H3 Sigmas by Name (STRING -> SIGMAS)

H3 Sigmas by Name is the sibling of H3 Sampler by Name, doing for the noise schedule what that node does for the sampler: it converts a STRING scheduler name plus steps into a real SIGMAS object, so a single master control can drive the schedule across the whole graph. Without it, you'd be typing the same scheduler into several different nodes and hoping they never disagree. With it, one string fanning out to several of these adapters means every sampling node runs the identical schedule.

It's exactly the sort of node that looks pointless until you've burned a render on a mismatch - one stage at beta, the other at karras, and the two halves of the chain refuse to blend. MiniMax H3 is a flow-matching-style model where the sigma schedule genuinely changes the result, and the pack's own workflows ship on specific schedules (the CORE path uses beta, the full path uses RES4LYF's beta57). This node is how those schedules get into the graph from one place.

How it works

It wraps ComfyUI's built-in BasicScheduler - the same thing a KSampler uses when you pick a scheduler from its dropdown - but takes the scheduler name as a linked STRING instead of a per-node combo. You supply:

• model - the loaded H3 model, needed because sigma schedules are model-dependent.
• scheduler (STRING, forced input) - any scheduler name: beta, karras, simple, exponential, ddim_uniform, normal, and the rest.
• steps (INT, forced input, default 12) - how many steps the schedule spans.
• denoise (FLOAT, default 1.0) - a full-strength schedule by default; lower it only when you're deliberately doing partial denoising.

The output is a single SIGMAS socket for a custom sampler's sigmas input. If the scheduler name is wrong, you get the same kind of explicit error as the sampler adapter - named and early, not silent.

Installing it

Part of the ComfyUI-H3-Multishot pack:

cd ComfyUI/custom_nodes
git clone https://github.com/jlucasmcrell/ComfyUI-H3-Multishot

Or search H3 Multishot in ComfyUI Manager. Requires ComfyUI v0.30.0+. No extra Python dependencies - the pack's requirement list is deliberately empty because ComfyUI already ships everything it imports.

Gotchas

Two things worth knowing. First, scheduler and steps are forced inputs, so a bare typed widget won't work - they're meant to be wired from a master control. Second, if the full workflow's beta57 scheduler looks like it's missing, that's not this node's fault: beta57 comes from the RES4LYF pack (ClownsharkBatwing's sampler pack), and the workflow ships with RES4LYF as a dependency. Without it, switch the scheduler string to beta - the measured cost is roughly lip-sync 8/10 vs 10/10, everything else equal.