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black-forest-labs/flux-2-klein-4b-lora/text-to-imageFrom 3 credits per image· Create Image

FLUX.2 Klein 4B LoRA runs Black Forest Labs' FLUX.2 [klein] 4B, the fast distilled 4-billion-parameter model released under Apache 2.0 on 15 January 2026, with up to three of your own LoRA files per request. Text to image in nine aspect ratios up to 2048 pixels, and editing from up to three source images, with no review of prompts, weights or results.

Call it with the model name black-forest-labs/flux-2-klein-4b-lora/text-to-image on POST /jobs/createTask, from 3 credits per image ($0.03). New accounts get 30 free credits to try it in the Playground first.

  • Create Image
  • Edit Image
  • Up to 2K
  • Up to 3 reference images
  • 9 aspect ratios
  • Loads your own LoRA
by Black Forest LabsGet API keyFLUX.2 Klein 4B LoRA examples and prompts →

Introduction

FLUX.2 Klein 4B LoRA Text to image makes one image from a written prompt on Black Forest Labs' FLUX.2 [klein] 4B, the fast distilled 4-billion-parameter model released under Apache 2.0, with up to three of your own LoRA files loaded. Nothing is filtered.

Choose a mode by starting material

What you haveMode
a written description and a LoRAFLUX.2 Klein 4B LoRA Text to image
one to three pictures to change or combineFLUX.2 Klein 4B LoRA Image edit

Key features

Results in seconds

The distilled build finished most of our text-to-image requests in about 4 seconds of model time, which makes it practical to try several seeds and LoRA scales for one idea.

LoRAs from both Klein 4B builds

LoRAs trained on FLUX.2 [klein] 4B and on Klein Base 4B both loaded in our tests. Files for FLUX.1 or for the 9B Klein models load without an error and do nothing.

Request parameters

ParameterRequiredDescription
aspect_ratioNoThe shape of the frame: wide, square or tall. 1:1 · 16:9 · 9:16 · 4:3 · 3:4 · 3:2 · 2:3 · 21:9 · 9:21 · Default: 1:1
lorasNoLoad your own LoRA files to lock in a style or character. Default: []
promptYesDescribe the subject, setting, light and style in plain sentences. Put a LoRA trigger phrase first.
resolutionNoOutput size. Bigger sizes look sharper and cost more. 1k · 2k · Default: 1k
seedNoReuse the same number to get a repeatable result. ≥ 0 · ≤ 2147483647

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.

OptionCredits per image≈ USD
Standard2.34$0.023

Each task is rounded up to whole credits, so one run at the lowest tier costs 3 credits per image ($0.03).

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

Use cases

Running a LoRA you found

Paste the download link from Hugging Face or Civitai, set the scale and put the trigger first. No training, no hosting and no GPU: a LoRA you saw on a model hub becomes a plain API call that returns in seconds.

Fast drafts for a bigger model

Try compositions, outfits and LoRA scales quickly here at the 1k tier, then render the chosen frame at 2k or hand the prompt to a slower model for the final image.

Prompt guide & pro tips

Trigger first, then full sentences

Start with the trigger phrase from the LoRA page, then describe subject, clothing, place and light. Name the lens and the grade for photographic results.

Push faint styles to 1.5 or 2

Style LoRAs show less on this distilled build. Raise the scale step by step and compare with the same seed; at 4 the image fell apart in our test.

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.

Keep signs out of the frame

The model writes garbled words on signs and labels. Describe signs as blank or leave them out unless the text matters.

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/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-2-klein-4b-lora/text-to-image",
  "input": {
    "prompt": "A ceramic teapot on a linen cloth, soft window light, muted palette",
    "aspect_ratio": "1:1",
    "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

How much does the FLUX.2 Klein 4B LoRA API cost?

FLUX.2 Klein 4B LoRA starts at 3 credits ($0.03) per image with Create Image, its cheapest task. Credits are the same as on the website (1 credit = $0.01), new accounts get 30 free credits, and failed tasks are refunded.

What is the model name for FLUX.2 Klein 4B LoRA in the API?

Put black-forest-labs/flux-2-klein-4b-lora/text-to-image for Create Image; black-forest-labs/flux-2-klein-4b-lora/edit for Edit Image in the model field of POST /jobs/createTask.

What is the difference from FLUX.2 Klein Base 4B LoRA?

Both run Black Forest Labs' 4B Klein model. This one is the distilled build, made to finish in a few steps: in our tests it was about four times faster and followed edit instructions more reliably. Base 4B is the undistilled build its makers recommend for training; it is slower, gives more varied results and shows style LoRAs more strongly.

Which LoRAs work here?

Files trained for FLUX.2 [klein] 4B or Klein Base 4B. LoRAs from both builds loaded in our tests. LoRAs for FLUX.1 or the 9B Klein models load silently and have no effect.

My LoRA loaded but nothing changed. Why?

It was probably trained for another base model, or it needs its trigger phrase. Check the LoRA page for the trigger and put it first. Style LoRAs can also be faint on this distilled build; try a scale of 1.5 to 2.

What are the limits of the FLUX.2 Klein 4B LoRA API?

Resolutions: 1K · 2K; Aspect ratios: 1:1 · 16:9 · 9:16 · 4:3 · 3:4 · 3:2 +3; Prompt length (characters): 5,000. Requests outside these limits are rejected before anything is charged.

Can I try FLUX.2 Klein 4B LoRA without writing code?

Yes. The Playground runs FLUX.2 Klein 4B LoRA on your PopNow credits, needs no API key, and shows the matching code for every run.

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.

More about FLUX.2 Klein 4B LoRA