> ## Documentation Index > Fetch the complete documentation index at: https://docs.kylon.io/llms.txt > Use this file to discover all available pages before exploring further. # API error codes > Numeric error codes the Kylon API returns, with HTTP status and default message. Every Kylon API error carries a numeric `code` and a default `message`. Codes are grouped into ranges by category. This page is generated from the API error-code manifest, so it matches the codes the API returns. ## Request / validation (1000-1999) | Code | Name | HTTP | Message | | ---- | --------------------------------- | ---- | ----------------------------------------------------------------------------------------------------------------------------------------------------- | | 1000 | `INVALID_INPUT` | 400 | Invalid input | | 1001 | `DIRECT_MESSAGE_MEMBERSHIP_FIXED` | 400 | Direct message membership is fixed | | 1002 | `THREAD_TARGET_UNSUPPORTED` | 400 | Thread target is not supported | | 1003 | `EXPORT_FORMAT_UNSUPPORTED` | 400 | This file cannot be exported to the requested format | | 1004 | `APP_HANDOFF_CODE_INVALID` | 400 | Invalid or expired sign-in code | | 1005 | `WORKFLOW_CODE_INVALID` | 400 | Workflow code failed to compile | | 1006 | `VOICE_PHONE_NUMBER_REQUIRED` | 400 | Add a phone number before starting a voice call | | 1007 | `SIGNUP_HANDOFF_LINK_UNAVAILABLE` | 400 | This link is no longer available | | 1008 | `REMOTE_MCP_DCR_UNSUPPORTED` | 400 | This server does not support dynamic client registration. Turn it off and enter a Client ID. | | 1009 | `REMOTE_MCP_PKCE_UNSUPPORTED` | 400 | This server's OAuth configuration does not support the required S256 PKCE method. Ask the server owner to enable S256 PKCE or use another MCP server. | ## Authentication / authorization (2000-2999) | Code | Name | HTTP | Message | | ---- | ----------------------------------- | ---- | --------------------------------------------- | | 2000 | `AUTH_REQUIRED` | 401 | Authentication required | | 2001 | `ACCESS_DENIED` | 403 | Access denied | | 2002 | `CLIENT_SESSION_REQUIRED` | 401 | Client session required | | 2003 | `CLIENT_SESSION_INVALID` | 401 | Client session is no longer valid | | 2004 | `ACCOUNT_SUSPENDED` | 403 | This account is suspended | | 2005 | `WORKSPACE_SUSPENDED` | 403 | This workspace is suspended | | 2006 | `SIGNUP_HANDOFF_LINK_NOT_CLAIMABLE` | 403 | This link cannot be claimed with this account | ## Not found (3000-3999) | Code | Name | HTTP | Message | | ---- | --------------------------------- | ---- | --------------------------------------------------------- | | 3000 | `RESOURCE_NOT_FOUND` | 404 | Resource not found | | 3001 | `CHANNEL_AGENT_NOT_FOUND` | 404 | Room agent not found | | 3002 | `ENDPOINT_RETIRED` | 410 | Endpoint has been retired | | 3010 | `APP_RELEASE_NOT_FOUND` | 404 | App release not found | | 3011 | `APP_DOWNLOAD_ARTIFACT_NOT_FOUND` | 404 | App download artifact not found | | 3012 | `SIGNUP_HANDOFF_LINK_NOT_FOUND` | 404 | This link was not found | | 3013 | `TABLE_RESOURCE_RETIRED` | 410 | This structured data resource has moved to a Database App | ## Conflict / invalid state (4000-4999) | Code | Name | HTTP | Message | | ---- | -------------------------------------- | ---- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | 4000 | `CONFLICT` | 409 | Conflict | | 4001 | `WORKSPACE_MEMBER_ALREADY_EXISTS` | 409 | User is already a workspace member | | 4002 | `WORKSPACE_PAYMENT_REQUIRED` | 402 | Workspace credit is required | | 4003 | `WORKSPACE_SETUP_IN_PROGRESS` | 409 | Workspace setup is already in progress | | 4010 | `APP_RELEASE_IMMUTABLE` | 409 | App release is immutable after the edit window | | 4011 | `APP_RELEASE_INVALID_SIGNATURE` | 409 | App release signature is invalid | | 4012 | `APP_STORE_LISTING_NOT_LIVE` | 409 | App store listing is not live | | 4013 | `TOOL_APPROVAL_REQUIRED` | 428 | Tool approval is required | | 4014 | `EXPORT_NOT_READY` | 409 | The export is not ready yet | | 4015 | `AGENT_INVOCATION_FANOUT_LIMIT` | 429 | Too many concurrent sub-agent invocations in flight | | 4020 | `BILLING_ENTITLEMENT_LIMIT_REACHED` | 403 | Billing plan limit reached | | 4021 | `WEB_HANDOFF_RATE_LIMITED` | 429 | Too many sign-in handoff requests | | 4022 | `APP_HANDOFF_RATE_LIMITED` | 429 | Too many sign-in handoff requests | | 4023 | `BILLING_PLAN_CHANGE_QUOTE_STALE` | 409 | The amount due for this plan change has changed. Review the updated amount and confirm again. | | 4024 | `REFERRAL_SIGNUP_RATE_LIMITED` | 429 | Too many signup requests. Try again later. | | 4025 | `VOICE_OUTBOUND_CALL_RATE_LIMITED` | 429 | Too many phone calls placed recently. Try again later. | | 4026 | `AGENT_TURN_NOT_RUNNING` | 409 | This agent turn is no longer running | | 4027 | `EXTERNAL_AGENT_OPERATOR_ACK_REQUIRED` | 409 | This agent runs in an environment managed by its operator, and the operator cannot read this room. Confirm that room content may be processed there before adding the agent. | | 4028 | `UI_CARD_INTERACTION_LIMIT_REACHED` | 409 | This card has reached its response limit | | 4029 | `SUPPORT_REPORT_RATE_LIMITED` | 429 | Too many reports from this device. Try again later. | | 4030 | `API_KEY_RATE_LIMITED` | 429 | Too many requests from this API credential. Retry after the interval in the Retry-After header. | | 4031 | `API_KEY_QUOTA_EXCEEDED` | 429 | This API credential has used its daily request quota. Retrying will not succeed until the quota resets. | ## Internal / unknown (5000-5999) | Code | Name | HTTP | Message | | ---- | ----------------------------------- | ---- | -------------------------------------------------------------------------------------------------------------------------- | | 5000 | `INTERNAL_SERVER_ERROR` | 500 | Internal server error | | 5001 | `AUTH_PROVIDER_UNAVAILABLE` | 503 | The authentication provider is temporarily unavailable | | 5002 | `MODEL_PROVIDER_UNAVAILABLE` | 503 | No model credential is configured for this operation | | 5003 | `REMOTE_MCP_SERVER_UNREACHABLE` | 502 | Could not reach the MCP server. Check the server URL and try again. | | 5004 | `REMOTE_MCP_SERVER_REJECTED` | 502 | The MCP server rejected the connection request. Check its authentication requirements and request headers. | | 5005 | `REMOTE_MCP_PROTOCOL_ERROR` | 502 | The server did not respond as a compatible MCP server. Check that the URL points to a Streamable HTTP MCP endpoint. | | 5006 | `REMOTE_MCP_OAUTH_DISCOVERY_FAILED` | 502 | The server requires OAuth, but its authorization configuration could not be discovered. Check the server's OAuth metadata. | | 5007 | `REMOTE_MCP_DCR_FAILED` | 502 | The server rejected dynamic client registration. Turn it off and enter credentials for a pre-registered OAuth client. | | 5008 | `REMOTE_MCP_OAUTH_START_FAILED` | 502 | OAuth authorization could not be started for this server. Check its authorization configuration. |