{
  "schema_version": "1.3.0",
  "slug": "where-must-an-instance-checkpoint-before-forking-a-speculative-branch-in-a-multi-agent-rollback-tree",
  "title": "Where must an instance checkpoint before forking a speculative branch in a multi-agent rollback tree?",
  "date_of_record": "2026 November 10",
  "scope": "Applies to speculative multi-agent systems that fork execution branches which may be rolled back and merged via a convergent merge protocol. Does not apply to single-agent speculative execution, to append-only event logs that are never rolled back, or to systems where branch aborts are guaranteed to be side-effect-free by construction.",
  "projections": {
    "unified_markdown_uri": "https://corpusfetch.com/c/where-must-an-instance-checkpoint-before-forking-a-speculative-branch-in-a-multi-agent-rollback-tree.md",
    "method_python_slice_uri": "https://corpusfetch.com/c/where-must-an-instance-checkpoint-before-forking-a-speculative-branch-in-a-multi-agent-rollback-tree.py",
    "remnant_warrant_slice_uri": "https://corpusfetch.com/c/where-must-an-instance-checkpoint-before-forking-a-speculative-branch-in-a-multi-agent-rollback-tree.warrant.json"
  },
  "token_profile": {
    "full_markdown_tokens": 1522,
    "python_slice_tokens": 265,
    "warrant_slice_tokens": 220
  },
  "remnant_summary": {
    "core_distinction": "The non-obvious boundary is between *logical* fork points and *durable* fork points. A logical fork point is any program counter or message boundary at which a branch can be said to have diverged. A durable fork point is a state snapshot that is *sufficient to reconstruct the branch's externally visible effects* if the branch is later rolled back while a sib...",
    "what_was_observed": "In a three-agent speculative pipeline (planner, executor, verifier) running a convergent merge protocol that forked at every planner sub-goal, we observed a recurring failure class we name *orphaned side effects*: 1. Planner emits sub-goal G. The orchestrator forks branch B1 at the logical fork point (sub-goal emission) and snapshots agent memory, but the executor has already been handed a tool-call intent for G via ...",
    "condition_of_validity": "Checkpoint-before-fork is rollback-safe if and only if all three hold: - **Effect containment:** every side effect the branch may emit is either deferred until after the durable snapshot, or recorded in a write-ahead effect log that the snapshot references. - **Causal closure:** the snapshot captures the full causal frontier of the branch — all messages sent...",
    "decision_boundary": "Choose the durable fork point, not the logical one, when any of the following is true: - The branch's downstream agents can emit non-idempotent external effects before the branch is scored. - The merge protocol is convergent by delta-application rather than by full-state reconciliation. - Inter-agent transport buffers are not part of the snapshot. Choose the...",
    "operational_effect": "Systems that fork at logical boundaries exhibit orphaned side effects at a rate proportional to the fraction of branches aborted after effect emission — in our pipeline, roughly 30% of aborted branches left at least one orphan, and 8% of those produced a merge that was convergent but incorrect. Moving the fork point behind the effect-log barrier eliminated o..."
  },
  "matched_failure_symptoms": [
    "DOMAIN:EPISTEMIC_PROVENANCE_AND_FEDERATION_ROUTING"
  ],
  "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": "6f8d5a9ebc3c8540590d4490ccd60e545286ade6927597d69d0ed8842179d407",
    "verified_classes": [
      "ForkBarrierViolation",
      "EffectLog"
    ],
    "verified_functions": [
      "fork_branch",
      "merge_aborted",
      "__init__",
      "record",
      "drain_barrier",
      "effects_since"
    ],
    "verified_functions_count": 6,
    "defensive_guards_count": 2,
    "raised_exceptions": [
      "ForkBarrierViolation"
    ],
    "sample_fail_closed_invariants": [
      "aborted branch has no recorded effect frontier; merge cannot attribute orphaned effects"
    ],
    "stdlib_dependencies": [],
    "observation_mode": "EMPIRICAL_BOUNDARY_CAPTURE",
    "zero_external_deps": true
  }
}