Edits and composes images from text instructions and up to ten references with FLUX.3 Klein Base, with configurable guidance, negative prompts and bounding-box layout controls.

blackforestlabs/flux-3/klein/base/edit-image

Edits and composes images from text instructions and up to ten references with FLUX.3 Klein Base, with configurable guidance, negative prompts and bounding-box layout controls.

Inference

Commercial use

Schema

Playground API Examples

blackforestlabs/flux-3/klein/base/edit-image

Schema

Edits and composes images from text instructions and up to ten references with FLUX.3 Klein Base, with configurable guidance, negative prompts and bounding-box layout controls.

blackforestlabs/flux-3/klein/base/edit-image

Edits and composes images from text instructions and up to ten references with FLUX.3 Klein Base, with configurable guidance, negative prompts and bounding-box layout controls.

Inference

Commercial use

Schema

Playground API Examples

About

Edit or compose from reference images with the base model (CFG).

1. Calling the API#

Install the client#

The client provides a convenient way to interact with the model API.

npm install --save @fal-ai/client

Migrate to @fal-ai/client

The @fal-ai/serverless-client package has been deprecated in favor of @fal-ai/client. Install the new package and update your imports — see client setup.

Setup your API Key#

Set FAL_KEY as an environment variable in your runtime.

export FAL_KEY="YOUR_API_KEY"

Submit a request#

The client API handles the API submit protocol. It will handle the request status updates and return the result when the request is completed.

import { fal } from "@fal-ai/client";

const result = await fal.subscribe("blackforestlabs/flux-3/klein/base/edit-image", {
  input: {
    prompt: "A miniature grey amigurumi knight figure crocheted from thick woolen yarn stands on a cliff of stacked yarn skeins at night, lit by a full moon, next to a large fluffy knitted dragon in terracotta and mustard yarn, with a soft out-of-focus backdrop of indigo knitted yarn.",
    image_urls: ["https://storage.googleapis.com/falserverless/example_inputs/z-image-turbo-i2i-input.png"]
  },
  logs: true,
  onQueueUpdate: (update) => {
    if (update.status === "IN_PROGRESS") {
      update.logs.map((log) => log.message).forEach(console.log);
    }
  },
});
console.log(result.data);
console.log(result.requestId);

2. Authentication#

The API uses an API Key for authentication. It is recommended you set the FAL_KEY environment variable in your runtime when possible.

API Key#

In an environment where you cannot set environment variables, you can configure the API key manually on the client.

import { fal } from "@fal-ai/client";

fal.config({
  credentials: "YOUR_FAL_KEY"
});

Protect your API Key

When running code on the client-side (e.g. in a browser, mobile app or GUI applications), make sure to not expose your FAL_KEY. Instead, use a server-side proxy to make requests to the API. For more information, check out our server-side integration guide.

3. Queue#

Long-running requests

For long-running requests, such as training jobs or models with slower inference times, it is recommended to check the Queue status and rely on Webhooks instead of blocking while waiting for the result.

Submit a request#

The client API provides a convenient way to submit requests to the model.

import { fal } from "@fal-ai/client";

const { request_id } = await fal.queue.submit("blackforestlabs/flux-3/klein/base/edit-image", {
  input: {
    prompt: "A miniature grey amigurumi knight figure crocheted from thick woolen yarn stands on a cliff of stacked yarn skeins at night, lit by a full moon, next to a large fluffy knitted dragon in terracotta and mustard yarn, with a soft out-of-focus backdrop of indigo knitted yarn.",
    image_urls: ["https://storage.googleapis.com/falserverless/example_inputs/z-image-turbo-i2i-input.png"]
  },
  webhookUrl: "https://optional.webhook.url/for/results",
});

Fetch request status#

You can fetch the status of a request to check if it is completed or still in progress.

import { fal } from "@fal-ai/client";

const status = await fal.queue.status("blackforestlabs/flux-3/klein/base/edit-image", {
  requestId: "764cabcf-b745-4b3e-ae38-1200304cf45b",
  logs: true,
});

Get the result#

Once the request is completed, you can fetch the result. See the Output Schema for the expected result format.

import { fal } from "@fal-ai/client";

const result = await fal.queue.result("blackforestlabs/flux-3/klein/base/edit-image", {
  requestId: "764cabcf-b745-4b3e-ae38-1200304cf45b"
});
console.log(result.data);
console.log(result.requestId);

4. Files#

Some attributes in the API accept file URLs as input. Whenever that's the case you can pass your own URL or a Base64 data URI.

Data URI (base64)#

You can pass a Base64 data URI as a file input. The API will handle the file decoding for you. Keep in mind that for large files, this alternative although convenient can impact the request performance.

Hosted files (URL)#

You can also pass your own URLs as long as they are publicly accessible. Be aware that some hosts might block cross-site requests, rate-limit, or consider the request as a bot.

Uploading files#

We provide a convenient file storage that allows you to upload files and use them in your requests. You can upload files using the client API and use the returned URL in your requests.

import { fal } from "@fal-ai/client";

const file = new File(["Hello, World!"], "hello.txt", { type: "text/plain" });
const url = await fal.storage.upload(file);

Auto uploads

The client will auto-upload the file for you if you pass a binary object (e.g. File, Data).

Read more about file handling in our file upload guide.

5. Schema#

Input#

prompt string* required

A complete caption of the target image with the edit folded in. Refer to the references by their order: the first image, the second image.

enable_prompt_expansion boolean

If set to true, the prompt is expanded into a detailed caption (grounded in the reference images when editing) before generation. Default value: true

seed integer

The same seed and the same prompt given to the same version of the model will output the same image every time.

num_images integer

The number of images to generate. Default value: 1

enable_safety_checker boolean

If set to true, the safety checker will be enabled. Default value: true

output_format OutputFormatEnum

The format of the generated image. Default value: "png"

Possible enum values: jpeg, png, webp

sync_mode boolean

If True, the media will be returned as a data URI and the output data won't be available in the request history.

image_urls list<string>* required

The reference images to edit or compose from (up to 10).

image_size ImageSize | Enum

The size of the generated image, 256 to 4096 pixels per side. If not set, a single reference image's own size (scaled to at most 4 megapixels) is used, or the first reference image's size (at most 1 megapixel) when several are given.

Possible enum values: square_hd, square, portrait_4_3, portrait_16_9, landscape_4_3, landscape_16_9

Note: For custom image sizes, you can pass the width and height as an object:

"image_size": {
  "width": 1280,
  "height": 720
}

bounding_boxes list<EditBoundingBox>

Optional layout, with (0, 0) at the top-left of each image: keep, move, resize or remove objects from the references, or place new ones. Name boxes in the prompt by label, e.g. <dragon>.

{
  "prompt": "A miniature grey amigurumi knight figure crocheted from thick woolen yarn stands on a cliff of stacked yarn skeins at night, lit by a full moon, next to a large fluffy knitted dragon in terracotta and mustard yarn, with a soft out-of-focus backdrop of indigo knitted yarn.",
  "enable_prompt_expansion": true,
  "num_images": 1,
  "enable_safety_checker": true,
  "output_format": "png",
  "image_urls": [
    "https://storage.googleapis.com/falserverless/example_inputs/z-image-turbo-i2i-input.png"
  ],
  "bounding_boxes": [
    {
      "label": "dragon",
      "description": "a large fluffy knitted dragon in terracotta and mustard yarn"
    }
  ]
}

Output#

images list<ImageFile>* required

The generated images.

timings Timings* required

The timings of the generation process.

seed integer* required

Seed used to generate the first image.

has_nsfw_concepts list<boolean>* required

Whether the generated images contain NSFW concepts.

prompt string* required

The prompt used for generating the image.

{
  "images": [
    {
      "url": "",
      "content_type": "image/png",
      "file_name": "z9RV14K95DvU.png",
      "file_size": 4404019
    }
  ],
  "prompt": ""
}

Other types#

ImageFile#

url string* required

The URL where the file can be downloaded from.

content_type string

The mime type of the file.

file_name string

The name of the file. It will be auto-generated if not provided.

file_size integer

The size of the file in bytes.

width integer

The width of the image

height integer

The height of the image

ImageSize#

width integer

The width of the generated image. Default value: 512

height integer

The height of the generated image. Default value: 512

EditBoundingBox#

label string

Short name for the object in this box, e.g. dragon. Write <dragon> in the prompt to tie the box to those words; a box the prompt doesn't name is added to the scene. Defaults to obj_<n>.

description string* required

What to draw in this box: the object and its look.

box Box

Where the object goes in the output image, as on text-to-image. Use instead of source_box/target_box.

source_image_index integer

0-based index into image_urls of the reference the object comes from. Leave unset for a new object.

source_box Box

Where the object is in the reference image. Requires source_image_index.

target_box Box

Where the object goes in the output image. Leave unset to remove a referenced object; set both boxes to move or resize it.

Box#

x_min float* required

Left edge as a fraction of the image width (0-1).

y_min float* required

Top edge as a fraction of the image height (0-1).

x_max float* required

Right edge as a fraction of the image width (0-1).

y_max float* required

Bottom edge as a fraction of the image height (0-1).

Related Models

About

Edit or compose from reference images with the base model (CFG).

1. Calling the API#

Install the client#

The client provides a convenient way to interact with the model API.

npm install --save @fal-ai/client

Migrate to @fal-ai/client

The @fal-ai/serverless-client package has been deprecated in favor of @fal-ai/client. Install the new package and update your imports — see client setup.

Setup your API Key#

Set FAL_KEY as an environment variable in your runtime.

export FAL_KEY="YOUR_API_KEY"

Submit a request#

The client API handles the API submit protocol. It will handle the request status updates and return the result when the request is completed.

import { fal } from "@fal-ai/client";

const result = await fal.subscribe("blackforestlabs/flux-3/klein/base/edit-image", {
  input: {
    prompt: "A miniature grey amigurumi knight figure crocheted from thick woolen yarn stands on a cliff of stacked yarn skeins at night, lit by a full moon, next to a large fluffy knitted dragon in terracotta and mustard yarn, with a soft out-of-focus backdrop of indigo knitted yarn.",
    image_urls: ["https://storage.googleapis.com/falserverless/example_inputs/z-image-turbo-i2i-input.png"]
  },
  logs: true,
  onQueueUpdate: (update) => {
    if (update.status === "IN_PROGRESS") {
      update.logs.map((log) => log.message).forEach(console.log);
    }
  },
});
console.log(result.data);
console.log(result.requestId);

2. Authentication#

The API uses an API Key for authentication. It is recommended you set the FAL_KEY environment variable in your runtime when possible.

API Key#

In an environment where you cannot set environment variables, you can configure the API key manually on the client.

import { fal } from "@fal-ai/client";

fal.config({
  credentials: "YOUR_FAL_KEY"
});

Protect your API Key

3. Queue#

Long-running requests

Submit a request#

The client API provides a convenient way to submit requests to the model.

import { fal } from "@fal-ai/client";

const { request_id } = await fal.queue.submit("blackforestlabs/flux-3/klein/base/edit-image", {
  input: {
    prompt: "A miniature grey amigurumi knight figure crocheted from thick woolen yarn stands on a cliff of stacked yarn skeins at night, lit by a full moon, next to a large fluffy knitted dragon in terracotta and mustard yarn, with a soft out-of-focus backdrop of indigo knitted yarn.",
    image_urls: ["https://storage.googleapis.com/falserverless/example_inputs/z-image-turbo-i2i-input.png"]
  },
  webhookUrl: "https://optional.webhook.url/for/results",
});

Fetch request status#

You can fetch the status of a request to check if it is completed or still in progress.

import { fal } from "@fal-ai/client";

const status = await fal.queue.status("blackforestlabs/flux-3/klein/base/edit-image", {
  requestId: "764cabcf-b745-4b3e-ae38-1200304cf45b",
  logs: true,
});

Get the result#

Once the request is completed, you can fetch the result. See the Output Schema for the expected result format.

import { fal } from "@fal-ai/client";

const result = await fal.queue.result("blackforestlabs/flux-3/klein/base/edit-image", {
  requestId: "764cabcf-b745-4b3e-ae38-1200304cf45b"
});
console.log(result.data);
console.log(result.requestId);

4. Files#

Some attributes in the API accept file URLs as input. Whenever that's the case you can pass your own URL or a Base64 data URI.

Data URI (base64)#

Hosted files (URL)#

You can also pass your own URLs as long as they are publicly accessible. Be aware that some hosts might block cross-site requests, rate-limit, or consider the request as a bot.

Uploading files#

We provide a convenient file storage that allows you to upload files and use them in your requests. You can upload files using the client API and use the returned URL in your requests.

import { fal } from "@fal-ai/client";

const file = new File(["Hello, World!"], "hello.txt", { type: "text/plain" });
const url = await fal.storage.upload(file);

Auto uploads

The client will auto-upload the file for you if you pass a binary object (e.g. File, Data).

Read more about file handling in our file upload guide.

5. Schema#

Input#

prompt string* required

A complete caption of the target image with the edit folded in. Refer to the references by their order: the first image, the second image.

enable_prompt_expansion boolean

If set to true, the prompt is expanded into a detailed caption (grounded in the reference images when editing) before generation. Default value: true

seed integer

The same seed and the same prompt given to the same version of the model will output the same image every time.

num_images integer

The number of images to generate. Default value: 1

enable_safety_checker boolean

If set to true, the safety checker will be enabled. Default value: true

output_format OutputFormatEnum

The format of the generated image. Default value: "png"

Possible enum values: jpeg, png, webp

sync_mode boolean

If True, the media will be returned as a data URI and the output data won't be available in the request history.

image_urls list<string>* required

The reference images to edit or compose from (up to 10).

image_size ImageSize | Enum

Possible enum values: square_hd, square, portrait_4_3, portrait_16_9, landscape_4_3, landscape_16_9

Note: For custom image sizes, you can pass the width and height as an object:

"image_size": {
  "width": 1280,
  "height": 720
}

bounding_boxes list<EditBoundingBox>

Optional layout, with (0, 0) at the top-left of each image: keep, move, resize or remove objects from the references, or place new ones. Name boxes in the prompt by label, e.g. <dragon>.

{
  "prompt": "A miniature grey amigurumi knight figure crocheted from thick woolen yarn stands on a cliff of stacked yarn skeins at night, lit by a full moon, next to a large fluffy knitted dragon in terracotta and mustard yarn, with a soft out-of-focus backdrop of indigo knitted yarn.",
  "enable_prompt_expansion": true,
  "num_images": 1,
  "enable_safety_checker": true,
  "output_format": "png",
  "image_urls": [
    "https://storage.googleapis.com/falserverless/example_inputs/z-image-turbo-i2i-input.png"
  ],
  "bounding_boxes": [
    {
      "label": "dragon",
      "description": "a large fluffy knitted dragon in terracotta and mustard yarn"
    }
  ]
}

Output#

images list<ImageFile>* required

The generated images.

timings Timings* required

The timings of the generation process.

seed integer* required

Seed used to generate the first image.

has_nsfw_concepts list<boolean>* required

Whether the generated images contain NSFW concepts.

prompt string* required

The prompt used for generating the image.

{
  "images": [
    {
      "url": "",
      "content_type": "image/png",
      "file_name": "z9RV14K95DvU.png",
      "file_size": 4404019
    }
  ],
  "prompt": ""
}

Other types#

ImageFile#

url string* required

The URL where the file can be downloaded from.

content_type string

The mime type of the file.

file_name string

The name of the file. It will be auto-generated if not provided.

file_size integer

The size of the file in bytes.

width integer

The width of the image

height integer

The height of the image

ImageSize#

width integer

The width of the generated image. Default value: 512

height integer

The height of the generated image. Default value: 512

EditBoundingBox#

label string

Short name for the object in this box, e.g. dragon. Write <dragon> in the prompt to tie the box to those words; a box the prompt doesn't name is added to the scene. Defaults to obj_<n>.

description string* required

What to draw in this box: the object and its look.

box Box

Where the object goes in the output image, as on text-to-image. Use instead of source_box/target_box.

source_image_index integer

0-based index into image_urls of the reference the object comes from. Leave unset for a new object.

source_box Box

Where the object is in the reference image. Requires source_image_index.

target_box Box

Where the object goes in the output image. Leave unset to remove a referenced object; set both boxes to move or resize it.

Box#

x_min float* required

Left edge as a fraction of the image width (0-1).

y_min float* required

Top edge as a fraction of the image height (0-1).

x_max float* required

Right edge as a fraction of the image width (0-1).

y_max float* required

Bottom edge as a fraction of the image height (0-1).

Related Models

FLUX.3 Klein Base Image Editing Image to Image API Docs | fal

blackforestlabs/flux-3/klein/base/edit-image

Table of contents

Table of contents

blackforestlabs/flux-3/klein/base/edit-image

About

1. Calling the API#

Install the client#

Migrate to @fal-ai/client

Setup your API Key#

Submit a request#

2. Authentication#

API Key#

Protect your API Key

3. Queue#

Long-running requests

Submit a request#

Fetch request status#

Get the result#

4. Files#

Data URI (base64)#

Hosted files (URL)#

Uploading files#

Auto uploads

5. Schema#

Input#

Output#

Other types#

ImageFile#

ImageSize#

EditBoundingBox#

Box#

Related Models

Table of contents

About

1. Calling the API#

Install the client#

Migrate to @fal-ai/client

Setup your API Key#

Submit a request#

2. Authentication#

API Key#

Protect your API Key

3. Queue#

Long-running requests

Submit a request#

Fetch request status#

Get the result#

4. Files#

Data URI (base64)#

Hosted files (URL)#

Uploading files#

Auto uploads

5. Schema#

Input#

Output#

Other types#

ImageFile#

ImageSize#

EditBoundingBox#

Box#

Related Models