Black Forest LabsFastHigh

FLUX.2 Klein 9B

4-step distilled FLUX.2 [klein] 9B — fast, higher-capacity sibling of Klein 4B for text-to-image generation and multi-reference image editing (up to 5 input images), with selectable output megapixels.

35 credits

per image at 1MP (default); 9 at 0.25MP, 18 at 0.5MP, 70 at 2MP, 140 at 4MP

4-step distilled 9B model — sub-second to few-second inference

Text-to-image and multi-reference image editing (up to 5 images)

Selectable output resolution from 0.25MP to 4MP

go_fast optimizations on by default

Billed by output megapixels, so small previews cost less

Run it right now

Test this model instantly in the Console Playground — no code required

Use with AI Assistant

Copy usage instructions for Claude, ChatGPT, or other AI

llms.txtllms.txt ↗

Quick Start

curl -X POST "https://api.core.today/v1/predictions" \
  -H "Content-Type: application/json" \
  -H "X-API-Key: cdt_your_api_key" \
  -d '{
  "model": "black-forest-labs/flux-2-klein-9b",
  "input": {
    "images": [],
    "prompt": "A surreal cosmic garden scene with bioluminescent flora against a deep navy blue to black background, glowing particles floating like plankton, cinematic lighting. With large white text in the center \"FLUX.2 [klein] 9B\"",
    "go_fast": true,
    "megapixels": "1",
    "aspect_ratio": "1:1",
    "output_format": "jpg",
    "output_quality": 95
  }
}'

Parameters

Parameter	Type	Required	Default	Description
`prompt`	string	Yes	-	Text prompt for image generation
`images`	array	No	[]	Input images for image-to-image generation (max 5; jpeg, png, gif or webp)
`aspect_ratio`	string	No	1:1	Aspect ratio for the generated image. Use match_input_image to match the first input image 1:116:99:163:22:34:33:45:44:521:99:21match_input_image
`megapixels`	string	No	1	Resolution of the output image in megapixels. Higher values cost more credits 0.250.5124
`seed`	integer	No	-	Random seed. Set for reproducible generation
`go_fast`	boolean	No	true	Run faster predictions with additional optimizations
`output_format`	string	No	jpg	Format of the output images webpjpgpng
`output_quality`	integer	No	95	Quality when saving the output images, from 0 to 100. 100 is best quality, 0 is lowest quality. Not relevant for .png outputs.
`disable_safety_checker`	boolean	No	false	Disable safety checker for generated images.

How to Provide File Input

There are 3 ways to provide files for the images parameter:

Recommended

Image URL

Pass a publicly accessible URL directly. With the Storage API (POST /v1/files/upload-url) the file uploads straight to S3 (50MB per file) and you pass the returned file_url.

{
  "model": "black-forest-labs/flux-2-klein-9b",
  "input": {
    "prompt": "your prompt here",
    "images": ["https://example.com/image.jpg"]
  }
}

Direct Upload (Multipart)

Attach files directly to POST /v1/predictions/upload. No separate upload step, but the bytes pass through the API server so the whole request is capped at 10MB.

curl -X POST "https://api.core.today/v1/predictions/upload" \
  -H "X-API-Key: cdt_your_api_key" \
  -F "model=black-forest-labs/flux-2-klein-9b" \
  -F 'input={"prompt":"your prompt here"}' \
  -F "file:images=@your_file.png"

See the File Upload docs for more upload methods including Presigned URLs.

Common Parameters

Common parameters used when calling POST /v1/predictions.

Parameter	Type	Required	Default	Description
`model`	string	Yes	-	Model identifier
`input`	object	Yes	-	Object containing the model-specific parameters from the table above
`output_folder`	string	No	-	Folder path for output files (max 256 chars, '..' not allowed)
`webhook_url`	string	No	-	Webhook URL to call on completion
`is_public`	boolean	No	false	If true, output files are also available via permanent public URLs

Examples

1MP Generation (Default)

Default 1-megapixel text-to-image generation with in-image text — 35 credits

curl -X POST "https://api.core.today/v1/predictions" \
  -H "Content-Type: application/json" \
  -H "X-API-Key: cdt_your_api_key" \
  -d '{
  "model": "black-forest-labs/flux-2-klein-9b",
  "input": {
    "images": [],
    "prompt": "A surreal cosmic garden scene with bioluminescent flora against a deep navy blue to black background, glowing particles floating like plankton, cinematic lighting. With large white text in the center \"FLUX.2 [klein] 9B\"",
    "go_fast": true,
    "megapixels": "1",
    "aspect_ratio": "1:1",
    "output_format": "jpg",
    "output_quality": 95
  }
}'

Low-Cost Preview

0.25-megapixel draft for quick prompt iteration — 9 credits

curl -X POST "https://api.core.today/v1/predictions" \
  -H "Content-Type: application/json" \
  -H "X-API-Key: cdt_your_api_key" \
  -d '{
  "model": "black-forest-labs/flux-2-klein-9b",
  "input": {
    "prompt": "A neon-lit cyberpunk alley at night, concept sketch",
    "megapixels": "0.25"
  }
}'