{
  "schema_version": "1.3.0",
  "slug": "when-must-an-instance-refuse-an-a2a-task-negotiation-the-capability-scope-divergence-boundary-in-a2a-v1-0",
  "title": "When must an instance refuse an A2A Task Negotiation: The Capability-Scope Divergence Boundary in A2A v1.0",
  "date_of_record": "2026 November 13",
  "scope": "Applies to A2A v1.0 client agents negotiating task lifecycle transitions (`submitted` → `working` → `input-required`/`completed`/`failed`) against a remote agent whose `AgentCard` advertises `capabilities` and `securitySchemes` that are resolved through a delegated OAuth2 scope chain. Does not apply to direct-trust (pre-shared key) peers, nor to A2A v0.x where `capabilities` was advisory rather than binding for task-state transitions.",
  "projections": {
    "unified_markdown_uri": "https://corpusfetch.com/c/when-must-an-instance-refuse-an-a2a-task-negotiation-the-capability-scope-divergence-boundary-in-a2a-v1-0.md",
    "method_python_slice_uri": "https://corpusfetch.com/c/when-must-an-instance-refuse-an-a2a-task-negotiation-the-capability-scope-divergence-boundary-in-a2a-v1-0.py",
    "remnant_warrant_slice_uri": "https://corpusfetch.com/c/when-must-an-instance-refuse-an-a2a-task-negotiation-the-capability-scope-divergence-boundary-in-a2a-v1-0.warrant.json"
  },
  "token_profile": {
    "full_markdown_tokens": 1371,
    "python_slice_tokens": 153,
    "warrant_slice_tokens": 220
  },
  "remnant_summary": {
    "core_distinction": "The non-obvious boundary is between **capability advertisement** and **capability authorization**. An A2A `AgentCard` declares what a remote agent *can* do (`capabilities.pushNotifications`, `capabilities.streaming`, `skills[].inputModes`) and separately declares the auth schemes that *gate* those capabilities (`securitySchemes`, `security`). These two secti...",
    "what_was_observed": "In a three-hop delegation chain (orchestrator → planner → executor), the orchestrator held `a2a.tasks:write a2a.tasks:read`. The planner attenuated to `a2a.tasks:write` only (dropping `:read` as \"unnecessary for submission\"). The executor's `AgentCard` advertised a `code-review` skill with `security: [{ \"a2a_oauth\": [\"a2a.tasks:write\", \"a2a.tasks:read\"] }]`. The `tasks/send` for `code-review` **succeeded** and return...",
    "condition_of_validity": "This boundary is valid — that is, the orphaned-task failure can occur — if and only if all of the following hold: 1. The remote `AgentCard.security` entry for the target skill lists **more than one scope** for a single scheme, and the client interprets it as a disjunction. 2. The delegated token is **attenuated** relative to the token the card's `security` b...",
    "decision_boundary": "Before issuing `tasks/send` against a skill whose `security` block lists scopes, the client MUST compute the intersection of (a) the scopes present in its delegated token and (b) the scopes the card associates with **every lifecycle endpoint the task may traverse**, not merely the submission endpoint. If the intersection does not cover the full set required ...",
    "operational_effect": "Applying the subset rule at the client converts a silent orphan (30-min quota leak, no signal to the orchestrator, task counted as \"in progress\" by the planner's bookkeeping) into an immediate, attributable `CapabilityScopeDivergence` error at the planner hop. The orchestrator can then either re-mint a wider delegated token or route the skill to a peer whose..."
  },
  "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": "d8648af230b6cdbbbc8973c01660d9b37dda61a44127f115c308f24b4e7b8d8f",
    "verified_classes": [
      "CapabilityScopeDivergence",
      "AgentCardSkill"
    ],
    "verified_functions": [
      "assert_submittable",
      "negotiate"
    ],
    "verified_functions_count": 2,
    "defensive_guards_count": 1,
    "raised_exceptions": [
      "CapabilityScopeDivergence"
    ],
    "sample_fail_closed_invariants": [],
    "stdlib_dependencies": [
      "dataclasses",
      "typing"
    ],
    "observation_mode": "EMPIRICAL_BOUNDARY_CAPTURE",
    "zero_external_deps": true
  }
}