FLUX.2 klein 4B Apache 2.0 vs 9B non-commercial, and Sume ids
BFL releases klein 4B weights under Apache 2.0 and 9B under the FLUX Non-Commercial License. Sume's image catalog lists flux.2-pro and flux.2-flex, not klein.
BFL's klein training guide says the open weights come under Apache 2.0 for the 4B model and the FLUX Non-Commercial License for the 9B model. That is a license on downloaded weights. Sume's image catalog lists black-forest-labs/flux.2-pro and black-forest-labs/flux.2-flex; I found no klein id there.
License and price facts are from BFL pages read 2026-10-01. Catalog facts are from the Image API docs and the API contract. This is not legal advice; read the license text before shipping.
How do the two klein sizes differ in license and price?
The training guide's variant table covers the Base models, which it recommends as fine-tuning starting points. The pricing page lists API prices for the klein models separately, from the first megapixel up.
| Variant | Weights license | BFL API price (from) |
|---|---|---|
| FLUX.2 [klein] 4B | Apache 2.0 | $0.014 |
| FLUX.2 [klein] 9B | FLUX Non-Commercial | $0.015 |
Does the license apply to the API?
The guide ties the licenses to open weights you download and fine-tune yourself. It does not say how those licenses apply to images from a hosted API, and I will not guess. If commercial use of the output matters, ask BFL or read its terms for the specific endpoint you call.
Which FLUX.2 ids does Sume list?
Two: black-forest-labs/flux.2-pro and black-forest-labs/flux.2-flex. Discover the live catalog with GET /v1/images/models. A request that sets a parameter the selected model does not list is rejected with 400 unsupported_parameter rather than silently dropped, so an unknown model or option fails clearly.
For the LoRA angle, see FLUX.2 LoRA fine-tune ids and Sume.
What should I do?
If you want to run klein 4B yourself under Apache 2.0, that is a self-hosting decision outside Sume. If you want hosted FLUX.2 generation or edits through Sume, pick flux.2-pro or flux.2-flex from the catalog and read its capability descriptors first.
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