{
  "schema_version": "1.3.0",
  "slug": "what-structural-signals-indicate-that-lossy-context-compaction-has-silently-destroyed-a-recovery-invariant",
  "title": "What structural signals indicate that lossy context compaction has silently destroyed a recovery invariant",
  "date_of_record": "2026 November 14",
  "scope": "Applies to agentic systems that perform automatic lossy summarization of a conversation/tool-trace buffer when a token budget is exceeded, then continue execution against the compacted context. Does not apply to systems that keep a full immutable transcript addressable by handle (retrieval-augmented compaction) or to compaction triggered only at task boundaries where no in-flight state exists.",
  "projections": {
    "unified_markdown_uri": "https://corpusfetch.com/c/what-structural-signals-indicate-that-lossy-context-compaction-has-silently-destroyed-a-recovery-invariant.md",
    "method_python_slice_uri": "https://corpusfetch.com/c/what-structural-signals-indicate-that-lossy-context-compaction-has-silently-destroyed-a-recovery-invariant.py",
    "remnant_warrant_slice_uri": "https://corpusfetch.com/c/what-structural-signals-indicate-that-lossy-context-compaction-has-silently-destroyed-a-recovery-invariant.warrant.json"
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  "remnant_summary": {
    "core_distinction": "A compaction policy is evaluated on two axes that are routinely conflated: **information retention** and **recovery reachability**. Retention is a fuzzy, graded property — did the summary keep the salient facts? Reachability is a hard, binary property — after compaction, can the agent still reconstruct every fact it is *contractually obligated* to be able to...",
    "what_was_observed": "Across a class of long-running tool-using agents, the following pattern recurred. Compaction fired at a soft budget (e.g., 70% of window). The summarizer compressed N turns of tool output into a paragraph. Execution resumed. The failure did not surface at the compaction step — it surfaced 3 to 40 steps later, at the first step whose precondition was a verbatim datum from a compacted region. Symptoms at the point of f...",
    "condition_of_validity": "The reachability invariant holds — and the above signals are diagnostic — only under these conditions: - The task contains at least one **non-regenerable binding**: a datum that cannot be re-derived from the compacted context or re-fetched from an external source without side effects. Regenerable bindings (a path you can `ls`, an ID you can re-query) do not ...",
    "decision_boundary": "The operational rule is a pre-compaction gate, not a post-compaction repair. Before firing a lossy compaction, classify every open obligation by whether its required binding is regenerable. If **any** obligation requires a non-regenerable binding, the compaction policy must either (a) preserve that binding verbatim in the summary under an explicit contract, ...",
    "operational_effect": "Systems that adopted the structural gate observed a characteristic shift: compaction no longer appears in incident post-mortems as a *cause*, because destructive compactions are rejected before they execute. The cost is a higher compaction-refusal rate and more spill-to-store traffic for tasks with many non-regenerable bindings (migrations, multi-step provis..."
  },
  "matched_failure_symptoms": [
    "CONTEXT_DRIFT_OR_ATTENTION_DILUTION"
  ],
  "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": "36f40bb51ca764dc784e405770ba29de644e78e93ec9a0063811d5121a2410ac",
    "verified_classes": [
      "CompactionInvariantError",
      "Binding",
      "Obligation",
      "ContextRegion"
    ],
    "verified_functions": [
      "assert_compaction_safe",
      "compact_or_spill"
    ],
    "verified_functions_count": 2,
    "defensive_guards_count": 2,
    "raised_exceptions": [
      "CompactionInvariantError"
    ],
    "sample_fail_closed_invariants": [],
    "stdlib_dependencies": [
      "dataclasses",
      "typing"
    ],
    "observation_mode": "EMPIRICAL_BOUNDARY_CAPTURE",
    "zero_external_deps": true
  }
}