SN74LVC1G125

Yes, that's a real chip part number, and yes, the author named a ComfyUI node after it. The SN74LVC1G125 is a single bus buffer with an output-enable pin - in silicon, it either passes its input through or goes high-impedance (disconnected). This node does the software version: pass A through to Y, or block it, based on an enable toggle. mirabarukaso themed a whole little corner of the Mira pack after the 7400-series logic chips, and this is the buffer-gate one.

Under the whimsy it's a genuinely handy primitive: a conditional pass-through that works on any type. Because both A and Y are wildcard sockets, you can gate an image, a latent, a conditioning, a number - anything - on a single boolean. It's the "let this signal through only when the switch is on" node.

How it works

The logic is exactly the chip's truth table. When OE (output enable) is True, output Y equals input A. When OE is False, Y is None - nothing passes. That None is the interesting part: paired with a Mira node that reacts to None (their "Function Select Auto" picks whichever of two inputs isn't None, and "None To Zero" substitutes a default), you can build clean either/or routing without a big switch node. This gate decides whether a signal exists; another node decides what to do when it doesn't.

The inputs and outputs

• OE (BOOLEAN, default True) - the enable. True passes A; False blocks it.
• A (wildcard *) - the signal to gate. Any type.
• Y (wildcard *, output) - equals A when enabled, None when not.

Installing it

Install the pack. ComfyUI Manager: Manager -> Custom Nodes Manager, search ComfyUI_Mira, Install, restart. Or clone:

cd ComfyUI/custom_nodes
git clone https://github.com/mirabarukaso/ComfyUI_Mira.git

Restart, and if there's a load error run pip install -r requirements.txt inside the folder before restarting. No models.

Common issues

The thing that surprises people is what happens downstream when the gate is closed. Y becomes None, and a lot of ordinary ComfyUI nodes don't know what to do with a None input - they'll error rather than gracefully skip. This node is designed to feed None-aware nodes. If you wire a blocked Y straight into a normal image or conditioning node, expect it to complain. Route it through Mira's Function Select Auto or None To Zero to handle the empty case, which is the pattern the whole 74-family corner is built around.

The other note: the wildcard type means ComfyUI can't type-check the connection for you, so it's on you to keep A and its eventual consumer type-compatible. The gate passes whatever it's given, but the node downstream still has to accept that type.

It lives in ComfyUI_Mira, mirabarukaso's personal utility pack (they're better known for the WAI Character Select app). The 74-series naming is a bit of a dev in-joke - the README even links Wikipedia's list of 7400 chips - but the underlying node is a legitimately clean way to do conditional signal routing. If you want an XOR-style two-input version, its sibling SN74HC86 is right next to it in the menu.