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Image Model

Flux 3 Klein for Architecture and Interior Design

Flux 3 Klein is the small, fast model in Black Forest Labs' FLUX 3 family, released on 15 October 2026. In Fenestra it creates and edits architecture and interiors at 1K, 2K or 4K, and its Regional Edit boxes change one part of a view while the rest stays exactly as it was.

Two-storey house with a pale brick ground floor and a light oak upper storey, overcast daylight
The same house after a Regional Edit: charred black timber on the upper storey, the brick, garden and sky unchanged

Built for spatial design

Trusted by 20,000+ architects and designers

Mikhail Riches
Manchester Metropolitan University
Apo Projekt
Morgan Architects
VAPF LUXURY HOMES
Jacobs
Shop Architects
Drummond Projects
  • 20,000+architects & designers

What's New

What's New in Flux 3 Klein?

FLUX 3's native 4K and box-level editing, in a 5.6-billion-parameter model built for speed. Here's how that plays out on architecture work.

Edits stay inside the box

In our tests, a 2K Regional Edit left everything outside the boxes within a pixel of the original view. Draw a box, say what goes in it, and the rest of the render is untouched.

FLUX 3 quality, smaller model

Black Forest Labs' own evaluations rate it above Flux 2 Pro and Ideogram 4.5, and 91 Elo ahead of Flux 2 Klein 9B on text-to-image, at 5.6B parameters.

Built for quick rounds

It's one of the lowest-cost models in Fenestra, so it suits the early stage where you want ten options on the table before you pick one.

Native 4K

Pick 4K for the final board and it comes straight from the model, with no upscaler in the chain.

Workflow

How Do You Use Flux 3 Klein?

Upload a view, pick Flux 3 Klein in Create, Edit or Regional Edit, describe the result or draw boxes, then choose 1K, 2K or 4K. Nothing to install.

Step 1

Upload the view

A render, a viewport screenshot, a photograph or a sketch. JPG or PNG.

Step 2

Pick Flux 3 Klein

From the model list in Create, Edit or Regional Edit.

Step 3

Draw boxes, or describe the result

In Regional Edit, draw a box over each part to change and give it its own prompt. Elsewhere, describe the finished image and what stays.

Step 4

Download at the size you need

1K to explore, 2K for Regional Edits and client review, 4K for the final board.

Model Facts

Flux 3 Klein Specs at a Glance

Resolution, inputs and release details, and what you get back from it in Fenestra.

Brick and charred timber house at winter dusk with frost on the garden and lit windows, edited by Flux 3 Klein

Up to 4K

Native 4K from the model, no upscaler in the chain

Black Forest Labs

The team behind Flux 3, Flux 2 Pro and Flux Kontext

15 October 2026

Released by Black Forest Labs

1K · 2K · 4K

Pick the output resolution per generation

Create + Edit

Text-to-image and image editing in one model

Brick house with its upper storey re-clad in charred black timber by a Regional Edit in Flux 3 Klein

Regional Edit

Boxes with a prompt each; the rest of the view is left as it was

5.6B parameters

Open weights from Black Forest Labs; in Fenestra it runs in the cloud

Commercial rights

Included on every paid plan

Edits

What Is Flux 3 Klein Good For?

On architecture and interior work, these are the jobs we'd give it.

Regional edits

Quick options

Material swap

Interiors from text

Weather and time of day

Sketch to render

Prompts

How Do You Prompt Flux 3 Klein?

Describe the finished image with the change folded in, and name what should stay. Three generations and the exact prompt behind each.

01Create

A house from a text prompt

architectural photograph of a two-storey family house in a Copenhagen suburb, pale buff brick ground floor with deep-set windows, cantilevered upper storey clad in vertical light oak boards, flat roof with a thin zinc edge, front lawn with a gravel path and a low birch hedge, overcast soft daylight, eye-level three-quarter view from the street, 35mm lens

02Regional Edit

One box, nothing else moves

Box over the upper storey: the same upper storey clad in charred black timber boards, windows unchanged

03Edit

Winter dusk, same house

the same house and garden at dusk in winter, a light layer of snow on the lawn, the hedge and the roof edge, warm light in every window, deep blue sky, street lamps on, camera unchanged

What design teams say about Fenestra

More than 200,000 renders have been generated in Fenestra. Here is how practices use it on client work.

“Great tool for initial concepts. We provide new house and land packages and use Fenestra to update external colour scheme facade renders and floor plans for marketing purposes. Fenestra is a quick way to provide the images to clients to visualise their new home.
Michelle Morrison
Designer · Urbane Homes
Urbane Homes
“Fenestra is a great tool and works really well for us. We’re using it to help establish a new internal standard for visualisation across the office, making it easier for high-quality visuals to become part of our standard project package.
Bjørn Polzin
Head of Planning · apoprojekt
apoprojekt
“What sets Fenestra apart is the people behind it. The team is always available, genuinely listens to user needs, and provides a level of support that is responsive, approachable, and highly professional.
Raquel González
Real Estate Marketing Department · VAPF
VAPF

Pick your plan

Every tool in one license — for a desk of one or the whole studio. Upgrade or cancel anytime.

Save 20% on yearly plans

Individual

Perfect for students & solo designers

$10$8/mo

Billed yearly ($96/yr)

Save 20%
200credits /mo

4¢ per credit

~ 200 renders

~ 20 AI videos

Get Individual

Cancel anytime

  • ~100 enhanced renders /mo
  • Image editing
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  • Unlimited projects
  • Fast rendering
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  • Early access to new features
  • Shared credit pool
  • Admin controls
  • One invoice for the team

Pro

Popular

Perfect for Professionals

$35$28/mo

Billed yearly ($336/yr)

Save 20%
1,000credits /mo

2.8¢ per credit

~ 1,000 renders

~ 100 AI videos

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Private by default · We don't train on your data
  • ~500 enhanced renders /mo
  • Image editing
  • Invite people to edit your canvas
  • Unlimited projects
  • Fast rendering
  • Fast support
  • Early access to new features
  • Shared credit pool
  • Admin controls
  • One invoice for the team

Studio

Best value

For professionals and studios creating at scale

$60$48/mo

Billed yearly ($576/yr)

Save 20%
2k4k6k8k
2,000credits /mo

2.4¢ per credit

~ 2,000 renders

~ 200 AI videos

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Private by default · We don't train on your data
  • ~1,000 enhanced renders /mo
  • Professional image editing
  • Invite people to edit your canvas
  • Unlimited projects
  • Priority rendering
  • Priority support
  • Early access to new features
  • Shared credit pool
  • Admin controls
  • One invoice for the team

Teams

Perfect for small teams

$250$208/mo

Billed yearly ($2500/yr)

2 months free
5k10k
5,000shared credits /mo

Up to 5 seats

~ 5,000 renders

~ 500 AI videos

Get Teams

Cancel anytime

Private by default · We don't train on your data
  • ~2,500 enhanced renders /mo
  • Professional image editing
  • Invite people to edit your canvas
  • Unlimited projects
  • Priority rendering
  • Priority support
  • Early access to new features
  • Shared credit pool
  • Admin controls
  • One invoice for the team

Enterprise.

Volume pricing, SSO, dedicated onboarding, private deployment.

Book a demo

Flux 3 Klein FAQs

What you'll want to know before putting Flux 3 Klein on a client job.

Flux 3 Klein, full name FLUX 3 Image Klein, is the 5.6-billion-parameter image model Black Forest Labs released on 15 October 2026. It has the full FLUX 3 Image model's native 4K, local editing and layout boxes in a smaller, faster model. In Fenestra it's in Create, Edit and Regional Edit.
Flux 3 is the larger model; Klein is the small, fast one from the same family. Both edit locally, output at 1K, 2K and 4K, and work with Regional Edit in Fenestra. We'd use Klein for quick rounds and box edits, and Flux 3 for the final hero image and for composing a room from several references. Klein uses fewer credits.
Use Flux 3 Klein to create from text, for Regional Edit boxes, for 4K, or for quick low-cost rounds. Use Krea 3 Edit for edits to an existing view that follow a detailed brief, like a line drawing and a material palette, with Medium, High or Ultra quality at 1K or 2K. Both are in Fenestra, so run the same edit through each and keep the better one.
Open a project and pick Flux 3 Klein in Create, Edit or Regional Edit. In Create and Edit, describe the finished image with the change folded in and name what should stay. In Regional Edit, draw a box over each part to change and give it its own prompt. Then set the resolution: 2K is what we use for Regional Edits.
Yes. Everything you generate on a paid plan comes with full commercial rights, covering client presentations, competition submissions, your website and social channels.
Its weights are open under the FLUX Kommunity License, which allows free commercial use for individuals and companies with under $5M annual revenue. Larger organisations need a licence or the API. In Fenestra you don't need the weights or a GPU: it runs in the cloud, and everything you make on a paid plan comes with commercial rights.
On Black Forest Labs' own evaluations it gains 91 Elo over Flux 2 Klein 9B in text-to-image and 70 in image editing, with 38% fewer parameters. It also adds native 4K and layout boxes. Flux 2 Klein 4B is still in the model list if you want to compare the two on your own view.
It's included on every Fenestra plan and is one of the lowest-cost models we offer. The cost scales with resolution, so 4K costs the most, and the exact figure is on the generate button before you run it.
A text prompt in Create, or a JPG or PNG view to edit: a render, a viewport screenshot, a photograph or a sketch. To furnish a room from a board of reference pieces, we'd reach for Flux 3 or Nano Banana 2.1 instead.

Start with one view.