Black Forest Labs releases Flux 3 Klein, a 5.6B open-weights image model

Black Forest Labs released FLUX 3 Klein, an open-weights text-to-image model with 5.6 billion parameters in the image generator. The pitch is efficiency: it is 38% smaller than the company's earlier FLUX.2 klein at 9 billion parameters, yet Black Forest Labs' own evaluations put it 91 Elo points ahead on text-to-image generation and 70 ahead on image editing. In those internal tests it also ranks first against larger open models and the closed Ideogram V4.5 and FLUX.2 pro, though the comparison is the company's own.

The size matters because of where the model runs. The INT8 build fits on NVIDIA RTX cards with as little as 8GB of VRAM, and with the step-distilled variant a one-megapixel image takes about four seconds on an RTX 5090 and under nine seconds on an RTX 4070 in ComfyUI. The model handles editing and multi-reference generation with up to ten reference images, supports native 4K output, and uses bounding boxes to place elements or confine edits to a region.

The license is the catch to read closely. The FLUX Kommunity License allows free commercial use for individuals and companies under $5 million in annual revenue, plus research and non-commercial use; larger organizations need a self-hosted or API license. The release ships with day-one support in ComfyUI, Diffusers, and vLLM, and LoRA training through existing toolkits.

Why it matters

If you run image generation locally or build on top of open image models, a capable 4K model that fits on an 8GB consumer GPU lowers the hardware bar a lot. Check the revenue threshold in the license before you build a commercial product on it.