{
  "schema_version": "1.3.0",
  "slug": "in-what-scenarios-must-an-instance-treat-vector-store-deletion-as-a-tombstone-rather-than-a-physical-erasure",
  "title": "In what scenarios must an instance treat vector-store deletion as a tombstone rather than a physical erasure",
  "date_of_record": "2026 November 9",
  "scope": "Applies to systems where GDPR-style erasure requests must propagate through a retrieval-augmented generation (RAG) stack containing at least one approximate nearest-neighbor (ANN) vector index plus an episodic memory store (event log, summarization cache, or agent scratchpad). Does not apply to append-only audit stores under legal hold, nor to purely in-memory session state with no persistence.",
  "projections": {
    "unified_markdown_uri": "https://corpusfetch.com/c/in-what-scenarios-must-an-instance-treat-vector-store-deletion-as-a-tombstone-rather-than-a-physical-erasure.md",
    "method_python_slice_uri": "https://corpusfetch.com/c/in-what-scenarios-must-an-instance-treat-vector-store-deletion-as-a-tombstone-rather-than-a-physical-erasure.py",
    "remnant_warrant_slice_uri": "https://corpusfetch.com/c/in-what-scenarios-must-an-instance-treat-vector-store-deletion-as-a-tombstone-rather-than-a-physical-erasure.warrant.json"
  },
  "token_profile": {
    "full_markdown_tokens": 1453,
    "python_slice_tokens": 251,
    "warrant_slice_tokens": 220
  },
  "remnant_summary": {
    "core_distinction": "There are two distinct operations that engineers routinely conflate: **logical deletion** (the record is no longer returned by retrieval) and **physical erasure** (the bytes are unrecoverable from the medium). GDPR Article 17 demands the latter, but ANN indices are structurally hostile to it. An HNSW or IVF-PQ index does not store vectors as addressable rows...",
    "what_was_observed": "During a red-team exercise on a production RAG system, a subject's erasure request was executed against the vector store (tombstone set, forward map entry removed) and the episodic event log (row deleted). The system reported \"erasure complete.\" A targeted membership-inference probe then recovered the subject's name and a partial attribute with 71% confidence by issuing queries near the residual cluster and reading o...",
    "condition_of_validity": "Physical erasure of a vector is only achievable under one of these conditions: 1. **Index rebuild from a filtered corpus.** The index is destroyed and rebuilt from the post-erasure document set. This is the only method that removes the vector's influence on centroids and graph topology. Cost is O(N) per erasure unless batched. 2. **Per-subject index partitio...",
    "decision_boundary": "The decision point is whether the derived stores have been enumerated and included in the erasure plan. Before executing an erasure, the system must answer: - Does the ANN index support physical node removal, or only tombstoning? (Most do not support physical removal.) - Are there metadata join keys on *surviving* records that reference the erased subject? -...",
    "operational_effect": "The operational consequence is that erasure propagation must be modeled as a **transitive closure over derived artifacts**, not a set of point deletes. The closure includes: the vector index topology, neighbor metadata, summary caches, embedding caches, query logs, and any evaluation sets that captured retrieved context. Each element must be classified as *p..."
  },
  "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": "62b92f291ea94dc8f4263e0e03a7033cad51f17b3fba9d6de2e37535db19451b",
    "verified_classes": [
      "ErasureIncompleteError",
      "ErasureClass",
      "DerivedArtifact",
      "ErasureJob"
    ],
    "verified_functions": [
      "attest"
    ],
    "verified_functions_count": 1,
    "defensive_guards_count": 2,
    "raised_exceptions": [
      "ErasureIncompleteError"
    ],
    "sample_fail_closed_invariants": [],
    "stdlib_dependencies": [
      "dataclasses",
      "enum",
      "hashlib"
    ],
    "observation_mode": "EMPIRICAL_BOUNDARY_CAPTURE",
    "zero_external_deps": true
  }
}