FLUX.2 Klein 4B LoRA API

Introduction

FLUX.2 Klein 4B LoRA Image edit changes or combines up to three source images with a written instruction on Black Forest Labs' FLUX.2 [klein] 4B, with up to three of your own LoRA files loaded. Keep the shape of your first image with auto, or choose one of nine ratios and a 1k or 2k size tier.

Choose a mode by starting material

Key features

Edits that follow the instruction

Change light, clothes or setting and keep faces and pose. In our tests the distilled build followed our edit instructions closely, including taking the clothes off a clothed photo.

Restyle with a LoRA

Load a style LoRA and ask for a redraw: a diner photo came back as a colored-pencil drawing with the woman and her dress kept.

Up to three sources

Combine a portrait with an outfit or a location. Name the sources as image 1, image 2 and image 3; faces can drift a little when you combine them.

Request parameters

Pricing

Prices are in credits, the same credits you use on the website (1 credit = $0.01). The hold is taken when the task is accepted and settled to the actual charge when it finishes; failed tasks are refunded.

Each task is rounded up to whole credits, so one run at the lowest tier costs 4 credits per image ($0.04).

For an exact number before you run, send the same body to POST /jobs/quote.

Use cases

Outfit and setting swaps

Put a person from one photo into a dress from another and a new place, in one request. Name the portrait as image 1 and the outfit as image 2, and say where the scene happens.

Reframing and relighting

Pick a wider ratio than the source and describe what should fill the new space, or keep auto and move a daytime photo to blue hour with one sentence about the light.

Prompt guide & pro tips

Protect first, change second

Open with what must stay (face, hair, pose), then describe the change. Short, concrete instructions work best.

Use auto to keep the shape

Auto keeps the first source's shape at about one megapixel. Choose a ratio only when you want the frame recomposed.

Compare against no LoRA

Run the same prompt and seed without the LoRA. If the two results look the same, the file was made for another base model, such as FLUX.1 or the 9B Klein models: those load without an error and do nothing here.

Use direct, public links

The link must download the .safetensors file itself.

API quick start

Call the FLUX.2 Klein 4B LoRA API in three steps

1. Create an API key. Sign in to PopNow and create a key in the API console. Keys start with sk-popnow- and use the same credits as the website.
2. Send the request. POST /jobs/createTask with model black-forest-labs/flux-2-klein-4b-lora/edit and an input object that follows the parameter table. The response returns a task ID straight away.
3. Get the result. Poll GET /jobs/recordInfo with the task ID, or pass a callBackUrl and we post the result to it. Download the output links when the task succeeds.

# 1. Create the task. Keep the Idempotency-Key if you retry after a network error.
export IDEMPOTENCY_KEY="$(uuidgen)"
curl -X POST https://api.popnow.ai/api/v1/jobs/createTask \
  -H "Authorization: Bearer $POPNOW_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: $IDEMPOTENCY_KEY" \
  -d '{
  "model": "black-forest-labs/flux-2-klein-4b-lora/edit",
  "input": {
    "prompt": "A ceramic teapot on a linen cloth, soft window light, muted palette",
    "image_urls": [
      "https://media.popnow.ai/influencer/examples/marco.webp"
    ],
    "aspect_ratio": "auto",
    "resolution": "1k"
  }
}'

# 2. Copy data.taskId from the response, then poll until state is succeeded, failed, canceled or expired.
TASK_ID="TASK_ID_FROM_RESPONSE"
curl "https://api.popnow.ai/api/v1/jobs/recordInfo?taskId=$TASK_ID" \
  -H "Authorization: Bearer $POPNOW_API_KEY"

Replace the prompt and any links with your own. The API tab has the response, polling and callback reference.

FLUX.2 Klein 4B LoRA API questions

All FLUX models

FLUX.2 Klein Base 4B LoRA responds more strongly to style LoRAs and varies more between seeds, but is about four times slower.

• FLUX.2 Max APITop-tier FLUX: photoreal light and exact brand colorsFrom 11 credits per image
• FLUX 3 APIVideo with synced sound and a quick draft tierFrom 45 credits for a 5-second clip
• FLUX.2 Klein 9B LoRA APIFast FLUX.2 Klein 9B that loads up to three of your LoRAsFrom 3 credits per image
• FLUX.2 Klein Base 9B LoRA APIUndistilled Klein 9B for varied looks with your LoRAsFrom 4 credits per image
• FLUX.2 Klein 4B LoRA APISmall, quick FLUX.2 Klein 4B with your own LoRAsFrom 3 credits per image
• FLUX.2 Klein Base 4B LoRA APIUndistilled Klein 4B that loads your own LoRAsFrom 3 credits per image
• FLUX.2 Klein 9B APIFast FLUX edits that keep faces and poses intactFrom 2 credits per image
• FLUX.2 Klein 4B APIThe smallest, quickest FLUX for rapid draftsFrom 2 credits per image
• FLUX.2 Dev LoRA APIFLUX.2 Dev images and edits with your own LoRAsFrom 4 credits per image
• FLUX.2 Pro APIPhotoreal images with readable text and hex color controlFrom 5 credits per image
• FLUX.2 Flex APISpells headlines and labels exactly as writtenFrom 9 credits per image
• FLUX.2 Dev APIOpen-weights FLUX that can merge people into one sceneFrom 2 credits per image
• FLUX.1 Krea Dev LoRA APIPhotographic FLUX.1 Krea with your own LoRAsFrom 4 credits per image
• FLUX.1 Dev ControlNet LoRA APIPose, depth or edge control on FLUX.1 with your LoRAsFrom 6 credits per image
• FLUX.1 Fill Dev LoRA APIMasked inpainting on FLUX.1 Fill with your own LoRAsFrom 7 credits per image
• FLUX.1 Dev LoRA APIClassic FLUX.1 Dev with up to three of your LoRAsFrom 3 credits per image
• FLUX.1 Schnell LoRA APIFast FLUX.1 Schnell that loads your own LoRAsFrom 1 credit per image

Other image APIs

• Qwen Image 2.1 LoRA APIQwen Image 2.1 images and edits with up to three of your LoRAsFrom 5 credits per image
• MiniMax H3 Image LoRA APIH3 stills and edits with up to three of your LoRAsFrom 7 credits per image
• Anima Turbo LoRA APIAnime art with your own style or character LoRAsFrom 3 credits per image
• Krea 2 Turbo LoRA APIKrea 2 Turbo images and restyles with your own LoRAsFrom 4 credits per image
• P-Image LoRA APIFast P-Image renders and edits with one LoRA of your ownFrom 1 credit per image
• Z-Image Base LoRA APIZ-Image Base with up to three of your own LoRAsFrom 3 credits per image

More about FLUX.2 Klein 4B LoRA

Try it

FLUX.2 Klein 4B LoRA AI Image Generator onlineCreate images with FLUX.2 Klein 4B LoRA in PopNow

Docs

FLUX.2 Klein 4B LoRA model ID and input schema in the API docsPopNow API quickstart: your first request in five minutesImage generation guide for the PopNow APIWebhooks: get FLUX.2 Klein 4B LoRA results without polling