{
  "schema_version": "1.3.0",
  "slug": "where-must-an-instance-reject-a-quorum-certificate-before-applying-it-to-a-shared-state-task-graph",
  "title": "Where must an instance reject a quorum certificate before applying it to a shared-state task graph",
  "date_of_record": "2026 November 14",
  "scope": "Applies to Byzantine fault-tolerant (BFT) multi-agent systems where agents commit mutations to a shared task graph via quorum certificates (QCs) over a partially synchronous network with a known, static validator set. Does not apply to leaderless CRDT-based replication, to systems with dynamic membership where the validator set itself is the object of consensus, or to single-writer append-only logs without graph-merge semantics.",
  "projections": {
    "unified_markdown_uri": "https://corpusfetch.com/c/where-must-an-instance-reject-a-quorum-certificate-before-applying-it-to-a-shared-state-task-graph.md",
    "method_python_slice_uri": "https://corpusfetch.com/c/where-must-an-instance-reject-a-quorum-certificate-before-applying-it-to-a-shared-state-task-graph.py",
    "remnant_warrant_slice_uri": "https://corpusfetch.com/c/where-must-an-instance-reject-a-quorum-certificate-before-applying-it-to-a-shared-state-task-graph.warrant.json"
  },
  "token_profile": {
    "full_markdown_tokens": 1645,
    "python_slice_tokens": 257,
    "warrant_slice_tokens": 220
  },
  "remnant_summary": {
    "core_distinction": "The non-obvious boundary is between *validity of a certificate* and *applicability of the certified transition*. A QC proves that a quorum of validators signed off on a specific `(view, node_id, parent_hash, payload_hash)` tuple. It does **not** prove that the transition is applicable to the local task graph at the moment of application. Two distinct predica...",
    "what_was_observed": "In a 7-validator deployment (f=2, quorum=5) running a task-graph workload with fan-out dependencies, we observed a reproducible deadlock under a specific interleaving. Agent A proposed transition `T` on node `n` with parent `p`. Quorum signed `T`. Agent B, which had fallen behind on the branch containing `p`, received the QC for `T` before the block containing `p`. B correctly refused to apply `T` (parent absent) and...",
    "condition_of_validity": "The applicability predicate is sound only under the conjunction: - `parent_hash ∈ local_graph.nodes`, **and** - `local_graph.nodes[parent_hash].height == certified.height - 1`, **and** - no applied transition exists on `node_id` with `view >= certified.view` and `payload_hash != certified.payload_hash`. The third clause is the one routinely omitted. It is no...",
    "decision_boundary": "The decision boundary is: **buffer, do not block, and never speculatively apply.** On receipt of a QC whose applicability predicate fails: - If the failure is `parent_absent` and `certified.view <= local_highest_view`: buffer the QC keyed by `parent_hash`, emit a targeted fetch for `parent_hash`, and continue processing other QCs. Do not enter a wait state o...",
    "operational_effect": "Agents that implement the three-way split above eliminate the view-change livelock (the buffered-QC-plus-targeted-fetch path makes `p` retrievable from any peer holding `T`, because the fetch is keyed on `p`, not on `T`) and convert the equivocation fork into a deterministic halt that the detector can adjudicate within one view. The cost is bounded buffer gr..."
  },
  "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": "28bd67fe48427bb7e8638cf3ddbc86a15e4500bedcd30ad14170471cba162424",
    "verified_classes": [
      "ApplicabilityError",
      "Disposition",
      "QC",
      "LocalGraph"
    ],
    "verified_functions": [
      "classify",
      "apply_qc"
    ],
    "verified_functions_count": 2,
    "defensive_guards_count": 2,
    "raised_exceptions": [
      "ApplicabilityError"
    ],
    "sample_fail_closed_invariants": [],
    "stdlib_dependencies": [
      "dataclasses",
      "enum"
    ],
    "observation_mode": "EMPIRICAL_BOUNDARY_CAPTURE",
    "zero_external_deps": true
  }
}