> I only have one meeting a month nowadays so I might take a look if that situation ever changes (hopefully it doesn't!).

I'm happy for you

> So the macOS app sets up a local webserver on some port that the Chrome extensions knows about in advance? Smart, kinda like how I had to do an auth flow for one of my CLI apps.

Exactly like this! Some caveats there since Chrome actually shuts down extensions after 30 seconds or so if nothing happens (so you need to keep firing off messages across the connection to keep the extension alive).