Thanks @eskimo. The error is NSXPCConnectionInterrupted (4097). The UI app is not sandboxed, it will be deployed with Developer ID for internal use. The call is coming from a SwiftUI Button action that the user taps on, and works correctly for functions that don't have a reply block.
davidholmes
Users receive reputation points by contributing quality content to the forums.
Posts include post and replies published on the forums.
Post authors can mark replies as Accepted to indicate successful solutions.
Apple Developer Forums admins can mark replies as Apple Recommended to indicate an approved solution
Last seen
User for
Post
Replies
Boosts
Views
Activity
Correction, we are now getting the NSCocoaErrorDomain Code=4099 error. But at some point yesterday it was 4097.
@eskimo I think I got it. NSXPCConnection invalidate() was being called too early in the client. Still have some learning to do for managing the connection state.