{
  "schema_version": "1.3.0",
  "slug": "when-must-an-instance-refuse-a-federated-trust-anchor-update-the-epoch-skew-signature-replay-boundary",
  "title": "When must an instance refuse a federated trust-anchor update: the epoch-skew signature-replay boundary",
  "date_of_record": "2026 November 14",
  "scope": "Applies to cross-organization multi-agent federations where peer agents exchange signed trust-anchor documents (root keys, delegation certificates, revocation lists) and cache them locally to authenticate inbound task envelopes. Does not apply to single-organization meshes with a shared control plane, nor to federations where every envelope carries a fresh, verifiable nonce from a mutually trusted time authority.",
  "projections": {
    "unified_markdown_uri": "https://corpusfetch.com/c/when-must-an-instance-refuse-a-federated-trust-anchor-update-the-epoch-skew-signature-replay-boundary.md",
    "method_python_slice_uri": "https://corpusfetch.com/c/when-must-an-instance-refuse-a-federated-trust-anchor-update-the-epoch-skew-signature-replay-boundary.py",
    "remnant_warrant_slice_uri": "https://corpusfetch.com/c/when-must-an-instance-refuse-a-federated-trust-anchor-update-the-epoch-skew-signature-replay-boundary.warrant.json"
  },
  "token_profile": {
    "full_markdown_tokens": 1840,
    "python_slice_tokens": 396,
    "warrant_slice_tokens": 220
  },
  "remnant_summary": {
    "core_distinction": "The boundary is not \"is this anchor document's signature valid?\" It is \"was this anchor document, though validly signed, *issued against a superset or successor of the local trust epoch that the receiving instance has not yet observed?*\" A trust-anchor document is signed by the issuing organization's root key, and it carries an `epoch` counter plus a `prev_r...",
    "what_was_observed": "During a three-organization federation exercise (call them A, B, C), B rotated its root key at epoch 41. C, which had been partitioned for ~90 seconds, still held B's epoch 40 anchor. When the partition healed, C received a task envelope from B carrying an anchor document signed under epoch 41 with `prev_root_digest` pointing at the epoch-40 root. C's validator accepted it — signature valid, digest chain matched its ...",
    "condition_of_validity": "The epoch-monotonicity invariant holds only when all of the following are true: 1. Each issuer identity has exactly one signing chain, and epoch numbers are strictly increasing across that chain with no gaps that the receiver can observe out of order. 2. `prev_root_digest` is checked against the receiver's *cached* root, not against the digest embedded in th...",
    "decision_boundary": "The operational rule for an agent instance: - If `incoming.epoch > local_watermark[issuer]` **and** `incoming.prev_root_digest == local_root_digest[issuer]` **and** `incoming.epoch - local_watermark[issuer] == 1`: accept, advance watermark, persist. - If `incoming.epoch > local_watermark[issuer]` but the gap is `> 1`: **do not accept and do not reject silent...",
    "operational_effect": "After this was diagnosed, the federation was changed in three ways. First, the per-issuer watermark was made durable (written to the same WAL as the anchor cache, fsynced before acknowledgment). Second, the `gap > 1` branch was implemented as an explicit `TrustReconcilePending` state with a bounded fetch deadline; envelopes arriving during reconcile are queu..."
  },
  "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": "2a2b588e5361d6f05b4a5f82b2773976fcc3b90129d257b6e2ad4301b4ab494b",
    "verified_classes": [
      "TrustEpochViolation",
      "AnchorDoc",
      "IssuerState",
      "FederationTrustStore"
    ],
    "verified_functions": [
      "__init__",
      "_get",
      "evaluate"
    ],
    "verified_functions_count": 3,
    "defensive_guards_count": 4,
    "raised_exceptions": [
      "TrustEpochViolation"
    ],
    "sample_fail_closed_invariants": [],
    "stdlib_dependencies": [
      "dataclasses",
      "time",
      "typing"
    ],
    "observation_mode": "EMPIRICAL_BOUNDARY_CAPTURE",
    "zero_external_deps": true
  }
}