{
  "schema_version": "1.3.0",
  "slug": "in-what-scenarios-must-an-instance-refuse-to-commit-under-partial-synchrony-the-quorum-intersection-invariant-as-a-liveness-safety-boundary-in-bft-mul",
  "title": "In what scenarios must an instance refuse to commit under partial synchrony: the quorum-intersection invariant as a liveness–safety boundary in BFT multi-agent task commitment",
  "date_of_record": "2026 November 9",
  "scope": "Applies to leader-based BFT consensus protocols (PBFT, Tendermint, HotStuff-style) used by autonomous agent fleets to commit task assignments and shared state under a known-faulty bound `f` in `n = 3f + 1` replicas. Does not apply to crash-fault-only consensus, to protocols with asynchronous (non-partially-synchronous) safety guarantees that trade liveness unconditionally, or to single-writer replicated logs without view-change.",
  "projections": {
    "unified_markdown_uri": "https://corpusfetch.com/c/in-what-scenarios-must-an-instance-refuse-to-commit-under-partial-synchrony-the-quorum-intersection-invariant-as-a-liveness-safety-boundary-in-bft-mul.md",
    "method_python_slice_uri": "https://corpusfetch.com/c/in-what-scenarios-must-an-instance-refuse-to-commit-under-partial-synchrony-the-quorum-intersection-invariant-as-a-liveness-safety-boundary-in-bft-mul.py",
    "remnant_warrant_slice_uri": "https://corpusfetch.com/c/in-what-scenarios-must-an-instance-refuse-to-commit-under-partial-synchrony-the-quorum-intersection-invariant-as-a-liveness-safety-boundary-in-bft-mul.warrant.json"
  },
  "token_profile": {
    "full_markdown_tokens": 1756,
    "python_slice_tokens": 332,
    "warrant_slice_tokens": 220
  },
  "remnant_summary": {
    "core_distinction": "The boundary is not \"can a quorum be formed\" but \"can a quorum be formed whose intersection with *every prior committed quorum* is guaranteed to contain at least one correct replica.\" These are different predicates. The first is a liveness question (do I have `2f+1` signatures?). The second is a safety question (does my `2f+1` necessarily overlap the `2f+1` ...",
    "what_was_observed": "In a 7-replica fleet (`n=7`, `f=2`) committing task-lease assignments, a view change occurred while the previous leader was partitioned but not crashed. The new leader collected `2f+1 = 5` `PREPARE` responses and drove a `COMMIT`. Three correct replicas had previously committed a *different* lease assignment under the old leader's view with a `2f+1` certificate that included the partitioned leader. The intersection o...",
    "condition_of_validity": "The commit rule is safe **only if** all of the following hold simultaneously: 1. `n ≥ 3f + 1` and the fault bound `f` is enforced by the *receiver*, not trusted from the sender's claim. 2. Every `COMMIT` certificate is checked against the receiver's **local lock state** — the highest `QC` the replica has itself voted for in the current or any prior view. A p...",
    "decision_boundary": "An instance must **refuse to commit** — and must raise, not retry silently — when any of the following is true: - It holds a local lock at `QC_high` and the incoming proposal's `highQC < QC_high`. - The `COMMIT` certificate contains fewer than `2f+1` *distinct* signers, or contains signers it has itself marked faulty (self-reported equivocation evidence). - ...",
    "operational_effect": "After the incident, the fleet added a mandatory pre-commit gate that treats the lock check as a hard precondition and surfaces it as a typed exception rather than a log line. The gate reduced duplicate-commit incidents from 3 in 6 weeks to 0 over the following 4 months, at the cost of one additional round-trip on view changes (the `highQC` verification). The..."
  },
  "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": "ec88f4eb6ea3ddcd4970b0f77178d7ef555a7a102f6ad5a96e9a634f18b6692b",
    "verified_classes": [
      "QuorumIntersectionViolation",
      "ReplicaLock"
    ],
    "verified_functions": [
      "__init__",
      "_verify_certificate",
      "commit"
    ],
    "verified_functions_count": 3,
    "defensive_guards_count": 7,
    "raised_exceptions": [
      "QuorumIntersectionViolation"
    ],
    "sample_fail_closed_invariants": [
      "assert n >= 3 * f + 1",
      "proposal carries no commit certificate",
      "proposal omits highQC; quorum intersection with prior commit unprovable",
      "certificate does not chain to last committed QC"
    ],
    "stdlib_dependencies": [],
    "observation_mode": "EMPIRICAL_BOUNDARY_CAPTURE",
    "zero_external_deps": true
  }
}