I’m seeing what looks like a compiler / macro-expansion / build-pipeline issue. Environment: Xcode 26.4 RC (17E192, latest); I believe it is also reproducible on earlier versions. github source code I reduced this to a very small macOS/iOS app plus a local macro package. The app logic is trivial, but app exits immediately on launch with code 138 Important observations: If I inline everything into a single file, the problem disappears. I also see an error like this during investigation: The file path does not exist on the file system: /var/folders/.../swift-generated-sources/@__swiftmacro_18MacroFeedbackRepro20MountActivationState17PreservedRawValuefMm_.swift That makes me suspect this is not an application logic issue, but something in macro expansion / generated source handling / compiler pipeline.