FLUX.2 [klein] 4B

Name: FLUX.2 [klein] 4B
Brand: Black Forest Labs
Price: 0.001 USD
Availability: InStock

AI Image Editing Model

Image

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

Try Model

2048 x 2048

Max Resolution

Supported Modes

Text to Image Image Edit

Active

Details

Model ID

flux.2-klein-4b

Also known as: flux-2-klein-4b

Creator

Black Forest Labs

Family

flux.2

Max Input Images

Ready to integrate?

Access flux.2-klein-4b via our unified API.

Create Account

Available at 2 providers

Starting from

$0.0010 /image via Replicate · +1 more

Prices shown are in USD · Some prices estimated from per-megapixel or per-token pricing

See all providers

Providers & Pricing (3)

FLUX.2 [klein] 4B is available from 3 providers, with per-image pricing starting at $0.001 through Replicate.

Replicate

Text to Image Image Edit

replicate/flux.2-klein-4b

Provider Model ID: black-forest-labs/flux-2-klein-4b

$0.0010 /input megapixel

View pricing details

fal.ai

Text to Image

fal/flux.2-klein-4b

Provider Model ID: fal-ai/flux-2/klein/4b

$0.0050 /megapixel

View pricing details

fal.ai

Image Edit

fal/flux.2-klein-4b-edit

Provider Model ID: fal-ai/flux-2/klein/4b/edit

$0.010 /input megapixel

View pricing details

flux-2-klein-4b API OpenAI-compatible

Base URL

https://api.lumenfall.ai/openai/v1

Model

flux.2-klein-4b

Code Examples

Text to Image

/v1/images/generations

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": "..." }] }

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);

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 -X POST \

  https://api.lumenfall.ai/openai/v1/images/edits \

  -H "Authorization: Bearer $LUMENFALL_API_KEY" \

  -F "model=flux.2-klein-4b" \

  -F "[email protected]" \

  -F "prompt=Add a starry night sky to this image" \

  -F "size=1024x1024"

# Response:

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

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);

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)

Parameter Normalization

How we handle parameters across different providers

Not every provider speaks the same language. When you send a parameter, we handle it in one of four ways depending on what the model supports:

Behavior	What happens	Example
`passthrough`	Sent as-is to the provider	style, quality
`renamed`	Same value, mapped to the field name the provider expects	prompt
`converted`	Transformed to the provider's native format	size
`emulated`	Works even if the provider has no concept of it	n, response_format

Parameters we don't recognize pass straight through to the upstream API, so provider-specific options still work.

Full API Reference Authentication, endpoints, and more

Gallery

View all 4 images

FLUX.2 [klein] 4B FAQ

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.

Try FLUX.2 [klein] 4B in Playground

Generate images with custom prompts — no API key needed.

Open Playground