Black Forest Labs 发布 FLUX 3 Image Klein 开源权重模型

Today we are releasing FLUX 3 Image Klein, a 5.6B parameter open weights model for text-to-image generation, image editing and multi-reference generation with up to 10 reference images. It shares core capabilities with the full FLUX 3 Image model: native 4K generation, pixel-perfect editing, and bounding boxes that control where elements are placed or confine edits to a defined area.

FLUX 3 Image Klein builds on FLUX 3's shared learnings across images, video and audio. Images contribute spatial detail, video adds motion and physical dynamics, and audio provides information about events and interactions. Together, these signals help the model generate images that feel grounded in the real world.

The release includes a base model for fine-tuning and a step distilled model for low-latency generation, along with FP8, INT8 and NVFP4 builds developed with NVIDIA support, under the FLUX Kommunity License.

Try it in the BFL API · Download the weights

Leading open weights quality with fewer parameters

In internal evaluations, FLUX 3 Image Klein ranks first in text-to-image, multi-reference generation and image editing, ahead of larger open weights models. It also rates above the closed models in the comparison, Ideogram V4.5 and FLUX.2 [pro]. At 5.6B parameters, it is the smallest open model in the comparison, against 7B for Qwen-Image 2.1 and 12.9B for Krea 2. Compared with FLUX.2 [klein] 9B, it gains 91 Elo in text-to-image and 70 in image editing, with 38% fewer parameters.

FLUX 3 Image Klein was also optimized for consumer GPUs. Fewer parameters make it practical to run locally and cheaper to adapt, and teams with data sovereignty or local deployment requirements can evaluate and adapt the model on their own infrastructure. This is also key for on-device image editing, allowing consumers to edit images directly on their favorite laptops. The generator weights require 11.2 GB in BF16 and 5.6 GB in FP8. With the INT8 build, FLUX 3 Image Klein runs on NVIDIA GeForce RTX GPUs with as little as 8GB of VRAM, through ComfyUI or Diffusers, extending what FLUX.2 [klein] started to even smaller hardware. With the distilled model and the INT8 build, it generates a 1MP image in about 4 seconds on an NVIDIA GeForce RTX 5090 and under 9 seconds on an RTX 4070 through ComfyUI.

The base checkpoint is built for fine-tuning: Diffusers and Ostris's AI Toolkit support LoRA training from day one, and NVIDIA's NeMo AutoModel ships recipes that work directly from the released checkpoints.

For even faster production workloads that need lower latency, we also work with teams on specific customizations that get you there. Get in touch.

On the speed–quality frontier

FLUX 3 Image Klein also extends the speed–quality Pareto frontier. Through the BFL API, it delivers lower latency than Qwen-Image 2.1, FLUX.2 [pro], Ideogram V4.5 and Krea 2, and the highest rating at its latency and above. In the charts below, the violet line traces the highest rating available at each latency and the gray line shows the previous frontier.

Latency is measured end to end, from request submission to the finished 1 MP image, including queueing. FLUX 3 Image Klein was timed on our servers. Other models were timed from the client, which includes polling and network time. Krea 2 was timed on its Medium tier; its Large tier took 31.1 seconds for text-to-image.

Get started

FLUX 3 Image Klein is available today as open weights and through the BFL API.

Try it

• BFL API: the distilled model is available as flux-3-image-klein, with prompt upsampling and pixel restoration, which preserves unedited regions of an image exactly. Pricing starts at $0.009 per 1K image.
• Playground or Hugging Face.

Build with it

• Weights on Hugging Face: base and distilled.
• Reference inference code, including a Gradio demo for bounding-box control.
• Try it out on Hugging Face Spaces.
• Day-one support in ComfyUI, Hugging Face Diffusers, TensorRT-LLM, SGLang Diffusion and vLLM-Omni.
• LoRA training with Ostris's AI Toolkit and recipes in NVIDIA NeMo AutoModel.
• Trained on NVIDIA GB200 NVL72 and optimized for NVIDIA's accelerated computing platform, serving through NVIDIA TensorRT LLM, vLLM-Omni and SGLang Diffusion.
• On NVIDIA GB300, the distilled model generates a 1MP image in under 0.6 seconds in NVFP4. Serving a LoRA adds around 5% to generation time.

License

The weights are available under the FLUX Kommunity License, which allows free commercial use for individuals and companies with annual revenue under $5M, alongside research and non-commercial use. Larger organizations can deploy commercially through our self-hosted licensing options or API.

Safety

In an effort to make AI technology both open and safe, we implement multiple safeguards throughout the model development lifecycle to combat misuse. These include dataset filters during pre-training to limit exposure to harmful content, and targeted fine-tuning during post-training to suppress harmful behaviors, making it progressively harder to elicit harmful content. Ahead of the release, the FLUX 3 Image Klein checkpoints were rigorously red teamed internally and evaluated by our external safety partner Cinder, demonstrating substantially fewer vulnerabilities than other popular open weights models. More on our safety methodology is available here.

FLUX 3 Image Klein is the second open weights release from the FLUX 3 family, following FLUX 3 Action. More will follow.

Learn more

• FLUX 3: Real World Models, the research behind the FLUX 3 family
• FLUX 3 Action, our open weights 7B model for robot control

Citation

If you use FLUX 3 Image Klein in your work, please cite:

@misc{bfl2026flux3image,
  author       = {{Black Forest Labs}},
  title        = {{FLUX} 3 Image Klein},
  year         = {2026},
  url          = {https://bfl.ai/blog/flux-3-image-klein},
}