H3RelayInternalSegmentSave

In a long-form H3 Relay movie, H3RelayInternalSegmentSave is the moment a shot stops being a draft and becomes canonical. You review the raw clip, you like it, and this node writes it to disk as an H.264 segment plus a safetensors resume checkpoint - the exact prompt metadata, the generated-audio WAV, and workflow-recovery sidecars. Every later stage (continuation, LTX finishing, assembly) builds on what this node commits. It's the "accept" step, and H3 Relay is structured so you do this before paying for any expensive enhancement.

It's another vendored node from the Comfy-Org MiniMax H3 Contex Loop runtime, re-registered under H3 Relay's namespace - the conditioning/minimax/contex_loop category is the tell. But in this pack it's load-bearing: the resumability story only works because a saved segment is the unit of "accepted work."

What you feed it

Three required inputs, and the tooltips are unusually specific because getting these wrong produces hard errors:

• state (H3_CHAIN_STATE) - current state from H3 Chain Current Shot.
• images (IMAGE) - delivered frames after MiniMax H3 Contex Loop Trim. The frame count must exactly match the scene's planned delivered length.
• sampled_latent (LATENT) - raw sampler output before VAE decoding. Its compact audio/video streams are what get saved for checkpoint resume and audio context.

Two optional inputs:

• audio (AUDIO) - delivered decoded audio after Loop Trim with match_tail enabled. The tooltip is blunt: connect it in every audio mode to preserve H3's generated sound as WAV sidecars. H3's native stereo audio is the whole reason to be here, so don't skip it.
• images_with_overlap (IMAGE) - blend-ready output from Loop Trim, required only when your Plan has video_blend_frames above 0.

Outputs and the one error you'll hit

It outputs segment (H3_CHAIN_SEGMENT - the persisted scene record for Review Gate and Loop End) and a status string with the saved scene number, paths, frame count, and duration.

The classic beginner failure: a frame-count mismatch. The node computes what you delivered versus what the plan promised and raises "produced N delivered frames; expected M" if they disagree. The fix is in the tooltip - wire the decoded images through Loop Trim before this node, so trimming happens before you commit. Feed it raw sampler output and it will rightly refuse to save a segment that won't line up with the rest of the chain.

Install

Shared pack install: ComfyUI Manager → search H3 Relay → restart, or git clone https://github.com/akatz-ai/h3-relay into custom_nodes. Requires ComfyUI 0.32.0+, FFmpeg on PATH, and the MiniMax H3 models from MODELS.md (separately licensed - check the H3 Community License territory clauses before you start).