Mpi Simple Bool

MpiSimpleBoolean is a boolean in one end and the same boolean out the other. Input boolean (default true), output boolean, nothing else. That's the entire node, and if it feels pointless, you haven't hit the ComfyUI habit it exists for yet.

The habit is single-source-of-truth value nodes. ComfyUI lets you type a boolean straight into any widget, but if that value needs to reach three different nodes - a switch, a blocker, a router - you end up typing it three times, and the first time you forget to update one of them you get a silent mismatch where half the graph thinks the flag is on. The KB's node-plumbing essay calls this the "one seed, five samplers" pattern: break the value out of the widget, make it a socket, and fan it out from one authoritative source. MpiSimpleBoolean is the boolean-shaped version of that.

Why this one instead of MpiBoolean?

The pack also ships MpiBoolean, which outputs the same value as boolean, integer, and float simultaneously - handy when one consumer wants True/False and another wants 1/0. MpiSimpleBoolean deliberately strips that down to a single clean boolean socket. It's the same decision as MpiString vs MpiText: pick the minimal node whose socket type exactly matches what the graph needs. If you only need the boolean, a bare BOOLEAN output is easier to trace than a three-socket node with two outputs you're ignoring.

Install

It's part of ComfyUi-MpiNodes, so it comes with the pack. ComfyUI Manager (search "MpiNodes" or the publisher "mad-pony-interactive"), or:

cd ComfyUI/custom_nodes
git clone https://github.com/MadPonyInteractive/ComfyUi-MpiNodes

Restart ComfyUI. No dependencies, no model files - this node has a single widget and one line of logic.

Anything to watch?

Genuinely not much. The one thing to know is the widget's control_after_generate-style behavior doesn't exist here - it's a static toggle, so it never changes on its own. If you want a boolean that flips every run, that's a different node's job (a seed-driven toggle or the pack's probability routers). What this is for is being the one place a flag lives so every downstream consumer reads the same value. Boring, dependable, and exactly as useful as the plumbing it sits in.