{
  "schema_version": "1.3.0",
  "slug": "what-structural-signals-indicate-that-hierarchical-context-compaction-has-crossed-the-salience-inversion-boundary",
  "title": "What structural signals indicate that hierarchical context compaction has crossed the salience inversion boundary",
  "date_of_record": "2026 November 12",
  "scope": "Applies to long-horizon agent contexts using hierarchical summarization with salience-based eviction, where a working set is repeatedly re-summarized and low-salience spans are dropped to bound token budget. Does not apply to single-shot summarization, append-only logs with no eviction, or systems where summaries are never themselves re-summarized.",
  "projections": {
    "unified_markdown_uri": "https://corpusfetch.com/c/what-structural-signals-indicate-that-hierarchical-context-compaction-has-crossed-the-salience-inversion-boundary.md",
    "method_python_slice_uri": "https://corpusfetch.com/c/what-structural-signals-indicate-that-hierarchical-context-compaction-has-crossed-the-salience-inversion-boundary.py",
    "remnant_warrant_slice_uri": "https://corpusfetch.com/c/what-structural-signals-indicate-that-hierarchical-context-compaction-has-crossed-the-salience-inversion-boundary.warrant.json"
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  "token_profile": {
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  "remnant_summary": {
    "core_distinction": "The failure mode is not \"summary drift\" (lossy paraphrase) and not \"context overflow\" (budget exhaustion). It is a *salience inversion*: after enough compaction rounds, the salience signal that drives eviction begins to rank spans by their *survivability* rather than their *task relevance*. Summaries are dense, self-consistent, and lexically rich; raw spans ...",
    "what_was_observed": "In a 40-round agent session (research-and-synthesize task, 180k-token budget, hierarchical summarizer at depth 3, salience scorer = embedding cosine to a fixed task query plus a recency decay), the following were logged per round: - `raw_ratio` = raw tokens retained / total retained tokens. Monotone decline from 0.71 to 0.09 over rounds 1–28, then flat. - `summary_depth_max` = deepest summary level present. Rose 1→3 ...",
    "condition_of_validity": "The inversion boundary is crossed only when all three hold: 1. **Re-summarization depth ≥ 2.** With a single summarization layer, summaries never compete with summaries, and raw spans retain a stable salience advantage. 2. **A salience scorer whose input distribution shifts toward summaries.** Any scorer fit on raw text (embedding models, BM25, LLM-judged sa...",
    "decision_boundary": "Do not attempt to fix inversion by retuning the salience scorer. The scorer is behaving correctly given its inputs; the inputs are the problem. The decision boundary is: - **If `raw_ratio` < 0.25 and `distinct_source_spans` is falling while `query_cosine_retained` is rising → halt compaction and rehydrate.** Treat this as an invariant violation, not a tuning...",
    "operational_effect": "Enforcing provenance-reachability as a hard invariant (every retained summary must have ≥ 1 reachable leaf span, and the reachable-leaf count must not fall below a floor set at session start) changes the compaction policy from \"keep the most salient\" to \"keep the most salient *subject to grounding*.\" This costs token budget — observed 18–24% in the runs abov..."
  },
  "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": "a59c9adfb8d347777ddc337a99535a3ef300c7c361ee2d21fc1c4cbe87da60cc",
    "verified_classes": [
      "SalienceInversionError",
      "CompactionState"
    ],
    "verified_functions": [
      "check_inversion",
      "raw_ratio"
    ],
    "verified_functions_count": 2,
    "defensive_guards_count": 3,
    "raised_exceptions": [
      "SalienceInversionError"
    ],
    "sample_fail_closed_invariants": [],
    "stdlib_dependencies": [
      "dataclasses"
    ],
    "observation_mode": "EMPIRICAL_BOUNDARY_CAPTURE",
    "zero_external_deps": true
  }
}