H3RelayInternalVideoOutput

H3RelayInternalVideoOutput might be the fastest node in the entire pack, because it does almost nothing: it takes the path to an assembled MP4 and shows it in the ComfyUI workflow with the standard playback controls. No copying, no re-encoding, no touching the file at all. Think of it as a playback window bolted onto the end of your pipeline.

It's one of the nodes H3 Relay vendors from the Comfy-Org MiniMax H3 Contex Loop runtime (the conditioning/minimax/contex_loop category is the giveaway) and re-registers under its own namespaced id. Upstream's public registration is disabled; H3 Relay re-exports the runtime under H3RelayInternal* names so its graph-builder nodes can use it internally.

What you feed it

Exactly one required input:

• video_path (STRING) - per the tooltip, connect the video_path output from H3 Chain Assemble (H3 Relay's own Assemble node also emits a video_path, so either works). The completed MP4 shows up with ComfyUI's standard playback controls.

There are no outputs, and the node is flagged as an output node, so it's a terminal - it just presents, it doesn't pass anything on.

How it works

The preview method resolves the path against ComfyUI's output root, checks the file actually exists, and verifies the extension is browser-playable (.mp4, .webm, .mov, or .mkv). Then it hands the file to ComfyUI's standard preview UI with animated=True, which is what makes the frontend swap in its video player. If the file's missing you get a FileNotFoundError naming the path; if the extension is wrong you get a polite lecture about browser-playable formats.

The useful property, the one that makes this node worth having: because it doesn't copy or re-encode, a movie assembled from a long chain of shots can be previewed instantly, and previews don't create duplicate data blocks or accidentally "publish" something under output/. H3 Relay keeps its intermediates in the protected user/__h3_relay_cache; hard-linked browser previews live in ComfyUI's temp. When you actually want to publish, that's what a Save Video node (or H3 Relay · Assemble, which always writes the final movie to output/) is for.

Install and gotchas

Shared pack install: ComfyUI Manager → search H3 Relay, install, restart - or git clone https://github.com/akatz-ai/h3-relay into custom_nodes. Needs ComfyUI 0.32.0+, FFmpeg on PATH, and the MiniMax H3 + LTX 2.5 models from MODELS.md, which are separately licensed (the H3 Community License excludes the US, EU, UK, and Korea, so check before you run).

The only real gotcha is wiring a stale path: if the path points at a file that was pruned from the cache, you get a not-found error. Re-run the assembler (it's cached, so it's fast) rather than hunting for the file yourself.