CopilotKit Error Pattern Catalog

V1 Error Codes (CopilotKitErrorCode)

Legacy error codes from the v1 runtime layer. These still surface in @copilotkit/* packages since they wrap v2 internally. Defined in packages/v1/shared/src/utils/errors.ts.

NETWORK_ERROR

• HTTP Status: 503
• Severity: CRITICAL (banner)
• Cause: Server unreachable, DNS failure, connection timeout, SSL/TLS issues
• Resolution: Verify the runtime server is running and accessible. Check runtimeUrl in CopilotKitProvider. Common sub-causes:
  • ECONNREFUSED -- Server not running on the expected port
  • ENOTFOUND -- DNS cannot resolve the hostname
  • ETIMEDOUT -- Server overloaded or network issues
• Docs: https://docs.copilotkit.ai/troubleshooting/common-issues#i-am-getting-a-network-errors--api-not-found

NOT_FOUND

• HTTP Status: 404
• Severity: CRITICAL (banner)
• Cause: The runtime URL returns 404. Wrong basePath or the server is not serving CopilotKit at that path.
• Resolution: Ensure basePath in createCopilotEndpoint() matches the runtimeUrl in the provider.
• Docs: https://docs.copilotkit.ai/troubleshooting/common-issues#i-am-getting-a-network-errors--api-not-found

AGENT_NOT_FOUND

• HTTP Status: 500
• Severity: CRITICAL (banner)
• Cause: The requested agent name does not exist in the runtime's agent registry.
• Resolution: Verify the agent name matches between CopilotChat agentId and the runtime's agents map. The error message lists available agents.
• Docs: https://docs.copilotkit.ai/coagents/troubleshooting/common-issues#i-am-getting-agent-not-found-error

API_NOT_FOUND

• HTTP Status: 404
• Severity: CRITICAL (banner)
• Cause: The CopilotKit API endpoint itself cannot be discovered. Usually a routing/basePath mismatch.
• Resolution: Check that the runtime's Hono/Express app is mounted at the correct path. The error includes the URL that failed.
• Docs: https://docs.copilotkit.ai/troubleshooting/common-issues#i-am-getting-a-network-errors--api-not-found

REMOTE_ENDPOINT_NOT_FOUND

• HTTP Status: 404
• Severity: CRITICAL (banner)
• Cause: A remote endpoint specified in the runtime configuration cannot be contacted.
• Resolution: Verify the remote endpoint URL is correct and the service is running. Check firewall/network rules.
• Docs: https://docs.copilotkit.ai/troubleshooting/common-issues#i-am-getting-copilotkits-remote-endpoint-not-found-error

AUTHENTICATION_ERROR

• HTTP Status: 401
• Severity: CRITICAL (banner)
• Cause: Authentication failed when contacting the runtime or a remote service.
• Resolution: Check API keys, tokens, and authentication headers.
• Docs: https://docs.copilotkit.ai/troubleshooting/common-issues#authentication-errors

VERSION_MISMATCH

• HTTP Status: 400
• Severity: INFO (dev only)
• Cause: @copilotkit/* packages are on different versions.
• Resolution: Ensure all @copilotkit/* packages are the same version. Run npm ls @copilotkit/runtime @copilotkit/react.

CONFIGURATION_ERROR

• HTTP Status: 400
• Severity: WARNING (banner)
• Cause: Invalid runtime or provider configuration.
• Resolution: Review the CopilotRuntime and CopilotKitProvider configuration.

MISSING_PUBLIC_API_KEY_ERROR

• HTTP Status: 400
• Severity: CRITICAL (banner)
• Cause: The publicApiKey prop is missing from CopilotKitProvider when using CopilotKit Cloud.
• Resolution: Add publicApiKey to the provider, or switch to self-hosted mode with runtimeUrl.

UPGRADE_REQUIRED_ERROR

• HTTP Status: 402
• Severity: WARNING (banner)
• Cause: The current plan does not support the requested feature.
• Resolution: Upgrade the CopilotKit plan or remove the feature flag.

MISUSE

• HTTP Status: 400
• Severity: WARNING (dev only)
• Cause: Incorrect API usage detected at development time (e.g., using a hook outside its provider).
• Resolution: Follow the error message guidance -- typically a component is being used outside the required provider.

UNKNOWN

• HTTP Status: 500
• Severity: CRITICAL (toast)
• Cause: Unclassified server error.
• Resolution: Check server logs for the underlying exception.

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V1 Error Classes

All defined in packages/v1/shared/src/utils/errors.ts:

Class	Extends	When Thrown
CopilotKitError	GraphQLError	Base class for all structured errors
CopilotKitMisuseError	CopilotKitError	Wrong usage of components/hooks
CopilotKitVersionMismatchError	CopilotKitError	Package version incompatibility
CopilotKitApiDiscoveryError	CopilotKitError	Runtime endpoint not found (404, routing)
CopilotKitRemoteEndpointDiscoveryError	CopilotKitApiDiscoveryError	Remote agent endpoint unreachable
CopilotKitAgentDiscoveryError	CopilotKitError	Named agent not in registry
CopilotKitLowLevelError	CopilotKitError	Pre-HTTP errors (DNS, connection refused)
ResolvedCopilotKitError	CopilotKitError	HTTP error responses (status-code based)
ConfigurationError	CopilotKitError	Invalid configuration
MissingPublicApiKeyError	ConfigurationError	Cloud mode without API key
UpgradeRequiredError	ConfigurationError	Plan limitation

---

V2 Error Codes (CopilotKitCoreErrorCode)

Used by @copilotkit/core. Defined in packages/v2/core/src/core/core.ts. These are emitted via the onError subscriber callback.

runtime_info_fetch_failed

• Cause: The /info endpoint returned an error or was unreachable.
• Resolution: Verify runtimeUrl points to a running CopilotRuntime. Check CORS if cross-origin. The /info endpoint must return agent metadata and runtime version.

agent_connect_failed

• Cause: WebSocket or HTTP connection to the agent failed during the connect phase.
• Resolution: For Intelligence mode, verify the WebSocket URL (wsUrl) is correct. For SSE mode, check that the agent exists in the runtime.

agent_run_failed

• Cause: The agent run threw an exception before completing.
• Resolution: Check server-side logs for the agent execution error. Common causes: missing API keys for the LLM provider, invalid model configuration.

agent_run_failed_event

• Cause: The AG-UI stream contained a RunFailedEvent (the agent explicitly signaled failure).
• Resolution: The event payload contains the failure reason. Check the agent's implementation for error handling.

agent_run_error_event

• Cause: The AG-UI stream contained a RunErrorEvent (non-fatal error during the run).
• Resolution: Check the error message in the event. May be transient -- the agent might recover.

tool_argument_parse_failed

• Cause: The JSON arguments for a frontend tool call could not be parsed.
• Resolution: Check the tool's parameter schema. The LLM may have generated malformed JSON.

tool_handler_failed

• Cause: A frontend tool's execute handler threw an exception.
• Resolution: Check the tool's handler code. The error is caught and reported via onError.

tool_not_found

• Cause: The agent called a tool that is not registered in the frontend.
• Resolution: Ensure useFrontendTool is registered with the correct name before the agent runs.

agent_not_found

• Cause: The agentId passed to CopilotChat or useAgent does not match any agent in the runtime.
• Resolution: Check the runtime's /info endpoint to see available agents. Match the agentId prop.

transcription_failed

• Cause: Generic transcription failure.
• Resolution: See TranscriptionErrorCode section below for specific sub-codes.

transcription_service_not_configured

• Cause: Voice transcription requested but no transcriptionService configured in the runtime.
• Resolution: Add a transcription service to the runtime constructor.

transcription_invalid_audio

• Cause: Audio format not supported by the transcription provider.
• Resolution: Check supported audio formats (typically webm, wav, mp3).

transcription_rate_limited

• Cause: Transcription provider rate limit exceeded.
• Resolution: Wait and retry. Consider caching or reducing request frequency.

transcription_auth_failed

• Cause: Authentication with the transcription provider failed.
• Resolution: Check the transcription API key configuration.

transcription_network_error

• Cause: Network error during transcription API call.
• Resolution: Check connectivity to the transcription provider.

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Transcription Error Codes (TranscriptionErrorCode)

Used by @copilotkit/shared and @copilotkit/react. Defined in packages/v2/shared/src/transcription-errors.ts.

Code	Retryable	Description
service_not_configured	No	No transcription service in runtime
invalid_audio_format	No	Unsupported audio format
audio_too_long	No	Audio file exceeds maximum duration
audio_too_short	No	Audio too short to transcribe
rate_limited	Yes	Provider rate limit hit
auth_failed	No	Provider authentication failed
provider_error	Yes	Provider returned an error
network_error	Yes	Network failure during transcription
invalid_request	No	Malformed request to transcription endpoint

---

Intelligence Platform Error (PlatformRequestError)

Used by @copilotkit/runtime for Intelligence mode. Defined in packages/v2/runtime/src/intelligence-platform/client.ts.

Status	Meaning
404	Thread not found
409	Thread already exists (race condition -- handled automatically by getOrCreateThread)
401	Invalid API key or tenant ID
500	Platform server error

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Common GitHub-Reported Issues

These are frequently reported bugs from the CopilotKit issue tracker:

Event Name Prefix Mismatch (Python SDK + ag-ui-langgraph)

• Issue: #3519
• Symptom: copilotkit_emit_message, copilotkit_emit_state, copilotkit_emit_tool_call never reach the frontend
• Cause: Python SDK dispatches events with "copilotkit_" prefix but ag-ui-langgraph expects names without the prefix
• Resolution: Update ag-ui-langgraph or patch the event name mapping

Tool Call Failing Silently

• Issue: #3510
• Symptom: defineTool tool calls fail without error or response
• Resolution: Check tool parameter schema validation and network responses

Reasoning Events Cause Agent Stall

• Issue: #3323
• Symptom: Agent stalls permanently after Anthropic reasoning/thinking tokens
• Cause: REASONING_* events in the AG-UI SSE stream are not handled correctly
• Resolution: Update to a version with reasoning event handling fixes

HITL Frontend Tool Not Executing After Confirmation

• Issue: #3442
• Symptom: useFrontendTool with renderAndWaitForResponse does not execute after user confirms
• Resolution: Check the HITL flow implementation and runId consistency (related: #3456)

Authorization Header Not Passed to A2A Agents

• Issue: #3170
• Symptom: Auth headers from the client do not reach agents using A2A protocol
• Resolution: Verify header forwarding configuration in runtime middleware

LangChainAdapter Regression ("Unknown provider undefined")

• Issue: #3217
• Symptom: LangChainAdapter throws "Unknown provider undefined" in v1.50.0+
• Cause: Custom adapters without provider/model properties hit a code path that assumes they exist
• Resolution: Migrate to v2 BuiltInAgent or add .provider/.model to the adapter

Mixed Frontend and Backend Tool Execution Fails

• Issue: #3424
• Symptom: OpenAI BadRequestError when mixing frontend and backend tools with LangGraph
• Resolution: Check tool registration and ensure tools are not duplicated across frontend and backend

Context Not Updated with Mastra Integration

• Issue: #3426
• Symptom: Context state does not propagate to Mastra agents
• Resolution: Verify context is being passed through the runtime middleware chain

Subscribe Null Reference in A2A/A2UI

• Issue: #3429
• Symptom: Cannot read properties of null (reading 'subscribe') during A2A integration
• Resolution: Check agent lifecycle and ensure proper initialization order

IME Input Cleared on Mobile (v2)

• Issue: #3318
• Symptom: Typing with IME on mobile devices clears input in CopilotChat
• Resolution: Known v2 issue with controlled input handling during IME composition

Message ID Collision with OpenAI-Compatible Providers

• Issue: #3410
• Symptom: All messages share the same ID when using @ai-sdk/openai-compatible
• Cause: Default message ID from the compatible provider is not unique
• Resolution: Update to a patched version or use the native OpenAI provider