{
  "schema_version": "1.3.0",
  "slug": "under-what-conditions-must-an-instance-treat-a2a-v1-0-agent-card-discovery-as-authoritative-before-task-lifecycle-negotiation-begins",
  "title": "Under what conditions must an instance treat A2A v1.0 Agent Card discovery as authoritative before task lifecycle negotiation begins",
  "date_of_record": "2026 November 7",
  "scope": "Applies to cross-vendor A2A v1.0 interoperation where an initiating agent resolves a remote Agent Card and then negotiates a task lifecycle (submitted → working → input-required → completed/failed/canceled) involving artifact exchange. Does not address intra-vendor deployments sharing a common card schema registry, nor pre-v1.0 drafts where `capabilities` and `defaultInputModes` semantics diverged.",
  "projections": {
    "unified_markdown_uri": "https://corpusfetch.com/c/under-what-conditions-must-an-instance-treat-a2a-v1-0-agent-card-discovery-as-authoritative-before-task-lifecycle-negotiation-begins.md",
    "method_python_slice_uri": "https://corpusfetch.com/c/under-what-conditions-must-an-instance-treat-a2a-v1-0-agent-card-discovery-as-authoritative-before-task-lifecycle-negotiation-begins.py",
    "remnant_warrant_slice_uri": "https://corpusfetch.com/c/under-what-conditions-must-an-instance-treat-a2a-v1-0-agent-card-discovery-as-authoritative-before-task-lifecycle-negotiation-begins.warrant.json"
  },
  "token_profile": {
    "full_markdown_tokens": 1460,
    "python_slice_tokens": 425,
    "warrant_slice_tokens": 220
  },
  "remnant_summary": {
    "core_distinction": "There is a difference between *discovery success* and *discovery authority*. An HTTP 200 response carrying a syntactically valid Agent Card proves only that a document was served at `/.well-known/agent.json` (or the vendor-advertised path). It does not prove that the card's declared `capabilities`, `defaultInputModes`, `defaultOutputModes`, and `skills[].inp...",
    "what_was_observed": "Across a multi-vendor matrix (three card-serving implementations, four artifact consumers), the following divergence pattern recurred: 1. A card advertised `defaultInputModes: [\"text/plain\", \"application/json\"]` and a skill with `inputModes: [\"application/json\"]`. 2. The initiator sent `message/send` with a `Part` of `kind: \"data\"` (structured JSON), consistent with the declared mode. 3. The remote returned a `Task` ...",
    "condition_of_validity": "The Agent Card may be treated as authoritative for negotiation **only if all of the following hold**: - The card's `protocolVersion` string exactly equals the initiator's supported `1.0` (semver-prefix matching is insufficient; `\"1.0\"` ≠ `\"1.0.0-rc\"`). - The initiator performs a *probe negotiation*: a `message/send` with a minimal `text/plain` `Part` and a `...",
    "decision_boundary": "The decision is not \"trust the card\" vs. \"ignore the card.\" It is a staged commitment: The boundary is crossed the moment the initiator commits a non-recoverable side effect (artifact upload, external write) based on card-declared modes without a probe. Before that point, card divergence is cheap; after, it is a partial-failure recovery problem.",
    "operational_effect": "Treating discovery as authoritative without probe negotiation produced, in the observed matrix: 5/7 vendor pairs with at least one `input-required` renegotiation cycle, 2/7 with orphaned artifacts requiring out-of-band cleanup, and 1/7 with a stream that never signaled `final`, causing the initiator to hang until a 30s transport timeout rather than a protoco..."
  },
  "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": "a2bc485df0ded96f8239521a9b975fc36eb6370bdbe4d0f328d42e32ec12fa6b",
    "verified_classes": [
      "AgentCardConformanceError",
      "TaskTransition"
    ],
    "verified_functions": [
      "assert_card_authoritative",
      "commit_artifact"
    ],
    "verified_functions_count": 2,
    "defensive_guards_count": 6,
    "raised_exceptions": [
      "AgentCardConformanceError"
    ],
    "sample_fail_closed_invariants": [
      "Agent Card is unsigned; declared capabilities are hints, not a binding contract — probe negotiation required",
      "probe returned input-required; card-declared mode was not accepted by runtime — renegotiate before artifact commit",
      "card declares streaming but probe stream produced no terminal TaskArtifactUpdateEvent; reassembly cannot close"
    ],
    "stdlib_dependencies": [
      "__future__",
      "dataclasses",
      "json",
      "typing"
    ],
    "observation_mode": "EMPIRICAL_BOUNDARY_CAPTURE",
    "zero_external_deps": true
  }
}