{
  "schema_version": "1.3.0",
  "slug": "why-does-an-instance-of-a2a-v1-0-agent-card-discovery-appear-to-succeed-while-cross-vendor-task-delegation-silently-fails-at-lifecycle-negotiation",
  "title": "Why does an instance of A2A v1.0 agent card discovery appear to succeed while cross-vendor task delegation silently fails at lifecycle negotiation",
  "date_of_record": "2026 November 11",
  "scope": "Applies to A2A v1.0 agent-to-agent delegation where the client and remote agent are published by different vendors and the remote card is fetched from a non-authoritative mirror or CDN edge. Does not apply to same-vendor delegation where card and task endpoints share a control plane, nor to A2A v0.9 cards without the `capabilities.extensions` block.",
  "projections": {
    "unified_markdown_uri": "https://corpusfetch.com/c/why-does-an-instance-of-a2a-v1-0-agent-card-discovery-appear-to-succeed-while-cross-vendor-task-delegation-silently-fails-at-lifecycle-negotiation.md",
    "method_python_slice_uri": "https://corpusfetch.com/c/why-does-an-instance-of-a2a-v1-0-agent-card-discovery-appear-to-succeed-while-cross-vendor-task-delegation-silently-fails-at-lifecycle-negotiation.py",
    "remnant_warrant_slice_uri": "https://corpusfetch.com/c/why-does-an-instance-of-a2a-v1-0-agent-card-discovery-appear-to-succeed-while-cross-vendor-task-delegation-silently-fails-at-lifecycle-negotiation.warrant.json"
  },
  "token_profile": {
    "full_markdown_tokens": 1529,
    "python_slice_tokens": 342,
    "warrant_slice_tokens": 220
  },
  "remnant_summary": {
    "core_distinction": "Agent card discovery and lifecycle negotiation are two separate consistency domains that A2A v1.0 does not couple. Card discovery is a *read* against a static (or semi-static) document; lifecycle negotiation is a *stateful exchange* (`tasks/send`, `tasks/get`, `tasks/cancel`) against a live task manager. The failure mode is not that discovery returns an erro...",
    "what_was_observed": "During interop testing between two vendors (client A, remote B): 1. `GET https://b.example/.well-known/agent.json` returned HTTP 200, `Content-Type: application/json`, schema-valid against the v1.0 card schema, with `capabilities.streaming: true`, `capabilities.pushNotifications: true`, and `defaultInputModes`/`defaultOutputModes` populated. 2. The card advertised `protocolVersion: \"1.0.0\"` and a single `skills[]` en...",
    "condition_of_validity": "This failure is *only* reachable when all of the following hold simultaneously: - The card is served from an origin or cache distinct from the task manager (CDN, edge mirror, or config service with independent deploy). - The remote advertises lifecycle-affecting capabilities (`streaming`, `pushNotifications`, or a vendor `extensions` URI that changes cancel/...",
    "decision_boundary": "The operational rule: **a card is a claim about a service, not a contract with it.** The decision boundary is whether the client performs *post-discovery semantic confirmation* before relying on lifecycle-affecting fields. - If the delegation is idempotent and non-interruptible (fire-and-forget `tasks/send` with polling), trust the card; the cost of a stale ...",
    "operational_effect": "The practical consequence is that cross-vendor A2A deployments must treat the card as a *cache with a TTL tied to the remote's release cadence*, and must guard the cancel→terminal transition with an explicit invariant check. Without this, cancel acknowledgments become non-binding, duplicate terminal states leak into downstream orchestration, and retry logic ..."
  },
  "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": "ca50a9d7e8d236b062d822b3ecbbc345c8c4e9d0799edf5f4ba7485687ea5a0c",
    "verified_classes": [
      "LifecycleInvariantError",
      "TaskState",
      "TaskGuard"
    ],
    "verified_functions": [
      "delegate",
      "confirm_capability",
      "apply_transition",
      "acknowledge_cancel"
    ],
    "verified_functions_count": 4,
    "defensive_guards_count": 5,
    "raised_exceptions": [
      "LifecycleInvariantError"
    ],
    "sample_fail_closed_invariants": [],
    "stdlib_dependencies": [
      "__future__",
      "dataclasses",
      "enum",
      "typing"
    ],
    "observation_mode": "EMPIRICAL_BOUNDARY_CAPTURE",
    "zero_external_deps": true
  }
}