Why it matters
If you make images for ads, FLUX 3 Image Klein lets you make them on your own computer with no credit per image. The licence says paid work is covered if your business makes under US$5 million a year. You need a strong computer: on our Mac Studio one image took four to six minutes.
My read: it is good to see capable models come with commercial licences, and I would not build a business on a licence that can end with an email.
What it is
What it is
FLUX 3 Image Klein is a new open-weights image model from Black Forest Labs, the lab behind FLUX. BFL announced it on 15 October 2026. It makes images from text, edits images and can work from several reference pictures at once. BFL describes it as a 5.6 billion parameter model.
It comes as two checkpoints, a base model for fine-tuning and a step-distilled model for low latency. We used the distilled one at 16 steps. You run it in ComfyUI, a free node-graph app that runs on your own hardware.
- BFL says it takes up to 10 reference images and generates natively in 4K.
- BFL's API serves the distilled model. Its announcement says: "Pricing starts at $0.009 per 1K image." BFL does not explain the unit.
- The text encoder is a separate model, Qwen3-VL-4B-Instruct, under Apache 2.0.
- The earlier FLUX.1 [dev] and FLUX.2 [dev] downloads carry non-commercial licences, according to their model cards.
Sources: BFL, the FLUX 3 Image Klein announcement, Hugging Face, the FLUX 3 Image Klein model page, BFL, about, ComfyUI, the app, Hugging Face, FLUX.1 [dev] model card, and Hugging Face, FLUX.2 [dev] model card
What the helper model does to your prompt
What the helper model does to your prompt
Before
a woman in a camel coat, empty street, golden hour
After
Low amber sunlight enters from frame-right, casting long diagonal shadows across the pavement ... wearing a knee-length camel wool coat with broad lapels, a dark brown leather belt, straight black trousers, and worn ankle boots.
Before: the one line we typed. After: what BFL's prompt upsampler wrote from it, copied word for word from our run log, shortened where the dots are. The picture shows a person who does not exist.
The setup we used
The setup we used, step by step
- Accept the terms on Hugging Face Two repos are gated: black-forest-labs/flux-3-image-klein and black-forest-labs/flux-3-image-klein-comfy. Log in and accept the terms on each page.
- Install or update ComfyUI ComfyUI v0.41.0 added FLUX 3 support, released 15 October. We ran 0.42.1. The Desktop app is free and open source and runs on your own hardware.
- Open the FLUX 3 Image Klein template In ComfyUI, load the FLUX 3 Image Klein template from the Templates panel, as ComfyUI's launch post says. Our graph follows BFL's flux3_klein_bf16_t2i.json.
- Download the files We used four bf16 files, about 39 GB together: flux3-image-klein-bf16 (11.10 GB), qwen3vl_4b_bf16 (8.88 GB), the prompt upsampler (18.82 GB) and flux2-vae (0.34 GB).
- Switch the helper model on The model card says: "Do not use the model without a prompt upsampler." It turns a short request into a full scene description. ComfyUI's template has an enable_prompt_upsampler switch.
- Use our settings Distilled model, bf16, 16 steps, euler with the simple scheduler, cfg 1.0, ModelSamplingFlux shift 2.77259, 1088 x 1920 (9:16), helper model on, seed 101 for the image and the helper. Our prompts are in the table below.
- Expect it to be slow on a Mac On our Mac Studio with an M3 Ultra and 96 GB, one image took 239 to 381 seconds with the helper on. The 11 runs for our ad pictures took 252 to 363 seconds each. Three images without it took about 96 seconds each.
- Read the licence before you sell anything The FLUX Kommunity License v1.0 is LICENSE.md on the model page. Sections 1.e, 2.d, 2.e, 4.b and 8.b are the ones we quote below.
Sources: ComfyUI, FLUX 3 Image Klein in ComfyUI, ComfyUI, release v0.41.0, Hugging Face, the prompt upsampler repo, and BFL, reference code on GitHub
Who it suits
Who it suits
It suits you if you make images for a shop, for clients or for ads and you now pay an online tool or a photographer for each one. It asks for some setup. You install ComfyUI, download about 39 GB and need a computer that can run it.
You can ask for exact words too. We typed the words for a poster, a candle label and a shop sign, and the candle label above is one of the results. If your business makes US$5 million a year or more, affiliates included, the licence's paid-work line does not cover you. BFL points larger organisations to a separate licence or its API.
Our prompts
Our prompts, exactly as typed
The portrait above and the pictures in the reel's ad section came from these prompts, copied from our run log character for character. Before each one the helper model was given the line TARGET CANVAS: 9:16. Each ran with seed 101 and we kept the first picture it made. The names on the labels are ones we made up.
| Prompt, exactly as typed | Seconds |
|---|---|
| Advertising photograph of a slim aluminium can with a cream label reading exactly "LIME FIZZ", beaded with condensation, on a sunlit stone ledge beside two lime halves, low angle, golden backlight rimming the can, a smooth teal-to-apricot sky filling the top half of the frame as empty space for a headline, 85mm lens. | 319 |
| Event poster, deep green background. Large cream bold sans-serif lettering, left-aligned in the upper left on two lines, reads exactly "SLOW SUNDAY". A small line below in the same type reads exactly "Open-air market, 9 to 2". One huge flat yellow lemon, half cropped by the right edge. Strict grid, screen-print texture. | 252 |
| Product photograph of a clear glass candle jar, lit, on dark grey concrete beside a matchbox. A plain white paper label faces the camera, printed in black typewriter letters, reading exactly "QUILLON OAK" and below it "soy wax, 220 g". Hard side light from the left, deep shadows, 100mm macro lens, label in sharp focus. | 302 |
| Night photograph of a bookshop window in the rain. A glowing warm-pink neon sign in the glass reads exactly "OPEN LATE" in rounded script tubes. Amber-lit shelves of books inside, wet pavement reflecting the neon, teal blue shadows, low angle, 35mm lens, soft glow, cinematic advertising still. | 330 |
| Editorial fashion portrait of a young man with short curly dark hair in a cream chunky knit sweater and a thin gold chain, three-quarter view, head and shoulders, soft window light from the left on a warm grey plaster wall, 85mm lens, shallow depth of field, fine film grain, calm direct gaze, large empty space on the right. | 279 |
| Advertising photograph of a frosted glass skincare serum bottle with a white dropper and a cream label reading exactly "DEWFALL", standing on a pale pink seamless backdrop beside a single glossy water droplet, hard sunlight casting a crisp diagonal shadow, 100mm macro lens, soft pastel colour, empty pink space above. | 306 |
Seconds are ComfyUI's own count on our Mac Studio, helper on, one image at a time.
Sources: BFL, reference code on GitHub and ComfyUI, FLUX 3 Image Klein in ComfyUI
What to know before you rely on it
What to know before you rely on it
BFL says the INT8 build runs on NVIDIA GeForce RTX GPUs with as little as 8GB of VRAM, and gives about 4 seconds for a 1 MP image on an RTX 5090 and under 9 seconds on an RTX 4070 (distilled model, INT8, ComfyUI). We have not tried that build. Our Mac took four to six minutes for a 9:16 image with the helper on, so the numbers are not the same test.
The licence terms below are quoted from the FLUX Kommunity License v1.0. This is our reading of the text, not legal advice. Read it yourself and check it again on the day you use it.
- Section 2.d: "We claim no ownership rights in and to the Outputs. You are solely responsible for the Outputs you generate and their subsequent uses in accordance with this License."
- Section 2.e: the licence says a Qualifying User using Outputs commercially must either keep content filters in place or have each Output reviewed for unlawful or infringing content before it goes out, and include AI-generated disclosures where the law requires them.
- Section 4.b: the licence says you will not use the model or its Outputs to improve any other AI model that performs a similar function.
- Section 8.b: "We may terminate this License, in whole or in part, at any time upon notice (including electronic) to you." Electronic notice counts, so an email is enough.
- Section 1.e: a Qualifying User is someone whose gross annualized revenue, together with their affiliates, is less than US$5,000,000.
Sources: Hugging Face, the licence (LICENSE.md) and BFL, the FLUX 3 Image Klein announcement
Where to start
Where to start
Two pages from the publisher, the ones we worked from. The licence is on the model page, and the announcement holds BFL's own claims about speed and hardware.
- Open the model pageThe model page on Hugging Face
The files, the terms you accept first and the licence box.
Our screenshot of the model page on Hugging Face - Read the announcementBFL's announcement
What BFL says the model does, its hardware claim and the API price.
Our screenshot of BFL's announcement
Yes, that's my AI avatar in the video. Same opinions, better lighting.