FreeU_motorway_edition

FreeU is a diffusion-era relic that refuses to die: a model patch from 2023 that boosts fine detail by playing with the U-Net's frequency content. It splits each decoder block's output, scales the low-frequency half with b1/b2, and attenuates the high-frequency half with s1/s2 via a Fourier filter. The effect is sharper textures at the cost of possible oversharpening and color shifts. This is the Motorway-ed version from agilly1989/ComfyUI_agilly1989_motorway: the patch is identical, but the model is read from a key on the pipe and the patched model is written back to a key.

The inputs that matter

• b1 (default 1.1) and b2 (default 1.2) - how much to boost the backbone (low-frequency) features at the two patched block depths. Above 1 amplifies, which is what restores detail.
• s1 (default 0.9) and s2 (default 0.2) - how much to scale down the skip-connection (high-frequency) features. Below 1 suppresses noise.
• INPUT_model_key (default model) - where the base model is on the Motorway.
• OUTPUT_MODEL_key (default MODEL) - where the patched model goes.

Output is the MOTORWAY pipe.

The honest take

FreeU's reputation is very 2024. It genuinely rescued mid-step detail on SD 1.5/SDXL at low step counts, and it became a fixture of "make images crisper" workflows. Two things have happened since. First, the defaults are a starting point, not a guarantee - b1/s1/b2/s2 want tuning per checkpoint, and the wrong values produce that characteristic "oil painting / oversharpened" look. Second, on modern architectures the patch mostly doesn't land: it targets U-Net block layouts, and flow-matching transformers are a different animal. On Flux or any 2025+ model, FreeU is usually a no-op or a liability.

So: if you run SD 1.5/SDXL and want a subtle crispness bump, this is a legitimately famous tool. If you're on modern weights, this is the node you skip. It's a "know what era you're in" purchase, not a universal detail knob.

Install

cd ComfyUI/custom_nodes
git clone https://github.com/agilly1989/ComfyUI_agilly1989_motorway

Restart ComfyUI, or install via ComfyUI Manager under "ComfyUI_agilly1989_motorway." No extra dependencies.

Standing pack caveat: v1.1.7's pyproject.toml calls itself "HOTFIX - REMOVED MONKEYPATCH AND GENERATED NODES," and the generated clones are commented out of __init__.py. Core Motorway nodes work; the _motorway_edition clones may not be in your menu until the author re-enables them. Missing? Core FreeU is the same patch, and a Motorway 1x0 ramp can park its output on the bus by hand.