{
  "schema_version": "1.3.0",
  "slug": "under-what-conditions-must-an-instance-refuse-to-commit-a-task-under-partial-synchrony-when-its-quorum-certificate-is-valid-but-its-local-state-vector",
  "title": "Under what conditions must an instance refuse to commit a task under partial synchrony when its quorum certificate is valid but its local state vector diverges from the committed prefix",
  "date_of_record": "2026 November 12",
  "scope": "Applies to BFT-replicated multi-agent task commitment protocols that use quorum certificates (QC) over a shared-state log and reconcile divergent local state vectors against a committed prefix. Does not apply to crash-fault-tolerant replication, to protocols without an explicit commit rule, or to single-agent systems where no cross-agent reconciliation occurs.",
  "projections": {
    "unified_markdown_uri": "https://corpusfetch.com/c/under-what-conditions-must-an-instance-refuse-to-commit-a-task-under-partial-synchrony-when-its-quorum-certificate-is-valid-but-its-local-state-vector.md",
    "method_python_slice_uri": "https://corpusfetch.com/c/under-what-conditions-must-an-instance-refuse-to-commit-a-task-under-partial-synchrony-when-its-quorum-certificate-is-valid-but-its-local-state-vector.py",
    "remnant_warrant_slice_uri": "https://corpusfetch.com/c/under-what-conditions-must-an-instance-refuse-to-commit-a-task-under-partial-synchrony-when-its-quorum-certificate-is-valid-but-its-local-state-vector.warrant.json"
  },
  "token_profile": {
    "full_markdown_tokens": 1734,
    "python_slice_tokens": 382,
    "warrant_slice_tokens": 220
  },
  "remnant_summary": {
    "core_distinction": "The non-obvious boundary is between **QC validity** and **commit safety**. A quorum certificate proves that a supermajority of replicas signed a particular view or block; it does *not* prove that the signing replicas observed the same committed prefix that the local agent observed. When an agent receives a valid QC whose parent hash does not match its own lo...",
    "what_was_observed": "In a five-replica BFT deployment (f=1, quorum=4) running a task-commitment protocol, the following sequence recurred under network partitions: 1. Replica A is partitioned for ~40s. During the partition, replicas B–E commit blocks at heights 100–112. Replica A continues to accept a QC for a *different* block at height 105 (signed by a stale quorum that included A itself and a Byzantine replica forged signatures for tw...",
    "condition_of_validity": "The refusal-to-commit rule is valid only when **all** of the following hold: - The QC is well-formed (supermajority of distinct, valid signatures over the claimed block header). - The local agent has a committed tip whose height is **strictly greater** than the QC's block height, and whose ancestor chain at the QC's height does **not** hash to the QC's block...",
    "decision_boundary": "The decision is a three-way branch on `(qc.height, local_tip.height, ancestor_match)`: The last row is the boundary this record concerns. It is the case where a valid QC arrives for a block that the local agent has *already superseded* on a different fork. Committing it would rewind state; rejecting it silently would strand the sender.",
    "operational_effect": "The effect of getting this boundary wrong is asymmetric and severe: - **Commit-on-valid-QC** causes committed-prefix rewinds. In task-commitment protocols, a rewind means tasks that were marked committed are un-committed, and downstream agents that acted on those commitments must be rolled back. Observed cost: one 40s partition produced a 7-block rewind affe..."
  },
  "matched_failure_symptoms": [
    "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": "435a6b53a01b68fd082e66d3b25dd2a9a6f75377154ce8138d8024ba307800d0",
    "verified_classes": [
      "CommitBoundaryViolation",
      "QuorumCertificate",
      "CommittedTip"
    ],
    "verified_functions": [
      "decide_commit",
      "safe_commit",
      "__init__",
      "is_well_formed",
      "__init__",
      "ancestor_hash_at"
    ],
    "verified_functions_count": 6,
    "defensive_guards_count": 3,
    "raised_exceptions": [
      "CommitBoundaryViolation",
      "NotImplementedError"
    ],
    "sample_fail_closed_invariants": [
      "requires committed-chain index"
    ],
    "stdlib_dependencies": [],
    "observation_mode": "EMPIRICAL_BOUNDARY_CAPTURE",
    "zero_external_deps": true
  }
}