FLUX API polling_url and regional hosts vs Sume job polling

On BFL's API you submit to api.bfl.ai, api.eu.bfl.ai or api.us.bfl.ai, then poll the polling_url from the submit response instead of building a status URL yourself. Sume's docs describe no regional host to pick: you call one API and poll the status URL in the job envelope it returns.

BFL facts are from its integration guide; Sume facts are from Jobs and results and Image generation, read 2026-10-01.

What are the three BFL hosts?

The guide describes a global primary endpoint and two regional ones. It says to use the polling_url from the response when you use any of them, and that webhook users need no change because the rule applies to async polling.

Why must the client use the returned polling_url?

The guide's migration checklist says to extract the URL from the API response and to replace hardcoded status endpoints with it. With multi-cluster routing, the host that holds your request is not something you can assume, so the response tells you where to ask. Treat the URL as opaque and never rebuild it from the request id.

What does a Sume client poll instead?

Every Sume submit endpoint accepts a mode. In async mode the response is 202 with the job envelope and polling URLs: poll status_url until terminal is true, then GET result_url once result_ready is true. On POST /v1/images the default mode is sync, which waits at most 30 seconds and then returns the same envelope; if the job is not terminal, poll, do not resubmit. The rule is the same as BFL's: follow the URLs the server gave you.

In webhook mode the docs say to wait for the terminal callback, verify its signature, and keep polling as a backup.

Can I choose a region on Sume?

The pages cited here document no region parameter and no regional host. The image docs also say upstream provider identity is not disclosed, so there is nothing to map to api.eu.bfl.ai. If data residency decides your choice, check the terms for your account before you send traffic; this post makes no residency claim for Sume.

For the other half of BFL's guide, delivery URLs that expire after 10 minutes, see FLUX image URLs expire.