I filed this as FB21309274 (EventKit: Semantics of startDateComponents are undefined and ignored by Native UI)

Assuming you're writing in Swift, you can wrap EKEventStore in an Actor. This makes sure that EKEventStore is only accessed from a single thread, while you can make async calls from any other thread without worrying about locks - the use of Actor takes care of that.

I experimented with this more, by removing increasingly larger portions of the interaction with SwifData, and finally realized: the freezes are caused by the Xcode debugger session, and have nothing to do with SwiftData or ModelActor. I saw the "not reporting this hang" messages in the logs, but didn't realize what Xcode was trying to tell me. If it instead said something like "hang likely caused by the debugger session" it would have been much easier to understand than "not reporting".

I noticed the same message when using a wheel style Picker widget: scrolling it fast up and down causes this message to appear. I'm curious if anybody knows what and at which level generates this message. For example, can I instruct the Picker to not generate any events until the wheel settles on one of the options? The message is when the wheel is "flying" through the available options, without settling on any of them, due to inertia. There's some interaction with the OS because as the Picker is passing through options (without settling on them) it's providing a gentle haptic feedback, and a soft tick.

I'm seeing a similar issue with using SDL2 with Xcode 15.3. When I clean the build directory (command+shift+K), my command line utility compiles directly afterwards. But subsequent builds attempts fail, and I'm getting a message header files are not found. A documentation build fails every time, and so far seems the most reliable way to reproduce the issue.