# FLUX.2 [klein] 9B

> Black Forest Labs' distilled 9 billion parameter image generation model with sub-second inference and multi-reference support

## Quick Reference

- Model ID: flux.2-klein-9b
- Creator: Black Forest Labs
- Status: active
- Family: flux.2
- Base URL: https://api.lumenfall.ai/openai/v1

## Specifications

- Max Resolution: 2048x2048
- Max Input Images: 4
- Input Modalities: text, image
- Output Modalities: image
- Supported Modes: Text to Image, Image Edit

## API Parameters

The compiled parameter schema for this model is available via the API: `GET /v1/models/flux.2-klein-9b?schema=true`.

### Core Parameters

- `prompt` (string) — REQUIRED: Text prompt for image generation. Modes: Text to Image, Image Edit
- `seed` (integer): Random seed for reproducibility. Modes: Text to Image, Image Edit

### Size & Layout

- `size` (string): Image dimensions as WxH pixels (e.g. "1024x1024") or aspect ratio (e.g. "16:9"). Values: auto, 1563x670, 670x1564, 1365x768, 768x1365, 1254x836, 836x1254, 887x1182, 1024x1024, 1145x916, 916x1145, 1183x887. Modes: Text to Image, Image Edit
- `aspect_ratio` (string): Aspect ratio of the output image (e.g. "16:9", "1:1"). Values: auto, 9:21, 9:16, 2:3, 3:4, 4:5, 1:1, 5:4, 4:3, 3:2, 16:9, 21:9. Modes: Text to Image, Image Edit
- `resolution` (string): Output resolution tier (e.g. "1K", "4K"). Values: auto, 1K. Modes: Text to Image, Image Edit

### Media Inputs

- `image` (file) — REQUIRED: Input image(s) to edit. Modes: Image Edit

### Output & Format

- `response_format` (string): How to return the image. Default: url. Values: url, b64_json. Modes: Text to Image, Image Edit
- `output_format` (string): Output image format. Values: png, jpeg, gif, webp, avif. Modes: Text to Image, Image Edit
- `output_compression` (integer): Compression level for lossy formats (JPEG, WebP, AVIF). Modes: Text to Image, Image Edit
- `n` (integer): Number of images to generate. Default: 1. Modes: Text to Image, Image Edit

### Additional Parameters

- `disable_safety_checker` (boolean): Disable safety checker for generated images.. Modes: Text to Image, Image Edit. Only available via replicate
- `enable_safety_checker` (boolean): If set to true, the safety checker will be enabled.. Modes: Text to Image, Image Edit. Only available via fal
- `go_fast` (boolean): Run faster predictions with additional optimizations.. Modes: Text to Image, Image Edit. Only available via replicate
- `megapixels` (string): Resolution in megapixels. Values: 0.25, 0.5, 1, 2, 4. Modes: Text to Image, Image Edit. Only available via replicate
- `num_inference_steps` (integer): The number of inference steps to perform.. Modes: Text to Image, Image Edit. Only available via fal
- `output_quality` (integer): Quality when saving the output images, from 0 to 100. 100 is best quality, 0 is lowest quality. Not relevant for .png outputs.. Modes: Text to Image, Image Edit. Only available via replicate
- `sync_mode` (boolean): If `True`, the media will be returned as a data URI. Output is not stored when this is True.. Modes: Text to Image, Image Edit. Only available via fal


## Model Identifiers

- Primary Slug: flux.2-klein-9b
- Aliases: flux-2-klein-9b

## Dates

- Released: January 2026

## Tags

image-generation, text-to-image, image-editing, open-weights

## Available Providers

### Replicate

- Config Key: replicate/flux.2-klein-9b
- Provider Model ID: black-forest-labs/flux-2-klein-9b
- Pricing: $0.0020/megapixel, $0.015/megapixel
  - Source: https://replicate.com/black-forest-labs/flux-2-klein-9b

### fal.ai

- Config Key: fal/flux.2-klein-9b
- Provider Model ID: fal-ai/flux-2/klein/9b
- Pricing: $0.0060/megapixel
  - Source: https://fal.ai/models/fal-ai/flux-2/klein/9b

### fal.ai

- Config Key: fal/flux.2-klein-9b-edit
- Provider Model ID: fal-ai/flux-2/klein/9b/edit
- Pricing: $0.011/megapixel, $0.011/megapixel
  - Source: https://fal.ai/models/fal-ai/flux-2/klein/9b/edit


## Arena Benchmarks

### Pose & Character Mashup

- Elo: 1159
- Record: 6W / 3L / 0T (9 battles)
- Rank: #3 of 14

### Magic Burger Explosion: Fiery Photorealism Challenge

- Elo: 1142
- Record: 5W / 5L / 2T (12 battles)
- Rank: #5 of 19

### Outfit Transfer Challenge

- Elo: 1059
- Record: 1W / 4L / 1T (6 battles)
- Rank: #11 of 16

### Chalkboard Menu

- Elo: 1055
- Record: 2W / 6L / 0T (8 battles)
- Rank: #17 of 25


## Use Cases & Category Performance

### Photorealism (Text-to-Image)

- Rank: #15 of 38
- Elo: 1204
- Record: 7W / 10L / 2T (19 battles)
- Win Rate: 36.8%

### Text Rendering (Text-to-Image)

- Rank: #23 of 37
- Elo: 1191
- Record: 7W / 10L / 2T (19 battles)
- Win Rate: 36.8%

### Product, Branding & Commercial (Text-to-Image)

- Rank: #22 of 29
- Elo: 1156
- Record: 5W / 5L / 2T (12 battles)
- Win Rate: 41.7%

### Photorealism (Image Editing)

- Rank: #17 of 17
- Elo: 1104
- Record: 1W / 3L / 1T (5 battles)
- Win Rate: 20.0%


## Image Gallery

8 images available for this model. Browse all at https://lumenfall.ai/models/black-forest-labs/flux.2-klein-9b/gallery

### Curated Examples

- [Cinematic wide shot of a sophisticated, high-end boutique storefront at dusk. The shop window is ...](https://assets.lumenfall.ai/21DXmWV9AX_Gf751UclKPTkkH_nCCINAi6JWjcUhmq4/rs:fit:1500:1500/plain/gs://lumenfall-prod-assets/n4y1vvhfakobbard923hz6liyh77@jpeg)
- [A high-end cinematic close-up of a vintage 1950s camera lens reflecting a sun-drenched Italian co...](https://assets.lumenfall.ai/PkiWHEdS26cHPcm_9yBpaSXH5RgnEENPopBomEl3mGI/rs:fit:1500:1500/plain/gs://lumenfall-prod-assets/z89mwfn35gzu0t4suxdnrn2korop@jpeg)
- [A hyper-realistic close-up of a weathered, vintage leather traveler's journal resting on a rustic...](https://assets.lumenfall.ai/qRBEPxku-A9MCAVoUgfrTW5esYaEyswBF4OcgTtQRks/rs:fit:1500:1500/plain/gs://lumenfall-prod-assets/9otlhkaizlrav8xejgv4qnn4kicw@jpeg)
- [A vintage wooden storefront for a bookstore called "THE TURNING PAGE" in crisp, elegant gold lett...](https://assets.lumenfall.ai/4NzFv1G_l8dxmIcKx501bL3VghvNWgwpX76A55jFdYY/rs:fit:1500:1500/plain/gs://lumenfall-prod-assets/pss6bd98sdf711lsyi5vu0d5ilfz@jpeg)

### Arena Competition Results

- [Pose & Character Mashup](https://assets.lumenfall.ai/_8_giA4GhBmOd0y4BDYWBdnBu3AHJ236Vf-ojNN0bUo/rs:fit:1500:1500/plain/gs://lumenfall-prod-assets/j8xxq29wu8fp4zjg6b52q76pvayt@jpeg): #3 of 14 (Elo 1159)
- [Magic Burger Explosion: Fiery Photorealism Challenge](https://assets.lumenfall.ai/vq2I7ygDfgqNPT6BAflzcA6xEJAnZAxDheQL08mvC3s/rs:fit:1500:1500/plain/gs://lumenfall-prod-assets/9iyyim6zz3h95bhky1h4tbl2gvsx@jpeg): #5 of 19 (Elo 1142)
- [Outfit Transfer Challenge](https://assets.lumenfall.ai/BSvBEdqQ-305cNj3akrzidGjLUigLcm1jNtToh1rJ0A/rs:fit:1500:1500/plain/gs://lumenfall-prod-assets/69k8fulmmld865idj2lepyo2s2ae@jpeg): #11 of 16 (Elo 1059)
- [Chalkboard Menu](https://assets.lumenfall.ai/nudQ6ngFs1bWkidkkTlibGgW41DzGv8qZg3t3_LVHXA/rs:fit:1500:1500/plain/gs://lumenfall-prod-assets/d52nexxp3chu888g7uxrwx4v9tn6@jpeg): #17 of 25 (Elo 1055)

## Example Prompt

The following prompt was used to generate an example image in our playground:

A vintage wooden storefront for a bookstore called "THE TURNING PAGE" in crisp, elegant gold lettering on the window. A cozy interior is visible with floor-to-ceiling shelves. On the sidewalk bench, a capybara sits quietly reading a newspaper.

## Code Examples

### Text to Image (/v1/images/generations)

#### cURL

curl -X POST \
  https://api.lumenfall.ai/openai/v1/images/generations \
  -H "Authorization: Bearer $LUMENFALL_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "flux.2-klein-9b",
    "prompt": "",
    "size": "1024x1024"
  }'

# Response:
# { "created": 1234567890, "data": [{ "url": "https://...", "revised_prompt": "..." }] }

#### JavaScript

import OpenAI from 'openai';

const client = new OpenAI({
  apiKey: 'YOUR_API_KEY',
  baseURL: 'https://api.lumenfall.ai/openai/v1'
});

const response = await client.images.generate({
  model: 'flux.2-klein-9b',
  prompt: '',
  size: '1024x1024'
});

// { created: 1234567890, data: [{ url: "https://...", revised_prompt: "..." }] }
console.log(response.data[0].url);

#### Python

from openai import OpenAI

client = OpenAI(
    api_key="YOUR_API_KEY",
    base_url="https://api.lumenfall.ai/openai/v1"
)

response = client.images.generate(
    model="flux.2-klein-9b",
    prompt="",
    size="1024x1024"
)

# { created: 1234567890, data: [{ url: "https://...", revised_prompt: "..." }] }
print(response.data[0].url)

### Image Edit (/v1/images/edits)

#### cURL

curl -X POST \
  https://api.lumenfall.ai/openai/v1/images/edits \
  -H "Authorization: Bearer $LUMENFALL_API_KEY" \
  -F "model=flux.2-klein-9b" \
  -F "image=@source.png" \
  -F "prompt=Add a starry night sky to this image" \
  -F "size=1024x1024"

# Response:
# { "created": 1234567890, "data": [{ "url": "https://...", "revised_prompt": "..." }] }

#### JavaScript

import OpenAI from 'openai';
import fs from 'fs';

const client = new OpenAI({
  apiKey: 'YOUR_API_KEY',
  baseURL: 'https://api.lumenfall.ai/openai/v1'
});

const response = await client.images.edit({
  model: 'flux.2-klein-9b',
  image: fs.createReadStream('source.png'),
  prompt: 'Add a starry night sky to this image',
  size: '1024x1024'
});

// { created: 1234567890, data: [{ url: "https://...", revised_prompt: "..." }] }
console.log(response.data[0].url);

#### Python

from openai import OpenAI

client = OpenAI(
    api_key="YOUR_API_KEY",
    base_url="https://api.lumenfall.ai/openai/v1"
)

response = client.images.edit(
    model="flux.2-klein-9b",
    image=open("source.png", "rb"),
    prompt="Add a starry night sky to this image",
    size="1024x1024"
)

# { created: 1234567890, data: [{ url: "https://...", revised_prompt: "..." }] }
print(response.data[0].url)


## Frequently Asked Questions

### How much does FLUX.2 [klein] 9B cost?

FLUX.2 [klein] 9B starts at $0.006 per image through Lumenfall. Pricing varies by provider. Lumenfall does not add any markup to provider pricing.

### How do I use FLUX.2 [klein] 9B via API?

You can use FLUX.2 [klein] 9B through Lumenfall's OpenAI-compatible API. Send requests to the unified endpoint with model ID "flux.2-klein-9b". Code examples are available in Python, JavaScript, and cURL.

### Which providers offer FLUX.2 [klein] 9B?

FLUX.2 [klein] 9B is available through Replicate and fal.ai on Lumenfall. Lumenfall automatically routes requests to the best available provider.

### What is the maximum resolution for FLUX.2 [klein] 9B?

FLUX.2 [klein] 9B supports images up to 2048x2048 resolution.

## Links

- Model Page: https://lumenfall.ai/models/black-forest-labs/flux.2-klein-9b
- About: https://lumenfall.ai/models/black-forest-labs/flux.2-klein-9b/about
- Providers, Pricing & Performance: https://lumenfall.ai/models/black-forest-labs/flux.2-klein-9b/providers
- API Reference: https://lumenfall.ai/models/black-forest-labs/flux.2-klein-9b/api
- Benchmarks: https://lumenfall.ai/models/black-forest-labs/flux.2-klein-9b/benchmarks
- Use Cases: https://lumenfall.ai/models/black-forest-labs/flux.2-klein-9b/use-cases
- Gallery: https://lumenfall.ai/models/black-forest-labs/flux.2-klein-9b/gallery
- Playground: https://lumenfall.ai/playground?model=flux.2-klein-9b
- API Documentation: https://docs.lumenfall.ai