LC Stop 🛑

ComfyUI will happily run a thirty-node graph end to end without giving you a chance to look at the halfway result. Most of the time that's the point. But when the second half of your workflow is expensive - a big upscale, a tiled pass, a video encode - you sometimes want it to stop at a checkpoint so you can inspect the frame before committing. LC Stop is that checkpoint: a breakpoint you drop into the graph.

The behavior is a pass-through plus an interrupt. When enable is ON, the node passes its data through and then stops the queue - so whatever upstream produced is available for inspection, and the run halts right there. You continue by hitting the play button on the node's title bar or queueing again. When enable is OFF (or the node is bypassed), it passes data through without stopping - the whole graph runs as if the node weren't there.

How it works

Mechanically it's the mxStop pattern: any-type input in, same data out, and an interrupt_processing() call when enabled. Because the input and output are * (wildcard), you can drop it anywhere in a graph without caring what type is flowing - model, latent, image, conditioning, whatever. It also declares VALIDATE_INPUTS so the type-checker leaves it alone.

The inputs

• In - anything, passed straight through.
• enable - the switch: ON = "stop here" (labeled STOP), OFF = pass through silently.

Output: Out, the same value that came in.

Where it earns its keep

• Before a heavy upscale or detailer pass, so you can verify the base image is worth spending the render on.
• Between generation and post-process, as a manual "inspect before committing" gate.
• In interactive setups where you want a human decision point mid-graph.

Install

It's in the LC123 pack - ComfyUI Manager (search "LC123") or:

cd ComfyUI/custom_nodes
git clone https://github.com/lonecatone23/ComfyUI_LC123_nodes

Restart. No extra pip packages; MIT licensed. Cloud-hosted ComfyUI won't have LC123 until you request it - request or run local.

The honest caveat

A stop node pauses the whole queue, which means if you forget it's enabled, your batch grinds to a halt at a checkpoint you didn't mean to keep. That's why the enable switch exists - use it, and get in the habit of leaving it OFF until you actually want a pause. It's a tiny tool with one job, but for expensive two-stage graphs it's the difference between trusting the process and watching it.