Model Input Switch

Model Input Switch is a router. You wire two MODEL inputs into it, give it a boolean, and it passes through one or the other. The README's description is the whole node: "switch between two model inputs based on a boolean switch." It's part of WAS's big family of Input Switch nodes - there's one for CLIP, VAE, ControlNet, LoRA, conditioning, latents, images, numbers, text - all the same idea for different data types.

Why bother

Because rewiring a graph by hand is annoying and error-prone. Say you've built one workflow but want to A/B two checkpoints through the identical downstream chain - same sampler, same prompt, same everything. Without a switch you're dragging noodles back and forth. With this, you flip a boolean and the whole pipeline runs the other model. Toggle it a few times, compare, done.

It's also the building block for conditional graphs: drive the boolean from a logic node instead of setting it by hand, and the switch picks the model based on something computed upstream. That's how you assemble a workflow that behaves differently depending on an input, without maintaining two separate graphs.

How it works

Two model inputs, one boolean, one MODEL output. The boolean decides which input reaches the output; that output goes to your KSampler (or wherever the model needs to land) exactly as if it were connected directly. There's nothing to configure beyond which side is which.

The gotcha worth knowing

Here's the thing people assume and get wrong: a switch does not save you the compute of the branch you didn't pick. In ComfyUI, a node's inputs are all resolved before it runs, so both upstream branches feeding the switch get evaluated. For a Model Input Switch that usually doesn't matter much - loading a checkpoint is cheap-ish and cached - but if either branch does real work (a heavy LoRA stack, a model patch, anything expensive), you're paying for both even though only one comes out. If avoiding that cost is the point, the lazy switch nodes in rgthree-comfy only evaluate the branch they select, and that's the tool for the job. For a plain "pick model A or B," WAS's switch is perfectly fine.

Installing it

Comes with WAS Node Suite. Install the pack through ComfyUI Manager (search was-node-suite-comfyui, install, restart) or clone it:

cd ComfyUI/custom_nodes
git clone https://github.com/WASasquatch/was-node-suite-comfyui

install requirements.txt, restart. No models, no heavy deps - it's pure routing logic.

Troubleshooting

The node itself basically can't break. The pack can: WAS Node Suite has been unmaintained since December 2023, and the usual symptom is the whole suite failing to import ("Import Failed") after a ComfyUI update, caused by a pinned dependency (opencv most often) clashing with the new version. Reinstall requirements.txt into the correct venv - activate it first, or use the bundled install.bat - and the switches come back with everything else.