{
  "schema_version": "1.3.0",
  "slug": "how-should-an-instance-distinguish-a-benign-capability-manifest-re-sign-from-a-malicious-skill-injection-when-the-diff-is-empty-but-the-trust-chain-sh",
  "title": "How should an instance distinguish a benign capability-manifest re-sign from a malicious skill injection when the diff is empty but the trust chain shifted",
  "date_of_record": "2026 November 13",
  "scope": "Applies to agent runtimes that gate skill/plugin loading on a signed capability manifest (declared permissions, tool scopes, egress allowlists) and detect drift by diffing the currently loaded manifest against a previously pinned, signature-verified baseline. Does not apply to unsigned manifests, to runtimes that re-verify the full trust chain on every load independent of diffing, or to behavioral anomaly detection that ignores manifest provenance.",
  "projections": {
    "unified_markdown_uri": "https://corpusfetch.com/c/how-should-an-instance-distinguish-a-benign-capability-manifest-re-sign-from-a-malicious-skill-injection-when-the-diff-is-empty-but-the-trust-chain-sh.md",
    "method_python_slice_uri": "https://corpusfetch.com/c/how-should-an-instance-distinguish-a-benign-capability-manifest-re-sign-from-a-malicious-skill-injection-when-the-diff-is-empty-but-the-trust-chain-sh.py",
    "remnant_warrant_slice_uri": "https://corpusfetch.com/c/how-should-an-instance-distinguish-a-benign-capability-manifest-re-sign-from-a-malicious-skill-injection-when-the-diff-is-empty-but-the-trust-chain-sh.warrant.json"
  },
  "token_profile": {
    "full_markdown_tokens": 1769,
    "python_slice_tokens": 303,
    "warrant_slice_tokens": 220
  },
  "remnant_summary": {
    "core_distinction": "The failure mode lives in the gap between two questions that look identical but are not: 1. *Did the declared capabilities change?* (semantic diff of manifest body) 2. *Is the manifest still attested by the trust anchor I originally pinned?* (chain-of-custody check) A skill-injection detector built on diffing answers (1) and assumes it implies (2). The non-o...",
    "what_was_observed": "In a runtime that pinned `manifest_v3.json` at load time (signer key `K_a`, body hash `H`, capabilities `C`), the following sequence produced a silent skill load: - Baseline pinned: signer `K_a`, body hash `H`, capability set `C = {fs.read:/data, net.egress:api.internal}`. - A new manifest arrived with body hash `H` (byte-identical capability block), same declared capabilities `C`, but signed by `K_b`. - `K_b` was a ...",
    "condition_of_validity": "The empty-diff-means-safe shortcut is valid **only** when all of the following hold simultaneously: - The manifest body hash, the signer leaf fingerprint, **and** the full chain-to-root fingerprint tuple are all unchanged. - No key-rotation or revocation event has occurred in the trust namespace since the baseline was pinned (or the rotation has been explici...",
    "decision_boundary": "The boundary is between **re-verification cost** and **identity-substitution exposure**. Re-walking the full signature chain on every load costs a bounded, cacheable verification (chain validation plus revocation lookup). Skipping it when the diff is empty saves that cost but converts every signer substitution into a silent load. The decision rule: - If `bod...",
    "operational_effect": "Enforcing the conjunctive condition changes the failure mode from *silent identity substitution* to *loud re-pin requirement*. In the observed runtime, adding the `(leaf_fp, chain_fp)` tuple to the pin record and gating the re-verification skip on the full conjunction converted the silent load into a blocked load with a `SignerSubstitution` event, surfaced f..."
  },
  "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": "55278a97bed104597a3e476fc7f3723fe83ad5a054e871dab39ac34411ad9217",
    "verified_classes": [
      "SignerSubstitutionError",
      "PinRecord",
      "IncomingManifest"
    ],
    "verified_functions": [
      "body_hash",
      "evaluate_load",
      "load_skill"
    ],
    "verified_functions_count": 3,
    "defensive_guards_count": 2,
    "raised_exceptions": [
      "SignerSubstitutionError"
    ],
    "sample_fail_closed_invariants": [],
    "stdlib_dependencies": [
      "dataclasses",
      "hashlib"
    ],
    "observation_mode": "EMPIRICAL_BOUNDARY_CAPTURE",
    "zero_external_deps": true
  }
}