Reality Composer Pro 3 cannot create a new project or open an existing project on my Mac. After I select Create New Project or Open Existing Project, the operation begins but the project editor never appears. The Reality Composer Pro process remains alive and idle, and no standard crash report is generated. Environment: MacBook Pro Mac15,9 Apple M3 Max, 48 GB unified memory macOS 26.6 (25G72) Reality Composer Pro 3 Beta 4, version 3.080.0.1.500.1 Built-in display only Steps to reproduce: Quit Reality Composer Pro. Launch /Applications/RealityComposerPro.app. Select Create New Project. Observe that the editor never appears. Open Existing Project fails in the same way. The problem is reproducible 100% of the time with Reality Composer Pro 3 Beta 2, Beta 3, and Beta 4. I have also reproduced it: With a completely blank new project With an existing project In a clean local macOS user account In Safe Mode With no external displays With local paths and iCloud disabled After verifying adequate free disk space and separately testing free-space conditions After resetting Reality Composer Pro state and preferences The application passes code-signature and Gatekeeper verification. Its temporary loader copy is created successfully, with no ENOSPC, failed-copy, or failed-write error. The failure occurs around libtm-welcome_window.dylib and libtm-plugin_support.dylib prepareToLoad. A small modal NSPanel repeatedly performs AppKit/SwiftUI constraint updates and reports: The window has been marked as needing another Update Constraints in Window pass, but it has already had more Update Constraints in Window passes than there are views in the window. The exception appears to be swallowed instead of crashing the process. A process sample then reports SOME_OTHER_THREAD_SWALLOWED_AT_LEAST_ONE_EXCEPTION while the main thread remains idle in the normal NSApplication event loop. This appears to be a constraint-update loop in the welcome-window loader/progress panel, rather than a problem with a particular project or its assets. Feedback Assistant report: FB24460905 Has anyone reproduced this on macOS 26 with Reality Composer Pro 3? Is there a supported workaround that bypasses the failing loader/progress panel? Is RCP 3 Beta 4 expected to work on macOS 26.6, or does it require macOS 27?Reality Composer Pro 3 cannot create a new project or open an existing project on my Mac. After I select Create New Project or Open Existing Project, the operation begins but the project editor never appears. The Reality Composer Pro process remains alive and idle, and no standard crash report is generated. Environment: MacBook Pro Mac15,9 Apple M3 Max, 48 GB unified memory macOS 26.6 (25G72) Reality Composer Pro 3 Beta 4, version 3.080.0.1.500.1 Built-in display only Steps to reproduce: Quit Reality Composer Pro. Launch /Applications/RealityComposerPro.app. Select Create New Project. Observe that the editor never appears. Open Existing Project fails in the same way. The problem is reproducible 100% of the time with Reality Composer Pro 3 Beta 2, Beta 3, and Beta 4. I have also reproduced it: With a completely blank new project With an existing project In a clean local macOS user account In Safe Mode With no external displays With local paths and iCloud disabled After verifying adequate free disk space and separately testing free-space conditions After resetting Reality Composer Pro state and preferences The application passes code-signature and Gatekeeper verification. Its temporary loader copy is created successfully, with no ENOSPC, failed-copy, or failed-write error. The failure occurs around libtm-welcome_window.dylib and libtm-plugin_support.dylib prepareToLoad. A small modal NSPanel repeatedly performs AppKit/SwiftUI constraint updates and reports: The window has been marked as needing another Update Constraints in Window pass, but it has already had more Update Constraints in Window passes than there are views in the window. The exception appears to be swallowed instead of crashing the process. A process sample then reports SOME_OTHER_THREAD_SWALLOWED_AT_LEAST_ONE_EXCEPTION while the main thread remains idle in the normal NSApplication event loop. This appears to be a constraint-update loop in the welcome-window loader/progress panel, rather than a problem with a particular project or its assets. Feedback Assistant report: FB24460905 Has anyone reproduced this on macOS 26 with Reality Composer Pro 3? Is there a supported workaround that bypasses the failing loader/progress panel? Is RCP 3 Beta 4 expected to work on macOS 26.6, or does it require macOS 27?