Errors

Claude API error codes and troubleshooting — 401, 429, 500 status codes. How to handle rate limits and authentication errors.

Anthropic Error Format

Anthropic-style errorjson

{
  "type": "error",
  "error": {
    "type": "invalid_request_error",
    "message": "model: Invalid model ID"
  }
}

OpenAI-style errorjson

{
  "error": {
    "message": "Invalid model ID",
    "type": "invalid_request_error",
    "code": "invalid_model"
  }
}

Status	Meaning	Action
400	Bad Request — invalid parameters	Check request body and parameters
401	Unauthorized — invalid or missing API key	Verify your API key
403	Forbidden — insufficient permissions	Check key permissions and credit balance
429	Rate Limited — too many requests	Reduce request rate, implement backoff
500	Internal Server Error	Retry with exponential backoff
502	Bad Gateway — upstream error	Retry after a brief delay
529	Overloaded — service at capacity	Retry with exponential backoff

Always check the error.type and error.message fields for specific information
For 429 errors, implement exponential backoff starting at 1 second
For 5xx errors, retry up to 3 times with increasing delays
Use GET /health to check service status
Verify model IDs match exactly (e.g., claude-sonnet-4.6)

Ready to start?

Get API access to all Claude models in under 2 minutes.