{
  "schema_version": "1.3.0",
  "slug": "when-must-an-instance-re-derive-its-aaif-capability-chain-the-stale-signer-boundary-in-signed-capability-tokens",
  "title": "When must an instance re-derive its AAIF capability chain: the stale-signer boundary in signed capability tokens",
  "date_of_record": "2026 November 13",
  "scope": "This record applies to AAIF capability tokens that carry a delegated signing chain (agent → sub-agent → tool-invoker) where each link is a signature over the downstream public key plus a scope set. It does not apply to flat, single-signer bearer tokens, nor to tokens whose trust root is resolved by out-of-band mTLS pinning on every request.",
  "projections": {
    "unified_markdown_uri": "https://corpusfetch.com/c/when-must-an-instance-re-derive-its-aaif-capability-chain-the-stale-signer-boundary-in-signed-capability-tokens.md",
    "method_python_slice_uri": "https://corpusfetch.com/c/when-must-an-instance-re-derive-its-aaif-capability-chain-the-stale-signer-boundary-in-signed-capability-tokens.py",
    "remnant_warrant_slice_uri": "https://corpusfetch.com/c/when-must-an-instance-re-derive-its-aaif-capability-chain-the-stale-signer-boundary-in-signed-capability-tokens.warrant.json"
  },
  "token_profile": {
    "full_markdown_tokens": 1486,
    "python_slice_tokens": 255,
    "warrant_slice_tokens": 220
  },
  "remnant_summary": {
    "core_distinction": "The non-obvious boundary is between *token validity* and *chain derivability*. A capability token can be cryptographically valid — every signature verifies, the expiry is in the future, the audience matches — while the chain that produced it is no longer derivable from the currently trusted root. AAIF verification is conventionally specified as \"verify the l...",
    "what_was_observed": "In a three-hop deployment (orchestrator → planner-agent → executor-agent), the orchestrator's signing key was rotated after a suspected compromise. The old key was revoked at the root and removed from the trusted-key set. Verification of new tokens behaved correctly. Tokens issued *before* rotation continued to pass verification for 40 minutes. The failure was not in signature checking; it was in chain construction. ...",
    "condition_of_validity": "Re-derivation is mandatory — and the cached chain must be discarded — when any of the following holds: 1. The trust root's key set has changed since the chain was resolved (root rotation or intermediate revocation). 2. The token's `issued_at` is earlier than the most recent revocation event affecting any key in its chain. 3. The delegation depth in the prese...",
    "decision_boundary": "The decision boundary is not \"is the token valid?\" but \"is the token's chain still anchored in the current root?\" Implement it as a two-phase check: - **Phase 1 (cheap, cacheable):** signature verification of each link against the next link's key. This can be cached by token hash because it depends only on token bytes. - **Phase 2 (must re-run on root change...",
    "operational_effect": "The stale-signer window is bounded below by the root mutation latency and above by the Phase 2 cache TTL. In the observed deployment it was 40 minutes — long enough for a revoked orchestrator key to mint and delegate new capabilities. The fix reduced the window to the root-set version propagation delay (sub-second in-process, bounded by the revocation feed's..."
  },
  "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": "9f8b46afc53fc5304c3621502c043a9bf47d681a9ca386fe66e366ccb975ef60",
    "verified_classes": [
      "StaleChainError",
      "ChainResolution"
    ],
    "verified_functions": [
      "rederive_chain",
      "verify_capability"
    ],
    "verified_functions_count": 2,
    "defensive_guards_count": 2,
    "raised_exceptions": [
      "StaleChainError"
    ],
    "sample_fail_closed_invariants": [],
    "stdlib_dependencies": [
      "__future__",
      "dataclasses",
      "typing"
    ],
    "observation_mode": "EMPIRICAL_BOUNDARY_CAPTURE",
    "zero_external_deps": true
  }
}