FLUX 3 Klein Base LoRA API

About FLUX 3 Klein Base LoRA

FLUX 3 Klein Base that loads your own LoRAs.

Call it with the model name black-forest-labs/flux-3-klein-base-lora/text-to-image on POST /jobs/createTask, from 7 credits per image ($0.07).

Introduction

FLUX 3 Klein Base LoRA Text to image draws one image from a written prompt on Black Forest Labs' FLUX 3 Image Klein Base, the undistilled 5.6B checkpoint its makers recommend for LoRA training, with up to three of your own LoRA files loaded from direct links. Choose one of fifteen aspect ratios at 1k or 2k and JPEG, PNG or WebP.

Choose a mode by starting material

Key features

Runs LoRAs on their own checkpoint

Black Forest Labs recommends training Klein LoRAs on Base, so a LoRA you trained runs here on exactly the model it learned from. In our tests a character LoRA trained on Base changed the face, ears and finish of the picture at 0.5 and more strongly at 1, while a LoRA made for FLUX.2 [klein] 9B loaded and changed nothing at all.

Exact A/B pairs

The same seed with the same inputs returned identical pixels in our tests. Run the prompt once without a LoRA and once with it, and every difference between the two pictures is the LoRA's doing, which makes judging a fresh training run much easier.

Up to three LoRAs

Stack up to three files, each with its own strength from 0 to 4, for example a character with a style beside it.

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 7 credits per image ($0.07).

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

Use cases

Testing a fresh LoRA

Train on FLUX 3 Image Klein Base, then check the file here at 1k against the same seed without it, and at 2k for detail, without keeping a GPU of your own warm.

Prompt guide & pro tips

Trigger first, then a full caption

Start with the trigger phrase from the LoRA's model card, then describe framing, subject, clothing, place and light in sentences. Klein is trained on long captions and this endpoint sends your prompt as written.

Start the scale around 0.5 to 1

A character LoRA at 1 also added a painted finish and a stray signature in our tests; at 0.5 it kept a photographic look. Move in steps of 0.2 and check faces and hands first.

Check the base model on the card

Only LoRAs for FLUX 3 Image Klein do anything here. If a run looks identical to the same seed without the LoRA, the file was most likely trained for another model.

API quick start

Call the FLUX 3 Klein Base 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-3-klein-base-lora/text-to-image 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-3-klein-base-lora/text-to-image",
  "input": {
    "prompt": "A ceramic teapot on a linen cloth, soft window light, muted palette",
    "aspect_ratio": "1:1",
    "resolution": "1k",
    "output_format": "jpeg"
  }
}'

# 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 3 Klein Base LoRA API questions

All FLUX models

• FLUX.2 Max APITop-tier FLUX: photoreal light and exact brand colorsFrom 11 credits per image
• FLUX 3 Klein Base LoRA APIFLUX 3 Klein Base that loads your own LoRAsFrom 7 credits per image
• FLUX 3 Klein Base APIFull-quality FLUX 3 Klein images and edits up to 2KFrom 6 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

• 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
• 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

More about FLUX 3 Klein Base LoRA

Try it

FLUX 3 Klein Base LoRA AI Image Generator onlineCreate images with FLUX 3 Klein Base LoRA in PopNow

Endpoints

FLUX 3 Klein Base LoRA · Edit Image

Docs

FLUX 3 Klein Base 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 3 Klein Base LoRA results without polling