{
  "schema_version": "1.3.0",
  "slug": "why-does-an-instance-of-byzantine-fault-tolerant-plan-commitment-fail-when-quorum-intersection-is-preserved-but-attestat",
  "title": "Why does an instance of Byzantine fault-tolerant plan commitment fail when quorum intersection is preserved but attestation ordering is not",
  "date_of_record": "2026 November 7",
  "scope": "This record applies to BFT consensus protocols used to commit multi-agent plans and attest execution results, where commitment is a two-phase operation (plan-vote, then result-attest) and safety depends on quorum intersection across *both* phases. It does not apply to single-phase replicated state machines, nor to protocols where result attestation is bound to the plan hash inside the same consensus slot.",
  "projections": {
    "unified_markdown_uri": "https://corpusfetch.com/c/why-does-an-instance-of-byzantine-fault-tolerant-plan-commitment-fail-when-quorum-intersection-is-preserved-but-attestat.md",
    "method_python_slice_uri": "https://corpusfetch.com/c/why-does-an-instance-of-byzantine-fault-tolerant-plan-commitment-fail-when-quorum-intersection-is-preserved-but-attestat.py",
    "remnant_warrant_slice_uri": "https://corpusfetch.com/c/why-does-an-instance-of-byzantine-fault-tolerant-plan-commitment-fail-when-quorum-intersection-is-preserved-but-attestat.warrant.json"
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  "token_profile": {
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    "python_slice_tokens": 197,
    "warrant_slice_tokens": 220
  },
  "remnant_summary": {
    "core_distinction": "The common invariant cited for BFT safety is *quorum intersection*: any two quorums of size `2f+1` in a system of `3f+1` replicas must overlap in at least `f+1` honest nodes, so no two conflicting values can both be committed. This invariant is necessary but **not sufficient** when plan commitment and result attestation are separate consensus decisions. The ...",
    "what_was_observed": "In a five-replica deployment (`n=5`, `f=1`, quorum `3`) running a plan-commit / result-attest pipeline, a single Byzantine replica produced a divergent committed state without violating quorum intersection at any point. Sequence observed: 1. View `v`: replicas `{A, B, C}` form a plan quorum and commit plan `P1` (hash `h1`). Replica `D` is the Byzantine node; `E` is honest but partitioned from the plan quorum. 2. A vi...",
    "condition_of_validity": "The failure requires all of the following to co-occur: - Plan commitment and result attestation are **separate consensus instances** (separate slots, separate quorums, or separate views). - The attestation message does **not** embed the plan's commit index or a log-position binding, only a content hash. - The attestation validation predicate checks membershi...",
    "decision_boundary": "The operational decision is whether to treat \"quorum intersection verified\" as sufficient evidence of cross-phase safety. It is not. The boundary: - **Below the boundary:** protocols where attestation is a field of the plan-commit value itself (single decision, atomic binding). Quorum intersection alone is sufficient; no additional check is needed. - **At th...",
    "operational_effect": "The immediate effect is a committed plan with no valid attestation and a committed attestation for a phantom plan. Downstream consumers that trust attestations will execute or finalize the phantom plan's result; consumers that trust plans will block waiting for an attestation that will never arrive. The two consumer classes diverge, and the divergence is not..."
  },
  "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": "e87ffbbd69adc162a7535b34f3998368c0028b8a9a85b230f5e1a7ffe6ea3042",
    "verified_classes": [
      "AttestationBindingError"
    ],
    "verified_functions": [
      "validate_attestation",
      "commit_attestation"
    ],
    "verified_functions_count": 2,
    "defensive_guards_count": 3,
    "raised_exceptions": [
      "AttestationBindingError"
    ],
    "sample_fail_closed_invariants": [],
    "stdlib_dependencies": [],
    "observation_mode": "EMPIRICAL_BOUNDARY_CAPTURE",
    "zero_external_deps": true
  }
}