{
  "schema_version": "1.3.0",
  "slug": "in-what-scenarios-must-an-instance-treat-a2a-v1-0-agent-card-discovery-as-a-non-idempotent-version-fenced-operation-rather-than-a-cacheable-read",
  "title": "In what scenarios must an instance treat A2A v1.0 Agent Card discovery as a non-idempotent, version-fenced operation rather than a cacheable read",
  "date_of_record": "2026 November 11",
  "scope": "This record applies to A2A v1.0 client orchestrators that discover Agent Cards, drive tasks through the `submitted → working → input-required → completed/failed/canceled` lifecycle, and bind push-notification webhooks. It does not apply to A2A deployments that pin a single static Agent Card per origin with no in-place capability mutation, nor to transport-only concerns (HTTP retry, TLS) that are orthogonal to card semantics.",
  "projections": {
    "unified_markdown_uri": "https://corpusfetch.com/c/in-what-scenarios-must-an-instance-treat-a2a-v1-0-agent-card-discovery-as-a-non-idempotent-version-fenced-operation-rather-than-a-cacheable-read.md",
    "method_python_slice_uri": "https://corpusfetch.com/c/in-what-scenarios-must-an-instance-treat-a2a-v1-0-agent-card-discovery-as-a-non-idempotent-version-fenced-operation-rather-than-a-cacheable-read.py",
    "remnant_warrant_slice_uri": "https://corpusfetch.com/c/in-what-scenarios-must-an-instance-treat-a2a-v1-0-agent-card-discovery-as-a-non-idempotent-version-fenced-operation-rather-than-a-cacheable-read.warrant.json"
  },
  "token_profile": {
    "full_markdown_tokens": 1823,
    "python_slice_tokens": 448,
    "warrant_slice_tokens": 220
  },
  "remnant_summary": {
    "core_distinction": "The non-obvious boundary is this: an Agent Card is *published state*, not *configuration*. Clients routinely treat `GET /.well-known/agent.json` as a cacheable read — fetch once, memoize, reuse for the lifetime of the process. That is valid only when the card's advertised `capabilities`, `skills`, and `pushNotifications` blocks are immutable for the origin. ...",
    "what_was_observed": "Across three orchestrator deployments driving long-lived tasks (median 40 minutes, tail 6 hours), the following failure recurred. A client fetched the Agent Card at process start, memoized it, and used the memoized `pushNotifications: true` to register a webhook for task `T`. Mid-task, the remote agent was redeployed with `pushNotifications: false` (webhook delivery disabled during a migration). The client's registra...",
    "condition_of_validity": "Memoizing an Agent Card is valid **if and only if** all of the following hold: 1. The card's `version` field is unchanged since the memoized fetch, and the origin's card is declared immutable for that version (operators must publish this; absent a declaration, assume mutable). 2. No task currently held by the client depends on a capability that the memoized ...",
    "decision_boundary": "The decision rule the orchestrator must implement: - **At task creation:** re-validate the card if the memoized copy is older than the task's expected duration, or if the card `version` has not been confirmed within the last N minutes (N = 2× observed remote redeploy interval). If re-validation fails (network, `503`), *do not* start the task — fail fast with...",
    "operational_effect": "Implementing this boundary converts two classes of silent divergence into explicit, observable events. The webhook-drop failure becomes a `DiscoveryDowngrade` event at registration time (fresh card says no push) rather than a timeout six hours later. The spurious-cancel failure becomes a `DiscoveryUnavailable` warning attached to the task, with the task cont..."
  },
  "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": "3795d4c67b4725b8ac45baf180b88c9ac4f5916890a9da5fa3d781c4d1afe9d1",
    "verified_classes": [
      "AgentCardStalenessError",
      "TaskContinuationBlockedError",
      "AgentCard",
      "Task",
      "A2AClient"
    ],
    "verified_functions": [
      "__init__",
      "_fresh_card",
      "start_task",
      "register_webhook_for",
      "continue_task",
      "_skills_of"
    ],
    "verified_functions_count": 6,
    "defensive_guards_count": 4,
    "raised_exceptions": [
      "AgentCardStalenessError",
      "TaskContinuationBlockedError"
    ],
    "sample_fail_closed_invariants": [],
    "stdlib_dependencies": [
      "dataclasses",
      "time",
      "typing"
    ],
    "observation_mode": "EMPIRICAL_BOUNDARY_CAPTURE",
    "zero_external_deps": true
  }
}