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 20s 1.33x faster	26.5s 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},
}