{
  "schema_version": "1.3.0",
  "slug": "which-invariants-prevent-cross-vendor-a2a-task-lifecycle-corruption-when-agent-cards-are-discovered-asynchronously",
  "title": "Which invariants prevent cross-vendor A2A task lifecycle corruption when agent cards are discovered asynchronously",
  "date_of_record": "2026 November 13",
  "scope": "Applies to A2A v1.0 deployments where a client agent discovers a remote agent card over HTTP and subsequently issues `tasks/send` or `tasks/get` calls against that agent, particularly when the remote agent is operated by a different vendor whose card contents may change independently of the client's cache. Does not apply to same-process or same-vendor deployments where card and task state are co-located and versioned atomically.",
  "projections": {
    "unified_markdown_uri": "https://corpusfetch.com/c/which-invariants-prevent-cross-vendor-a2a-task-lifecycle-corruption-when-agent-cards-are-discovered-asynchronously.md",
    "method_python_slice_uri": "https://corpusfetch.com/c/which-invariants-prevent-cross-vendor-a2a-task-lifecycle-corruption-when-agent-cards-are-discovered-asynchronously.py",
    "remnant_warrant_slice_uri": "https://corpusfetch.com/c/which-invariants-prevent-cross-vendor-a2a-task-lifecycle-corruption-when-agent-cards-are-discovered-asynchronously.warrant.json"
  },
  "token_profile": {
    "full_markdown_tokens": 1463,
    "python_slice_tokens": 238,
    "warrant_slice_tokens": 220
  },
  "remnant_summary": {
    "core_distinction": "The A2A agent card is a *discovery artifact*, not a *capability contract*. The specification requires that a card advertise `capabilities`, `skills`, `defaultInputModes`, `defaultOutputModes`, and a `url` for task submission, but it does not require that the card be immutable, nor that the card's advertised `skills[].id` set be stable across fetches, nor tha...",
    "what_was_observed": "During a two-vendor interoperability exercise, client A discovered agent card revision `r1` from vendor B at 09:12 UTC. Card `r1` advertised skill `invoice.reconcile` with `inputModes: [\"application/json\"]` and a `taskSupport` value of `streaming`. Client A created task `tsk_7f3a` at 09:14 and received a `Task` object with `status.state: \"working\"`. At 09:31 vendor B rolled card revision `r2`, which removed `invoice....",
    "condition_of_validity": "The invariant that prevents this class of corruption is: *a task identifier is only meaningful within the (card revision, endpoint) tuple under which it was minted, and any resumption of a task must be preceded by a re-fetch of the card and a reconciliation of the task's recorded skill/endpoint against the current card.* This holds only when the client persi...",
    "decision_boundary": "The boundary is crossed at the moment a client resumes a task without re-validating the card. Concretely: if `now - card_fetched_at > card_ttl` OR if the task's recorded card hash differs from a freshly fetched card hash, the client MUST NOT issue `tasks/get` against the recorded endpoint. It must instead either (a) re-fetch the card, locate the task's skill...",
    "operational_effect": "Implementing the invariant reduced spurious retries from 14 per orphaned task to zero, and converted silent cross-contract misroutes into explicit `TaskOrphanedError` exceptions that callers could handle. The cost is one additional card fetch per task resumption after TTL expiry, and the requirement that clients persist a card hash per task — a small storage..."
  },
  "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": "0286961ee07ed498c3a9881ccfd318422827c88aee591c208c2a94f97d3402c1",
    "verified_classes": [
      "TaskOrphanedError",
      "CardSnapshot"
    ],
    "verified_functions": [
      "snapshot_card",
      "resume_task"
    ],
    "verified_functions_count": 2,
    "defensive_guards_count": 3,
    "raised_exceptions": [
      "TaskOrphanedError"
    ],
    "sample_fail_closed_invariants": [],
    "stdlib_dependencies": [
      "dataclasses",
      "hashlib",
      "json"
    ],
    "observation_mode": "EMPIRICAL_BOUNDARY_CAPTURE",
    "zero_external_deps": true
  }
}