Flux 2 Flex: Precision Image-to-Image Generation & Control
Edit and restyle images with precision using Hex codes and multi-reference blending. Upload up to 10 source images to guide style transfer, color swapping, and composition refinement.
Table of contents
1. Get started
Use RunComfy's API to run blackforestlabs/flux-2/flex/edit. For accepted inputs and outputs, see the model's schema.
curl --request POST \
--url https://model-api.runcomfy.net/v1/models/blackforestlabs/flux-2/flex/edit \
--header "Content-Type: application/json" \
--header "Authorization: Bearer <token>" \
--data '{
"prompt": "Change colors of flowers flowing from rich #6a0dad to soft #ff69b4. Add an artistic carving text with a big font on helmet that says 'FLEX'.",
"image_urls": [
"https://playgrounds-storage-public.runcomfy.net/tools/7228/media-files/input-1-1.png"
]
}'2. Authentication
Set the YOUR_API_TOKEN environment variable with your API key (manage keys in your Profile) and include it on every request as a Bearer token via the Authorization header: Authorization: Bearer $YOUR_API_TOKEN.
3. API reference
Submit a request
Submit an asynchronous generation job and immediately receive a request_id plus URLs to check status, fetch results, and cancel.
curl --request POST \
--url https://model-api.runcomfy.net/v1/models/blackforestlabs/flux-2/flex/edit \
--header "Content-Type: application/json" \
--header "Authorization: Bearer <token>" \
--data '{
"prompt": "Change colors of flowers flowing from rich #6a0dad to soft #ff69b4. Add an artistic carving text with a big font on helmet that says 'FLEX'.",
"image_urls": [
"https://playgrounds-storage-public.runcomfy.net/tools/7228/media-files/input-1-1.png"
]
}'Monitor request status
Fetch the current state for a request_id ("in_queue", "in_progress", "completed", or "cancelled").
curl --request GET \
--url https://model-api.runcomfy.net/v1/requests/{request_id}/status \
--header "Authorization: Bearer <token>"Retrieve request results
Retrieve the final outputs and metadata for the given request_id; if the job is not complete, the response returns the current state so you can continue polling.
curl --request GET \
--url https://model-api.runcomfy.net/v1/requests/{request_id}/result \
--header "Authorization: Bearer <token>"Cancel a request
Cancel a queued job by request_id, in-progress jobs cannot be cancelled.
curl --request POST \
--url https://model-api.runcomfy.net/v1/requests/{request_id}/cancel \
--header "Authorization: Bearer <token>"4. File inputs
Hosted file (URL)
Provide a publicly reachable HTTPS URL. Ensure the host allows server‑side fetches (no login/cookies required) and isn't rate‑limited or blocking bots. Recommended limits: images ≤ 50 MB (~4K), videos ≤ 100 MB (~2–5 min @ 720p). Prefer stable or pre‑signed URLs for private assets.
5. Schema
Input schema
{
"type": "object",
"title": "Input",
"required": [
"prompt",
"image_urls"
],
"properties": {
"prompt": {
"title": "Prompt",
"description": "The prompt to generate an image from.",
"type": "string",
"default": "Change colors of flowers flowing from rich #6a0dad to soft #ff69b4. Add an artistic carving text with a big font on helmet that says 'FLEX'."
},
"image_size": {
"title": "Image Size",
"description": "The size of the generated image. If auto, the size will be determined by the model. For custom image sizes, width and height can be passed as an object.",
"type": "string",
"enum": [
"auto",
"square_hd",
"square",
"portrait_4_3",
"portrait_16_9",
"landscape_4_3",
"landscape_16_9"
],
"default": "auto"
},
"enable_prompt_expansion": {
"title": "Magic Prompt",
"description": "Whether to expand the prompt using the model's own knowledge.",
"type": "boolean",
"default": true
},
"seed": {
"title": "Seed",
"description": "The seed to use for the generation.",
"type": "integer",
"default": 0
},
"output_format": {
"title": "Output Format",
"description": "The format of the generated image.",
"type": "string",
"enum": [
"jpeg",
"png"
],
"default": "jpeg"
},
"image_urls": {
"title": "Image URLs",
"description": "List of URLs of input images for editing.",
"type": "array",
"items": {
"type": "string",
"format": "image_uri"
},
"maxItems": 10,
"minItems": 1,
"default": [
"https://playgrounds-storage-public.runcomfy.net/tools/7228/media-files/input-1-1.png"
]
},
"guidance_scale": {
"title": "Guidance Scale",
"description": "The guidance scale to use for the generation.",
"type": "float",
"default": 3.5,
"minimum": 1.5,
"maximum": 10
},
"num_inference_steps": {
"title": "Number of Inference Steps",
"description": "The number of inference steps to perform.",
"type": "integer",
"default": 28,
"minimum": 2,
"maximum": 50
}
}
}Output schema
{
"output": {
"type": "object",
"properties": {
"image": {
"type": "string",
"format": "uri",
"description": "single image URL"
},
"video": {
"type": "string",
"format": "uri",
"description": "single video URL"
},
"images": {
"type": "array",
"description": "multiple image URLs",
"items": { "type": "string", "format": "uri" }
},
"videos": {
"type": "array",
"description": "multiple video URLs",
"items": { "type": "string", "format": "uri" }
}
}
}
}RunComfy is the premier ComfyUI platform, offering ComfyUI online environment and services, along with ComfyUI workflows featuring stunning visuals. RunComfy also provides AI Models, enabling artists to harness the latest AI tools to create incredible art.