I'm wedging variations with a Wedge TOP and cooking my SOP network through an HDA Processor. I want the Switch SOP to pick its input based on the current wedge, but referencing the wedge attribute on the Switch doesn't seem to work.

I tried putting @wedgeindex in the Switch's Input parameter, and also tried a custom attribute I created on the Wedge node (@variant). Neither seems to resolve correctly when the network cooks through TOPs.

A few details:

Houdini 20.5
Switch SOP inside an HDA called by HDA Processor
Wedge TOP creates attributes: wedgeindex, variant (integer, range 0–3)
Switch has 4 inputs
Questions:

What is the correct expression syntax for the Switch Input parameter in this setup?
Should I use @wedgeindex, P@variant, or something else?
Does the Switch need to be configured differently when cooked via TOPs vs. interactively?
Any working examples would be appreciated. Thanks!