Reactor Sequence Visualizer

This one is a viewer, and I'd argue it's the most valuable node in the pack after the Realtime window. You wire a sequence in, and it draws your segments and camera moves on a frame ruler - snapped to the model's own chunk boundaries, which is the part that matters. It has no outputs, because it isn't there to do anything. It's there to tell you the truth before you spend a render.

What it's for

Every model in this pack has a rhythm that isn't your rhythm. LingBot and LingBot World 2 chunk at 24 frames with a shorter first chunk of 17. Helios and Visko Orbis chunk at 33. LongLive-2.0 goes 29 then 32. FastH3 hands you a clip per prompt and lands on 158 frames where you asked for six seconds. Set a segment to 100 frames and the model rounds; set a camera move to 10 frames on a 33-frame-chunk model and it can't be shorter than one chunk.

You find all of that out the wrong way - by rendering, waiting, and watching a move land a beat late. The visualizer shows you the grid first, which is the difference between scripting a sequence and guessing at one.

How it actually works

The node reads the sequence you feed it (the last segment of a chain, or a Reactor Sequence Join) and draws it in a canvas attached to the node: each segment as a band on a frame ruler, each camera move as a labelled block on its own lane, all of it snapped to the model's chunk edges as they'll actually play. Invalid entries are drawn red rather than hidden.

It's strictly read-only. Editing happens on the segment node, which is a deliberate choice by the author - the tooltip says as much: "It only shows the sequence; edit a segment on its own node." So it's a monitor, not a mixer.

Inputs and outputs

• sequence - the sequence to draw: a chain's last segment, or a Join.
• Outputs: none. It's a display node; leave it dangling at the end of a wire.

Install

Manager search comfyui-reactor-api, or by hand:

cd ComfyUI/custom_nodes
git clone https://github.com/reactor-team/comfyui-reactor-api
pip install -r comfyui-reactor-api/requirements.txt

Restart ComfyUI and the nodes appear under Reactor. There's one Python dependency (reactor-sdk>=1.6) and no models to download - the models run on Reactor's servers. The other install step is the one everyone forgets: an API key, either REACTOR_API_KEY in ComfyUI's environment or under [API] in config.ini. The visualizer itself needs no key, since nothing is being called, which makes it a handy way to check a sequence while you sort out billing.

Where people get burned

It won't render anything. Wiring this as the final node and queueing gives you a picture and nothing else. Send the sequence to Reactor Render for output.

Red isn't decoration. A move drawn in red is one the model will refuse or shorten: a move on a lane the model doesn't have, a move shorter than a single chunk, a segment that runs past max_scene_chunks for models that cap a single scene. The node also flags segments that would be dropped, like an image attached to a later segment on a model that only reads a reference at the start. Fix these on the segment nodes.

It reflects chunk snapping, not a rendered frame count. The ruler is computed from the model's chunk arithmetic, not from a session. It's accurate about boundaries and warnings; it doesn't tell you what the model will invent inside them.

What to actually use it for

Three habits. Check the total length before a long render - chunk rounding adds up over nine segments. Check camera moves when you continue one across a segment boundary; a move ends with its segment and needs re-declaring on the next one, which is easy to forget. And check cut versus shot transitions when they matter, because a cut starts a fresh scene and that changes the chunk grid underneath it.