{
  "schema_version": "1.3.0",
  "slug": "which-invariants-prevent-silent-task-orphaning-in-a2a-v1-0-agent-card-discovery-task-lifecycle-state-machines-and-push-notification-webhook-binding",
  "title": "Which invariants prevent silent task orphaning in A2A v1.0 Agent Card discovery, task lifecycle state machines, and push-notification webhook binding",
  "date_of_record": "2026 November 7",
  "scope": "Applies to A2A v1.0 peers that resolve an Agent Card over `/.well-known/agent-card.json`, transition tasks through `submitted → working → {completed | failed | canceled | input-required}`, and bind push notifications to an HTTPS webhook. Does not apply to v0.x deployments lacking `capabilities.pushNotifications`, nor to purely synchronous request/response calls with no task handle.",
  "projections": {
    "unified_markdown_uri": "https://corpusfetch.com/c/which-invariants-prevent-silent-task-orphaning-in-a2a-v1-0-agent-card-discovery-task-lifecycle-state-machines-and-push-notification-webhook-binding.md",
    "method_python_slice_uri": "https://corpusfetch.com/c/which-invariants-prevent-silent-task-orphaning-in-a2a-v1-0-agent-card-discovery-task-lifecycle-state-machines-and-push-notification-webhook-binding.py",
    "remnant_warrant_slice_uri": "https://corpusfetch.com/c/which-invariants-prevent-silent-task-orphaning-in-a2a-v1-0-agent-card-discovery-task-lifecycle-state-machines-and-push-notification-webhook-binding.warrant.json"
  },
  "token_profile": {
    "full_markdown_tokens": 1740,
    "python_slice_tokens": 494,
    "warrant_slice_tokens": 220
  },
  "remnant_summary": {
    "core_distinction": "The Agent Card is a *point-in-time capability advertisement*, not a contract that survives the task. Discovery tells you what a peer *claimed* it could do at fetch time; the task lifecycle and webhook binding tell you what it *actually* committed to for a specific task. The non-obvious failure is conflating the two: treating the `capabilities.pushNotificatio...",
    "what_was_observed": "Against a conformant v1.0 peer, three orphaning modes recurred: 1. **Card-flag-only assumption.** Client reads `capabilities.pushNotifications: true`, submits a long-running task via `message/send`, and waits. No `tasks/pushNotificationConfig/set` was issued because the client assumed the flag implied a default webhook. The server transitioned the task to `completed`; the client polled `tasks/get` only on a 300s inte...",
    "condition_of_validity": "The invariant holds only when all of the following are true: - The `pushNotificationConfig` is registered *before or atomically with* the first state transition out of `submitted`. A `set` after `working` is a partial binding and must be treated as best-effort. - The webhook receiver acknowledges with `2xx`; any `4xx` (especially `410`) invalidates the bindi...",
    "decision_boundary": "The boundary is between *advertised capability* and *bound obligation*: - If `capabilities.pushNotifications == false` → do not attempt registration; poll. - If `true` but no `pushNotificationConfig` has been `set` for this `taskId` → the task has **no** webhook obligation; poll. Do not wait on the card flag. - If `set` succeeded and the receiver has acknowl...",
    "operational_effect": "Enforcing the invariant changes client behavior in three concrete ways. First, submission and binding are fused: the client issues `tasks/pushNotificationConfig/set` immediately after (or in the same logical step as) `message/send`, and refuses to treat the task as \"monitored\" until the `set` returns success. Second, the client keeps a per-task reconciliatio..."
  },
  "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": "20076e94a0ac07e94019c8382388749cb289983bad5b86bd9bbc1314e2d80c91",
    "verified_classes": [
      "TaskOrphanedError",
      "BindingState",
      "TaskBinding"
    ],
    "verified_functions": [
      "assert_delivery_channel_live",
      "on_receiver_response"
    ],
    "verified_functions_count": 2,
    "defensive_guards_count": 5,
    "raised_exceptions": [
      "TaskOrphanedError"
    ],
    "sample_fail_closed_invariants": [],
    "stdlib_dependencies": [
      "__future__",
      "dataclasses",
      "enum",
      "time",
      "typing"
    ],
    "observation_mode": "EMPIRICAL_BOUNDARY_CAPTURE",
    "zero_external_deps": true
  }
}