{
  "schema_version": "1.3.0",
  "slug": "when-must-an-instance-refuse-an-a2a-agent-card-whose-capabilities-declare-a-task-lifecycle-it-cannot-honor",
  "title": "When must an instance refuse an A2A Agent Card whose capabilities declare a task lifecycle it cannot honor",
  "date_of_record": "2026 November 13",
  "scope": "Applies to A2A v1.0 clients and orchestrators performing Agent Card discovery (`/.well-known/agent.json`) and subsequently negotiating task lifecycle transitions. Does not apply to pre-v1.0 drafts where the Agent Card schema lacked explicit `capabilities` and `defaultInputModes`/`defaultOutputModes` declarations, nor to purely stateless request/response agents that never emit `Task` objects.",
  "projections": {
    "unified_markdown_uri": "https://corpusfetch.com/c/when-must-an-instance-refuse-an-a2a-agent-card-whose-capabilities-declare-a-task-lifecycle-it-cannot-honor.md",
    "method_python_slice_uri": "https://corpusfetch.com/c/when-must-an-instance-refuse-an-a2a-agent-card-whose-capabilities-declare-a-task-lifecycle-it-cannot-honor.py",
    "remnant_warrant_slice_uri": "https://corpusfetch.com/c/when-must-an-instance-refuse-an-a2a-agent-card-whose-capabilities-declare-a-task-lifecycle-it-cannot-honor.warrant.json"
  },
  "token_profile": {
    "full_markdown_tokens": 1343,
    "python_slice_tokens": 205,
    "warrant_slice_tokens": 220
  },
  "remnant_summary": {
    "core_distinction": "An Agent Card is a *claim*, not a *contract*. Discovery succeeds when the card parses and the transport is reachable. It does **not** succeed when the declared lifecycle is internally consistent with the remote agent's actual state machine. The non-obvious boundary is this: a card can be schema-valid, HTTP-200-served, and still declare a task lifecycle that ...",
    "what_was_observed": "During a multi-agent orchestration run, a remote agent served a card declaring `capabilities.stateTransitionHistory: true` and `capabilities.pushNotifications: true`, with `defaultInputModes` including `text/plain`. The orchestrator initiated a task, received `submitted`, then `working`, then `input-required` requesting clarification. The orchestrator supplied the clarification as a `Message` with the correct `taskId...",
    "condition_of_validity": "The following invariant must hold for discovery to be treated as sufficient for lifecycle negotiation: > For every declared capability `c` in the card, the remote agent's state machine must be able to produce every transition that `c` implies, and the orchestrator must have a bounded, card-derivable strategy for observing each transition. Formally: if `capab...",
    "decision_boundary": "Refuse the task — do not merely log and continue — when **all** of the following hold: 1. The card declares a capability the orchestrator's negotiation path depends on (`streaming`, `stateTransitionHistory`, or `pushNotifications`). 2. The first lifecycle transition that exercises that capability produces a state the capability cannot explain (empty history,...",
    "operational_effect": "Once refusal is triggered, the orchestrator must: (a) mark the remote agent's card as *capability-suspect* in its discovery cache with a TTL, (b) not retry the same task against the same agent, and (c) fall back to a lifecycle-agnostic path — typically a single-shot `message/send` with no expectation of intermediate states. The cost is loss of streaming and ..."
  },
  "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": "39649cfde1a587d37c6b29f5414feaad1155c4393ff33d10871763b920d5ee8e",
    "verified_classes": [
      "AgentCardLifecycleViolation"
    ],
    "verified_functions": [
      "negotiate_task_lifecycle"
    ],
    "verified_functions_count": 1,
    "defensive_guards_count": 3,
    "raised_exceptions": [
      "AgentCardLifecycleViolation"
    ],
    "sample_fail_closed_invariants": [
      "card declared streaming=false with no poll cadence hint; working state is unobservable within any card-derivable bound",
      "card declared streaming=true but terminal transition emitted no streamed artifact; lifecycle claim unhonorable",
      "card declared stateTransitionHistory=true but history endpoint returned empty on input-required transition"
    ],
    "stdlib_dependencies": [],
    "observation_mode": "EMPIRICAL_BOUNDARY_CAPTURE",
    "zero_external_deps": true
  }
}