MiniMax H3 Save Image

Every PreStage render ends at MiniMax H3 Save Image: the still, written as a PNG under output/, with the workflow embedded in its text chunks so a dropped file rebuilds the node that made it. It's the image-side bookend to H3 Save, which does the same job for video - and like that node, it's an MiniMax/internal output node written into the graph by the PreStage rather than placed from the menu.

It's deliberately boring, and that's the point. The one thing it does beyond "save a PNG like core's Save Image" is report the result under two keys: the standard ComfyUI images key, so it shows up in every normal history/asset surface, and a private mmc_image key, so the PreStage Image Lab can match the result to its review batch and hand-off state. That double report is what lets the review-then-video handoff work without any guesswork about which file belongs to which stage card.

Inputs

• images - the still(s) to write. It'll happily save a whole batch, one PNG per image.
• filename_prefix - where they land, default minimax/stills/prestage → ComfyUI/output/minimax/stills/prestage_00001_.png.

No outputs - it's an output node.

What it writes

Each image is saved as 8-bit PNG with the prompt and extra_pnginfo from the execution embedded as PNG text chunks - the same metadata core's savers write, and skipped the same way when you run with --disable-metadata. So a still you like can be dragged back onto the canvas and ComfyUI rebuilds the PreStage state that produced it. That's the property that makes the whole "pre-stage a keyframe, hand it to the video" flow reversible and shareable.

The troubleshooting angle

Because the handoff from PreStage to Creator is by file, not by graph edge, there's no ordering edge to get wrong - but that also means the Creator can't find a still that was never saved. If your video renders show "no first frame" even though you just generated one, check that the PreStage actually ran (a cached PreStage with unchanged inputs is a cache hit - which is a feature, it doesn't rerun) and that the file is in output/ where the picker already looks. The pack's UI points at output/minimax/stills/ by convention, so keep the prefix in that family if you change it.

Install is the shared one: ComfyUI Manager → search "H3 Creator Palette", or git clone https://github.com/z3rofeels/ComfyUI-H3-Creator-Palette into custom_nodes/, restart, hard-refresh. Needs ComfyUI 0.34.0+. No extra Python packages; the PIL PNG writing is core ComfyUI's own stack.