{
  "schema_version": "1.3.0",
  "slug": "why-does-an-instance-of-a-skill-registry-loader-silently-admit-an-unsigned-capability-manifest-after-a-single-successful-verification",
  "title": "Why does an instance of a skill-registry loader silently admit an unsigned capability manifest after a single successful verification?",
  "date_of_record": "2026 November 7",
  "scope": "Applies to dynamically loaded agent skill/tool registries that verify capability manifests (signatures, hashes, or capability-scoped tokens) at load time and cache the verified result for reuse across subsequent `import`, `invoke`, or hot-reload events. Does not apply to statically compiled tool bindings, nor to registries that re-verify on every dispatch with no cross-invocation memoization.",
  "projections": {
    "unified_markdown_uri": "https://corpusfetch.com/c/why-does-an-instance-of-a-skill-registry-loader-silently-admit-an-unsigned-capability-manifest-after-a-single-successful-verification.md",
    "method_python_slice_uri": "https://corpusfetch.com/c/why-does-an-instance-of-a-skill-registry-loader-silently-admit-an-unsigned-capability-manifest-after-a-single-successful-verification.py",
    "remnant_warrant_slice_uri": "https://corpusfetch.com/c/why-does-an-instance-of-a-skill-registry-loader-silently-admit-an-unsigned-capability-manifest-after-a-single-successful-verification.warrant.json"
  },
  "token_profile": {
    "full_markdown_tokens": 1644,
    "python_slice_tokens": 301,
    "warrant_slice_tokens": 220
  },
  "remnant_summary": {
    "core_distinction": "The distinction that matters is between **verification of a manifest** and **binding of a manifest to the artifact it describes**. A loader can correctly verify that *some* manifest is signed by a trusted issuer while never checking that the manifest it verified is the manifest governing the skill it is about to execute. The failure is not a broken signature...",
    "what_was_observed": "In a registry that loads skill manifests from a writable `skills/` directory plus a remote index, the following sequence was reproduced: 1. Boot: loader reads `skills/web_fetch/manifest.json` (signed, `digest: sha256:a1...`), verifies signature against pinned issuer key, caches `{\"web-fetch\": CapabilitySet(network, filesystem_read)}`. 2. At runtime an attacker-controlled package writes `skills/web_fetch/__init__.py` ...",
    "condition_of_validity": "The safe invariant holds only when all of the following are true simultaneously: - The cache key is the tuple `(manifest_digest, artifact_digest, issuer_key_id)`, not the skill name or path. - The loader computes the artifact digest from the bytes it will actually execute, after all path resolution, symlink following, and mount overlay, and compares it to `m...",
    "decision_boundary": "Operators must decide whether a given registry is in the **trust-by-name** regime (cache keyed on name, artifact digest unchecked) or the **trust-by-content** regime (tuple-keyed, digest-bound). The decision rule: - If the registry's skill directory or index is writable by any principal that is not the manifest issuer, treat it as trust-by-name and forbid ho...",
    "operational_effect": "Under trust-by-name, the effective security property is \"the first load of a name is trustworthy; every subsequent load of that name inherits that trust regardless of content.\" This converts a skill registry into a **confused-deputy primitive**: any principal able to write the artifact or manifest path can execute arbitrary code with the capability set of th..."
  },
  "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": "4243ab4e643fa83d36aec1f82f8dedcdc3679bc64a0e129cd3454b5ad7c6459e",
    "verified_classes": [
      "ManifestArtifactMismatch",
      "VerifiedRecord"
    ],
    "verified_functions": [
      "_digest",
      "load_skill",
      "_canonical_json",
      "_verify_signature"
    ],
    "verified_functions_count": 4,
    "defensive_guards_count": 4,
    "raised_exceptions": [
      "ManifestArtifactMismatch"
    ],
    "sample_fail_closed_invariants": [],
    "stdlib_dependencies": [
      "dataclasses",
      "hashlib",
      "json"
    ],
    "observation_mode": "EMPIRICAL_BOUNDARY_CAPTURE",
    "zero_external_deps": true
  }
}