flux-2-pro-preview vs flux-2-pro: which id does Sume send?

On Sume you send black-forest-labs/flux.2-pro, and you cannot choose between BFL's flux-2-pro-preview and its fixed flux-2-pro snapshot. BFL's FLUX.2 overview describes the preview endpoint as its latest FLUX.2 [pro] model and the non-preview endpoint as a snapshot that will not change. Sume's Image API page says it serves each catalog model through one sume endpoint and does not disclose the upstream provider, so the docs do not say which BFL endpoint sits behind the id.

BFL's text is from its FLUX.2 overview, read 2026-10-02. Sume's is from the Sume Image API page, read the same day.

What is the difference on BFL's side?

BFL says preview endpoints are where its latest improvements land first. It lists flux-2-pro-preview (latest FLUX.2 [pro]), flux-2-pro (a fixed snapshot, "suitable for workflows that require reproducibility"), flux-2-klein-9b-preview and flux-2-klein-9b. It also says both kinds share one API contract: the request and response format is identical and only the model weights differ.

Can I pick the endpoint through Sume?

No parameter does it. Sume's docs say allowed_passthrough_parameters is empty for every endpoint in v1, so provider.options must be omitted or empty, and that multi-provider routing fields are accepted but inert. Any provider slug other than sume returns 400 provider_not_available.

What should I do if I need reproducible FLUX.2 images?

Treat the Sume id as the contract you have. Save the image URL and the job result you got, rather than assuming a later call reproduces it. Sume also does not serve a seed: it is in the schema, but no model advertises it, and sending one returns 400 unsupported_parameter.

If reproducibility from BFL's own snapshot matters to you more than going through one Sume API, that is a reason to call BFL directly. Sume's docs do not claim the snapshot behind its id.