Agent):

~~~json
{
  "iss": "spiffe://meddev.example/agent/spec-reviewer",
  "sub": "spiffe://meddev.example/agent/spec-reviewer",
  "aud": "spiffe://meddev.example/agent/code-gen",
  "iat": 1772064150,
  "exp": 1772064750,
  "wid": "c2d3e4f5-a6b7-8901-cdef-012345678901",
  "tid": "a1b2c3d4-0001-0000-0000-000000000001",
  "exec_act": "review_requirements_spec",
  "par": [],
  "pol": "spec_review_policy_v2",
  "pol_decision": "approved",
  "regulated_domain": "medtech",
  "model_version": "spec-review-v3.1",
  "inp_hash": "sha-256:n4bQgYhMfWWaL-qgxVrQFaO_TxsrC4Is0V1sFbDwCgg",
  "out_hash": "sha-256:LCa0a2j_xo_5m0U8HTBBNBNCLXBkg7-g-YpeiGJm564"
}
~~~

Task 2 (Code Generation Agent):

~~~json
{
  "iss": "spiffe://meddev.example/agent/code-gen",
  "sub": "spiffe://meddev.example/agent/code-gen",
  "aud": "spiffe://meddev.example/agent/test-runner",
  "iat": 1772064200,
  "exp": 1772064800,
  "wid": "c2d3e4f5-a6b7-8901-cdef-012345678901",
  "tid": "a1b2c3d4-0001-0000-0000-000000000002",
  "exec_act": "implement_module",
  "par": ["a1b2c3d4-0001-0000-0000-000000000001"],
  "pol": "coding_standards_v3",
  "pol_decision": "approved",
  "regulated_domain": "medtech",
  "model_version": "codegen-v2.4"
}
~~~

Task 3 (Autonomous Test Agent):

~~~json
{
  "iss": "spiffe://meddev.example/agent/test-runner",
  "sub": "spiffe://meddev.example/agent/test-runner",
  "aud": "spiffe://meddev.example/agent/build",
  "iat": 1772064260,
  "exp": 1772064860,
  "wid": "c2d3e4f5-a6b7-8901-cdef-012345678901",
  "tid": "a1b2c3d4-0001-0000-0000-000000000003",
  "exec_act": "execute_test_suite",
  "par": ["a1b2c3d4-0001-0000-0000-000000000002"],
  "pol": "test_coverage_policy_v1",
  "pol_decision": "approved",
  "regulated_domain": "medtech",
  "exec_time_ms": 4523
}
~~~

Task 4 (Build Agent):

~~~json
{
  "iss": "spiffe://meddev.example/agent/build",
  "sub": "spiffe://meddev.example/agent/build",
  "aud": "spiffe://meddev.example/human/release-mgr-42",
  "iat": 1772064310,
  "exp": 1772064910,
  "wid": "c2d3e4f5-a6b7-8901-cdef-012345678901",
  "tid": "a1b2c3d4-0001-0000-0000-000000000004",
  "exec_act": "build_release_artifact",
  "par": ["a1b2c3d4-0001-0000-0000-000000000003"],
  "pol": "build_validation_v2",
  "pol_decision": "approved",
  "regulated_domain": "medtech",
  "out_hash": "sha-256:Ry1YfOoW2XpC5Mq8HkGzNx3dL9vBa4sUjE7iKt0wPZc"
}
~~~

Task 5 (Human Release Manager Approval):

~~~json
{
  "iss": "spiffe://meddev.example/human/release-mgr-42",
  "sub": "spiffe://meddev.example/human/release-mgr-42",
  "aud": "spiffe://meddev.example/system/ledger",
  "iat": 1772064510,
  "exp": 1772065110,
  "wid": "c2d3e4f5-a6b7-8901-cdef-012345678901",
  "tid": "a1b2c3d4-0001-0000-0000-000000000005",
  "exec_act": "approve_release",
  "par": ["a1b2c3d4-0001-0000-0000-000000000004"],
  "pol": "release_approval_policy",
  "pol_decision": "approved",
  "pol_enforcer": "spiffe://meddev.example/human/release-mgr-42",
  "witnessed_by": [
    "spiffe://meddev.example/audit/qa-observer-1"
  ],
  "regulated_domain": "medtech"
}
~~~

The resulting DAG records the complete SDLC: spec review preceded
implementation, implementation preceded testing, testing preceded
build, and a human release manager approved the final release
with independent witness attestation.

~~~
task-...-0001 (review_requirements_spec)
  |
  v
task-...-0002 (implement_module)
  |
  v
task-...-0003 (execute_test_suite)
  |
  v
task-...-0004 (build_release_artifact)
  |
  v
task-...-0005 (approve_release) [human, witnessed]
~~~

An FDA auditor reconstructs this DAG by querying the audit ledger
for all ECTs with wid "c2d3e4f5-a6b7-8901-cdef-012345678901" and
verifying each signature.  The DAG provides cryptographic evidence
that the SDLC followed the prescribed process with human oversight
at the release gate.

## Example 3: Parallel Execution with Join
{:numbered="false"}

A workflow where two tasks execute in parallel and a third task
depends on both:

~~~
task-...-0001 (assess_risk)
  |            \
  v             v
task-...-0002  task-...-0003
(check         (verify
compliance)    liquidity)
  |            /
  v           v
task-...-0004 (execute_trade)
~~~

Task 004 ECT payload:

~~~json
{
  "iss": "spiffe://bank.example/agent/execution",
  "sub": "spiffe://bank.example/agent/execution",
  "aud": "spiffe://bank.example/system/ledger",
  "iat": 1772064250,
  "exp": 1772064850,
  "wid": "d3e4f5a6-b7c8-9012-def0-123456789012",
  "tid": "f1e2d3c4-0004-0000-0000-000000000004",
  "exec_act": "execute_trade",
  "par": [
    "f1e2d3c4-0002-0000-0000-000000000002",
    "f1e2d3c4-0003-0000-0000-000000000003"
  ],
  "pol": "trade_execution_policy_v3",
  "pol_decision": "approved",
  "regulated_domain": "finance"
}
~~~

The "par" array with two entries records that both compliance
checking and liquidity verification were completed before trade
execution.

# Acknowledgments
{:numbered="false"}

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.