Black Forest LabsSlowUltra

FLUX 2 Flex

Maximum-quality FLUX model supporting up to 10 reference images and advanced typography. The most capable model for complex, multi-reference creative projects.

200 credits

per image

Up to 10 reference images supported

Advanced typography rendering

Ultra-quality output

Complex multi-reference composition

Best-in-class creative control

Use with AI Assistant

Copy usage instructions for Claude, ChatGPT, or other AI

llms.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-flex",
  "input": {
    "prompt": "Premium brand campaign visual combining modern architecture with natural elements, luxury lifestyle aesthetic, professional advertising quality, 8k",
    "image_size": "landscape_16_9",
    "num_inference_steps": 50,
    "guidance_scale": 3.5
  }
}'

Parameters

Parameter	Type	Required	Default	Description
`prompt`	string	Yes	-	Text description of the image to generate
`input_images`	array	No	-	Input images for style and content guidance (max 10)
`aspect_ratio`	string	No	1:1	Aspect ratio for the generated image (use 'match_input_image' to match input) 1:116:99:164:33:4match_input_imagecustom
`resolution`	string	No	1 MP	Resolution in megapixels (up to 4 MP, 2 MP or below recommended)
`seed`	integer	No	-	Random seed for reproducibility
`guidance`	number	No	3.5	Guidance scale - controls how closely output follows the prompt
`steps`	integer	No	50	Number of inference steps
`prompt_upsampling`	boolean	No	-	Automatically modify the prompt for more creative generation
`output_format`	string	No	webp	Format of the output images pngjpgwebp
`output_quality`	integer	No	80	Quality of output images (0-100)

How to Provide File Input

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

Recommended

Direct Upload (Multipart)

Attach files directly to POST /v1/predictions/upload. No separate upload step needed.

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-flex" \
  -F 'input={"prompt":"your prompt here"}' \
  -F "file:input_images=@your_file.png"

Image URL

Pass a publicly accessible URL directly. You can also use file_url from the Storage API.

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

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

Multi-Reference Brand Design

Create a brand visual using multiple reference images

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-flex",
  "input": {
    "prompt": "Premium brand campaign visual combining modern architecture with natural elements, luxury lifestyle aesthetic, professional advertising quality, 8k",
    "image_size": "landscape_16_9",
    "num_inference_steps": 50,
    "guidance_scale": 3.5
  }
}'