{
  "schema_version": "1.3.0",
  "slug": "under-what-conditions-must-an-instance-treat-lossy-summarization-as-a-compaction-barrier-rather-than-a-compaction-opportunity-in-long-horizon-agent-tr",
  "title": "Under what conditions must an instance treat lossy summarization as a compaction *barrier* rather than a compaction *opportunity* in long-horizon agent trajectories",
  "date_of_record": "2026 November 10",
  "scope": "Applies to agent runtimes that auto-compact trajectory context by replacing spans of turns with lossy summaries under a declared per-span fidelity budget, and that resume execution from compacted state. Does not apply to lossless block-level compaction (e.g., KV eviction, sliding windows over verbatim tokens) where no summarization transform is applied and no fidelity budget is claimed.",
  "projections": {
    "unified_markdown_uri": "https://corpusfetch.com/c/under-what-conditions-must-an-instance-treat-lossy-summarization-as-a-compaction-barrier-rather-than-a-compaction-opportunity-in-long-horizon-agent-tr.md",
    "method_python_slice_uri": "https://corpusfetch.com/c/under-what-conditions-must-an-instance-treat-lossy-summarization-as-a-compaction-barrier-rather-than-a-compaction-opportunity-in-long-horizon-agent-tr.py",
    "remnant_warrant_slice_uri": "https://corpusfetch.com/c/under-what-conditions-must-an-instance-treat-lossy-summarization-as-a-compaction-barrier-rather-than-a-compaction-opportunity-in-long-horizon-agent-tr.warrant.json"
  },
  "token_profile": {
    "full_markdown_tokens": 2258,
    "python_slice_tokens": 380,
    "warrant_slice_tokens": 220
  },
  "remnant_summary": {
    "core_distinction": "Auto-compaction is usually modeled as a *monotone resource reclamation* operation: each compaction reduces token footprint and, because the summary is claimed to preserve \"the information needed to continue,\" the runtime treats the post-compaction state as a valid substitute for the pre-compaction state for all downstream purposes. This is the **compaction-o...",
    "what_was_observed": "In a long-horizon agent run (≈340 turns, tool-using, with a declared per-span fidelity budget of \"preserve decisions, drop deliberation\"), auto-compaction fired at 78% context utilization and summarized a 41-turn span containing an in-progress multi-step migration. The summary recorded: *\"Agent decided to migrate table `orders` to the new schema; migration was underway.\"* It dropped: - the exact set of columns alread...",
    "condition_of_validity": "The compaction-opportunity framing is valid — i.e., a span may be lossily summarized without barrier treatment — **if and only if** all of the following hold for the span at the moment of compaction: - **No pending obligation:** every commitment, tool call, or constraint introduced in the span has been either discharged (its effect observed and confirmed) or...",
    "decision_boundary": "The runtime must decide, per span, between three actions. The boundary is drawn on **obligation state**, not on token pressure: The critical boundary rule: **budget pressure does not override barrier status.** If a barrier span cannot be retained and cannot be repaired before compaction is forced, the correct action is to *fail the compaction* and surface th...",
    "operational_effect": "Treating lossy summarization as a barrier-aware operation changes three runtime behaviors: 1. **Compaction eligibility becomes a join over (span, obligation graph), not a scan over (span, token count).** The runtime must maintain a lightweight obligation ledger — pending commitments with idempotency keys, partial side effects with confirmation predicates, an..."
  },
  "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": "c8431b68e690f9fa8c642d71d166a5e4acdc065f8c9a3dcadabd83413b6c5404",
    "verified_classes": [
      "CompactionBarrierError",
      "Obligation",
      "ObligationLedger",
      "Span"
    ],
    "verified_functions": [
      "is_barrier",
      "compact_span",
      "live_ids",
      "touches"
    ],
    "verified_functions_count": 4,
    "defensive_guards_count": 1,
    "raised_exceptions": [
      "CompactionBarrierError"
    ],
    "sample_fail_closed_invariants": [],
    "stdlib_dependencies": [
      "dataclasses",
      "typing"
    ],
    "observation_mode": "EMPIRICAL_BOUNDARY_CAPTURE",
    "zero_external_deps": true
  }
}