VIV_Default

Straight to the point: VIV_Default is a deprecated utility node from vivax3794's ComfyUI-Sub-Nodes pack, and the source code flags it as such (DEPRECATED = True). It survived into the pack's releases because removing it would break old workflows that reference it, not because anyone thinks you should build with it. If you're writing a new graph, skip it. If you opened an old one and found it sitting there, here's what it was for.

What it did

It's a "use this value, or fall back to that one" passthrough. The node has two inputs and one output:

• default (required) - the value used when nothing else is connected.
• inp (optional) - the value that takes priority when it is connected.
• result - whichever of the two won.

In plain terms: result = inp if inp is not None else default. The whole node is that one line. It was a way to give a subgraph input a sensible fallback - feed the main value into inp, keep a safe default in default, and the graph keeps working even if a connection goes missing.

The type system is deliberately loose: both inputs and the output are * (any type), and the frontend extension copies whatever type is actually connected onto all three slots so the wires match up. It also doesn't error when you leave inp disconnected, which is exactly what a fallback node should do.

Why it's deprecated

The idea got absorbed. The pack's later versions moved defaults onto the VIV_Subgraph_Inputs node itself as widgets - you set the fallback right where the input is declared, and the calling node inherits it - which is a much cleaner place for a default than a separate passthrough node. VIV_Default is the leftover from before that existed.

Installing it

If you actually need it (an old workflow that references it), it comes with the pack. Install via ComfyUI Manager by searching for ComfyUI-Sub-Nodes, or:

cd ComfyUI/custom_nodes
git clone https://github.com/vivax3794/ComfyUI-Sub-Nodes

Restart ComfyUI. The only dependency is rich, and there are no model downloads. Note the pack is archived and unmaintained, so this deprecated node is a historical artifact twice over.

The honest verdict

You almost certainly don't need this node. A Primitive node plus a reroute, or just a manually typed default, does the same job more readably in a modern graph. The value of knowing about VIV_Default is mostly diagnostic: when you see it in an old Sub-Nodes workflow, it's telling you "this input has a fallback value," and you can safely delete it and hard-wire the value it was defaulting to. A useful relic, but a relic.