FLUX.2 [klein] 4B is Black Forest Labs's Apache 2.0 licensed compact image model. It delivers sub-second text-to-image, image editing, and multi-reference generation from a single checkpoint.
import { experimental_generateImage as generateImage } from 'ai';
const result = await generateImage({ model: 'bfl/flux-2-klein-4b', prompt: 'A red balloon on a wooden table.'});Black Forest Labs released FLUX.2 [klein] 4B on N/A as the entry point of the Klein family: compact image models Black Forest Labs positions for minimal latency. "Klein" is German for "small," reflecting the model's compact parameter footprint and minimal latency target.
The Apache 2.0 license separates Klein 4B from the rest of the FLUX family. Klein 9B carries the FLUX Non-Commercial License (NCL), and FLUX.2 Pro is a proprietary API model. Klein 4B places no commercial use restrictions on its weights. You can deploy it in commercial products, include it in open-source projects, and redistribute derivative works without seeking additional permission from Black Forest Labs.
The model unifies text-to-image generation, image-to-image editing, and multi-reference generation in a single checkpoint. Black Forest Labs describes Klein 4B as "compact but capable." The entire inference pipeline targets under 500 milliseconds.