Grok API Error Codes Explained

Cause: Malformed JSON body, an unknown parameter, or an invalid parameter combination.

Fix: Log the full response body — xAI returns a message field naming the offending parameter. Validate the payload against the OpenAI-compatible chat completions shape before sending.

Cause: Missing, malformed, revoked, or mistyped API key in the Authorization header.

Fix: Confirm the header is exactly "Authorization: Bearer xai-...". Strip trailing newlines picked up from .env files or CI secret stores, and re-issue the key in console.x.ai if it was rotated.

Cause: Valid key, but the account is not entitled to the model, endpoint, or feature requested.

Fix: Check model entitlements for your organization. This also appears when billing is not configured or a spend limit has been reached — rotating the key will not help.

Cause: Wrong path, or a model ID that does not exist (model_not_found).

Fix: Base URL must be https://api.x.ai/v1. Fetch the live model list rather than hard-coding an ID that may have been superseded.

Cause: Semantically invalid request — usually prompt plus max_tokens exceeding the context window, or an unsupported tool/response_format combination.

Fix: Count tokens before sending and cap max_tokens against the remaining window. Drop unsupported parameters rather than passing an entire OpenAI request through untouched.

Cause: Account rate limit hit — requests per minute or tokens per minute.

Fix: Exponential backoff with jitter, plus a client-side queue. Read the rate limit response headers to see which limit tripped rather than guessing.

Cause: Server-side fault inside xAI. Not caused by your payload.

Fix: Retry with backoff. Sustained 500s across multiple models indicate a real incident — check status.x.ai and fail over.

Cause: Edge or gateway timeout in front of the model servers, often during a long non-streaming completion.

Fix: Switch long generations to streaming so the connection produces bytes early, and raise your client read timeout above your worst-case generation time.

Cause: Capacity exhaustion or maintenance — the model is temporarily unable to accept work.

Fix: Back off, then fail over to a secondary provider if the window exceeds your latency budget. Alert on sustained 503s; they are the clearest early signal of an xAI incident.

What does a 429 error mean on the Grok API?

A 429 means you exceeded an account-level rate limit — either requests per minute or tokens per minute. xAI limits scale with your account tier and usage history rather than a single published free-tier number, so two keys on the same organization can hit 429 at different volumes. Back off exponentially (1s, 2s, 4s) and queue burst traffic client-side instead of firing concurrent retries, which only deepens the limit.

Is a Grok API 401 error the same as a 403?

No. A 401 Unauthorized means the API key itself was rejected — missing Authorization header, a typo, a revoked key, or a key pasted with trailing whitespace. A 403 Forbidden means the key is valid but not entitled to what you asked for: a model your team has not been granted, or an endpoint outside your plan. Rotating the key fixes a 401 and does nothing for a 403.

Which Grok API errors should I retry automatically?

Retry 429, 500, 502, 503 and 504 with exponential backoff and jitter. Never blindly retry 400, 401, 403, 404 or 422 — those are deterministic client-side faults and the identical request will fail identically, burning quota and latency budget. A retry policy that does not distinguish the two classes is the single most common cause of a small xAI incident turning into a full outage for your app.

Why am I getting model_not_found from api.x.ai?

The model string in your request body does not match an ID your account can call. The usual causes are a display name instead of an API ID (sending "Grok 3" rather than grok-3), a model that has since been superseded, or a model your organization has not been enabled for — which surfaces as 403 rather than 404 in some cases. List the models your key can actually reach from the models endpoint rather than hard-coding a string in application code.

How do I tell a Grok API error from an xAI outage?

Look at the spread. Errors concentrated on one endpoint, one model, or one key are almost always your request. A simultaneous jump in 500s and 503s across every model and every key is an incident — confirm against status.x.ai, or watch apistatuscheck.com/api/grok for independent uptime checks and alerts that fire before the official status page is updated.