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FLUX.2 [klein] 4B

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.

Image Gen
index.ts
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.'
});
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Frequently Asked Questions

  • What does the Apache 2.0 license allow for FLUX.2 [klein] 4B?

    Apache 2.0 permits unrestricted commercial use, modification, redistribution, and sublicensing of the model weights. Black Forest Labs adds no additional terms on top of the standard Apache 2.0 conditions. You can incorporate Klein 4B into commercial products or open-source projects without seeking separate permission.

  • Is the Klein 4B available through AI Gateway the same as the open-weight release?

    The API version is the step-distilled variant, optimized for inference speed. The undistilled Klein 4B Base is available as open weights for workflows that need the full training signal rather than minimum generation latency.

  • What image tasks does FLUX.2 [klein] 4B support?

    Klein 4B handles text-to-image (T2I), image-to-image editing (I2I), and multi-reference generation in a single unified model. You don't need separate checkpoints for different task types.

  • How does Klein 4B differ from Klein 9B in terms of licensing?

    Klein 4B is Apache 2.0, fully open for commercial and non-commercial use. Klein 9B is released under the FLUX Non-Commercial License, which restricts commercial deployment. For production commercial pipelines that need open licensing, Klein 4B is the appropriate choice.

  • What does FLUX.2 [klein] 4B cost per image?

    Current pricing is shown on this page. AI Gateway routes across providers, and rates may vary by provider.