# FLUX.2 [klein] 4B Base LoRA

> Image-to-image editing with LoRA support for FLUX.2 [klein] 4B Base from Black Forest Labs. Specialized style transfer and domain-specific modifications.


## Overview

- **Endpoint**: `https://fal.run/fal-ai/flux-2/klein/4b/base/edit/lora`
- **Model ID**: `fal-ai/flux-2/klein/4b/base/edit/lora`
- **Category**: image-to-image
- **Kind**: inference


## Pricing

Requests cost **$0.016** per megapixel of input and output. Input images will be resized to 1MP. For example, a 1024x1024 generation with 512*512 size image input will cost **0.032** (1 MP input + 1 MP output, each costing **0.016**).

For more details, see [fal.ai pricing](https://fal.ai/pricing).

## API Information

This model can be used via our HTTP API or more conveniently via our client libraries.
See the input and output schema below, as well as the usage examples.


### Input Schema

The API accepts the following input parameters:


- **`prompt`** (`string`, _required_):
  The prompt to edit the image.
  - Examples: "Change his clothes to casual suit and tie"

- **`negative_prompt`** (`string`, _optional_):
  Negative prompt for classifier-free guidance. Describes what to avoid in the image. Default value: `""`
  - Default: `""`

- **`guidance_scale`** (`float`, _optional_):
  Guidance scale for classifier-free guidance. Default value: `5`
  - Default: `5`
  - Range: `0` to `20`

- **`seed`** (`integer`, _optional_):
  The seed to use for the generation. If not provided, a random seed will be used.

- **`num_inference_steps`** (`integer`, _optional_):
  The number of inference steps to perform. Default value: `28`
  - Default: `28`
  - Range: `4` to `50`

- **`image_size`** (`ImageSize | Enum`, _optional_):
  The size of the generated image. If not provided, uses the input image size.
  - One of: ImageSize | Enum
  - Examples: {"height":1152,"width":2016}

- **`num_images`** (`integer`, _optional_):
  The number of images to generate. Default value: `1`
  - Default: `1`
  - Range: `1` to `4`

- **`acceleration`** (`AccelerationEnum`, _optional_):
  The acceleration level to use for image generation. Default value: `"regular"`
  - Default: `"regular"`
  - Options: `"none"`, `"regular"`, `"high"`

- **`sync_mode`** (`boolean`, _optional_):
  If `True`, the media will be returned as a data URI. Output is not stored when this is True.
  - Default: `false`

- **`enable_safety_checker`** (`boolean`, _optional_):
  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`
  - Default: `true`

- **`output_format`** (`OutputFormatEnum`, _optional_):
  The format of the generated image. Default value: `"png"`
  - Default: `"png"`
  - Options: `"jpeg"`, `"png"`, `"webp"`

- **`image_urls`** (`list<string>`, _required_):
  The URLs of the images for editing. A maximum of 4 images are allowed.
  - Array of string
  - Examples: ["https://storage.googleapis.com/falserverless/example_inputs/flux2_dev_edit_input.png"]

- **`loras`** (`list<fal-ai_flux-2-klein_LoRAInput>`, _optional_):
  List of LoRA weights to apply (maximum 3).
  - Default: `[]`
  - Array of fal-ai_flux-2-klein_LoRAInput



**Required Parameters Example**:

```json
{
  "prompt": "Change his clothes to casual suit and tie",
  "image_urls": [
    "https://storage.googleapis.com/falserverless/example_inputs/flux2_dev_edit_input.png"
  ]
}
```

**Full Example**:

```json
{
  "prompt": "Change his clothes to casual suit and tie",
  "guidance_scale": 5,
  "num_inference_steps": 28,
  "image_size": {
    "height": 1152,
    "width": 2016
  },
  "num_images": 1,
  "acceleration": "regular",
  "enable_safety_checker": true,
  "output_format": "png",
  "image_urls": [
    "https://storage.googleapis.com/falserverless/example_inputs/flux2_dev_edit_input.png"
  ],
  "loras": []
}
```


### Output Schema

The API returns the following output format:

- **`images`** (`list<ImageFile>`, _required_):
  The generated images
  - Array of ImageFile

- **`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.
  - Array of boolean

- **`prompt`** (`string`, _required_):
  The prompt used for generating the image.



**Example Response**:

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


## Usage Examples

### cURL

```bash
curl --request POST \
  --url https://fal.run/fal-ai/flux-2/klein/4b/base/edit/lora \
  --header "Authorization: Key $FAL_KEY" \
  --header "Content-Type: application/json" \
  --data '{
     "prompt": "Change his clothes to casual suit and tie",
     "image_urls": [
       "https://storage.googleapis.com/falserverless/example_inputs/flux2_dev_edit_input.png"
     ]
   }'
```

### Python

Ensure you have the Python client installed:

```bash
pip install fal-client
```

Then use the API client to make requests:

```python
import fal_client

def on_queue_update(update):
    if isinstance(update, fal_client.InProgress):
        for log in update.logs:
           print(log["message"])

result = fal_client.subscribe(
    "fal-ai/flux-2/klein/4b/base/edit/lora",
    arguments={
        "prompt": "Change his clothes to casual suit and tie",
        "image_urls": ["https://storage.googleapis.com/falserverless/example_inputs/flux2_dev_edit_input.png"]
    },
    with_logs=True,
    on_queue_update=on_queue_update,
)
print(result)
```

### JavaScript

Ensure you have the JavaScript client installed:

```bash
npm install --save @fal-ai/client
```

Then use the API client to make requests:

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

const result = await fal.subscribe("fal-ai/flux-2/klein/4b/base/edit/lora", {
  input: {
    prompt: "Change his clothes to casual suit and tie",
    image_urls: ["https://storage.googleapis.com/falserverless/example_inputs/flux2_dev_edit_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);
```


## Additional Resources

### Documentation

- [Model Playground](https://fal.ai/models/fal-ai/flux-2/klein/4b/base/edit/lora)
- [API Documentation](https://fal.ai/models/fal-ai/flux-2/klein/4b/base/edit/lora/api)
- [OpenAPI Schema](https://fal.ai/api/openapi/queue/openapi.json?endpoint_id=fal-ai/flux-2/klein/4b/base/edit/lora)

### fal.ai Platform

- [Platform Documentation](https://fal.ai/docs/documentation)
- [Python Client](https://fal.ai/docs/api-reference/client-libraries/python)
- [JavaScript Client](https://fal.ai/docs/api-reference/client-libraries/javascript)

### Other agent-readable surfaces

This file covers one model. To find anything else:

- [Platform overview](https://fal.ai/llms.txt): Entry points and representative endpoint IDs
- [Documentation index](https://fal.ai/docs/llms.txt): Every documentation page
- [Full documentation text](https://fal.ai/docs/llms-full.txt): The whole documentation inlined
- Any other model: `https://fal.ai/models/<endpoint-id>/llms.txt`