Text-to-image generation with FLUX.2 [klein] 9B Base from Black Forest Labs. Enhanced realism, crisper text generation, and native editing capabilities.

fal-ai/flux-2/klein/9b/base

Text-to-image generation with FLUX.2 [klein] 9B Base from Black Forest Labs. Enhanced realism, crisper text generation, and native editing capabilities.

Inference

Commercial use

Streaming

Schema

LLMs

Playground API

SandboxOpen in Sandbox

About

Text-to-image with FLUX.2 [klein] 9B base model. Higher quality with 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("fal-ai/flux-2/klein/9b/base", {
  input: {
    prompt: "A cyberpunk samurai standing in neon-lit Tokyo street at night, rain-soaked pavement reflecting holographic advertisements in pink and blue, steam rising from street vents, wearing futuristic armor with glowing accents, cinematic composition, Unreal Engine 5 quality, ray-traced reflections, shallow depth of field, hyper-detailed"
  },
  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);

Streaming#

This model supports streaming requests. You can stream data directly to the model and get the result in real-time.

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

const stream = await fal.stream("fal-ai/flux-2/klein/9b/base", {
  input: {
    prompt: "A cyberpunk samurai standing in neon-lit Tokyo street at night, rain-soaked pavement reflecting holographic advertisements in pink and blue, steam rising from street vents, wearing futuristic armor with glowing accents, cinematic composition, Unreal Engine 5 quality, ray-traced reflections, shallow depth of field, hyper-detailed"
  }
});

for await (const event of stream) {
  console.log(event);
}

const result = await stream.done();

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("fal-ai/flux-2/klein/9b/base", {
  input: {
    prompt: "A cyberpunk samurai standing in neon-lit Tokyo street at night, rain-soaked pavement reflecting holographic advertisements in pink and blue, steam rising from street vents, wearing futuristic armor with glowing accents, cinematic composition, Unreal Engine 5 quality, ray-traced reflections, shallow depth of field, hyper-detailed"
  },
  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("fal-ai/flux-2/klein/9b/base", {
  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("fal-ai/flux-2/klein/9b/base", {
  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

The prompt to generate an image from.

negative_prompt string

Negative prompt for classifier-free guidance. Describes what to avoid in the image. Default value: ""

guidance_scale float

Guidance scale for classifier-free guidance. Default value: 5

seed integer

The seed to use for the generation. If not provided, a random seed will be used.

num_inference_steps integer

The number of inference steps to perform. Default value: 28

image_size ImageSize | Enum

The size of the image to generate. Default value: landscape_4_3

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
}

num_images integer

The number of images to generate. Default value: 1

acceleration AccelerationEnum

The acceleration level to use for image generation. Default value: "regular"

Possible enum values: none, regular, high

sync_mode boolean

If True, the media will be returned as a data URI. Output is not stored when this is True.

enable_safety_checker boolean

If set to true, the safety checker will be enabled. Disabling it requires account authorization; unauthorized requests are always checked, and images flagged as unsafe are returned as black images. Default value: true

output_format OutputFormatEnum

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

Possible enum values: jpeg, png, webp

{
  "prompt": "A cyberpunk samurai standing in neon-lit Tokyo street at night, rain-soaked pavement reflecting holographic advertisements in pink and blue, steam rising from street vents, wearing futuristic armor with glowing accents, cinematic composition, Unreal Engine 5 quality, ray-traced reflections, shallow depth of field, hyper-detailed",
  "guidance_scale": 5,
  "num_inference_steps": 28,
  "image_size": "landscape_4_3",
  "num_images": 1,
  "acceleration": "regular",
  "enable_safety_checker": true,
  "output_format": "png"
}

Output#

images list<ImageFile>* required

The generated images

timings Timings* required

seed integer* required

Seed of the generated Image. It will be the same value of the one passed in the input or the randomly generated that was used in case none was passed.

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": "https://v3b.fal.media/files/b/0a8a69bc/EaxKO6wroq3eaDb2Znfpo.png"
    }
  ],
  "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

Related Models

Loading API documentation…

1. Calling the API

2. Authentication

API Key

3. Queue

4. Files

5. Schema

About

Text-to-image with FLUX.2 [klein] 9B base model. Higher quality with 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("fal-ai/flux-2/klein/9b/base", {
  input: {
    prompt: "A cyberpunk samurai standing in neon-lit Tokyo street at night, rain-soaked pavement reflecting holographic advertisements in pink and blue, steam rising from street vents, wearing futuristic armor with glowing accents, cinematic composition, Unreal Engine 5 quality, ray-traced reflections, shallow depth of field, hyper-detailed"
  },
  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);

Streaming#

This model supports streaming requests. You can stream data directly to the model and get the result in real-time.

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

const stream = await fal.stream("fal-ai/flux-2/klein/9b/base", {
  input: {
    prompt: "A cyberpunk samurai standing in neon-lit Tokyo street at night, rain-soaked pavement reflecting holographic advertisements in pink and blue, steam rising from street vents, wearing futuristic armor with glowing accents, cinematic composition, Unreal Engine 5 quality, ray-traced reflections, shallow depth of field, hyper-detailed"
  }
});

for await (const event of stream) {
  console.log(event);
}

const result = await stream.done();

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("fal-ai/flux-2/klein/9b/base", {
  input: {
    prompt: "A cyberpunk samurai standing in neon-lit Tokyo street at night, rain-soaked pavement reflecting holographic advertisements in pink and blue, steam rising from street vents, wearing futuristic armor with glowing accents, cinematic composition, Unreal Engine 5 quality, ray-traced reflections, shallow depth of field, hyper-detailed"
  },
  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("fal-ai/flux-2/klein/9b/base", {
  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("fal-ai/flux-2/klein/9b/base", {
  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

The prompt to generate an image from.

negative_prompt string

Negative prompt for classifier-free guidance. Describes what to avoid in the image. Default value: ""

guidance_scale float

Guidance scale for classifier-free guidance. Default value: 5

seed integer

The seed to use for the generation. If not provided, a random seed will be used.

num_inference_steps integer

The number of inference steps to perform. Default value: 28

image_size ImageSize | Enum

The size of the image to generate. Default value: landscape_4_3

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
}

num_images integer

The number of images to generate. Default value: 1

acceleration AccelerationEnum

The acceleration level to use for image generation. Default value: "regular"

Possible enum values: none, regular, high

sync_mode boolean

If True, the media will be returned as a data URI. Output is not stored when this is True.

enable_safety_checker boolean

output_format OutputFormatEnum

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

Possible enum values: jpeg, png, webp

{
  "prompt": "A cyberpunk samurai standing in neon-lit Tokyo street at night, rain-soaked pavement reflecting holographic advertisements in pink and blue, steam rising from street vents, wearing futuristic armor with glowing accents, cinematic composition, Unreal Engine 5 quality, ray-traced reflections, shallow depth of field, hyper-detailed",
  "guidance_scale": 5,
  "num_inference_steps": 28,
  "image_size": "landscape_4_3",
  "num_images": 1,
  "acceleration": "regular",
  "enable_safety_checker": true,
  "output_format": "png"
}

Output#

images list<ImageFile>* required

The generated images

timings Timings* required

seed integer* required

Seed of the generated Image. It will be the same value of the one passed in the input or the randomly generated that was used in case none was passed.

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": "https://v3b.fal.media/files/b/0a8a69bc/EaxKO6wroq3eaDb2Znfpo.png"
    }
  ],
  "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

fal-ai/flux-2/klein/9b/base

fal-ai/flux-2/klein/9b/base

fal-ai/flux-2/klein/9b/base

Table of contents

1. Calling the API

2. Authentication

3. Queue

4. Files

5. Schema

About

1. Calling the API#

Install the client#

Migrate to @fal-ai/client

Setup your API Key#

Submit a request#

Streaming#

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#

Related Models

Table of contents

1. Calling the API

2. Authentication

3. Queue

4. Files

5. Schema

About

1. Calling the API#

Install the client#

Migrate to @fal-ai/client

Setup your API Key#

Submit a request#

Streaming#

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#

Related Models