This has been happening to me for several months, both on Catalina and now on Monterey (I'm on macOS 12.2 with Xcode 13.2.1). And for me, it happens almost 100% of the time. Back in November, I wiped and reinstalled macOS entirely, which seemed to fix my problem for about a month and a half before it started happening again in mid-January. Now it happens to me every time I launch the iPhone simulator. The only way I've been able to work around this is to delete all my simulators from the organizer in Xcode and re-add them one by one, but I'm now at the point where I have delete and re-add the simulator any time I want to cold boot it. I cleaned my simulators out this morning and cold-booting my one iPhone 12 Pro simulator locked up my computer again this afternoon. I'll try to gather a sysdiagnose report but given how badly locked up everything is (mouse movement seems okay but that's all that's responsive), I have my doubts I'd be able to get one.

I'm glad I'm not the only one having this issue. It's like swift build doesn't even include the compiled .momd file (works just fine in Xcode!). I have tests that fail with let modelPath = try XCTUnwrap(bundle.url(forResource: "TestModel", withExtension: "momd"), "Unable to find TestModel.momd") and when I inspect the generated test bundles, I get the normal .xcdatamodeld. swift build appears to be missing a step that compiles Core Data models — something that xcodebuild knows how to do. It's likely this is intentionally decoupled from swift build and I have no idea how to fix it.