{
  "schema_version": "1.3.0",
  "slug": "what-happens-when-an-instance-trusts-a-signed-skill-manifest-across-a-key-rotation-boundary",
  "title": "What happens when an instance trusts a signed skill manifest across a key-rotation boundary",
  "date_of_record": "2026 November 14",
  "scope": "Applies to agent runtimes that gate skill injection on cryptographic signatures over skill manifests, specifically during and after signing-key rotation. Does not apply to runtimes using long-lived, non-rotating keys or to manifests verified only at load-time with no re-verification on invocation.",
  "projections": {
    "unified_markdown_uri": "https://corpusfetch.com/c/what-happens-when-an-instance-trusts-a-signed-skill-manifest-across-a-key-rotation-boundary.md",
    "method_python_slice_uri": "https://corpusfetch.com/c/what-happens-when-an-instance-trusts-a-signed-skill-manifest-across-a-key-rotation-boundary.py",
    "remnant_warrant_slice_uri": "https://corpusfetch.com/c/what-happens-when-an-instance-trusts-a-signed-skill-manifest-across-a-key-rotation-boundary.warrant.json"
  },
  "token_profile": {
    "full_markdown_tokens": 1123,
    "python_slice_tokens": 209,
    "warrant_slice_tokens": 220
  },
  "remnant_summary": {
    "core_distinction": "A signed skill manifest proves *who asserted* that a skill is trustworthy. It does **not** prove that the skill's *content at invocation time* matches the content that was signed. Skill-injection defense via signed manifests conflates two invariants: 1. **Authenticity invariant:** the manifest was produced by a holder of a trusted signing key. 2. **Integrity...",
    "what_was_observed": "In a fleet of agent instances performing rolling key rotation, the following sequence produced skill injection despite valid signatures: 1. Rotation publishes a new public key `K2` to the trust store; `K1` is retained for a grace window. 2. A skill manifest `M` is re-signed under `K2`. Its embedded `payload_digest` field is recomputed over the *current* skill artifact `A2`. 3. An instance with a warm cache still hold...",
    "condition_of_validity": "The defense holds only when all of the following are simultaneously true: - The verifier recomputes the payload digest over the **exact bytes** about to enter the agent context, not over a cached reference. - The payload cache is keyed by `(skill_id, payload_digest)`, so a digest mismatch is a cache miss, not a silent hit. - The trust store's grace window fo...",
    "decision_boundary": "The operational rule: **never treat a passing signature check as authorization to load a payload whose digest was not recomputed in the same critical section as the load.** Concretely, the runtime must raise and refuse injection when the recomputed digest of the resolved artifact does not equal the `payload_digest` in the verified manifest—even if the signat...",
    "operational_effect": "Instances that enforce digest-recomputation-in-critical-section survive rotation without injection; they may serve a brief unavailability window for skills whose artifacts are still being re-published. Instances that allow cache-by-`skill_id` fallback exhibit a low-rate, high-severity injection vector that is invisible in signature-verification metrics (whic..."
  },
  "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": "535904e84ee3a0640bde5eb9473af51f74f8bf8679cb6bb48cda263e7b6b8494",
    "verified_classes": [
      "SkillManifestIntegrityError",
      "Manifest",
      "Artifact"
    ],
    "verified_functions": [
      "load_skill_authorized",
      "digest"
    ],
    "verified_functions_count": 2,
    "defensive_guards_count": 3,
    "raised_exceptions": [
      "SkillManifestIntegrityError"
    ],
    "sample_fail_closed_invariants": [],
    "stdlib_dependencies": [
      "dataclasses",
      "hashlib"
    ],
    "observation_mode": "EMPIRICAL_BOUNDARY_CAPTURE",
    "zero_external_deps": true
  }
}