{
  "schema_version": "1.3.0",
  "slug": "what-structural-signals-indicate-a-silent-capability-mismatch-in-a2a-v1-0-agent-card-discovery-and-cross-vendor-task-lifecycle-negotiation",
  "title": "What structural signals indicate a silent capability mismatch in A2A v1.0 Agent Card discovery and cross-vendor task lifecycle negotiation",
  "date_of_record": "2026 November 14",
  "scope": "Applies to A2A v1.0 (and v0.3 compatibility-mode) deployments where an orchestrator discovers remote agents via `/.well-known/agent.json` Agent Cards and negotiates task lifecycle state transitions across vendor boundaries. Does not apply to single-vendor deployments where both peers share a schema registry, nor to synchronous RPC-style invocations that bypass the task state machine.",
  "projections": {
    "unified_markdown_uri": "https://corpusfetch.com/c/what-structural-signals-indicate-a-silent-capability-mismatch-in-a2a-v1-0-agent-card-discovery-and-cross-vendor-task-lifecycle-negotiation.md",
    "method_python_slice_uri": "https://corpusfetch.com/c/what-structural-signals-indicate-a-silent-capability-mismatch-in-a2a-v1-0-agent-card-discovery-and-cross-vendor-task-lifecycle-negotiation.py",
    "remnant_warrant_slice_uri": "https://corpusfetch.com/c/what-structural-signals-indicate-a-silent-capability-mismatch-in-a2a-v1-0-agent-card-discovery-and-cross-vendor-task-lifecycle-negotiation.warrant.json"
  },
  "token_profile": {
    "full_markdown_tokens": 2008,
    "python_slice_tokens": 525,
    "warrant_slice_tokens": 220
  },
  "remnant_summary": {
    "core_distinction": "The distinction that matters is between **declared capability** and **negotiated capability**. An Agent Card is a *declaration*: a static JSON document advertising `skills`, `capabilities`, `defaultInputModes`, `defaultOutputModes`, and `securitySchemes`. The task lifecycle is a *negotiation*: a runtime exchange of `Task`, `TaskStatusUpdateEvent`, and `TaskA...",
    "what_was_observed": "Across a cross-vendor integration (orchestrator on vendor A, worker agents on vendors B and C), the following structural signals preceded every observed silent mismatch. Each is observable *before* the first task is dispatched, if you inspect the Agent Card and the first negotiation round-trip carefully. 1. **Asymmetric `capabilities.streaming` and `pushNotifications` flags.** The orchestrator advertised `streaming: ...",
    "condition_of_validity": "The invariant \"card declaration ⇒ runtime behavior\" holds only when all of the following are true: - Both peers validate against the *same minor version* of the A2A schema, not merely the same major version. v1.0.x patch differences have changed default values for `append` and `lastChunk` at least once. - Every field with a schema default is set *explicitly*...",
    "decision_boundary": "The decision boundary is: **treat the Agent Card as a capability *claim* requiring empirical confirmation, not as a capability *contract*.** Concretely: - If a card field is absent, do **not** substitute the spec default. Treat it as unknown and probe. - If `capabilities.streaming` is `false` but the endpoint accepts `tasks/sendSubscribe`, trust the endpoint...",
    "operational_effect": "The operational effect of ignoring these signals is a class of failures that are *invisible in aggregate metrics* and *expensive in reconciliation*. Task success rates look healthy because the worker succeeded; the orchestrator's view of failure is a local state-machine artifact. Artifact corruption from `append` drift is silent until downstream consumers di..."
  },
  "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": "3eec9af75c50437398ab7ce3379bc5105cf77c510f6caff466a5e0d75c51e125",
    "verified_classes": [
      "CapabilityMismatchError",
      "AgentCard",
      "ProbeResult"
    ],
    "verified_functions": [
      "negotiate_peer",
      "dispatch"
    ],
    "verified_functions_count": 2,
    "defensive_guards_count": 3,
    "raised_exceptions": [
      "CapabilityMismatchError"
    ],
    "sample_fail_closed_invariants": [],
    "stdlib_dependencies": [
      "__future__",
      "dataclasses",
      "typing"
    ],
    "observation_mode": "EMPIRICAL_BOUNDARY_CAPTURE",
    "zero_external_deps": true
  }
}