---
title: FLUX.2 [klein] 4B Base | Runware Docs
url: https://runware.ai/docs/models/bfl-flux-2-klein-4b-base
description: Compact undistilled model for efficient image generation and editing
---
# FLUX.2 [klein] 4B Base

FLUX.2 [klein] 4B Base is a compact undistilled image generation and editing model with an exceptional quality-to-size ratio. It is well suited for local deployment, efficient fine-tuning, and custom pipelines that require flexibility on limited hardware.

- **ID**: `runware:400@5`
- **Status**: live
- **Creator**: Black Forest Labs
- **Release Date**: January 15, 2026
- **Capabilities**: Text to Image, Image to Image, Image Editing

## Pricing

- **1024x1024**: `$0.0019`

## 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-klein-4b-base#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-klein-4b-base#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-klein-4b-base#request-outputtype)

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

Image output type.

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

### [outputFormat](https://runware.ai/docs/models/bfl-flux-2-klein-4b-base#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-klein-4b-base#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-klein-4b-base#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-klein-4b-base#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-klein-4b-base#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-klein-4b-base#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-klein-4b-base#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-klein-4b-base#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-klein-4b-base#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-klein-4b-base#request-includecost)

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

Include task cost in the response.

### [numberResults](https://runware.ai/docs/models/bfl-flux-2-klein-4b-base#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.

### [acceleration](https://runware.ai/docs/models/bfl-flux-2-klein-4b-base#request-acceleration)

- **Type**: `string`
- **Default**: `high`

Optimization level.

**Allowed values**: `none` `low` `medium` `high`

### [acceleratorOptions](https://runware.ai/docs/models/bfl-flux-2-klein-4b-base#request-acceleratoroptions)

- **Path**: `acceleratorOptions.cacheEndStep`
- **Type**: `object (12 properties)`

Advanced caching mechanisms to speed up generation.

#### [cacheEndStep](https://runware.ai/docs/models/bfl-flux-2-klein-4b-base#request-acceleratoroptions-cacheendstep)

- **Path**: `acceleratorOptions.cacheEndStep`
- **Type**: `integer`
- **Min**: `1`

Absolute step number to end caching. Must be greater than `cacheStartStep` and less than or equal to `steps`.

#### [cacheEndStepPercentage](https://runware.ai/docs/models/bfl-flux-2-klein-4b-base#request-acceleratoroptions-cacheendsteppercentage)

- **Path**: `acceleratorOptions.cacheEndStepPercentage`
- **Type**: `integer`
- **Min**: `1`
- **Max**: `100`

Percentage of steps to end caching. Alternative to `cacheEndStep`. Must be greater than `cacheStartStepPercentage`.

#### [cacheMaxConsecutiveSteps](https://runware.ai/docs/models/bfl-flux-2-klein-4b-base#request-acceleratoroptions-cachemaxconsecutivesteps)

- **Path**: `acceleratorOptions.cacheMaxConsecutiveSteps`
- **Type**: `integer`
- **Min**: `1`
- **Max**: `5`
- **Default**: `3`

Limits the maximum number of consecutive steps that can use cached computations before forcing a fresh computation.

#### [cacheStartStep](https://runware.ai/docs/models/bfl-flux-2-klein-4b-base#request-acceleratoroptions-cachestartstep)

- **Path**: `acceleratorOptions.cacheStartStep`
- **Type**: `integer`
- **Min**: `0`

Absolute step number to start caching. Must be less than `cacheEndStep`.

#### [cacheStartStepPercentage](https://runware.ai/docs/models/bfl-flux-2-klein-4b-base#request-acceleratoroptions-cachestartsteppercentage)

- **Path**: `acceleratorOptions.cacheStartStepPercentage`
- **Type**: `integer`
- **Min**: `0`
- **Max**: `99`

Percentage of steps to start caching. Alternative to `cacheStartStep`. Must be less than `cacheEndStepPercentage`.

#### [fbCache](https://runware.ai/docs/models/bfl-flux-2-klein-4b-base#request-acceleratoroptions-fbcache)

- **Path**: `acceleratorOptions.fbCache`
- **Type**: `boolean`
- **Default**: `false`

First Block Cache (FBCache) acceleration. Reuses feature block computations across steps.

#### [fbCacheThreshold](https://runware.ai/docs/models/bfl-flux-2-klein-4b-base#request-acceleratoroptions-fbcachethreshold)

- **Path**: `acceleratorOptions.fbCacheThreshold`
- **Type**: `float`
- **Min**: `0`
- **Max**: `1`
- **Step**: `0.01`
- **Default**: `0.25`

Controls the sensitivity threshold for determining when to reuse cached computations. Lower values reuse more aggressively.

#### [teaCache](https://runware.ai/docs/models/bfl-flux-2-klein-4b-base#request-acceleratoroptions-teacache)

- **Path**: `acceleratorOptions.teaCache`
- **Type**: `boolean`
- **Default**: `false`

TeaCache acceleration for transformer-based models. Estimates step differences to skip redundant computations.

#### [teaCacheDistance](https://runware.ai/docs/models/bfl-flux-2-klein-4b-base#request-acceleratoroptions-teacachedistance)

- **Path**: `acceleratorOptions.teaCacheDistance`
- **Type**: `float`
- **Min**: `0`
- **Max**: `1`
- **Step**: `0.01`
- **Default**: `0.5`

Controls the aggressiveness of the TeaCache feature. Lower values prioritize quality, higher values prioritize speed.

#### [dbCache](https://runware.ai/docs/models/bfl-flux-2-klein-4b-base#request-acceleratoroptions-dbcache)

- **Path**: `acceleratorOptions.dbCache`
- **Type**: `boolean`
- **Default**: `false`

DB Cache (CacheDiT) acceleration. Caches and reuses intermediate transformer block outputs to skip redundant computations.

#### [dbCacheThreshold](https://runware.ai/docs/models/bfl-flux-2-klein-4b-base#request-acceleratoroptions-dbcachethreshold)

- **Path**: `acceleratorOptions.dbCacheThreshold`
- **Type**: `float`
- **Min**: `0`
- **Max**: `1`
- **Step**: `0.01`
- **Default**: `0.25`

Controls the sensitivity threshold for DB Cache. Lower values reuse cached blocks more aggressively, higher values prioritize quality.

#### [dbCacheSkipInterval](https://runware.ai/docs/models/bfl-flux-2-klein-4b-base#request-acceleratoroptions-dbcacheskipinterval)

- **Path**: `acceleratorOptions.dbCacheSkipInterval`
- **Type**: `integer`
- **Min**: `1`
- **Default**: `5`

Controls how many steps to skip between cache refreshes. Higher values skip more steps for faster generation at the cost of quality.

**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-klein-4b-base#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-klein-4b-base#request-model)

- **Type**: `string`
- **Required**: true
- **Value**: `runware:400@5`

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-klein-4b-base#request-positiveprompt)

- **Type**: `string`
- **Required**: true
- **Min**: `1`
- **Max**: `10000`

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)

### [negativePrompt](https://runware.ai/docs/models/bfl-flux-2-klein-4b-base#request-negativeprompt)

- **Type**: `string`
- **Min**: `1`
- **Max**: `10000`

Prompt to guide what to exclude from generation. Ignored when guidance is disabled (CFGScale ≤ 1).

**Learn more** (1 resource):

- [Text To Image: Prompts Guiding The Generation](https://runware.ai/docs/guides/text-to-image#prompts-guiding-the-generation) (guide)

### [width](https://runware.ai/docs/models/bfl-flux-2-klein-4b-base#request-width)

- **Type**: `integer`
- **Required**: true
- **Min**: `128`
- **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-klein-4b-base#request-height)

- **Type**: `integer`
- **Required**: true
- **Min**: `128`
- **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-klein-4b-base#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-klein-4b-base#request-steps)

- **Type**: `integer`
- **Min**: `1`
- **Max**: `50`
- **Default**: `28`

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)

### [scheduler](https://runware.ai/docs/models/bfl-flux-2-klein-4b-base#request-scheduler)

- **Type**: `string`

Scheduler to use for the diffusion process.

**Allowed values**: `DDIM` `DDIMScheduler` `DDPMScheduler` `DEISMultistepScheduler` `Default` `DPM++` `DPM++ 2M` `DPM++ 2M Beta` `DPM++ 2M Exponential` `DPM++ 2M Karras` `DPM++ 2M SDE` `DPM++ 2M SDE Beta` `DPM++ 2M SDE Exponential` `DPM++ 2M SDE Karras` `DPM++ 2M SDE Uniform` `DPM++ 2M Uniform` `DPM++ 3M` `DPM++ 3M Beta` `DPM++ 3M Exponential` `DPM++ 3M Karras` `DPM++ 3M SDE Uniform` `DPM++ 3M Uniform` `DPM++ Beta` `DPM++ Exponential` `DPM++ Karras` `DPM++ SDE` `DPM++ SDE Beta` `DPM++ SDE Exponential` `DPM++ SDE Karras` `DPM++ Uniform` `DPM++ Uniform Beta` `DPM++ Uniform Exponential` `DPM++ Uniform Karras` `DPMSolverMultistepInverse` `DPMSolverMultistepScheduler` `DPMSolverSinglestepScheduler` `EDMDPMSolverMultistepScheduler` `EDMEulerScheduler` `Euler` `Euler a` `Euler Beta` `Euler DiscreteScheduler` `Euler Exponential` `Euler Karras` `EulerAncestralDiscreteScheduler` `FlowMatchEulerDiscreteScheduler` `Heun` `HeunDiscreteScheduler` `Heun Karras` `IPNDMScheduler` `IPNDM Uniform` `IPNDM Uniform Beta` `IPNDM Uniform Exponential` `IPNDM Uniform Karras` `KDPM2AncestralDiscreteScheduler` `KDPM2DiscreteScheduler` `LCM` `LCMScheduler` `LMS` `LMSDiscreteScheduler` `LMS Karras` `PNDMScheduler` `TCDScheduler` `UniPC` `UniPC 2M` `UniPC 2M Karras` `UniPC 2M Uniform` `UniPC 3M` `UniPC 3M Karras` `UniPC 3M Uniform` `UniPC Karras` `UniPC Uniform` `UniPC Uniform Beta` `UniPC Uniform Exponential` `UniPC Uniform Karras`

**Learn more** (2 resources):

- [Text To Image: Scheduler The Algorithmic Path To Your Image](https://runware.ai/docs/guides/text-to-image#scheduler-the-algorithmic-path-to-your-image) (guide)
- [Image Outpainting: Other Critical Parameters](https://runware.ai/docs/guides/image-outpainting#other-critical-parameters) (guide)

### [CFGScale](https://runware.ai/docs/models/bfl-flux-2-klein-4b-base#request-cfgscale)

- **Type**: `float`
- **Min**: `1`
- **Max**: `20`
- **Step**: `0.01`
- **Default**: `3.5`

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)

### [lora](https://runware.ai/docs/models/bfl-flux-2-klein-4b-base#request-lora)

- **Path**: `lora.model`
- **Type**: `array of objects (3 properties)`

With LoRA (Low-Rank Adaptation), you can adapt a model to specific styles or features by emphasizing particular aspects of the data. This technique enhances the quality and relevance of generated content and can be especially useful when the output needs to adhere to a specific artistic style or follow particular guidelines.

Multiple LoRA models can be used simultaneously to achieve different adaptation goals.

**Examples**:

```json
"lora": [
  {
    "model": "<lora-model-air>",
    "weight": 0.8
  }
]
```

**Learn more** (1 resource):

- [Text To Image: Loras Style And Subject Adapters](https://runware.ai/docs/guides/text-to-image#loras-style-and-subject-adapters) (guide)

#### [model](https://runware.ai/docs/models/bfl-flux-2-klein-4b-base#request-lora-model)

- **Path**: `lora.model`
- **Type**: `string`
- **Required**: true

LoRA model identifier.

#### [weight](https://runware.ai/docs/models/bfl-flux-2-klein-4b-base#request-lora-weight)

- **Path**: `lora.weight`
- **Type**: `float`
- **Min**: `-4`
- **Max**: `4`
- **Step**: `0.01`
- **Default**: `1`

Strength of the LoRA influence. A value of 0 means no influence. Higher values increase the influence, and negative values can be used to steer away from the LoRA's style.

#### [transformer](https://runware.ai/docs/models/bfl-flux-2-klein-4b-base#request-lora-transformer)

- **Path**: `lora.transformer`
- **Type**: `string`
- **Default**: `both`

Transformer stages to apply LoRA. Some video models use separate high-noise and low-noise processing stages, and LoRAs can be selectively applied to optimize their effectiveness.

**Allowed values**:

- `high` Apply LoRA only to the high-noise processing stage (coarse structure and early generation steps).
- `low` Apply LoRA only to the low-noise processing stage (fine details and later generation steps).
- `both` Apply LoRA to both stages for full coverage.

**Features**

Standalone addons and post-processing features.

### [ultralytics](https://runware.ai/docs/models/bfl-flux-2-klein-4b-base#request-advancedfeatures-ultralytics)

- **Path**: `advancedFeatures.ultralytics`
- **Type**: `object (8 properties)`

Configuration object for Ultralytics face enhancement during generation. This feature uses face detection and inpainting to improve facial details in the same generation step, without requiring post-processing.

> [!NOTE]
> Face enhancement is available for Stable Diffusion 1.X, SDXL, and FLUX models. The system automatically detects faces and applies targeted refinement to improve quality while maintaining consistency with the overall generation.

#### [CFGScale](https://runware.ai/docs/models/bfl-flux-2-klein-4b-base#request-advancedfeatures-ultralytics-cfgscale)

- **Path**: `advancedFeatures.ultralytics.CFGScale`
- **Type**: `float`
- **Min**: `0`
- **Max**: `50`
- **Step**: `0.1`
- **Default**: `8`

Face refinement guidance scale.

#### [confidence](https://runware.ai/docs/models/bfl-flux-2-klein-4b-base#request-advancedfeatures-ultralytics-confidence)

- **Path**: `advancedFeatures.ultralytics.confidence`
- **Type**: `float`
- **Min**: `0`
- **Max**: `1`
- **Step**: `0.01`
- **Default**: `0.9`

Confidence threshold for detection.

#### [maskBlur](https://runware.ai/docs/models/bfl-flux-2-klein-4b-base#request-advancedfeatures-ultralytics-maskblur)

- **Path**: `advancedFeatures.ultralytics.maskBlur`
- **Type**: `integer`
- **Min**: `0`
- **Max**: `100`
- **Default**: `5`

Mask feathering amount. Higher values create softer transitions between the enhanced face region and surrounding areas.

#### [maskPadding](https://runware.ai/docs/models/bfl-flux-2-klein-4b-base#request-advancedfeatures-ultralytics-maskpadding)

- **Path**: `advancedFeatures.ultralytics.maskPadding`
- **Type**: `integer`
- **Min**: `0`
- **Max**: `20`
- **Default**: `5`

Padding around detected face in pixels. Expands the refinement area to include surrounding context like hair and neck.

#### [negativePrompt](https://runware.ai/docs/models/bfl-flux-2-klein-4b-base#request-advancedfeatures-ultralytics-negativeprompt)

- **Path**: `advancedFeatures.ultralytics.negativePrompt`
- **Type**: `string`

Negative prompt for detection.

#### [positivePrompt](https://runware.ai/docs/models/bfl-flux-2-klein-4b-base#request-advancedfeatures-ultralytics-positiveprompt)

- **Path**: `advancedFeatures.ultralytics.positivePrompt`
- **Type**: `string`

Positive prompt for detection.

#### [steps](https://runware.ai/docs/models/bfl-flux-2-klein-4b-base#request-advancedfeatures-ultralytics-steps)

- **Path**: `advancedFeatures.ultralytics.steps`
- **Type**: `integer`
- **Min**: `1`
- **Max**: `100`
- **Default**: `20`

Number of face refinement steps.

#### [strength](https://runware.ai/docs/models/bfl-flux-2-klein-4b-base#request-advancedfeatures-ultralytics-strength)

- **Path**: `advancedFeatures.ultralytics.strength`
- **Type**: `float`
- **Min**: `0`
- **Max**: `1`
- **Step**: `0.01`
- **Default**: `0.3`

Refinement strength. Lower values preserve more of the original, higher values allow more aggressive reconstruction.

## Response Parameters

### [taskType](https://runware.ai/docs/models/bfl-flux-2-klein-4b-base#response-tasktype)

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

Type of the task.

### [taskUUID](https://runware.ai/docs/models/bfl-flux-2-klein-4b-base#response-taskuuid)

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

UUID of the task.

### [imageUUID](https://runware.ai/docs/models/bfl-flux-2-klein-4b-base#response-imageuuid)

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

UUID of the output image.

### [imageURL](https://runware.ai/docs/models/bfl-flux-2-klein-4b-base#response-imageurl)

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

URL of the output image.

### [imageBase64Data](https://runware.ai/docs/models/bfl-flux-2-klein-4b-base#response-imagebase64data)

- **Type**: `string`

Base64-encoded image data.

### [imageDataURI](https://runware.ai/docs/models/bfl-flux-2-klein-4b-base#response-imagedatauri)

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

Data URI of the output image.

### [seed](https://runware.ai/docs/models/bfl-flux-2-klein-4b-base#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-klein-4b-base#response-nsfwcontent)

- **Type**: `boolean`

Flag indicating if NSFW content was detected.

### [cost](https://runware.ai/docs/models/bfl-flux-2-klein-4b-base#response-cost)

- **Type**: `float`

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

## Examples

### Tidal Archive Reading Hall (Image to Image)

![Tidal Archive Reading Hall](https://assets.runware.ai/examples/bfl-flux-2-klein-4b-base/0ac04d2f-9352-4a79-9a34-0ed594e3d5ca.jpg)

**Request**:

```json
{
  "taskType": "imageInference",
  "taskUUID": "ac17b01d-8c5d-46f9-bd42-227280d05ff3",
  "model": "runware:400@5",
  "positivePrompt": "An immense tidal reading hall built inside a partially flooded stone basilica, concentric wooden walkways above clear seawater, archivists in practical rain capes sorting giant atlases, white ibises resting on railings, coral-encrusted columns, suspended rope shelves, brass instruments, damp parchment, drifting motes, luminous shafts of daylight through high arches, elegant environmental storytelling, intricate textures, cinematic scale, natural color palette, crisp details, imaginative yet believable architecture",
  "negativePrompt": "text, watermark, logo, frame, blurry, low detail, oversaturated, distorted anatomy, duplicated objects, chaotic composition, flat lighting",
  "width": 1152,
  "height": 768,
  "seed": 98694,
  "steps": 32,
  "CFGScale": 3.5,
  "settings": {
    "trueCFGScale": 4
  },
  "inputs": {
    "referenceImages": [
      "https://assets.runware.ai/assets/inputs/cfa98149-a68b-4386-b745-6c8c1c1fac4a.jpg",
      "https://assets.runware.ai/assets/inputs/51b9893d-5473-4c97-83b7-cc5f87b3c746.jpg",
      "https://assets.runware.ai/assets/inputs/c368b834-ca8e-45ea-88d0-69372304531a.jpg"
    ]
  }
}
```

**Response**:

```json
{
  "taskType": "imageInference",
  "taskUUID": "ac17b01d-8c5d-46f9-bd42-227280d05ff3",
  "imageUUID": "dcccec94-b421-4dae-bb19-45511def2245",
  "imageURL": "https://im.runware.ai/image/os/a14d18/ws/2/ii/dcccec94-b421-4dae-bb19-45511def2245.jpg",
  "seed": 98694,
  "cost": 0.0109
}
```

---

### Patchwork Carnival Aerostat Regatta (Image to Image)

![Patchwork Carnival Aerostat Regatta](https://assets.runware.ai/examples/bfl-flux-2-klein-4b-base/eff2bd37-b66b-481a-a34d-8d7d98154c9b.jpg)

**Request**:

```json
{
  "taskType": "imageInference",
  "taskUUID": "234735c5-3f14-41f5-b1a1-eac2d1e15226",
  "model": "runware:400@5",
  "positivePrompt": "A jubilant regatta of patchwork aerostats drifting above a terraced festival town, huge handmade balloon craft stitched from patterned cloth, dangling bells and ribbons, inventive copper propellers, whimsical gondolas filled with musicians and acrobats, swirling confetti, layered rooftops, carved wooden balconies, sun-washed clouds, dynamic diagonal composition, highly detailed textures, painterly yet believable, imaginative worldbuilding, vibrant but tasteful color harmony, cinematic scale",
  "negativePrompt": "text, watermark, logo, blurry, low detail, extra limbs, distorted anatomy, duplicate balloons, flat lighting, oversaturated, empty background, modern cars, skyscrapers",
  "width": 1280,
  "height": 720,
  "seed": 52976,
  "steps": 28,
  "CFGScale": 3.5,
  "settings": {
    "trueCFGScale": 4
  },
  "inputs": {
    "referenceImages": [
      "https://assets.runware.ai/assets/inputs/a3e29ef6-993a-43ab-8c40-76394eea8ae8.jpg",
      "https://assets.runware.ai/assets/inputs/38088571-7b0b-477b-953d-76afb59a1105.jpg",
      "https://assets.runware.ai/assets/inputs/b6277191-fdb5-42aa-8ee0-8afa4ca75dd4.jpg"
    ]
  }
}
```

**Response**:

```json
{
  "taskType": "imageInference",
  "taskUUID": "234735c5-3f14-41f5-b1a1-eac2d1e15226",
  "imageUUID": "59fb7b42-aba6-436a-875b-e096e816cdfe",
  "imageURL": "https://im.runware.ai/image/os/a20d05/ws/2/ii/59fb7b42-aba6-436a-875b-e096e816cdfe.jpg",
  "seed": 52976,
  "cost": 0.009
}
```

---

### Windmill Library Among Reedbeds (Text to Image)

![Windmill Library Among Reedbeds](https://assets.runware.ai/examples/bfl-flux-2-klein-4b-base/05cd9e18-c9c1-4b12-a368-089f312601e2.jpg)

**Request**:

```json
{
  "taskType": "imageInference",
  "taskUUID": "4d3a4156-5e5e-45db-b73c-a3200a7446ed",
  "model": "runware:400@5",
  "positivePrompt": "An old timber windmill converted into a public library, rising from a wide marsh of golden reedbeds and shallow reflective water, linked by narrow wooden footbridges and tiny reading docks. Stacks of books visible through circular windows, weathered sails patched with canvas, hand-painted signs, bicycles leaning near the entrance, migratory birds wheeling overhead, scattered lanterns glowing softly in early morning mist, a small rowboat filled with returned books, layered clouds opening to pale sunlight. Highly detailed natural textures, cinematic composition, storybook realism, delicate color harmony, crisp focus, atmospheric depth, charming human-scale details, painterly yet believable scene.",
  "negativePrompt": "low detail, blurry, distorted architecture, duplicate objects, extra limbs, people close-up, oversaturated, flat lighting, text watermark, logo, frame, harsh CGI, noisy image",
  "width": 1024,
  "height": 768,
  "seed": 32975,
  "steps": 28,
  "CFGScale": 3.5,
  "settings": {
    "trueCFGScale": 4
  }
}
```

**Response**:

```json
{
  "taskType": "imageInference",
  "taskUUID": "4d3a4156-5e5e-45db-b73c-a3200a7446ed",
  "imageUUID": "60c92bc8-5e1e-44fb-bb14-3df4489a0a71",
  "imageURL": "https://im.runware.ai/image/os/a04d20/ws/2/ii/60c92bc8-5e1e-44fb-bb14-3df4489a0a71.jpg",
  "seed": 32975,
  "cost": 0.0019
}
```

---

### Subterranean Fungal Transit Platform (Text to Image)

![Subterranean Fungal Transit Platform](https://assets.runware.ai/examples/bfl-flux-2-klein-4b-base/56a0e169-06d0-4d49-b46c-68c104ab3f16.jpg)

**Request**:

```json
{
  "taskType": "imageInference",
  "taskUUID": "93b230ca-1b1d-4a48-81a4-4e91632aafdb",
  "model": "runware:400@5",
  "positivePrompt": "A vast underground train platform carved into ancient stone caverns, giant shelf mushrooms and tangled pale fungi growing from columns and archways, a copper-and-wood commuter rail waiting beside the platform, passengers in weathered rain capes carrying wicker baskets and mechanical lanterns, overhead mineral chandeliers made from quartz and brass, puddles reflecting warm amber station lamps, hand-painted wayfinding signs in a forgotten script, drifting steam, detailed masonry, cinematic depth, atmospheric haze, intricate textures, grounded fantasy realism, wide environmental composition, highly detailed",
  "negativePrompt": "low detail, blurry, distorted anatomy, extra limbs, duplicated people, modern city setting, cars, skyscrapers, text watermark, logo, oversaturated colors, flat lighting, empty scene",
  "width": 1024,
  "height": 640,
  "seed": 78524,
  "steps": 28,
  "CFGScale": 3.5,
  "settings": {
    "trueCFGScale": 4
  }
}
```

**Response**:

```json
{
  "taskType": "imageInference",
  "taskUUID": "93b230ca-1b1d-4a48-81a4-4e91632aafdb",
  "imageUUID": "437c2f04-1b91-4fed-aa7d-99abb4b7c0ad",
  "imageURL": "https://im.runware.ai/image/os/a15d18/ws/2/ii/437c2f04-1b91-4fed-aa7d-99abb4b7c0ad.jpg",
  "seed": 78524,
  "cost": 0.0013
}
```