FLUX 3 Image: Native 4K, Bounding Boxes & Multi-Edit

👁 124 reads

Black Forest Labs released FLUX 3 Image on October 1, 2026 - the image generation component of the FLUX 3 family announced in July. Three features stand out: native 4K up to 5456 × 3072 px, scene composition using bounding boxes (each object gets coordinates), and editing multiple areas at once without touching the rest of the image. Through the fal.ai API it costs $0.024 per megapixel until October 8 (1K image ~$0.024, 4K ~$0.40), then double that. We tested it the same day.

The FLUX 3 family has now seen three releases. In July, Black Forest Labs showed a single model trained simultaneously on images, video, and audio. In August they released FLUX 3 Video, and on September 23 FLUX 3 Action for robot control. Images came last, after ten weeks of waiting.

What’s New in FLUX 3 Image

• Native 4K. Five resolution levels: 512sq, 768sq, 1k, 2k, and 4k. In 4k mode I got a 5456 × 3072 px image (16.8 Mpx) without separate upscaling.
• Bounding box composition. The canvas is a grid from 0 to 1000 regardless of aspect ratio. Each object gets an identifier, description, and bounding box in [y_min, x_min, y_max, x_max] format.
• Multiple edits at once. According to the maker, pixels outside the edited boxes remain bit-for-bit identical.
• Up to 10 reference images. In the prompt you reference them as ref_image_0 through ref_image_9. Through fal.ai each input image can be up to 4 Mpx.
• Better text rendering. The maker recommends the model for posters, ads, and infographics.
• Weights. Commercial license for weights is available immediately, and an open version is set to appear “within weeks.”

How a Bounding Box Prompt Looks

Instead of describing “lamp in the upper left corner,” you provide coordinates. Here’s my first test prompt, entered in the prompt field on fal.ai:

{"caption": "Editorial photo of a minimalist desk in a bright apartment, morning light, 35mm.",
 "elements": [
  {"id": "lamp_1", "bbox": [80, 60, 520, 300], "desc": "a brass desk lamp"},
  {"id": "plant_1", "bbox": [300, 700, 900, 960], "desc": "a tall monstera plant in a white pot"},
  {"id": "laptop_1", "bbox": [450, 320, 850, 680], "desc": "an open silver laptop showing a spreadsheet"},
  {"id": "mug_1", "bbox": [700, 80, 900, 260], "desc": "a red coffee mug with text "[BRAND]""}]}

Pricing and Access

At 1K resolution, FLUX 3 Image with the promotional pricing is several times cheaper than comparable models at highest quality. At 4K the difference disappears.

First Impressions from Testing

We ran three tests, each comparing FLUX 3 with top models: 4K under the magnifying glass, bounding box composition, and five edits in one prompt. Results and all images are in separate articles, with a summary in the FLUX hub.

• FLUX 3 under the magnifying glass: 4K vs. 6 models
• Bounding box composition: do objects land where you tell them
• 5 edits in one prompt: FLUX 3 vs. 6 models

// read moreFLUX 3 4K Test: Real Resolution vs 6 AI Image ModelsBenchmarksFLUX 3 Bounding Box Test vs 5 ModelsBenchmarksIdeogram 4.5: Multi-Edit Model That Doesn’t Break PhotosNews

Kinetyra