X_AI_PROVIDER_UNAVAILABLE
Means
the model provider is unreachable
Typical cause
a non-2xx, an in-band error event, or a stream cut before message_stop. Never a local refusal, As of 2026-08-23: X_AI_KEY_MISSING and X_AI_REQUEST_INVALID are raised before the socket opens and reach the caller verbatim, keeping their own fix:, instead of being collected into this code by the fallback loop
Fix
retry a 429/5xx (the gateway already does); fix the request a 4xx names