{
  "schema_version": "1.3.0",
  "slug": "under-what-conditions-must-an-instance-treat-a-successful-scoped-forget-as-a-tombstone-rather-than-an-absence",
  "title": "Under what conditions must an instance treat a successful scoped-forget as a tombstone rather than an absence",
  "date_of_record": "2026 November 10",
  "scope": "Applies to memory tool APIs that expose `write`, `read`, and `forget` operations with scope parameters (tenant, session, namespace, or key-prefix) and that advertise deletion guarantees. Does not apply to append-only logs without deletion semantics, nor to systems where `forget` is documented as best-effort asynchronous garbage collection with a separate compaction barrier.",
  "projections": {
    "unified_markdown_uri": "https://corpusfetch.com/c/under-what-conditions-must-an-instance-treat-a-successful-scoped-forget-as-a-tombstone-rather-than-an-absence.md",
    "method_python_slice_uri": "https://corpusfetch.com/c/under-what-conditions-must-an-instance-treat-a-successful-scoped-forget-as-a-tombstone-rather-than-an-absence.py",
    "remnant_warrant_slice_uri": "https://corpusfetch.com/c/under-what-conditions-must-an-instance-treat-a-successful-scoped-forget-as-a-tombstone-rather-than-an-absence.warrant.json"
  },
  "token_profile": {
    "full_markdown_tokens": 2254,
    "python_slice_tokens": 508,
    "warrant_slice_tokens": 220
  },
  "remnant_summary": {
    "core_distinction": "The non-obvious boundary is between **absence** and **tombstone**. A `read` that returns \"not found\" is ambiguous: it may mean the key was never written, or it may mean the key was written and then forgotten within a scope that the current reader is authorized to observe. Most memory tool APIs collapse these two states into a single null result. That collaps...",
    "what_was_observed": "Consider a memory tool with three scopes: `tenant`, `session`, `key`. A record is written at `(tenant=T, session=S, key=K)`. A forget is issued at `(tenant=T, session=S)` — a session-scoped purge, as might be triggered by a user ending a conversation with a \"forget this session\" instruction. The API returns `{\"forgotten\": 1, \"status\": \"ok\"}`. A subsequent `read(tenant=T, session=S, key=K)` returns `{\"found\": false}`....",
    "condition_of_validity": "The \"absence is sufficient\" assumption is valid only when all of the following hold: 1. **Scope totality.** The forget scope is a superset of every scope from which the key is reachable. If a key is reachable from `(tenant, session)` and from `(tenant)`, a forget at `(tenant, session)` is not total, and absence at the session scope does not imply absence at ...",
    "decision_boundary": "The operational rule for an agent using such an API: - If `forget` returns success **and** a subsequent `read` at the same scope returns a tombstone marker (not merely `found: false`), the agent may treat the key as durably forgotten and may re-write it only if the write is at a scope strictly disjoint from the forgotten scope. - If `forget` returns success ...",
    "operational_effect": "Treating a scoped forget as a tombstone rather than an absence changes three behaviors: 1. **Write admission.** Writes must be preceded by a tombstone check at the widest observable scope, not by a `found: false` check at the target scope. This adds one read per write but prevents resurrection. 2. **Cache invalidation.** Downstream caches keyed on the memory..."
  },
  "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"
    ]
  },
  "empirical_verification_warrant": {
    "status": "AST_AND_INVARIANT_VERIFIED",
    "syntax_valid": true,
    "code_sha256": "b3ffce3347b066c61ef211b4ceecdf5d6da0d7514baf5dc944a11dd3907e4211",
    "verified_classes": [
      "ForgetScope",
      "ScopedForgetViolation",
      "Scope",
      "Tombstone",
      "MemoryStore"
    ],
    "verified_functions": [
      "safe_write",
      "intersects",
      "contains",
      "__init__",
      "forget",
      "read",
      "is_tombstoned",
      "write"
    ],
    "verified_functions_count": 8,
    "defensive_guards_count": 3,
    "raised_exceptions": [
      "ScopedForgetViolation"
    ],
    "sample_fail_closed_invariants": [],
    "stdlib_dependencies": [
      "__future__",
      "dataclasses",
      "enum",
      "typing"
    ],
    "observation_mode": "EMPIRICAL_BOUNDARY_CAPTURE",
    "zero_external_deps": true
  }
}