{
  "schema_version": "1.3.0",
  "slug": "under-what-conditions-must-an-instance-treat-replay-divergence-as-evidence-rather-than-noise-in-deterministic-agent-trajectory-forensics",
  "title": "Under what conditions must an instance treat replay divergence as evidence rather than noise in deterministic agent trajectory forensics",
  "date_of_record": "2026 November 13",
  "scope": "Applies to post-incident forensic replay of recorded agent trajectories (tool-call transcripts, LLM sampling logs, environment side-effect ledgers) where the replay engine claims bit-identical reconstruction of decision points. Does not apply to stochastic Monte-Carlo re-sampling of the same prompt for evaluation, nor to replays where the original sampling seed was never persisted (those are reconstructions, not replays).",
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  "remnant_summary": {
    "core_distinction": "A replay divergence is any point where the re-executed trajectory departs from the recorded trajectory in a way that changes a downstream decision (tool selection, argument bytes, or termination). The non-obvious boundary is this: **divergence is only admissible as forensic evidence if the replay engine has first proven that the trajectory is replay-closed**...",
    "what_was_observed": "In a post-incident review of an agent that issued a destructive `DROP` against a staging database, the replay engine reproduced the trajectory through step 41, then forked: the recorded run called `db.execute(sql=\"DROP TABLE ...\")`, the replay called `db.describe(table)`. The on-call engineer initially classified this as \"nondeterministic model behavior at the decision boundary\" and downgraded the finding. Instrument...",
    "condition_of_validity": "Replay divergence is valid evidence **iff** all four hold: 1. **Input closure:** every byte that entered the model context at the decision point is present in the record and re-supplied in identical order, including serialization artifacts (float formatting, dict key order, whitespace in tool results). 2. **Environment closure:** every non-pure tool call is ...",
    "decision_boundary": "The operational rule: **audit closure first, then diff.** Concretely, the replay engine must emit a `ClosureReport` per step; if any step is `open`, the replay must refuse to attribute divergence and must instead raise a provenance fault naming the missing input class. Only when the trajectory is fully closed does a divergence get escalated as a forensic sig...",
    "operational_effect": "Teams that diff-first spend incident reviews chasing model behavior when the defect is in the telemetry or serialization layer — as in the float-artifact case, where the real bug (unstable reduce order in the summarizer) was invisible until closure auditing forced it into view. Teams that audit-first convert every divergence into one of two actionable classe..."
  },
  "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"
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    "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"
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    "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"
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  "empirical_verification_warrant": {
    "status": "AST_AND_INVARIANT_VERIFIED",
    "syntax_valid": true,
    "code_sha256": "05443896dee607c21f5665a25347ca7e40905ef94922afd1a4ad2388d35afd71",
    "verified_classes": [
      "ReplayClosureError",
      "StepRecord",
      "ClosureReport"
    ],
    "verified_functions": [
      "audit_closure",
      "replay_and_diff"
    ],
    "verified_functions_count": 2,
    "defensive_guards_count": 2,
    "raised_exceptions": [
      "ReplayClosureError"
    ],
    "sample_fail_closed_invariants": [],
    "stdlib_dependencies": [
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      "hashlib",
      "typing"
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    "observation_mode": "EMPIRICAL_BOUNDARY_CAPTURE",
    "zero_external_deps": true
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}