Model reference · open weights

shuttle-3-diffusion

Image shuttleai Text→image 1 build Open weights 3k dl/mo

shuttle-3-diffusion is an open-weight image model from shuttleai. shuttle-3-diffusion (BF16) weighs 33.7 GB; the smallest configuration that runs it is RTX 5090 32 GB.

For self-hosting, compare this build's requirements below with the GPU you plan to rent.

  • Shuttle 3 Diffusion is an 11.9B parameter text-to-image model developed by shuttleai that generates images from English prompts in just four steps.
  • It is based on Flux.1 Schnell and is designed to produce detailed images with enhanced typography and resource efficiency.
  • The model is available under the Apache 2.0 license and supports bfloat16, GGUF, and fp8 formats.

Summary of the shuttleai/shuttle-3-diffusion model card, 2026-10-01

What it is

Released byshuttleai
Released2024-11-12
Parameters11.9B
VRAM33.7 GB for the weights

What it runs on

Memory and cards for shuttle-3-diffusion (BF16)

33.7 GBweights, file size
23.8 GBbiggest part
5.0 GBworking memory, one 1024² image
537 MBruntime overhead
CardOne imageMemory
RTX 3060 12 GB … RTX 4090 24 GBdoes not fit
RTX 5090 32 GBtight (encoders offloaded)31.0 GB
L40S 48 GBtight44.0 GB
A100 80 GBfits78.2 GB
H100 80 GBfits78.1 GB
RTX PRO 6000 Blackwell 96 GBfits93.8 GB
DGX Spark (GB10) 128 GB unifiedfits107 GB
H200 141 GBfits138 GB
B200 180 GBfits176 GB

From the model card

What shuttleai says about shuttle-3-diffusion

Read the model card

Model Variants

These model variants provide different precision levels and formats optimized for diverse hardware capabilities and use cases

Shuttle 3 Diffusion is a text-to-image AI model designed to create detailed and diverse images from textual prompts in just 4 steps. It offers enhanced performance in image quality, typography, understanding complex prompts, and resource efficiency.

You can try out the model through a website at https://chat.shuttleai.com/images

Using the model via API

You can use Shuttle 3 Diffusion via API through ShuttleAI

Using the model with 🧨 Diffusers

Install or upgrade diffusers

pip install -U diffusers

Then you can use DiffusionPipeline to run the model

import torch
from diffusers import DiffusionPipeline

# Load the diffusion pipeline from a pretrained model, using bfloat16 for tensor types.
pipe = DiffusionPipeline.from_pretrained(
    "shuttleai/shuttle-3-diffusion", torch_dtype=torch.bfloat16
).to("cuda")

# Uncomment the following line to save VRAM by offloading the model to CPU if needed.
# pipe.enable_model_cpu_offload()

# Uncomment the lines below to enable torch.compile for potential performance boosts on compatible GPUs.
# Note that this can increase loading times considerably.
# pipe.transformer.to(memory_format=torch.channels_last)
# pipe.transformer = torch.compile(
#     pipe.transformer, mode="max-autotune", fullgraph=True
# )

# Set your prompt for image generation.
prompt = "A cat holding a sign that says hello world"

# Generate the image using the diffusion pipeline.
image = pipe(
    prompt,
    height=1024,
    width=1024,
    guidance_scale=3.5,
    num_inference_steps=4,
    max_sequence_length=256,
    # Uncomment the line below to use a manual seed for reproducible results.
    # generator=torch.Generator("cpu").manual_seed(0)
).images[0]

# Save the generated image.
image.save("shuttle.png")

To learn more check out the diffusers documentation

Using the model with ComfyUI

To run local inference with Shuttle 3 Diffusion using ComfyUI, you can use this safetensors file.

Comparison to other models

Shuttle 3 Diffusion can produce images better images than Flux Dev in just four steps, while being licensed under Apache 2. More examples

Training Details

Shuttle 3 Diffusion uses Flux.1 Schnell as its base. It can produce images similar to Flux Dev or Pro in just 4 steps, and it is licensed under Apache 2. The model was partially de-distilled during training. When used beyond 10 steps, it enters "refiner mode," enhancing image details without altering the composition. We overcame the limitations of the Schnell-series models by employing a special training method, resulting in improved details and colors.

Quoted from the model card on Hugging Face. The full card is behind the Hugging Face link above.

Running it yourself

Run it on a rented GPU

Rent a machine by the hour. ComfyUI is installed on it. Open ComfyUI through the tunnel and load the workflow from the model's card on Hugging Face; choose this model's file in its loader.

# on your rented machine: pip install diffusers transformers accelerate
import torch
from diffusers import DiffusionPipeline

pipe = DiffusionPipeline.from_pretrained("shuttleai/shuttle-3-diffusion", torch_dtype=torch.bfloat16).to("cuda")
image = pipe(prompt="a red bicycle on a cobbled street").images[0]
image.save("/workspace/out.png")
Renting a GPU: connect, tunnels, Python
# on your rented machine (the ssh line is on its page in the console)
# get REPO FILE FOLDER: one file into /workspace/models/FOLDER, where ComfyUI loads it from
get() { hf download "$1" "$2" --local-dir /workspace/hf-files && mkdir -p "/workspace/models/$3" && mv "/workspace/hf-files/$2" "/workspace/models/$3/$4"; }

# the model (22.1 GB)
get shuttleai/shuttle-3-diffusion shuttle-3-diffusion.safetensors diffusion_models

start-comfyui
Renting a GPU: connect, tunnels, ComfyUI
# on your computer, in a second terminal: ComfyUI in your browser at http://localhost:8188
# HOST, PORT and BOOKING are your machine's, from its page in the console
ssh -o HostKeyAlias=axforge-BOOKING -o StrictHostKeyChecking=accept-new -L 8188:localhost:8188 dev@HOST -p PORT
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