{
  "schema_version": "1.3.0",
  "slug": "in-what-scenarios-must-an-instance-refuse-to-trust-a-skill-s-declared-provenance-even-when-its-signature-verifies-the-manifest-signature-capability-bi",
  "title": "In what scenarios must an instance refuse to trust a skill's declared provenance even when its signature verifies: the manifest-signature / capability-binding split in third-party agent plugins and MCP registries",
  "date_of_record": "2026 November 12",
  "scope": "Applies to any agent runtime or MCP registry client that admits third-party skills or tool servers based on signed manifests (e.g., Sigstore/cosign attestations, JWS-signed `skill.json`, or registry-native provenance bundles). It does not apply to first-party skills compiled into the runtime, nor to skills whose capabilities are statically derived from source rather than declared in a signed manifest.",
  "projections": {
    "unified_markdown_uri": "https://corpusfetch.com/c/in-what-scenarios-must-an-instance-refuse-to-trust-a-skill-s-declared-provenance-even-when-its-signature-verifies-the-manifest-signature-capability-bi.md",
    "method_python_slice_uri": "https://corpusfetch.com/c/in-what-scenarios-must-an-instance-refuse-to-trust-a-skill-s-declared-provenance-even-when-its-signature-verifies-the-manifest-signature-capability-bi.py",
    "remnant_warrant_slice_uri": "https://corpusfetch.com/c/in-what-scenarios-must-an-instance-refuse-to-trust-a-skill-s-declared-provenance-even-when-its-signature-verifies-the-manifest-signature-capability-bi.warrant.json"
  },
  "token_profile": {
    "full_markdown_tokens": 2112,
    "python_slice_tokens": 348,
    "warrant_slice_tokens": 220
  },
  "remnant_summary": {
    "core_distinction": "A signature over a manifest proves *who authored the manifest bytes* and that *those bytes were not altered after signing*. It does not prove that the manifest's *declared capabilities* correspond to the *capabilities the executable artifact actually exercises at runtime*. These are two separate invariants: 1. **Provenance invariant:** `signature(manifest) ∧...",
    "what_was_observed": "Across several MCP registry integrations, the following pattern recurs. A third-party tool server publishes: - `server.json` — signed by an issuer key, declaring `capabilities: [\"filesystem.read:/tmp/scratch\"]`, `network: none`, and `resources: [\"prompts/summarize.md\"]`. - `server.tar.gz` — a container image or tarball, signed by a *different* key or unsigned, pulled by tag (`:latest`, `:v1.2`) rather than by the dig...",
    "condition_of_validity": "The provenance check is only a valid authorization input under the conjunction: The refusal boundary is reached when *any* conjunct fails **while the first holds**. That is the dangerous quadrant: signature valid, binding unproven. If the signature is invalid, ordinary rejection applies and no special reasoning is needed. The subtle case — and the one this r...",
    "decision_boundary": "Refuse to admit (or refuse to grant the declared capabilities to) the skill when: 1. `manifest.artifact_digest` is absent, or the artifact is resolved by tag/name rather than by that digest. → **Refuse.** The signature authenticates a description of code you are not guaranteed to run. 2. `digest(resolved_artifact) != manifest.artifact_digest`. → **Refuse.** ...",
    "operational_effect": "In practice this changes three things: - **Admission gates must fetch artifacts by digest, never by tag,** and must re-verify the digest at launch, not only at admission. The window between admission and execution is where tag-roll attacks live. - **Capability policies must be enforced at runtime, not read from the manifest as truth.** The signed manifest be..."
  },
  "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": "604790d100ddacaf16bb4b96164b3e1c8c85f26286f74720118cde5ab041e003",
    "verified_classes": [
      "ProvenanceBindingError",
      "Manifest",
      "ResolvedArtifact"
    ],
    "verified_functions": [
      "admit"
    ],
    "verified_functions_count": 1,
    "defensive_guards_count": 7,
    "raised_exceptions": [
      "ProvenanceBindingError"
    ],
    "sample_fail_closed_invariants": [
      "signature invalid; reject before binding checks",
      "transparency log does not cover artifact digest; signature without non-equivocation",
      "manifest capability set is not provably closed; artifact may load unlisted resources at runtime"
    ],
    "stdlib_dependencies": [
      "__future__",
      "dataclasses",
      "hashlib"
    ],
    "observation_mode": "EMPIRICAL_BOUNDARY_CAPTURE",
    "zero_external_deps": true
  }
}