By "open content," I did mean 'aevt'/'ocon'. So those events have no handler if we don't add one? SwiftUI won't add one of its own? Separately, can the onOpenURL path be used for general URL schemes (like FTP or Telnet), not just custom schemes for your own action handling?

It's now public

So I have to convert the Expectation initializers with “#expect” calls, right.

It’s the latter.

So, the same methods as Cocoa apps?

Where in the process do you insert the custom dictionary? Besides classic app formats, SwiftUI also supports UI/NSApplicationDrlegate, so one-time initiation can go there.

Thinking about a result builder

What kind of applications would request that from a different application?