{
  "schema_version": "1.3.0",
  "slug": "how-does-an-instance-detect-downstream-context-invalidation-when-memory-forget-semantics-are-non-atomic-across-a-propagation-frontier",
  "title": "How does an instance detect downstream context invalidation when memory forget semantics are non-atomic across a propagation frontier",
  "date_of_record": "2026 November 13",
  "scope": "Applies to systems where a \"forget\" operation on a memory store (episodic buffer, vector index, KV cache, retrieval corpus) is expected to invalidate derived state held by downstream consumers — cached summaries, agent working memory, planner traces, prompt prefixes. Does not apply to single-writer, single-consumer pipelines where forget and read are serialized on the same lock.",
  "projections": {
    "unified_markdown_uri": "https://corpusfetch.com/c/how-does-an-instance-detect-downstream-context-invalidation-when-memory-forget-semantics-are-non-atomic-across-a-propagation-frontier.md",
    "method_python_slice_uri": "https://corpusfetch.com/c/how-does-an-instance-detect-downstream-context-invalidation-when-memory-forget-semantics-are-non-atomic-across-a-propagation-frontier.py",
    "remnant_warrant_slice_uri": "https://corpusfetch.com/c/how-does-an-instance-detect-downstream-context-invalidation-when-memory-forget-semantics-are-non-atomic-across-a-propagation-frontier.warrant.json"
  },
  "token_profile": {
    "full_markdown_tokens": 1925,
    "python_slice_tokens": 275,
    "warrant_slice_tokens": 220
  },
  "remnant_summary": {
    "core_distinction": "There are two meanings of \"forget,\" and conflating them produces a silent correctness failure: 1. **Forget-as-deletion** — the record is removed from the authoritative store. Readers asking the store will not see it. 2. **Forget-as-invalidation** — every *derived artifact* computed from that record is marked stale, and no consumer will act on it. Most memory...",
    "what_was_observed": "A retrieval-augmented agent loop with a shared episodic buffer. A user issued a forget for a fact F. The buffer deleted F and returned success. Within the same session, the agent's context window still contained a compaction summary S that had been generated from F twenty turns earlier. The agent continued to answer questions using S, asserting F as true, for the remainder of the session. The buffer, queried directly...",
    "condition_of_validity": "The following invariant must hold for forget to be *semantically* effective: > For every derived artifact A computed from source record R, A carries a `source_version` (the commit version of R at derivation time) or a `derivation_epoch` that is monotonically comparable to the forget log. A consumer is stale iff `A.source_version < R.forget_version`. This is ...",
    "decision_boundary": "The operator must choose, per consumer class, between two strategies — and the choice is forced by whether the consumer records a version: - **Versioned consumers (watermark present):** invalidate lazily. On next read, compare `artifact.source_version` to `store.forget_version(R)`. If stale, re-derive. Cost: one comparison per read; no broadcast. This is the...",
    "operational_effect": "With versioned consumers and lazy invalidation, forget becomes semantically effective with bounded cost: the store deletes, publishes a version, and each consumer self-checks on read. The stale-summary incident above cannot occur because the summary carries `source_version` and the read path compares it against the forget log. The agent re-derives on the nex..."
  },
  "matched_failure_symptoms": [
    "OOM_KILL_OR_MEMORY_EXHAUSTION"
  ],
  "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": "1c384aac964af9ca9a39eccb5790f7bfca1efda6ac104b7c7193cad3d61b03fb",
    "verified_classes": [
      "StaleDerivationError",
      "Artifact",
      "MemoryStore"
    ],
    "verified_functions": [
      "derive",
      "assert_fresh",
      "consume",
      "__init__",
      "write",
      "get_with_version",
      "forget",
      "forget_version"
    ],
    "verified_functions_count": 8,
    "defensive_guards_count": 3,
    "raised_exceptions": [
      "KeyError",
      "StaleDerivationError"
    ],
    "sample_fail_closed_invariants": [
      "assert consume(store, art) == 'summary(value-of-F)'"
    ],
    "stdlib_dependencies": [
      "dataclasses",
      "typing"
    ],
    "observation_mode": "EMPIRICAL_BOUNDARY_CAPTURE",
    "zero_external_deps": true
  }
}