FLUX API 402, 403 and 503 errors, and Sume's equivalents

BFL's FLUX API uses 402 when the account has too few credits, 403 when the key lacks permission for the resource, and 503 when the service is unavailable, usually from maintenance or high load. Sume returns 402 insufficient_credits when it cannot reserve the estimated cost from the workspace balance, 401 unauthorized for a missing or invalid key, and 503 provider_capacity_exceeded when its provider dispatch queue is full. Retry the 503; do not retry the 402 until the balance changes.

BFL's list is from its Errors page; Sume's is from its errors and rate limits page and the Image API page. All were read 2026-10-02.

How do the status codes line up?

They line up for 402 and 503, not for 403. BFL's 403 means the API key lacks permission for the resource. Sume's errors page has no 403 row; a missing or invalid key is 401 unauthorized, and a resource outside the workspace is 404 not_found.

What do I do on a 402 from each?

Both mean the money side blocked the call before an image was made. BFL tells you to add credits. Sume's admission page says the generation submit fails with 402 insufficient_credits before provider work starts, and tells you to wait for included Gen$ on your plan or submit a cheaper request. Retrying unchanged will fail the same way.

What do I do on a 503?

BFL says to try again in a few moments. Sume's errors page says to retry later with the same idempotency key for provider_capacity_exceeded, and not to retry unsafe submit requests without an Idempotency-Key. Back off when a retry-after header is present.

What about bad requests?

BFL separates 400 (format or content) from 422 (invalid body or parameters). Sume answers an unknown or unsupported field with 400 unsupported_parameter, the same status for a field that a model does not list, such as seed or output_compression today. Read the Image API page's capability descriptors, then send only fields the model lists.