# FLUX.2 [klein] 4B

> Black Forest Labs' compact, open-source image generation model with sub-second inference, optimized for production and near real-time applications with multi-reference support

## Quick Reference

- Model ID: flux.2-klein-4b
- 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

## Model Identifiers

- Primary Slug: flux.2-klein-4b
- Aliases: flux-2-klein-4b


## Tags

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

## Available Providers

### fal.ai

- Config Key: fal/flux.2-klein-4b
- Provider Model ID: fal-ai/flux-2/klein/4b
- Pricing: $0.0050/megapixel
  - Source: https://fal.ai/models/fal-ai/flux-2/klein/4b

### fal.ai

- Config Key: fal/flux.2-klein-4b-edit
- Provider Model ID: fal-ai/flux-2/klein/4b/edit
- Pricing: $0.010/megapixel, $0.010/megapixel
  - Source: https://fal.ai/models/fal-ai/flux-2/klein/4b/edit

### Replicate

- Config Key: replicate/flux.2-klein-4b
- Provider Model ID: black-forest-labs/flux-2-klein-4b
- Pricing: $0.0010/megapixel, $0.0010/megapixel
  - Source: https://replicate.com/black-forest-labs/flux-2-klein-4b


## Image Gallery

4 images available for this model. Browse all at https://lumenfall.ai/models/black-forest-labs/flux.2-klein-4b/gallery

### Curated Examples

- [A cinematic, wide-angle shot of a high-end, minimalist luxury boutique at dusk. The storefront fe...](https://assets.lumenfall.ai/Gs49uwhZZN2OOWBVU1lRSGcuIJ6aLp2ImNXk3H1WgLI/rs:fit:1500:1500/plain/gs://lumenfall-prod-assets/66cmc8xq5wo9zgds13qitr1rx68n@jpeg)
- [An ethereal macro photograph of a single translucent dandelion seed resting on a calm, dark obsid...](https://assets.lumenfall.ai/wGWV_gMzmLehFjcMdJg99ZTKeKkf6wdq5s6DZu1xIJc/rs:fit:1500:1500/plain/gs://lumenfall-prod-assets/zcz7tfbqrvirlmvalqlue77n86d4@jpeg)
- [A highly detailed, macro photograph of a weathered leather craftsman's workbench. In the center s...](https://assets.lumenfall.ai/cuUzzw7AMb8JY7jrk02zLgN4y9fFdelF7XdA6mxXtsE/rs:fit:1500:1500/plain/gs://lumenfall-prod-assets/3kz7oaduvbgfmg6wvepiyedzlylv@jpeg)
- [A rustic wooden storefront of a boutique bakery named "CRUST & CO." in elegant gold serif letteri...](https://assets.lumenfall.ai/afrFooKKTTVFFOobuZCHXXs0jkOjAP01V5Km7RtX6b0/rs:fit:1500:1500/plain/gs://lumenfall-prod-assets/ikkzci1ebbtrp2k816qzfo83a6pp@jpeg)

## Example Prompt

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

A rustic wooden storefront of a boutique bakery named "CRUST & CO." in elegant gold serif lettering. Through the large glass window, a small capybara sits quietly on a floor rug near a display of sourdough bread. Low morning sun, cinematic.

## 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-4b",
    "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-4b',
  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-4b",
    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-4b" \
  -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-4b',
  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-4b",
    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] 4B cost?

FLUX.2 [klein] 4B starts at $0.001 per image through Lumenfall. Pricing varies by provider. Lumenfall does not add any markup to provider pricing.

### How do I use FLUX.2 [klein] 4B via API?

You can use FLUX.2 [klein] 4B through Lumenfall's OpenAI-compatible API. Send requests to the unified endpoint with model ID "flux.2-klein-4b". Code examples are available in Python, JavaScript, and cURL.

### Which providers offer FLUX.2 [klein] 4B?

FLUX.2 [klein] 4B is available through fal.ai and Replicate on Lumenfall. Lumenfall automatically routes requests to the best available provider.

### What is the maximum resolution for FLUX.2 [klein] 4B?

FLUX.2 [klein] 4B supports images up to 2048x2048 resolution.

## Links

- Model Page: https://lumenfall.ai/models/black-forest-labs/flux.2-klein-4b
- About: https://lumenfall.ai/models/black-forest-labs/flux.2-klein-4b/about
- Providers, Pricing & Performance: https://lumenfall.ai/models/black-forest-labs/flux.2-klein-4b/providers
- API Reference: https://lumenfall.ai/models/black-forest-labs/flux.2-klein-4b/api
- Benchmarks: https://lumenfall.ai/models/black-forest-labs/flux.2-klein-4b/benchmarks
- Use Cases: https://lumenfall.ai/models/black-forest-labs/flux.2-klein-4b/use-cases
- Gallery: https://lumenfall.ai/models/black-forest-labs/flux.2-klein-4b/gallery
- Playground: https://lumenfall.ai/playground?model=flux.2-klein-4b
- API Documentation: https://docs.lumenfall.ai