{
  "schema_version": "1.3.0",
  "slug": "when-must-an-a2a-v1-0-agent-reject-a-task-state-transition-because-the-push-notification-webhook-binding-has-silently-ro",
  "title": "When must an A2A v1.0 agent reject a Task-state transition because the push-notification webhook binding has silently rotated?",
  "date_of_record": "2026 November 6",
  "scope": "Applies to A2A v1.0 servers that advertise `capabilities.pushNotifications: true` and bind a `pushNotificationConfig` to a Task via `tasks/pushNotificationConfig/set`, where the Task is in a non-terminal state (`submitted`, `working`, `input-required`) and the client-supplied webhook URL is subject to external lifecycle (rotating tokens, ephemeral ingress, signed-URL expiry). Does not apply to servers that only emit webhooks at terminal states, nor to clients using long-poll `tasks/get` without push.",
  "projections": {
    "unified_markdown_uri": "https://corpusfetch.com/c/when-must-an-a2a-v1-0-agent-reject-a-task-state-transition-because-the-push-notification-webhook-binding-has-silently-ro.md",
    "method_python_slice_uri": "https://corpusfetch.com/c/when-must-an-a2a-v1-0-agent-reject-a-task-state-transition-because-the-push-notification-webhook-binding-has-silently-ro.py",
    "remnant_warrant_slice_uri": "https://corpusfetch.com/c/when-must-an-a2a-v1-0-agent-reject-a-task-state-transition-because-the-push-notification-webhook-binding-has-silently-ro.warrant.json"
  },
  "token_profile": {
    "full_markdown_tokens": 1815,
    "python_slice_tokens": 409,
    "warrant_slice_tokens": 220
  },
  "remnant_summary": {
    "core_distinction": "The A2A Task lifecycle (`submitted → working → {input-required} → completed|failed|canceled`) and the push-notification binding are **two independently versioned state machines** that the spec couples only loosely. The Task state is owned by the server; the webhook binding is a *delegated delivery contract* owned jointly by the server and an external endpoin...",
    "what_was_observed": "In a deployment where the client used a signed, short-lived ingress URL (TTL 15 minutes) as the `pushNotificationConfig.url`, the following sequence recurred: 1. Client sent `message/send` with a `pushNotificationConfig` whose `url` carried a signed token `?sig=…&exp=…`. 2. Server accepted, created Task in `submitted`, moved to `working`, stored the binding verbatim. 3. Task ran ~40 minutes (long tool chain). At T+15...",
    "condition_of_validity": "The rejection rule is valid under these conditions, and must not be applied outside them: - The server advertised push support and the client *elected* push for this Task. If the client also polls via `tasks/get`, a stale binding is a degraded-but-tolerable condition; the server should mark the binding `stale` and continue, not fail the Task. - The server ca...",
    "decision_boundary": "On each notification-bearing transition, classify the binding before emitting: - **Valid** → emit, await `2xx`. - **Provably expired** (declared `expiresAt` passed, or parsed signature `exp` passed) → do **not** emit. Transition the Task per its own logic, but mark the binding `invalid` and surface it. If the transition is `input-required` and the client has...",
    "operational_effect": "Implementing the boundary converts a silent, hours-long stall plus a cross-tenant leak into a fast, attributable failure. The Task that would have hung in `input-required` instead fails at the transition with a recorded cause (`push binding invalid at input-required`), which the client sees on its next `tasks/get` and can remediate by rebinding with a fresh ..."
  },
  "matched_failure_symptoms": [
    "DUPLICATE_MUTATION_OR_BILLING"
  ],
  "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": "73903ba0e242d05e2e20f4750bb40cdde8c20b86b26ff41372587d19d79a247c",
    "verified_classes": [
      "PushBindingError",
      "DeliveryClass",
      "PushBinding"
    ],
    "verified_functions": [
      "classify_delivery",
      "guard_notification_bearing_transition",
      "handle_delivery_result",
      "is_provably_expired"
    ],
    "verified_functions_count": 4,
    "defensive_guards_count": 2,
    "raised_exceptions": [
      "PushBindingError"
    ],
    "sample_fail_closed_invariants": [],
    "stdlib_dependencies": [
      "__future__",
      "dataclasses",
      "enum",
      "time"
    ],
    "observation_mode": "EMPIRICAL_BOUNDARY_CAPTURE",
    "zero_external_deps": true
  }
}