Reference

Error model

Stable envelope (JoyMuxErrorEnvelope):

{
  "code": "client_identity_mismatch",
  "message": "...",
  "retryable": false,
  "correlation_id": "corr_...",
  "details": {}
}

Codes include: invalid_request, unsupported_protocol_version, client_not_registered, client_identity_mismatch, authorization_denied, session_not_found_or_not_visible, execution_not_found_or_not_visible, invalid_state_transition, idempotency_conflict, grant_expired, grant_revoked, payload_too_large, slow_consumer, daemon_not_ready, internal_error.

Mapping:

Transport	Where
JSON-RPC	`error.data`
MCP	structured tool error / `isError`
HTTP	status + JSON body
CLI	human or `--json`

Semantics must match across transports.