MiniMax H3 Native Checkpoint Save

An H3 segment is expensive - minutes of sampling on a 12GB card. The Native Checkpoint Save exists so that work isn't one bad upscale away from the void. Its own docstring is refreshingly blunt: the node is a deliberately pass-through dependency. It writes the native segment to disk, and downstream LTX/Wan/RTX processing can't begin until that's done, so an upscale failure never discards the expensive H3 render. You can always come back to the checkpoint and try the finishing pass again.

What it does

Feed it images and audio plus the segment bookkeeping (current_segment, total_segments, fps, trim_head_frames), and it writes the segment to a numbered file under your output folder (IAMCCS/MiniMaxH3/segment by default, suffixed with the render id and stage label - so numbered filenames mean no take overwrites the last one). With merge_segments on, it also maintains a stitched master that grows as segments complete, and with queue_next_segment on, it triggers the queue loop to move to the next segment automatically. It passes images and audio back out (native_frames, native_audio) so the graph can keep flowing, and returns the resolved_render_id for downstream nodes to use.

It's an output node, so it's where a segment's native path terminates - and it takes the sampled_latent, motion_context, and motion_state inputs so the continuity handoff state gets persisted alongside the media.

How the pieces fit

In the full pipeline this is the gatekeeper between the generation backend and the upscale stage. The Generation V2 outputs native frames; this node commits them to disk; only then does the Native Master Load (or the upscale branch) get to see a complete programme. If you're hand-building and just want one segment saved with everything intact, this is the node - but note it demands the bookkeeping inputs, because the whole point is that it knows which segment it's committing.

Inputs and outputs

Required: images, audio, current_segment, total_segments, fps, trim_head_frames. Optional: bridge_images, resolved_render_id, filename_prefix, merge_segments, keep_segments, render_id, queue_next_segment, stage_label, sampled_latent, motion_context, motion_state. Outputs: native_frames, native_audio, resolved_render_id, report.

Installing it

Part of IAMCCS-nodes - ComfyUI Manager (search "IAMCCS") or git clone https://github.com/IAMCCS/IAMCCS-nodes.git into custom_nodes, restart. No extra dependencies beyond ComfyUI's native H3 support and ffmpeg for the encode.

Gotchas

trim_head_frames matters more than it looks: the saved segment is trimmed by that many frames, and if you feed the wrong value the timeline silently shifts. Keep render_id consistent across segments or the merge/checkpoint naming falls apart. And the pass-through is the feature - if an upscale fails, the checkpoint is your recovery point, so don't delete segment files while a render is still being finished.