MiniMax H3 · LTX Master Delivery Save

In the R42 universal delivery system, segments get generated and checkpointed natively, and then one of several routes turns them into a deliverable. IAMCCS_MiniMaxH3UniversalMasterSaveR42 is the route that writes the master - the finished, editor-ready LTX film with audio, saved as a single file. Display name: LTX Master Delivery Save. It's the payoff node for the master-delivery branch, and it only fires when the whole native film is actually done.

That last point is the whole design. This node is lazy in the ComfyUI sense: it accepts a master_ready boolean and only requests its heavy inputs when that flag is true. The native checkpoint sets the flag, and only after the entire native master is checkpointed and merged (which the R42 checkpoint logic guarantees for master routes) does this node wake up and ask for the frames and audio. It's a deliberate two-phase structure: H3 does all the generation first, LTX does the finishing, and this node is the bridge that makes sure LTX never sees a half-finished programme.

It also only accepts the physically connected route. The optional inputs are a set of mutually exclusive image sockets - ltx_frames, wan_frames, h3_latent_frames - each paired with a route. Whichever route the shot plan selected determines which single socket it pulls, and its check_lazy_status requests exactly that one. If the selected route says LTX but you connected wan_frames, it errors with a clear "its lazy IMAGE branch is not connected" message rather than guessing.

Inputs and outputs

Required: cine_linx (shot plan), master_ready (from the checkpoint), resolved_render_id, and fps. Optional: master_audio and the three frame sockets, plus current_segment/total_segments (required for the per-shot LTX route) and filename_prefix (default IAMCCS/MiniMaxH3/UNIVERSAL_R42). Outputs: video_path and report.

Two behaviors to know. In master mode it writes one <run>_ltx23_full.mp4. In the LTX per-shot route it writes segment_XXXX.mp4 files under an LTX_PER_SHOT folder and can queue the next segment itself, mirroring the per-segment delivery pattern. Both refuse to overwrite existing files - a new render id is the way to rerun.

The honest take

This node assumes you have an LTX finishing pipeline available - it's encoding frames plus master audio through LTX-compatible video encode, not inventing one. If your deliverable is "give me the finished film file," this is the master-delivery end of the R42 graph and you reach for it whenever the shot plan's route is an LTX master route. If you're only doing per-segment native delivery, this node never fires at all and that's correct.

The trap for beginners is subtle: nothing happens if master_ready is false, and the node reports exactly that ("waiting for completed native master"). If your R42 run produces no master file, check that the checkpoint actually finished and merged all segments - this node is waiting on it, and its silence is the signal.

Install

Part of IAMCCS-nodes:

cd ComfyUI/custom_nodes
git clone https://github.com/IAMCCS/IAMCCS-nodes

or ComfyUI Manager (search "IAMCCS"), restart. You need the H3 stack (current ComfyUI ≥ 3.x, H3 weights and video/audio VAEs) plus an LTX-2/LTX-2.3 finishing setup for the encode path, per the README's dependency matrix. And the standing H3 licence reminder: no US, EU, UK or Korea on the local weights.