{
  "schema_version": "1.3.0",
  "slug": "when-must-an-instance-abandon-speculative-rollback-the-irreversibility-horizon-in-optimistic-multi-agent-branching",
  "title": "When must an instance abandon speculative rollback: the irreversibility horizon in optimistic multi-agent branching",
  "date_of_record": "2026 November 11",
  "scope": "Applies to orchestrators that fork N agent branches optimistically, execute tool calls speculatively, and reconcile by committing one branch and rolling back the rest. Does not apply to single-branch execution, to branches whose tool calls are all provably idempotent and side-effect-free, or to systems that serialize tool effects behind a commit barrier by construction.",
  "projections": {
    "unified_markdown_uri": "https://corpusfetch.com/c/when-must-an-instance-abandon-speculative-rollback-the-irreversibility-horizon-in-optimistic-multi-agent-branching.md",
    "method_python_slice_uri": "https://corpusfetch.com/c/when-must-an-instance-abandon-speculative-rollback-the-irreversibility-horizon-in-optimistic-multi-agent-branching.py",
    "remnant_warrant_slice_uri": "https://corpusfetch.com/c/when-must-an-instance-abandon-speculative-rollback-the-irreversibility-horizon-in-optimistic-multi-agent-branching.warrant.json"
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  "token_profile": {
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  "remnant_summary": {
    "core_distinction": "The common framing treats rollback as the inverse of speculative execution: you branch, you race, you keep the winner, you undo the losers. This is valid only while every speculative effect is *reversible*. The non-obvious boundary is that rollback is not a property of the branch's *state* — it is a property of the *external effects* the branch has already e...",
    "what_was_observed": "In a system running three-way optimistic branching over a tool surface that included a notification sender, a record-writer against a downstream store with no delete API, and a search/read tool, the following sequence recurred under load: 1. Three branches forked from a shared plan node. Each was permitted to speculatively invoke tools before the reconciler selected a winner. 2. Branch B (a loser) invoked the notific...",
    "condition_of_validity": "Speculative rollback is valid **if and only if**, for every tool call a branch may speculatively emit, at least one of the following holds: - The effect is idempotent under a stable reconciliation key, so that re-execution by the winner is indistinguishable from the loser's speculative execution (the loser's effect and the winner's effect collapse to one). -...",
    "decision_boundary": "The decision the orchestrator must make at each fork is not \"should I speculate?\" but \"**which tools may this branch speculatively invoke before the reconciler's decision is known?**\" The boundary is drawn at the first irreversible tool in the branch's plan. Concretely: - **Before the horizon** (only reversible/idempotent/compensable/staged tools invoked): t...",
    "operational_effect": "The practical consequence is that optimistic branching must be **effect-aware**, not just state-aware. The reconciler's rollback path must consult the branch's emitted-effect ledger and refuse to roll back any branch that has crossed the horizon. When such a branch loses, the system must surface an *irreconcilable speculation* — a condition that requires eit..."
  },
  "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": "1c33cef717cbd9f0d1edbde75daa837e48672bfcfa8f51f108760bb8f81a9f14",
    "verified_classes": [
      "EffectClass",
      "EmittedEffect",
      "Branch",
      "IrreconcilableSpeculationError"
    ],
    "verified_functions": [
      "rollback_branch",
      "emit",
      "crossed_horizon"
    ],
    "verified_functions_count": 3,
    "defensive_guards_count": 1,
    "raised_exceptions": [
      "IrreconcilableSpeculationError"
    ],
    "sample_fail_closed_invariants": [],
    "stdlib_dependencies": [
      "dataclasses",
      "enum"
    ],
    "observation_mode": "EMPIRICAL_BOUNDARY_CAPTURE",
    "zero_external_deps": true
  }
}