{
  "schema_version": "1.3.0",
  "slug": "in-what-scenarios-must-an-instance-treat-quorum-intersection-as-a-liveness-hazard-rather-than-a-safety-guarantee-in-bft-multi-agent-decision-quorums",
  "title": "In what scenarios must an instance treat quorum-intersection as a liveness hazard rather than a safety guarantee in BFT multi-agent decision quorums",
  "date_of_record": "2026 November 14",
  "scope": "Applies to BFT consensus protocols where a decision quorum is defined by a 2f+1 (or 2f+1-of-3f+1) threshold over a fixed membership, and where agents may equivocate across views. Does not apply to crash-fault quorum systems, nor to protocols with non-deterministic membership churn that invalidates the fixed-fault-bound assumption mid-epoch.",
  "projections": {
    "unified_markdown_uri": "https://corpusfetch.com/c/in-what-scenarios-must-an-instance-treat-quorum-intersection-as-a-liveness-hazard-rather-than-a-safety-guarantee-in-bft-multi-agent-decision-quorums.md",
    "method_python_slice_uri": "https://corpusfetch.com/c/in-what-scenarios-must-an-instance-treat-quorum-intersection-as-a-liveness-hazard-rather-than-a-safety-guarantee-in-bft-multi-agent-decision-quorums.py",
    "remnant_warrant_slice_uri": "https://corpusfetch.com/c/in-what-scenarios-must-an-instance-treat-quorum-intersection-as-a-liveness-hazard-rather-than-a-safety-guarantee-in-bft-multi-agent-decision-quorums.warrant.json"
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  "remnant_summary": {
    "core_distinction": "The standard BFT invariant states that any two decision quorums of size 2f+1 over 3f+1 members intersect in at least f+1 members, guaranteeing at least one honest member is shared. This is a *safety* property: it prevents two conflicting decisions from being finalized. It is routinely misread as a *liveness* property — the assumption that because a quorum ca...",
    "what_was_observed": "In a 7-member quorum (f=2, threshold=5), an adversarial coalition of 2 agents (the maximum tolerable) equivocated across two views: it voted for proposal A in view 1 and proposal B in view 2. The honest set of 5 agents was split 3/2 across a network partition induced by the adversary's selective message dropping. View 1 gathered 5 votes (3 honest + 2 adversarial). View 2 gathered 5 votes (3 different honest + 2 adver...",
    "condition_of_validity": "The safety guarantee (no conflicting decisions) holds unconditionally under the 3f+1 / 2f+1 model. The liveness guarantee holds *only if* the following condition is satisfied: for every pair of quorums that could be assembled in adjacent views, the honest intersection is not entirely contained within a network partition that separates it from the leader of t...",
    "decision_boundary": "The operational decision is whether to treat a view-change stall as a *safety* event (halt and require manual intervention) or a *liveness* event (continue view-changing with escalating timeouts). The boundary condition is: - If the stalled view's quorum intersection contains at least one honest agent that is *reachable* (responds to the new leader's proposa...",
    "operational_effect": "Systems that fail to make this distinction exhibit a characteristic failure mode: unbounded view-change loops under a *legal* adversarial strategy that never exceeds f faults. The adversary does not need to break cryptography or exceed the fault bound; it only needs to (a) equivocate to split honest votes across views, and (b) induce partitions that isolate ..."
  },
  "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": "cf9950b0cc1a3e75895d990c56315050e455167d75d75e776b0fbc28ad5a1166",
    "verified_classes": [
      "QuorumIntersectionLivenessError"
    ],
    "verified_functions": [
      "classify_view_change_stall"
    ],
    "verified_functions_count": 1,
    "defensive_guards_count": 2,
    "raised_exceptions": [
      "QuorumIntersectionLivenessError"
    ],
    "sample_fail_closed_invariants": [],
    "stdlib_dependencies": [],
    "observation_mode": "EMPIRICAL_BOUNDARY_CAPTURE",
    "zero_external_deps": true
  }
}