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The Pioneer API uses standard HTTP status codes to communicate the outcome of every request. Codes in the 2xx range indicate success. Codes in the 4xx range indicate a problem with your request that you can fix. Codes in the 5xx range indicate a server-side issue.

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Error response format

All error responses include a JSON body with an error field and a human-readable message: 
{
  "error": "unauthorized",
  "message": "Invalid or missing API key."
}

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Status codes

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401 — Unauthorized

Your request did not include a valid API key, or the key has been revoked. How to fix: Verify that the X-API-Key header is present and contains your current key. If you recently revoked the key, generate a new one at Settings → API Keys. See Authentication for setup instructions.

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402 — Payment Required

A 402 response means your account has run out of credits. All API calls will fail until you add credits or upgrade your plan. Visit Settings → Billing or see Plans & Pricing to resolve this.
Your account does not have sufficient credits to complete the request. How to fix: Log in to pioneer.ai, go to Settings → Billing, and top up your balance or upgrade your plan.

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404 — Not Found

The resource you requested does not exist. This can happen when a dataset name, training job ID, evaluation ID, or project ID is misspelled or has been deleted. How to fix: Double-check the ID or name in the request path or body. Use the corresponding GET list endpoint (for example GET /felix/training-jobs) to confirm the resource exists.

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422 — Unprocessable Entity

The request body failed validation. A required field is missing, a field has the wrong type, or a value is outside the accepted range. How to fix: Review the error message for the specific field that failed. Common causes include:
  • Omitting base_model from POST /felix/training-jobs
  • Passing an unsupported task_type to POST /generate
  • Sending fewer than 1 or more than 1,000 strings in the inputs array for label-existing endpoints

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429 — Too Many Requests

You have exceeded the rate limit for this endpoint. The response includes a Retry-After header that specifies how many seconds to wait before retrying. How to fix: Respect the Retry-After value and back off before retrying. See Rate Limits for per-endpoint limits and a retry code pattern.

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500 — Internal Server Error

An unexpected error occurred on Pioneer’s servers. This is not caused by your request. How to fix: Wait a moment and retry. If the error persists, check pioneer.ai for any service status updates or contact support.