🔍 Sigma Viewer

SIGMAS is one of those ComfyUI types that's completely opaque until something goes wrong. It's just a tensor of numbers flowing between your scheduler and your sampler, and by default you have no way to look at it - you either trust the node that made it, or you don't. SigmaViewer is the fix: drop it into that connection and it hands the same schedule back out unchanged, plus a readable string of what's actually in it.

Why you'd want this at all

Every other node in this pack - the linear Z-Image-Turbo scheduler, the shift-based generic one, the resolution-aware Flux one, the preset picker - is generating a curve of sigma values you're trusting sight-unseen. Most of the time that's fine. But this pack's whole premise is that getting the shape of that curve wrong is exactly what breaks Z-Image-Turbo's distillation: the README is explicit that a non-linear schedule "breaks the distillation and produce[s] degraded results," and a wider community sweep on Z-Image Turbo found that reshaped schedules like Karras and exponential fail across the board on flow-matching models, not just underperform. When something looks off - burnt highlights, mushy detail, results that don't match what a working reference workflow produces - the honest first move is to check what you're actually feeding the sampler, not to guess. This node is that check.

The inputs and outputs that matter

It's deliberately minimal:

• sigmas (required, SIGMAS) - the schedule you want to inspect. Wire it in from whatever scheduler node is upstream - any of this pack's, or a stock ComfyUI one.

Two outputs:

• sigmas (SIGMAS) - the exact same values, unmodified. This node is a pass-through by design (its own description says so directly), so inserting it anywhere in your sigma chain changes nothing about your actual generation. It's safe to leave wired in permanently, not just for one-off debugging.
• info (STRING) - a text summary of the schedule. Route this into a text preview / "Show Text" node, or check ComfyUI's console output, to actually see the values rather than trusting them blind.

How to install it

Through ComfyUI Manager: search "ComfyUI-ZImageTurbo-FlowSampler," install, restart. Manually:

cd ComfyUI/custom_nodes
git clone https://github.com/capitan01R/ComfyUI-ZImageTurbo-FlowSampler

Restart afterward. Nothing else needed - this is the simplest node in the pack, no extra dependencies at all.

Common issues & troubleshooting

Not knowing where to look at the output. info is a STRING output, and ComfyUI doesn't display strings on the canvas by default - you need something downstream to render it, like a text-preview node, or you can check what gets printed to the console/log where ComfyUI is running.

Assuming it changes your generation. It doesn't, and shouldn't. If your results change after inserting SigmaViewer, something else in your graph moved at the same time - this node is explicitly a pass-through and isn't supposed to touch the values.

Using it to debug a problem that isn't actually about the schedule. If your sigmas look correct (a clean descending curve, right number of steps, ending at or near zero) but your images still look wrong, the issue is more likely your sampler choice, your CFG, or your model setup - not the scheduler. This node only tells you what numbers you're feeding the sampler, not whether the rest of your graph is doing the right thing with them.