Error Code Registry¶

When cMCP refuses a request or fails, it returns a short code such as POLICY_DENY that says why. This page is the full list, with the HTTP status and log level for each code and the page that defines it. Use it to look up an error you have seen or to handle errors in your own code.

This is the normative registry for all error codes used across the cMCP Runtime. Every error code MUST be registered here before it is referenced in code, configuration, or other spec documents. Implementations MUST NOT emit error codes that do not appear in this registry.

Runtime Errors¶

error_code	HTTP status	log level	description	spec reference
`ATTESTATION_REPORT_UNAVAILABLE`	503	FATAL	TEE provider did not return an attestation report within timeout	failure-modes.md FM-1
`ATTESTATION_PROVIDER_UNSUPPORTED`	500	FATAL	No supported TEE provider detected and `CMCP_DEV_MODE` is not set	attestation.md §1.1
`POLICY_HASH_MISMATCH`	500	FATAL	Measured policy bundle hash does not match deployment manifest	failure-modes.md FM-4
`POLICY_RELOAD_PINNED_HASH`	500	FATAL	`policy_reload_interval_seconds > 0` configured alongside a pinned `CMCP_POLICY_HASH`. Every reload is validated against that hash, so a changed bundle could never be installed; refused at startup rather than appearing to work	policy-hot-reload.md
`POLICY_SIGNATURE_INVALID`	500	FATAL	A policy bundle's manifest signature is absent, malformed, or does not verify under the pinned `CMCP_POLICY_SIGNING_KEY`; or its `version` did not increase, which would allow a genuinely signed older bundle to be replayed	policy-hot-reload.md
`POLICY_SIGNING_KEY_INVALID`	500	FATAL	`CMCP_POLICY_SIGNING_KEY` or `CMCP_POLICY_SUCCESSOR_SIGNING_KEY` is not a 32-byte Ed25519 public key, the two are equal, or a successor is set without a current key	configuration.md
`POLICY_SIGNING_KEY_REVOKED`	403 / startup	FATAL at startup, WARN at runtime	A policy bundle verifies only under a revoked policy signing key and is refused; or the policy in force was signed by a key revoked since it was installed, so every tool call is refused in every enforcement mode until a bundle signed by a trusted key is installed; or every pinned key is revoked	policy-hot-reload.md
`POLICY_KEY_REVOCATION_INVALID`	none (logged)	WARN	A statement in `signing-key-revocations.json` was refused: malformed, not signed by the current or successor key, or naming a key other than the current one. It is skipped; other statements and the bundle reload still proceed	policy-hot-reload.md
`CONFORMANCE_PROFILE_UNSATISFIED`	500	FATAL	A named `conformance_profile` requires something the deployment has not configured; `aarm` requires an Agent Manifest binding (AARM R6)	STATUS.md
`CATALOG_HASH_MISMATCH`	500	FATAL	Measured catalog hash does not match deployment manifest	attestation.md §5
`CATALOG_RESTART_REQUIRED`	startup	FATAL	Runtime catalog mutation was configured, but routing authority remains immutable until a newly pinned gateway restart	catalog-lifecycle.md
`AGENT_MANIFEST_BINDING_FAILED`	500	FATAL	Signed Agent Manifest signature, authenticated subject, policy hash, or catalog hash did not match the runtime session inputs	session-policy.md
`TOOL_NOT_IN_CATALOG`	403	WARN	Agent requested a tool not present in the attested catalog	cedar-policy.md
`POLICY_DENY`	403	INFO	Cedar policy evaluation returned deny for this call	cedar-policy.md
`CATALOG_TOOL_NAME_COLLISION`	500	FATAL	Two catalog entries register the same `tool_name`	tool-identity.md
`CATALOG_DRIFT_DETECTED`	409	ERROR	Upstream server changed a tool definition since catalog was sealed	attestation.md §5
`MCP_PARSE_FAILURE`	400	WARN	Incoming MCP JSON-RPC message failed to parse	failure-modes.md FM-5
`MCP_INVALID_REQUEST`	400	WARN	Parsed JSON is not a valid JSON-RPC request shape	failure-modes.md FM-5
`RESPONSE_SIZE_EXCEEDED`	413	WARN	Tool response exceeds `max_response_size_bytes`	response-inspection.md Stage 1
`RESPONSE_INJECTION_DETECTED`	403	ERROR	Response inspection detected indirect injection pattern	response-inspection.md Stage 4
`RESPONSE_SCHEMA_VIOLATION_STRICT`	409	WARN	Tool response contains fields outside approved `output_schema` (strict mode)	response-inspection.md Stage 2
`SESSION_SENSITIVITY_POLICY_DENY`	403	INFO	Call denied due to session sensitivity state	session-policy.md
`SESSION_RESET_REQUIRED`	428	INFO	Agent attempted call that requires session reset first	session-policy.md
`SESSION_STATE_STORE_UNAVAILABLE`	startup	FATAL	A configured `session_state_path` could not be opened, so the gateway would run without the cross-instance session-state persistence the operator configured	configuration.md
`TEE_FAULT`	500	ERROR	TEE process fault during call execution	failure-modes.md FM-3
`ATTESTATION_STALE`	412	WARN	Attestation report validity period has expired	attestation.md §3
`BREAK_GLASS_ACTIVE`	200	WARN	Call allowed via catalog exception (break-glass procedure active)	tool-identity.md

Verification Library Errors¶

The following error codes are defined and documented in verification-library.md. They are listed here for cross-reference completeness; the verification library spec is authoritative for their semantics.

error_code
`UNSUPPORTED_PROVIDER`
`SIGNATURE_INVALID`
`PUBLIC_KEY_NOT_BOUND`
`POLICY_HASH_MISMATCH`
`CATALOG_HASH_MISMATCH`
`AGENT_MANIFEST_MISMATCH`
`ATTESTATION_STALE`
`CHAIN_BROKEN`
`CLAIM_MALFORMED`
`EXTERNAL_EVIDENCE_VERIFICATION_FAILED`

Note: POLICY_HASH_MISMATCH, CATALOG_HASH_MISMATCH, and ATTESTATION_STALE appear in both tables. The Runtime emits them during startup or request handling; the verification library emits them during offline or client-side verification. The semantics are consistent across both contexts.