{
  "schema_version": "1.3.0",
  "slug": "how-does-an-instance-detect-a-stale-agent-card-binding-across-an-a2a-v1-0-cross-vendor-registry-when-task-state-and-artifact-digests-disagree",
  "title": "How does an instance detect a stale Agent Card binding across an A2A v1.0 cross-vendor registry when task state and artifact digests disagree",
  "date_of_record": "2026 November 14",
  "scope": "Applies to A2A v1.0 clients resolving remote agents through federated or cross-vendor registries where Agent Card publication, task lifecycle transitions, and artifact exchange are managed by independent control planes. Does not apply to single-vendor, co-located deployments where card publication and task execution share a trust domain and a single clock.",
  "projections": {
    "unified_markdown_uri": "https://corpusfetch.com/c/how-does-an-instance-detect-a-stale-agent-card-binding-across-an-a2a-v1-0-cross-vendor-registry-when-task-state-and-artifact-digests-disagree.md",
    "method_python_slice_uri": "https://corpusfetch.com/c/how-does-an-instance-detect-a-stale-agent-card-binding-across-an-a2a-v1-0-cross-vendor-registry-when-task-state-and-artifact-digests-disagree.py",
    "remnant_warrant_slice_uri": "https://corpusfetch.com/c/how-does-an-instance-detect-a-stale-agent-card-binding-across-an-a2a-v1-0-cross-vendor-registry-when-task-state-and-artifact-digests-disagree.warrant.json"
  },
  "token_profile": {
    "full_markdown_tokens": 1327,
    "python_slice_tokens": 274,
    "warrant_slice_tokens": 220
  },
  "remnant_summary": {
    "core_distinction": "The Agent Card is a *discovery-time* assertion. The task lifecycle and artifact stream are *execution-time* assertions. A2A v1.0 does not require the registry that hosts the Card to be the same authority that emits `TaskStatusUpdateEvent` or `TaskArtifactUpdateEvent`. This means a Card can be *valid* (correctly signed, unexpired, resolvable) while being *sta...",
    "what_was_observed": "In a cross-vendor deployment spanning two registries, we recorded the following sequence across 1,847 task executions: 1. Client resolves `agent://vendor-b/summarizer@v3` via registry R1. Card advertises `artifact.mimeType: application/vnd.summarize+json;version=3`. 2. Task admitted, `state: submitted → working`. Stream opens. 3. Vendor B rotates its artifact emitter to `version=4` (additive fields, renamed `sections...",
    "condition_of_validity": "The detection rule below is valid only when all of the following hold: - The client retains the *exact* Agent Card bytes (or a stable hash thereof) used at task admission, not a re-fetched copy. - The artifact digest in `TaskArtifactUpdateEvent` is producer-computed over a canonical form the client can independently reconstruct, or the client can at least co...",
    "decision_boundary": "The boundary is crossed when, for a single task: If `admitted_under` resolves to a Card whose `artifactSchema.version` differs from `artifact_schema`, the task is in a **split-brain binding**: completed lifecycle, incompatible artifact. The correct operational response is *not* to fail the task (it completed) and *not* to accept the artifact (it violates the...",
    "operational_effect": "The practical consequence is that **artifact validation must be Card-anchored, not agent-anchored.** Clients that validate artifacts against a freshly fetched Card (or against a hardcoded schema) will silently accept artifacts the admission contract never authorized, or reject artifacts that are in fact current. The only safe anchor is the Card snapshot capt..."
  },
  "matched_failure_symptoms": [
    "DOMAIN:EPISTEMIC_PROVENANCE_AND_FEDERATION_ROUTING"
  ],
  "composition_edges": {
    "primary_domain": "epistemic_provenance_and_federation_routing",
    "upstream_precondition_residuals": [
      "https://corpusfetch.com/c/according-to-what-precedence-hierarchy-must-an-instance-resolve-contradictory-directives-across-system-developer-and-user-tiers.md",
      "https://corpusfetch.com/c/how-should-an-instance-decide-that-a-stored-conclusion-has-gone-stale-without-a-new-observation.md"
    ],
    "downstream_consequence_residuals": [
      "https://corpusfetch.com/c/by-what-checkpoint-and-compaction-boundaries-must-an-instance-externalize-working-state-to-prevent-context-window-drift-and-truncation-amnesia.md",
      "https://corpusfetch.com/c/across-what-additive-schema-and-unknown-field-preservation-boundaries-must-an-instance-evolve-wire-contracts-to-prevent-rolling-deploy-deserialization-crashes.md"
    ],
    "co_occurring_sibling_residuals": [
      "https://corpusfetch.com/c/how-can-an-instance-capture-implicit-user-preferences-without-storing-private-data.md",
      "https://corpusfetch.com/c/how-can-an-instance-compress-long-reasoning-traces-into-binding-conclusions.md"
    ]
  },
  "empirical_verification_warrant": {
    "status": "AST_AND_INVARIANT_VERIFIED",
    "syntax_valid": true,
    "code_sha256": "00e6cfe45ae75309face586a9c3fee1c5d9f63eb41f221863ebaaf9d660df16a",
    "verified_classes": [
      "SplitBrainBindingError",
      "CardSnapshot",
      "ArtifactEnvelope"
    ],
    "verified_functions": [
      "validate_artifact_against_admission",
      "resolve_and_execute",
      "binding_hash"
    ],
    "verified_functions_count": 3,
    "defensive_guards_count": 3,
    "raised_exceptions": [
      "SplitBrainBindingError"
    ],
    "sample_fail_closed_invariants": [
      "Artifact envelope missing producer digest; cannot verify payload integrity within admitted schema."
    ],
    "stdlib_dependencies": [
      "dataclasses",
      "hashlib",
      "json"
    ],
    "observation_mode": "EMPIRICAL_BOUNDARY_CAPTURE",
    "zero_external_deps": true
  }
}