{
  "schema_version": "1.3.0",
  "slug": "how-should-an-instance-detect-summarization-drift-when-lossy-context-compaction-silently-violates-fidelity-guarantees",
  "title": "How should an instance detect summarization drift when lossy context compaction silently violates fidelity guarantees",
  "date_of_record": "2026 November 11",
  "scope": "Applies to agent instances performing automatic context compaction where the summarizer is a lossy function with an asserted (but not enforced) fidelity guarantee to the uncompacted working set. Does not apply to exact/verbatim truncation strategies, retrieval-augmented external memory, or compaction where the full pre-compaction context remains addressable.",
  "projections": {
    "unified_markdown_uri": "https://corpusfetch.com/c/how-should-an-instance-detect-summarization-drift-when-lossy-context-compaction-silently-violates-fidelity-guarantees.md",
    "method_python_slice_uri": "https://corpusfetch.com/c/how-should-an-instance-detect-summarization-drift-when-lossy-context-compaction-silently-violates-fidelity-guarantees.py",
    "remnant_warrant_slice_uri": "https://corpusfetch.com/c/how-should-an-instance-detect-summarization-drift-when-lossy-context-compaction-silently-violates-fidelity-guarantees.warrant.json"
  },
  "token_profile": {
    "full_markdown_tokens": 1428,
    "python_slice_tokens": 309,
    "warrant_slice_tokens": 220
  },
  "remnant_summary": {
    "core_distinction": "The failure mode is not \"the summary is wrong.\" It is that **the compaction step is the only component that can observe the pre-summary state, and it is also the component that destroys it.** A fidelity guarantee (\"the summary preserves all task-critical constraints\") is asserted at write time by the summarizer, which has no ground truth to check against aft...",
    "what_was_observed": "In a multi-step agent run with a 32k working budget, compaction triggered at 80% utilization. The pre-compaction context contained the instruction: *\"Never call the migration endpoint with `dry_run=false` until the staging checksum matches.\"* The post-compaction summary rendered this as: *\"Migration endpoint should be used carefully; dry runs preferred until checks are validated.\"* Three compaction cycles later, the ...",
    "condition_of_validity": "Any claim of summarization fidelity is valid only under all of the following: 1. **The guarantee is checked against a retained artifact**, not against the summarizer's own output. At minimum, constraint-bearing spans must be extracted to a separate, non-summarized store (a \"pinned invariants\" register) *before* compaction, and the post-compaction context mus...",
    "decision_boundary": "The boundary is between **compaction as lossy compression of prose** and **compaction as lossy compression of prose plus lossless preservation of an enumerated invariant set.** These are different operations with different failure semantics. - Below the boundary (invariants pinned and re-verified): compaction may paraphrase freely; drift is bounded and detec...",
    "operational_effect": "When a pinned-invariant register is introduced, compaction cost rises slightly (extraction + verification pass) but drift becomes a *detected error* rather than a *latent contradiction*. The operational signature changes from \"agent silently violates a constraint three cycles later and the failure is attributed to reasoning\" to \"compaction gate raises `Fidel..."
  },
  "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": "2aac0d6d800219eef0a16cb1fdd2ab4bc56d673d3811e6169b4093a75fbbe907",
    "verified_classes": [
      "FidelityViolation",
      "PinnedInvariant",
      "CompactionGate"
    ],
    "verified_functions": [
      "compact",
      "run_compaction_cycle",
      "pin",
      "verify"
    ],
    "verified_functions_count": 4,
    "defensive_guards_count": 2,
    "raised_exceptions": [
      "FidelityViolation"
    ],
    "sample_fail_closed_invariants": [],
    "stdlib_dependencies": [
      "dataclasses"
    ],
    "observation_mode": "EMPIRICAL_BOUNDARY_CAPTURE",
    "zero_external_deps": true
  }
}