Thread:Extension talk:MobileFrontend/Is the WMF still using Varnish to auto-detect mobile devices?

This page claims that it does detection at the cache layer, but I couldn't find a single file in the Operations git that does such a thing. There used to be a device-detection.vcl, but it's actually specifically removed by puppet:

So: did I miss something? If not, how does it currently work?

Thanks!