FlipSigmas_motorway_edition

FlipSigmas does one thing: it takes a list of sigma values - the noise levels your sampler steps through - and reverses their order. That's it. The reason that's a useful thing is that sigma schedules are directional. Normal denoising walks from loud to quiet; flip that and you're asking the sampler to walk from quiet to loud, which is exactly what a couple of weird-but-real advanced techniques want.

This is the Motorway-ed version from agilly1989/ComfyUI_agilly1989_motorway: it reads sigmas off the pipe under one key, reverses them, and writes them back under another.

The inputs

• INPUT_sigmas_key (default sigmas) - where the sigma tensor lives on the Motorway.
• OUTPUT_SIGMAS_key (default SIGMAS) - the key the reversed sigmas are written to.

Output is the MOTORWAY pipe. Two keys, one reversal, no widgets, no settings. It's about as thin a node as this pack has - which is fine, because the technique it serves is the interesting part.

Why you'd ever flip a schedule

The main reason is negative CFG, also known as the "prompt inversion" / unCLIP-style trick: you run the sampling with CFG scaled negative, so the model is pushed toward what it normally runs away from. A reversed sigma schedule is part of how people make that work in ComfyUI's custom-sampling setup. You'll also see it in some img2img and refiner schemes where the community found that walking the schedule backwards around a specific sigma range gives different, sometimes better, texture behavior.

Reality check: this is a niche power-user move, not a quality default. If you're new, don't add FlipSigmas to a workflow because a tutorial said it looks cool - add it when you specifically want negative-CFG-style behavior or a reverse pass. On modern flow-matching models the aggressive-schedule tricks mostly backfire anyway, so the audience for this node skews toward SD 1.5/SDXL experimentation.

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.

And the standing pack note: v1.1.7's pyproject.toml reads "HOTFIX - REMOVED MONKEYPATCH AND GENERATED NODES," with the clone nodes 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 FlipSigmas does the same reversal, and a ramp gets the sigmas onto the bus by hand.