---
title: FLUX.2 [flex] | Runware Docs
url: https://runware.ai/docs/models/bfl-flux-2-flex
description: Configurable FLUX.2 Flex for precise text aligned images
---
# FLUX.2 [flex]

FLUX.2 [flex] is a configurable text to image and image editing model built for precise text placement and stable layouts. It exposes sampling and guidance controls and supports up to ten reference images for consistent characters or products across complex compositions.

- **ID**: `bfl:6@1`
- **Status**: live
- **Creator**: Black Forest Labs
- **Release Date**: November 25, 2025
- **Capabilities**: Text to Image, Image to Image, Image Editing

## Pricing

~$0.1431 per megapixel

- **512×512**: `$0.06`
- **1024×1024**: `$0.06`

## Compatibility & Validation

`width` and `height` must be used together.

## Request Parameters

**API Options**

Platform-level options for task execution and delivery.

### [taskType](https://runware.ai/docs/models/bfl-flux-2-flex#request-tasktype)

- **Type**: `string`
- **Required**: true
- **Value**: `imageInference`

Identifier for the type of task being performed

### [taskUUID](https://runware.ai/docs/models/bfl-flux-2-flex#request-taskuuid)

- **Type**: `string`
- **Required**: true
- **Format**: `UUID v4`

UUID v4 identifier for tracking tasks and matching async responses. Must be unique per task.

### [outputType](https://runware.ai/docs/models/bfl-flux-2-flex#request-outputtype)

- **Type**: `string`
- **Default**: `URL`

Image output type.

**Allowed values**: `URL` `base64Data` `dataURI`

### [outputFormat](https://runware.ai/docs/models/bfl-flux-2-flex#request-outputformat)

- **Type**: `string`
- **Default**: `JPG`

Specifies the file format of the generated output. The available values depend on the task type and the specific model's capabilities.

- \`JPG\`: Best for photorealistic images with smaller file sizes (no transparency).
- \`PNG\`: Lossless compression, supports high quality and transparency (alpha channel).
- \`WEBP\`: Modern format providing superior compression and transparency support.

> [!NOTE]
> \*\*Transparency\*\*: If you are using features like background removal or LayerDiffuse that require transparency, you must select a format that supports an alpha channel (e.g., \`PNG\`, \`WEBP\`, \`TIFF\`). \`JPG\` does not support transparency.

**Allowed values**: `JPG` `PNG` `WEBP`

### [outputQuality](https://runware.ai/docs/models/bfl-flux-2-flex#request-outputquality)

- **Type**: `integer`
- **Min**: `20`
- **Max**: `99`
- **Default**: `95`

Compression quality of the output. Higher values preserve quality but increase file size.

### [webhookURL](https://runware.ai/docs/models/bfl-flux-2-flex#request-webhookurl)

- **Type**: `string`
- **Format**: `URI`

Specifies a webhook URL where JSON responses will be sent via HTTP POST when generation tasks complete. For batch requests with multiple results, each completed item triggers a separate webhook call as it becomes available.

**Learn more** (1 resource):

- [Webhooks](https://runware.ai/docs/platform/webhooks) (platform)

### [deliveryMethod](https://runware.ai/docs/models/bfl-flux-2-flex#request-deliverymethod)

- **Type**: `string`
- **Default**: `sync`

Determines how the API delivers task results.

**Allowed values**:

- `sync` Returns complete results directly in the API response.
- `async` Returns an immediate acknowledgment with the task UUID. Poll for results using getResponse.

**Learn more** (1 resource):

- [Task Polling](https://runware.ai/docs/platform/task-polling) (platform)

### [uploadEndpoint](https://runware.ai/docs/models/bfl-flux-2-flex#request-uploadendpoint)

- **Type**: `string`
- **Format**: `URI`

Specifies a URL where the generated content will be automatically uploaded using the HTTP PUT method. The raw binary data of the media file is sent directly as the request body. For secure uploads to cloud storage, use presigned URLs that include temporary authentication credentials.

**Common use cases:**

- **Cloud storage**: Upload directly to S3 buckets, Google Cloud Storage, or Azure Blob Storage using presigned URLs.
- **CDN integration**: Upload to content delivery networks for immediate distribution.

```text
// S3 presigned URL for secure upload
https://your-bucket.s3.amazonaws.com/generated/content.mp4?X-Amz-Signature=abc123&X-Amz-Expires=3600

// Google Cloud Storage presigned URL
https://storage.googleapis.com/your-bucket/content.jpg?X-Goog-Signature=xyz789

// Custom storage endpoint
https://storage.example.com/uploads/generated-image.jpg
```

The content data will be sent as the request body to the specified URL when generation is complete.

### [safety](https://runware.ai/docs/models/bfl-flux-2-flex#request-safety)

- **Path**: `safety.checkContent`
- **Type**: `object (2 properties)`

Content safety checking configuration for image generation.

#### [checkContent](https://runware.ai/docs/models/bfl-flux-2-flex#request-safety-checkcontent)

- **Path**: `safety.checkContent`
- **Type**: `boolean`
- **Default**: `false`

Enable or disable content safety checking. When enabled, defaults to `fast` mode.

#### [mode](https://runware.ai/docs/models/bfl-flux-2-flex#request-safety-mode)

- **Path**: `safety.mode`
- **Type**: `string`
- **Default**: `none`

Safety checking mode for image generation.

**Allowed values**:

- `none` Disables checking.
- `fast` Performs a single check.

### [ttl](https://runware.ai/docs/models/bfl-flux-2-flex#request-ttl)

- **Type**: `integer`
- **Min**: `60`

Time-to-live (TTL) in seconds for generated content. Only applies when `outputType` is `URL`.

### [includeCost](https://runware.ai/docs/models/bfl-flux-2-flex#request-includecost)

- **Type**: `boolean`
- **Default**: `false`

Include task cost in the response.

### [numberResults](https://runware.ai/docs/models/bfl-flux-2-flex#request-numberresults)

- **Type**: `integer`
- **Min**: `1`
- **Max**: `20`
- **Default**: `1`

Number of results to generate. Each result uses a different seed, producing variations of the same parameters.

**Inputs**

Input resources for the task (images, audio, etc). These must be nested inside the \`inputs\` object.

### [referenceImages](https://runware.ai/docs/models/bfl-flux-2-flex#request-inputs-referenceimages)

- **Path**: `inputs.referenceImages`
- **Type**: `array of strings`

List of reference images (UUID, URL, Data URI, or Base64).

**Generation Parameters**

Core parameters for controlling the generated content.

### [model](https://runware.ai/docs/models/bfl-flux-2-flex#request-model)

- **Type**: `string`
- **Required**: true
- **Value**: `bfl:6@1`

Identifier of the model to use for generation.

**Learn more** (3 resources):

- [Text To Image: Model Selection The Foundation Of Generation](https://runware.ai/docs/guides/text-to-image#model-selection-the-foundation-of-generation) (guide)
- [Image Inpainting: Model Specialized Inpainting Models](https://runware.ai/docs/guides/image-inpainting#model-specialized-inpainting-models) (guide)
- [Image Outpainting: Other Critical Parameters](https://runware.ai/docs/guides/image-outpainting#other-critical-parameters) (guide)

### [positivePrompt](https://runware.ai/docs/models/bfl-flux-2-flex#request-positiveprompt)

- **Type**: `string`
- **Required**: true
- **Min**: `1`
- **Max**: `32000`

Text prompt describing elements to include in the generated output.

**Learn more** (2 resources):

- [Text To Image: Prompts Guiding The Generation](https://runware.ai/docs/guides/text-to-image#prompts-guiding-the-generation) (guide)
- [Image Outpainting: Other Critical Parameters](https://runware.ai/docs/guides/image-outpainting#other-critical-parameters) (guide)

### [width](https://runware.ai/docs/models/bfl-flux-2-flex#request-width)

- **Type**: `integer`
- **Required**: true
- **Min**: `256`
- **Max**: `2048`
- **Step**: `16`

Width of the generated media in pixels.

**Learn more** (2 resources):

- [Image To Image: Dimensions Changing Aspect Ratio](https://runware.ai/docs/guides/image-to-image#dimensions-changing-aspect-ratio) (guide)
- [Image Outpainting: Dimensions Critical For Outpainting](https://runware.ai/docs/guides/image-outpainting#dimensions-critical-for-outpainting) (guide)

### [height](https://runware.ai/docs/models/bfl-flux-2-flex#request-height)

- **Type**: `integer`
- **Required**: true
- **Min**: `256`
- **Max**: `2048`
- **Step**: `16`

Height of the generated media in pixels.

**Learn more** (2 resources):

- [Image To Image: Dimensions Changing Aspect Ratio](https://runware.ai/docs/guides/image-to-image#dimensions-changing-aspect-ratio) (guide)
- [Image Outpainting: Dimensions Critical For Outpainting](https://runware.ai/docs/guides/image-outpainting#dimensions-critical-for-outpainting) (guide)

### [seed](https://runware.ai/docs/models/bfl-flux-2-flex#request-seed)

- **Type**: `integer`
- **Min**: `0`
- **Max**: `9223372036854776000`

Random seed for reproducible generation. When not provided, a random seed is generated in the unsigned 32-bit range.

**Learn more** (1 resource):

- [Text To Image: Seed Controlling Randomness Deterministically](https://runware.ai/docs/guides/text-to-image#seed-controlling-randomness-deterministically) (guide)

### [steps](https://runware.ai/docs/models/bfl-flux-2-flex#request-steps)

- **Type**: `integer`
- **Min**: `1`
- **Max**: `50`

Total number of denoising steps. Higher values generally produce more detailed results but take longer.

**Learn more** (1 resource):

- [Text To Image: Steps Trading Quality For Speed](https://runware.ai/docs/guides/text-to-image#steps-trading-quality-for-speed) (guide)

### [CFGScale](https://runware.ai/docs/models/bfl-flux-2-flex#request-cfgscale)

- **Type**: `float`
- **Min**: `1`
- **Max**: `20`
- **Step**: `0.01`
- **Default**: `2.5`

Guidance scale representing how closely the output will resemble the prompt. Higher values produce results more aligned with the prompt.

**Learn more** (1 resource):

- [Text To Image: Cfg Scale Balancing Creativity And Control](https://runware.ai/docs/guides/text-to-image#cfg-scale-balancing-creativity-and-control) (guide)

**Provider Settings**

Parameters specific to this model provider. These must be nested inside the \`providerSettings.bfl\` object.

### [promptUpsampling](https://runware.ai/docs/models/bfl-flux-2-flex#request-providersettings-bfl-promptupsampling)

- **Path**: `providerSettings.bfl.promptUpsampling`
- **Type**: `boolean`
- **Default**: `false`

Enable automatic enhancement and expansion of the input prompt.

### [safetyTolerance](https://runware.ai/docs/models/bfl-flux-2-flex#request-providersettings-bfl-safetytolerance)

- **Path**: `providerSettings.bfl.safetyTolerance`
- **Type**: `integer`
- **Min**: `0`
- **Max**: `6`
- **Default**: `2`

Tolerance level for content moderation. Lower values are stricter; higher values are more permissive.

## Response Parameters

### [taskType](https://runware.ai/docs/models/bfl-flux-2-flex#response-tasktype)

- **Type**: `string`
- **Required**: true
- **Value**: `imageInference`

Type of the task.

### [taskUUID](https://runware.ai/docs/models/bfl-flux-2-flex#response-taskuuid)

- **Type**: `string`
- **Required**: true
- **Format**: `UUID v4`

UUID of the task.

### [imageUUID](https://runware.ai/docs/models/bfl-flux-2-flex#response-imageuuid)

- **Type**: `string`
- **Required**: true
- **Format**: `UUID v4`

UUID of the output image.

### [imageURL](https://runware.ai/docs/models/bfl-flux-2-flex#response-imageurl)

- **Type**: `string`
- **Format**: `URI`

URL of the output image.

### [imageBase64Data](https://runware.ai/docs/models/bfl-flux-2-flex#response-imagebase64data)

- **Type**: `string`

Base64-encoded image data.

### [imageDataURI](https://runware.ai/docs/models/bfl-flux-2-flex#response-imagedatauri)

- **Type**: `string`
- **Format**: `URI`

Data URI of the output image.

### [seed](https://runware.ai/docs/models/bfl-flux-2-flex#response-seed)

- **Type**: `integer`

The seed used for generation. If none was provided, shows the randomly generated seed.

### [NSFWContent](https://runware.ai/docs/models/bfl-flux-2-flex#response-nsfwcontent)

- **Type**: `boolean`

Flag indicating if NSFW content was detected.

### [cost](https://runware.ai/docs/models/bfl-flux-2-flex#response-cost)

- **Type**: `float`

Task cost in USD. Present when `includeCost` is set to `true` in the request.

## Examples

### Floating Puppet Regatta Tableau (Image to Image)

![Floating Puppet Regatta Tableau](https://assets.runware.ai/examples/bfl-flux-2-flex/07ee295f-5a65-471a-8010-1b93ea78899a.jpg)

**Request**:

```json
{
  "taskType": "imageInference",
  "taskUUID": "17c1cda6-a7af-4476-a069-e3753eb413f1",
  "model": "bfl:6@1",
  "positivePrompt": "Create a richly detailed airborne regatta above a vast salt flat at golden sunrise, using the reference images to preserve the marionette captain, quilted sail materials, and cloud barge design. Show multiple puppet-crewed vessels drifting in layered formation through bright apricot and pale cyan sky, long reflections shimmering below. The main vessel dominates the foreground with crisp readable painted lettering on the sail: \"SKY HARBOR CUP\". Include smaller banners with clean simple text such as \"HEAT 3\" and \"NORTH WIND\". Emphasize precise composition, stable geometry, handcrafted textures, taut ropes, stitched cloth, varnished wood, tiny brass fittings, and playful theatrical charm. Cinematic wide shot, storybook realism, airy scale, high detail, elegant color harmony, gentle atmosphere, no modern city elements.",
  "width": 1344,
  "height": 768,
  "seed": 77612,
  "steps": 32,
  "CFGScale": 3.5,
  "providerSettings": {
    "bfl": {
      "promptUpsampling": true,
      "safetyTolerance": 2
    }
  },
  "inputs": {
    "referenceImages": [
      "https://assets.runware.ai/assets/inputs/17078c68-3b4f-46af-ab45-fdc8f39a2cc1.jpg",
      "https://assets.runware.ai/assets/inputs/d0d1a087-bbab-4a75-9025-ac01bbcdf610.jpg",
      "https://assets.runware.ai/assets/inputs/d367c73d-617c-444c-b902-fa61d7cffc78.jpg"
    ]
  }
}
```

**Response**:

```json
{
  "taskType": "imageInference",
  "taskUUID": "17c1cda6-a7af-4476-a069-e3753eb413f1",
  "imageUUID": "3c21742a-4414-444a-8562-a40e0a90bdac",
  "imageURL": "https://im.runware.ai/image/os/a14d18/ws/2/ii/3c21742a-4414-444a-8562-a40e0a90bdac.jpg",
  "seed": 77612,
  "cost": 0.24
}
```

---

### Glasshouse Automaton Floristry Display (Image to Image)

![Glasshouse Automaton Floristry Display](https://assets.runware.ai/examples/bfl-flux-2-flex/3b359e24-781e-4080-af5d-88d34198eb69.jpg)

**Request**:

```json
{
  "taskType": "imageInference",
  "taskUUID": "2ff8ac6e-fd1d-44fe-a79e-5e371798996d",
  "model": "bfl:6@1",
  "positivePrompt": "Create a whimsical late-afternoon glasshouse scene centered on an elegant brass automaton florist arranging rare blooms on a long wooden counter. Use the reference images to keep the machine design, greenhouse structure, and plant palette consistent. The composition should feel airy and meticulously organized, with hanging ferns, fogged glass panes, tiled flooring, labeled drawers, bundles of stems, and polished tools. Include a small hand-painted shop sign with clear readable text: \"VERDANT CLOCKWORK BLOOMS\". Refined cinematic realism, intricate materials, stable geometry, balanced depth, warm sunlight diffused through glass, crisp focus on the central display, charming invention and quiet wonder.",
  "width": 1280,
  "height": 768,
  "seed": 6530,
  "steps": 32,
  "CFGScale": 3.5,
  "providerSettings": {
    "bfl": {
      "promptUpsampling": true,
      "safetyTolerance": 2
    }
  },
  "inputs": {
    "referenceImages": [
      "https://assets.runware.ai/assets/inputs/56fd0fc2-71c5-4e8b-8bd9-f3b251742d8c.jpg",
      "https://assets.runware.ai/assets/inputs/012f7433-d4fa-4a2d-aa59-9a887c0bac05.jpg",
      "https://assets.runware.ai/assets/inputs/6c3ab5a1-be16-40c8-a4d4-98fa31be2339.jpg"
    ]
  }
}
```

**Response**:

```json
{
  "taskType": "imageInference",
  "taskUUID": "2ff8ac6e-fd1d-44fe-a79e-5e371798996d",
  "imageUUID": "5b8f76c5-2db7-4f90-b220-fb1ba9c77894",
  "imageURL": "https://im.runware.ai/image/os/a08d21/ws/2/ii/5b8f76c5-2db7-4f90-b220-fb1ba9c77894.jpg",
  "seed": 6530,
  "cost": 0.24
}
```