Black Forest Labs releases FLUX 3 Image Klein weights

Black Forest Labs released FLUX 3 Image Klein, a downloadable image model for text-to-image generation, image editing and compositions using as many as 10 reference images. The weights let developers run and adapt the model on their own hardware, but commercial output use under the accompanying free license is limited to qualifying users below a revenue threshold.

The company describes Klein as a 5.6-billion-parameter model. Black Forest Labs says in the model card that the count covers the image transformer and excludes the separate Qwen3-VL-4B-Instruct text encoder. Text-to-image generation, single-reference editing and multi-reference composition run through the same model.

The release includes an undistilled base checkpoint for fine-tuning, LoRA training and research, plus a 16-step distilled checkpoint for generation, editing and self-hosting. Black Forest Labs also lists FP8, INT8 and NVFP4 builds. The company says an INT8 build can run through ComfyUI or Diffusers on Nvidia GeForce RTX hardware with 8 GB of VRAM. That minimum-memory figure is a vendor claim, not an independently reproduced test.

Black Forest Labs published reference inference code with a local command-line interface and a Gradio demo. Its launch materials also list support for ComfyUI, Hugging Face Diffusers, TensorRT-LLM, SGLang Diffusion and vLLM-Omni.

Black Forest Labs defines a qualifying user in the FLUX Kommunity License as the licensee and its affiliates having less than $5 million in gross annualized revenue. Subject to the license terms, qualifying users may use outputs commercially and run the model or derivatives in production solely to generate those outputs. The grant is not blanket permission for every commercial use of the weights or derivatives. It also requires those users to maintain content filtering or review outputs for unlawful or infringing material before dissemination, and to provide AI disclosures where applicable law requires them. Uses outside that scope require separate commercial terms; Black Forest Labs points users to self-hosted licensing or its API.

Black Forest Labs said in its July FLUX 3 roadmap that open weights for a multimodal backbone would follow early-access testing. Klein provides downloadable, image-specific weights from the FLUX 3 family, but the roadmap named the broader planned model FLUX 3 Dev. Black Forest Labs has not said Klein replaces or completes that broader release, and its October post says more FLUX 3 open-weight releases will follow.