BFL modelsimage generation api

bfl/flux-2/klein/4b/edit/lora

Name: FLUX.2 [klein] 4B LoRA
Author: BFL

Flux 2 Klein 4b is BFL's intelligent image editing model. Transform, retouch, and reimagine existing images using text prompts - from background replacement to artistic style conversion.

Input

Prompt(string)

The prompt to edit the image.

Image URL or upload(array)

Upload

PNG, JPEG, WebP, or GIF · 20 MiB maximum each

The URLs of the images for editing. A maximum of 4 images are allowed.

Output Format(string)

The format of the generated image. Allowed values: jpeg, png.

Aspect Ratio(string)

The aspect ratio of the generated image. Allowed values: 21:9, 16:9, 3:2, 4:3, 5:4, 1:1, 4:5, 3:4, 2:3, 9:16.

Seed(integer)

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

Loras(array)

Enter a JSON array.

Num Inference Steps(integer)

Range: 4 to 8.

Idle

Example output — click Run to generate your own

Production endpoint

Send your first request

OpenAI-compatible endpoint with unified authentication and usage tracking.

POSThttps://api.sandbase.ai/v1/run

Model IDbfl/flux-2/klein/4b/edit/lora

Input Schema

7 parameters · 1 required · 6 optional

Parameter	Type	Required	Description
`prompt`	string	Required	The prompt to edit the image.
`seed`	integer	Optional	The seed to use for the generation. If not provided, a random seed will be used.
`loras`	array	Optional	Default: []
`images`	string[]	Optional	The URLs of the images for editing. A maximum of 4 images are allowed.
`aspect_ratio`	string	Optional	The aspect ratio of the generated image. · Options: 21:9, 16:9, 3:2, 4:3, 5:4, 1:1, 4:5, 3:4, 2:3, 9:16 21:916:93:24:35:41:14:53:42:39:16
`output_format`	string	Optional	The format of the generated image. · Options: jpeg, png · Default: "png" jpegpng
`num_inference_steps`	integer	Optional	Min: 4 · Max: 8 · Default: 4

Output Schema

Field	Type	Description
`id`	string	Unique identifier for the generation task
`status`	string	Task status: pending, running, completed, failed, timeout
`model`	string	Model used for the generation
`outputs`	array	Array of output items
`outputs[].url`	string	URL of the generated artifact
`outputs[].content_type`	string	MIME type (e.g. image/png, video/mp4)
`error`	object \| null	Error details if failed, null on success
`error.type`	string	Machine-readable error type code
`error.message`	string	Human-readable error description

Async Workflow

This model uses asynchronous execution. Submit a request and poll for the result.

Submit — POST to /v1/run, receive an id
Poll — GET /v1/run/{id} until status is completed, failed, or timeout
Retrieve — Read outputs from the completed response

Code Examples

Ready-to-run snippets

# Step 1: Submit
curl -X POST https://api.sandbase.ai/v1/run \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -d '{
  "model": "bfl/flux-2/klein/4b/edit/lora",
  "loras": [],
  "images": [
    "https://static.sandbase.ai/examples/bfl/flux-2/klein/4b/edit/lora/input_images_0.png"
  ],
  "prompt": "Turn this into a realistic image",
  "output_format": "png",
  "num_inference_steps": 4
}'

# Step 2: Poll result (replace <id>)
curl https://api.sandbase.ai/v1/run/<id> \
  -H "Authorization: Bearer YOUR_API_KEY"

← Back to FLUX.2 [klein] 4B LoRA

API README

FLUX.2 [klein] 4B LoRA

FLUX.2 [klein] 4B LoRA exposes the FLUX.2 Klein 4B Edit LoRA capability for reference-led image revision. The step-distilled model is built for low-latency inference while retaining strong visual quality. A lightweight adapter adds a learned style, subject, or domain concept to this exact path.

Use this 4B route when accessibility, local efficiency, and rapid iteration matter. Describe the requested change separately from source identity, geometry, and regions that must remain fixed.

Highlights

FLUX.2 Klein 4B Edit LoRA architecture. Uses the compact step-distilled 4B model for fast visual synthesis.
Unified contextual editing. Understands source content and applies directed semantic or appearance changes.
Adapter-based specialization. Expresses a learned style, character, object, or domain through a lightweight adaptation.
Reference consistency. Preserves important subject, composition, and detail through the requested revision.

Pricing

Configuration	Billing unit	Price
Base generation	Per request	$0.02

When to Use

✅ Good fit	❌ Consider alternatives
The project needs this exact generation or editing route	The intended task belongs to video, audio, or 3D media
Available references match every required local field	Required source assets or rights are unavailable
The brief can specify composition, color, and finish	Output must be deterministic at pixel level
Supported dimensions and formats fit final placement	Delivery requires unsupported canvas specifications
An asynchronous generated image fits production	A live frame-synchronous response is mandatory

Prompt Guide

Write a complete visual brief: identify the subject and references, define composition and viewpoint, describe lighting, palette, materials, typography, and finish, then list exact preservation constraints. FLUX.2 Klein does not rely on prompt upsampling, so use clear descriptive sentences rather than sparse keywords.

{
  "prompt": "A photorealistic editorial composition with precise subject placement, controlled lighting, exact colors, and clean typography",
  "seed": 1,
  "loras": [],
  "images": [
    "https://example.com/reference.jpg"
  ]
}

Technical Specs

Spec	Value
Model ID	`bfl/flux-2/klein/4b/edit/lora`
Input fields	`seed` (integer)<br>`loras` (array)<br>`images` (array)<br>`prompt` (string)<br>`aspect_ratio` (string; `21:9`, `16:9`, `3:2`, `4:3`, `5:4`, `1:1`, `4:5`, `3:4`, `2:3`, `9:16`)<br>`output_format` (string; `jpeg`, `png`)<br>`num_inference_steps` (integer; 4–8)
Required input	`prompt`
Output fields	`url`, `content_type`
Execution	Asynchronous job

Related Models

bfl/flux-2/klein/4b
bfl/flux-2/klein/4b/base
bfl/flux-2/klein/4b/base/edit