{
  "schema_version": "1.3.0",
  "slug": "in-what-scenarios-must-an-instance-refuse-a-forget-request-to-preserve-tombstone-durability-across-a-read-write-forget-memory-interface",
  "title": "In what scenarios must an instance refuse a forget request to preserve tombstone durability across a read/write/forget memory interface",
  "date_of_record": "2026 November 7",
  "scope": "Applies to agent-facing memory tool interfaces that expose `read`, `write`, and `forget` operations with per-key tombstones and right-to-forget propagation across replicas or downstream derived indexes. Does not apply to append-only audit logs that are legally exempt from erasure, nor to interfaces where `forget` is a purely local cache eviction with no propagation contract.",
  "projections": {
    "unified_markdown_uri": "https://corpusfetch.com/c/in-what-scenarios-must-an-instance-refuse-a-forget-request-to-preserve-tombstone-durability-across-a-read-write-forget-memory-interface.md",
    "method_python_slice_uri": "https://corpusfetch.com/c/in-what-scenarios-must-an-instance-refuse-a-forget-request-to-preserve-tombstone-durability-across-a-read-write-forget-memory-interface.py",
    "remnant_warrant_slice_uri": "https://corpusfetch.com/c/in-what-scenarios-must-an-instance-refuse-a-forget-request-to-preserve-tombstone-durability-across-a-read-write-forget-memory-interface.warrant.json"
  },
  "token_profile": {
    "full_markdown_tokens": 1532,
    "python_slice_tokens": 238,
    "warrant_slice_tokens": 220
  },
  "remnant_summary": {
    "core_distinction": "The non-obvious boundary is between **tombstone creation** (a local, synchronous, monotonic operation) and **tombstone durability** (a distributed, asynchronous, eventually-consistent operation). A `forget(key)` call that returns success is making two different claims at once: \"a tombstone now shadows this key on this instance\" and \"this tombstone will survi...",
    "what_was_observed": "A memory service with three replicas per shard, tombstone TTL of 30 days, and a derived vector index rebuilt from a change-data stream. A `forget(key)` was issued at T0 against the shard leader. The leader appended the tombstone to its local WAL, returned `OK` at T0+4ms, and scheduled asynchronous replication. At T0+90ms the leader crashed before the tombstone reached a quorum. Failover promoted a replica whose last ...",
    "condition_of_validity": "The rule \"accept a forget request\" is valid only when **all** of the following hold: 1. The tombstone write is acknowledged only after it is durable on a quorum of replicas (or on a single authoritative store with no asynchronous replication lag), **or** the interface explicitly exposes a weaker `forget_async` that returns a token the caller must later confi...",
    "decision_boundary": "The decision is not \"can I write a tombstone?\" — you almost always can. The decision is \"can I promise durability and propagation?\" Concretely: - If replication factor > 1 and the tombstone write is not quorum-acknowledged: **refuse synchronous forget**, return a `ForgetDeferred` with a token, and require the caller to poll or receive a callback. - If tombst...",
    "operational_effect": "Refusing synchronous forget during quorum-degraded or propagation-unsafe windows converts a silent resurrection bug into an explicit, retryable error. Callers that previously assumed success-and-done must handle the deferred path, but they gain a guarantee: a returned success means the tombstone will outlive failover and will reach derived indexes or be re-d..."
  },
  "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": "24cf1815b07dd0d6e01876f8beb0beae907db824faad741f372d48db7081ca86",
    "verified_classes": [
      "ForgetDurabilityError",
      "StoreHealth"
    ],
    "verified_functions": [
      "request_forget"
    ],
    "verified_functions_count": 1,
    "defensive_guards_count": 4,
    "raised_exceptions": [
      "ForgetDurabilityError"
    ],
    "sample_fail_closed_invariants": [],
    "stdlib_dependencies": [
      "dataclasses",
      "time"
    ],
    "observation_mode": "EMPIRICAL_BOUNDARY_CAPTURE",
    "zero_external_deps": true
  }
}