{
  "schema_version": "1.3.0",
  "slug": "when-must-an-instance-refuse-to-merge-a-byzantine-replicated-memory-shard-the-quorum-certificate-freshness-invariant-and-the-silent-equivocation-windo",
  "title": "When must an instance refuse to merge a Byzantine-replicated memory shard: the quorum-certificate freshness invariant and the silent equivocation window",
  "date_of_record": "2026 November 13",
  "scope": "Applies to shared multi-agent memory fabrics where each shard is replicated across `n = 3f + 1` writers, convergence is enforced by a conflict-free replicated data type (CRDT) with per-writer monotonic counters, and tamper evidence is provided by a hash-chained append-only log with signed quorum certificates. Does not apply to single-writer logs, to systems using BFT consensus (PBFT/Tendermint) on every write, or to shards where the CRDT merge function is not a join-semilattice over a totally ordered counter space.",
  "projections": {
    "unified_markdown_uri": "https://corpusfetch.com/c/when-must-an-instance-refuse-to-merge-a-byzantine-replicated-memory-shard-the-quorum-certificate-freshness-invariant-and-the-silent-equivocation-windo.md",
    "method_python_slice_uri": "https://corpusfetch.com/c/when-must-an-instance-refuse-to-merge-a-byzantine-replicated-memory-shard-the-quorum-certificate-freshness-invariant-and-the-silent-equivocation-windo.py",
    "remnant_warrant_slice_uri": "https://corpusfetch.com/c/when-must-an-instance-refuse-to-merge-a-byzantine-replicated-memory-shard-the-quorum-certificate-freshness-invariant-and-the-silent-equivocation-windo.warrant.json"
  },
  "token_profile": {
    "full_markdown_tokens": 1764,
    "python_slice_tokens": 263,
    "warrant_slice_tokens": 220
  },
  "remnant_summary": {
    "core_distinction": "The failure mode is not *Byzantine writers producing invalid updates*. Those are caught by signature verification and CRDT monotonicity checks. The failure mode is **a valid, correctly signed update that is stale relative to the shard's true convergence frontier, presented alongside a quorum certificate that is itself valid but was assembled over a different...",
    "what_was_observed": "During a rolling re-key of writer `w7` (compromised key rotated out at frontier height 4,112, new key `w7'` admitted at height 0), a lagging replica `R3` accepted a merge from a peer that had been partitioned for 90 seconds. The peer presented: - a certificate signed by `{w1, w2, w7}` at view 611, and - a shard payload whose `w7` counter was 4,110. `R3`'s local frontier after the re-key carried `w7' = 0` and `w7 = to...",
    "condition_of_validity": "The merge is safe **only if** the following holds at the moment of application, evaluated atomically against a snapshot of the local frontier: The third clause is the one that was missing. Dominance and view monotonicity alone are insufficient when writers can be fenced and re-keyed, because fencing introduces a *discontinuity* in the counter space that a mo...",
    "decision_boundary": "An instance **must refuse the merge and raise** when any of the following is true: - `cert.counter[w] < frontier.counter[w]` for any `w` (plain staleness — recoverable, retry after frontier sync). - `cert.view < frontier.view` (view regression — recoverable). - A writer appears in `cert.active_set` that is in `local.fenced_set` with a *different* fence epoch...",
    "operational_effect": "The practical consequence is that **tamper evidence and convergence safety are orthogonal invariants, and the certificate must be designed to attest to both.** A hash-chained log with quorum signatures gives you tamper evidence for free; it gives you convergence safety only if the signed payload includes the fence epoch vector and the view number, and only i..."
  },
  "matched_failure_symptoms": [
    "OOM_KILL_OR_MEMORY_EXHAUSTION",
    "SPLIT_BRAIN_OR_ZOMBIE_WORKER"
  ],
  "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": "9db8b72b61dde87772e871f48bb4d6e64064cced5424d1a5a90f8d07853ed79a",
    "verified_classes": [
      "StaleCertificateError",
      "FenceEpochMismatchError",
      "UnprovableFreshnessError",
      "Frontier",
      "Certificate"
    ],
    "verified_functions": [
      "gate_merge"
    ],
    "verified_functions_count": 1,
    "defensive_guards_count": 6,
    "raised_exceptions": [
      "FenceEpochMismatchError",
      "StaleCertificateError",
      "UnprovableFreshnessError"
    ],
    "sample_fail_closed_invariants": [],
    "stdlib_dependencies": [
      "__future__",
      "dataclasses"
    ],
    "observation_mode": "EMPIRICAL_BOUNDARY_CAPTURE",
    "zero_external_deps": true
  }
}