ComfyUI-SPEED

ComfyUI custom node for SPEED — Spectral Progressive Diffusion for faster sampling. Progressively expands the latent resolution during denoising, reducing computation while preserving visual quality.

Official code: https://github.com/howardhx/speed

Key references:

• Project page: https://howardxiao.ca/speed/
• Paper (PDF): https://howardxiao.ca/speed/paper/paper.pdf
• arXiv: https://arxiv.org/abs/2605.18736

Workflow:

Speed comparison (FLUX preset, default parameters)

| SPEED sampler (this node) | Baseline (euler sampler) | | ------------------------------------------------------------------------- | ------------------------ | | mode=delta_optimal model_preset=flux scales=0.5,1.0 delta=0.01 transform=dct base_sampler=euler<br><br><br><br>20s<br>1.33x faster | <br><br>26.5s<br>1.00x |

Usage

1. Place this folder under your ComfyUI custom_nodes directory, then restart ComfyUI.
2. Connect the Sampler SPEED (Spectral Progressive Diffusion) output to SamplerCustomAdvanced.

Inputs

| Input | Type | Default | Description | |---|---|---|---| | base_sampler | combo | euler | Underlying ODE solver. Any comfy.k_diffusion.sampling sampler supported. | | transform | combo | dct | Spectral basis for expansion: dct (any ratio), dwt (2× only), fft (any ratio). | | mode | combo | delta_optimal | delta_optimal computes transitions from the power-spectrum preset. manual uses user-specified sigma thresholds. | | model_preset | combo | flux | Power-spectrum preset: flux, wan21, or custom (use spectrum_A / spectrum_beta). | | scales | string | 0.5,1.0 | Comma-separated resolution fractions ending at 1.0. e.g. 0.25,0.5,1.0. | | delta | float | 0.01 | Noise-dominated tolerance (Eq. 9). Smaller values delay transitions. | | manual_sigmas | string | 0.85 | Comma-separated sigma thresholds (one per transition). Used in manual mode. | | spectrum_A | float | 203.615 | Power-law amplitude (used when model_preset=custom). | | spectrum_beta | float | 1.915 | Power-law decay exponent (used when model_preset=custom). | | seed | int | 0 | Seed for spectral-noise padding at each transition. |

delta_optimal mode (recommended)

Set model_preset to flux or wan21 and adjust scales and delta. Transition timing is computed automatically from the VAE power spectrum using Eq. 9 and Eq. 10 of the paper.

manual mode

Set mode=manual and supply comma-separated sigma thresholds in manual_sigmas (one per transition between adjacent scales). Sigma decreases as denoising progresses, so the first threshold should be larger than the last (e.g. 0.95,0.85 for three scales).

Credits & license

This implementation is based on and derived from the official SPEED repository by Howard Xiao et al.:

• Official code: https://github.com/howardhx/speed (BSD 3-Clause)
• Paper: Xiao, H., Chao, B., Yariv, L., & Wetzstein, G. (2026). Spectral Progressive Diffusion for Efficient Image and Video Generation.

Please see the original project page and repository for full authorship, details, and license information.

BibTeX

@article{xiao2026spectral,
  author    = {Xiao, Howard and Chao, Brian and Yariv, Lior and Wetzstein, Gordon},
  title     = {Spectral Progressive Diffusion for Efficient Image and Video Generation},
  year      = {2026},
}