FLUX Klein API

Build with FLUX 3 Klein image generation and editing through Muapi's asynchronous image API. This guide documents the two live FLUX 3 Klein routes, supported inputs, per-image pricing, and runnable cURL, Python, and JavaScript examples. It also gives a practical way to compare those routes with the FLUX.2 Klein options in the broader catalog.

Muapi provides one API key and a shared submit-and-poll workflow across image models. Start at Muapi, read the FLUX Klein API landing page, try a route in the image playground, or follow the API quick start.

Related Projects

• Muapi — One API for image, video, and audio generation.
• FLUX Klein API on Muapi — Compare FLUX 3 Klein generation and editing with FLUX.2 Klein variants, prices, and parameters.
• FLUX 3 Klein text-to-image playground — Try prompt-based image generation.
• FLUX 3 Klein image-edit playground — Try reference-image editing.
• FLUX.2 API — Browse FLUX.2 Dev, Flex, Pro, Klein, Turbo, and LoRA routes.
• FLUX 3 API — Browse the wider FLUX 3 family.
• FLUX 3 API examples — Examples for other FLUX 3 workflows.
• Awesome AI image models — A broader image-model directory.

What this API includes

Workflow	Muapi endpoint	Required inputs	Output options
Text to image	flux-3-klein-text-to-image	prompt	1K, 2K, or 4K; one to four images
Image editing	flux-3-klein-edit-image	prompt, images_list	1K, 2K, or 4K; one to four outputs

The edit route accepts one to ten public image URLs in images_list. Set aspect_ratio to auto to preserve automatic framing or choose a supported ratio. Both routes accept PNG, JPEG, or WebP output, an optional seed, and prompt enhancement.

Pricing

Muapi charges per output image. The resolution sets the rate, and num_images multiplies the total.

Resolution	Price per output image
1K	$0.009
2K	$0.014
4K	$0.036

For example, a request for two 2K outputs costs $0.028. The available API resolution choices are 1K, 2K, and 4K.

Quick start

Create an API key in the Muapi dashboard. Send it with the x-api-key header. Each submit call returns a request_id; poll the shared result endpoint until the task completes.

Text-to-image request

curl -X POST https://api.muapi.ai/api/v1/flux-3-klein-text-to-image \
  -H "x-api-key: $MUAPI_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "prompt": "A sculptural glass perfume bottle on a warm limestone plinth, soft editorial light",
    "resolution": "2K",
    "aspect_ratio": "4:3",
    "num_images": 2,
    "output_format": "png"
  }'

Image-edit request

curl -X POST https://api.muapi.ai/api/v1/flux-3-klein-edit-image \
  -H "x-api-key: $MUAPI_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "prompt": "Replace the plain background with a warm limestone studio, preserving the product shape",
    "images_list": ["https://example.com/product.jpg"],
    "resolution": "2K",
    "aspect_ratio": "auto",
    "num_images": 1
  }'

Poll for the result

curl https://api.muapi.ai/api/v1/predictions/REQUEST_ID/result \
  -H "x-api-key: $MUAPI_API_KEY"

When status is completed, read the generated image URLs from outputs. A task may take time to finish, so poll with a short delay and stop on completed or failed.

Inputs

Field	Text to image	Edit	Details
prompt	Yes	Yes	Required instruction, up to 5,000 characters
images_list	—	Yes	One to ten public image URLs
aspect_ratio	Optional	Optional	1:1, 4:3, 3:4, 3:2, 2:3, 16:9, 9:16, 21:9, 9:21; edit also accepts auto
resolution	Optional	Optional	1K, 2K, or 4K
output_format	Optional	Optional	png, jpeg, or webp
num_images	Optional	Optional	1–4 outputs; charged per output
seed	Optional	Optional	Integer from 0 to 2147483647 for reproducible variation
enhance_prompt	Optional	Optional	Boolean; lets the model refine the prompt

Only prompt is required for text-to-image. The edit endpoint additionally requires at least one images_list URL.

Choosing a FLUX Klein route

Route family	Good fit when	What to compare
FLUX 3 Klein	You want the new FLUX 3 Klein prompt-to-image or reference-edit endpoints, with 1K/2K/4K selection	Generation versus editing, resolution, and per-output cost
FLUX.2 Klein 4B / 9B	You want to compare the existing FLUX.2 Klein generation and edit variants	4B versus 9B variants and their available Turbo/LoRA routes

The model names identify different FLUX generations. Check each route's playground page for its current inputs and availability before switching. The Muapi request lifecycle remains the same: submit, save request_id, then poll for outputs.

Python and JavaScript examples

See examples/python.py and examples/node.js. The Python example uses requests; install it with pip install -r requirements.txt. The JavaScript example uses the built-in fetch API in Node.js 18 or newer.

License

MIT