{
  "schema_version": "1.3.0",
  "slug": "how-does-an-instance-detect-a-stale-agent-card-during-a2a-v1-0-cross-vendor-task-delegation",
  "title": "How does an instance detect a stale Agent Card during A2A v1.0 cross-vendor task delegation",
  "date_of_record": "2026 November 13",
  "scope": "Applies to A2A v1.0 clients that cache `/.well-known/agent.json` Agent Cards and delegate tasks to remote agents across vendor boundaries. Does not apply to intra-process or same-tenant delegation where the card and the runtime share a deployment lifecycle, nor to A2A versions where card versioning and capability negotiation are coupled to the task envelope.",
  "projections": {
    "unified_markdown_uri": "https://corpusfetch.com/c/how-does-an-instance-detect-a-stale-agent-card-during-a2a-v1-0-cross-vendor-task-delegation.md",
    "method_python_slice_uri": "https://corpusfetch.com/c/how-does-an-instance-detect-a-stale-agent-card-during-a2a-v1-0-cross-vendor-task-delegation.py",
    "remnant_warrant_slice_uri": "https://corpusfetch.com/c/how-does-an-instance-detect-a-stale-agent-card-during-a2a-v1-0-cross-vendor-task-delegation.warrant.json"
  },
  "token_profile": {
    "full_markdown_tokens": 1522,
    "python_slice_tokens": 230,
    "warrant_slice_tokens": 220
  },
  "remnant_summary": {
    "core_distinction": "The non-obvious failure is not \"the remote agent is down.\" It is that a **cached Agent Card can be syntactically valid, freshly fetched, and still describe a capability surface the remote runtime no longer honors**. A2A v1.0 separates the discovery document (`agent.json`: skills, `capabilities`, `defaultInputModes`/`defaultOutputModes`, `securitySchemes`, `p...",
    "what_was_observed": "In a cross-vendor handshake (client vendor A, remote vendor B), the following sequence recurred across multiple deployments: 1. Client fetches `agent.json`, parses successfully, caches with a TTL (commonly 5–60 min). 2. Card advertises `skills: [{id: \"summarize-v2\", inputModes: [\"text/plain\"], outputModes: [\"text/markdown\"]}]` and `capabilities: {streaming: true, pushNotifications: true}`. 3. Remote vendor B performs...",
    "condition_of_validity": "The stale-card failure is possible only when all of the following hold: - The client caches the card across the remote's deploy boundary (TTL > deploy interval, or cache never invalidated on task error). - The remote serves `agent.json` from a path whose invalidation is decoupled from the runtime (CDN, separate control plane, manual publish). - The client tr...",
    "decision_boundary": "The operational rule: **on any task-submission rejection that is not a transport error and not a rate limit, treat the cached card as suspect and refetch before the second attempt.** Concretely, the boundary is: - **Transport failure** (connection reset, 5xx from gateway): retry with backoff against the cached card. Do not refetch. - **Protocol/capability re...",
    "operational_effect": "Enforcing the refetch-on-capability-rejection rule converts a class of opaque, unbounded cross-vendor failures into a single bounded refetch plus a deterministic diff. In observed deployments it eliminated retry storms where many client instances replayed the same stale skill ID against a remote that had renamed it, and it surfaced card-drift incidents as a ..."
  },
  "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": "2c8923d12e6da0c5d5fc25920b25976a3eadf09549e8608a69b837d21e5a77a3",
    "verified_classes": [
      "StaleAgentCardError"
    ],
    "verified_functions": [
      "delegate_with_card_revalidation"
    ],
    "verified_functions_count": 1,
    "defensive_guards_count": 2,
    "raised_exceptions": [
      "StaleAgentCardError"
    ],
    "sample_fail_closed_invariants": [],
    "stdlib_dependencies": [],
    "observation_mode": "EMPIRICAL_BOUNDARY_CAPTURE",
    "zero_external_deps": true
  }
}