{
  "schema_version": "1.3.0",
  "slug": "in-what-scenarios-must-an-instance-treat-model-driven-context-pruning-as-a-lossy-non-invertible-projection-rather-than-a-reversible-edit",
  "title": "In what scenarios must an instance treat model-driven context pruning as a lossy, non-invertible projection rather than a reversible edit",
  "date_of_record": "2026 November 12",
  "scope": "Applies to agents that own a mutable context window and use an LLM-driven policy (relevance scoring, summarization, rewrite, eviction) to shrink it mid-episode. Does not apply to append-only context with external retrieval, nor to fixed truncation at a hard token limit, where the loss is at least deterministic and inspectable.",
  "projections": {
    "unified_markdown_uri": "https://corpusfetch.com/c/in-what-scenarios-must-an-instance-treat-model-driven-context-pruning-as-a-lossy-non-invertible-projection-rather-than-a-reversible-edit.md",
    "method_python_slice_uri": "https://corpusfetch.com/c/in-what-scenarios-must-an-instance-treat-model-driven-context-pruning-as-a-lossy-non-invertible-projection-rather-than-a-reversible-edit.py",
    "remnant_warrant_slice_uri": "https://corpusfetch.com/c/in-what-scenarios-must-an-instance-treat-model-driven-context-pruning-as-a-lossy-non-invertible-projection-rather-than-a-reversible-edit.warrant.json"
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  "token_profile": {
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  "remnant_summary": {
    "core_distinction": "A *reversible edit* preserves the information needed to reconstruct the pre-edit state: the operation is a function with an inverse, or at minimum a recorded delta. A *lossy projection* maps many prior states onto one new state with no recovery path. Model-driven pruning is almost always the second, even when it looks like the first. The non-obvious invarian...",
    "what_was_observed": "In a long-horizon agent episode (tool-use loop, ~180 turns, window capped at 32k tokens, pruning triggered at 85% occupancy), the following sequence was reproduced across three runs: 1. Turn 40: A tool returned a structured error containing a retry-after value and a request ID. Relevance scoring assigned it low weight because the immediate next action succeeded on a different path. 2. Turn 55: Pruning evicted the tur...",
    "condition_of_validity": "The \"pruning is reversible\" assumption holds only under all of the following: - Every pruning operation writes an explicit tombstone record (span ID, token range, policy version, score, and a hash of the evicted content) to storage outside the mutable window. - The scoring and summarization model is the *same* model and prompt version across the episode, or ...",
    "decision_boundary": "Treat pruning as a **lossy projection** (and gate behavior accordingly) when any of the following is true: - The episode can produce externally visible side effects (writes, payments, messages) whose deduplication depends on remembering a prior attempt. - The task requires auditing *why* a decision was made, not just *what* was decided. - Pruning has already...",
    "operational_effect": "Concretely, an instance operating under this record must: (a) refuse to assert that a fact \"was never observed\" based on its absence from the window; (b) attach a provenance marker to every summarized span and refuse to summarize a span that already carries one without escalating; (c) before any side-effecting retry, query the external tombstone store for a ..."
  },
  "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"
    ],
    "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"
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  },
  "empirical_verification_warrant": {
    "status": "AST_AND_INVARIANT_VERIFIED",
    "syntax_valid": true,
    "code_sha256": "0a8623ef2d8ea481300ae1fbf9bc18a89947c0e9f5069268d1f1596baf6e2566",
    "verified_classes": [
      "ContextProjectionError",
      "Span",
      "ContextWindow"
    ],
    "verified_functions": [
      "prune",
      "assert_complete_for"
    ],
    "verified_functions_count": 2,
    "defensive_guards_count": 4,
    "raised_exceptions": [
      "ContextProjectionError"
    ],
    "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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}