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FLUX.2 [klein] 9B

FLUX.2 [klein] 9B is Black Forest Labs's quality-focused small image model in the Klein family. It pairs a 9B flow model with an 8B Qwen3 text embedder and distills inference to four steps for sub-half-second latency.

Image Gen
index.ts
import { experimental_generateImage as generateImage } from 'ai';


const result = await generateImage({
  model: 'bfl/flux-2-klein-9b',
  prompt: 'A red balloon on a wooden table.'
});
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Frequently Asked Questions

  • Why does Klein 9B use a Qwen3 text embedder instead of a CLIP-based encoder?

    Qwen3 is a large-language-model-class text encoder that understands complex, multi-clause natural language prompts at a level that smaller CLIP-based encoders cannot match. This gives Klein 9B substantially better prompt adherence, particularly for detailed or compositionally complex image descriptions.

  • What is four-step distillation and why does it matter?

    Step distillation compresses the full denoising trajectory of a diffusion model into fewer inference steps without proportional quality loss. Klein 9B uses four steps, compared to the 20-50 steps a standard diffusion model might require. This enables sub-0.5-second generation while retaining high output quality.

  • Does Klein 9B support multi-reference generation?

    Yes. Multiple input images can be provided to blend concepts and guide composition at sub-second speed, a capability Black Forest Labs describes as uncommon for a model operating at this latency.

  • What license covers FLUX.2 [klein] 9B?

    Klein 9B uses the FLUX Non-Commercial License (NCL). Black Forest Labs renamed it from the FLUX [dev] Non-Commercial License and states there were no material changes to the license terms. Commercial production applications require Klein 4B (Apache 2.0) or a commercial Black Forest Labs offering.

  • How does Klein 9B's quality compare to much larger models?

    Klein 9B matches or exceeds models 5x its size in image quality benchmarks, attributed to the combination of the Qwen3 embedder, the 9B flow architecture, and step distillation training.

  • What does FLUX.2 [klein] 9B cost per image?

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