I have started to have issues with SwiftUI previews of iOS apps with projects under the Documents folder. I have experimented that in Xcode 26.4 and I am still seeing it in 26.5. The error is:
Cannot preview in this file.
Failed to launch xyz.abc.TestApp
Looking at the diagnostics, Xcode gets a permission denied error when trying to open
/Users/me/Documents/path/to/TestApp/DerivedData/TestApp/Build/Intermediates.noindex/TestApp.build/Debug-iphonesimulator/TestApp.build/Objects-normal/arm64/ContentView.1.preview-thunk-launch.o
Error details below. Note that I have set DerivedData folders relative to the projects' roots. Additional information:
I get errors on freshly created iOS projects, just trying to preview the default ContentView.
Xcode has full disk access set in System Preferences > Privacy & Security.
I have cleaned build folders, deleted the simulators, Xcode itself, cleared various caches, restarted and reinstalled Xcode to no avail.
Checking Editor > Canvas > Use Legacy Previews Execution did not fix it either.
Apps run fine in Simulator.
System info: macOS 26.4.1, Xcode 26.5 (17F42), MacBook Pro M1 and Mac Studio M2 Max.
I have found two ways to fix the problem while keeping DerivedData relative to the project's root:
create the project in some other “unprotected” directory (/Users/me/Developer in my case), or
uncheck Editor > Canvas > Automatically Refresh Canvas.
Either way makes previews work again.
Possibly related:
SwiftUI preview not working in Xcode 26 when “Automatically Refresh Canvas” is enabled
Xcode 13.2.1 - Simulator works, Preview doesn't
Excerpt from diagnostics:
| | [Remote] JITError
| |
| | ==================================
| |
| | | [Remote] CouldNotLoadInputObjectFile: Could not load object file during preview: /Users/me/Documents/TestApp/DerivedData/TestApp/Build/Intermediates.noindex/TestApp.build/Debug-iphonesimulator/TestApp.build/Objects-normal/arm64/ContentView.1.preview-thunk-launch.o
| | |
| | | path: /Users/me/Documents/TestApp/DerivedData/TestApp/Build/Intermediates.noindex/TestApp.build/Debug-iphonesimulator/TestApp.build/Objects-normal/arm64/ContentView.1.preview-thunk-launch.o
| | |
| | | ==================================
| | |
| | | | [Remote] XOJITError
| | | |
| | | | XOJITError: '/Users/me/Documents/TestApp/DerivedData/TestApp/Build/Intermediates.noindex/TestApp.build/Debug-iphonesimulator/TestApp.build/Objects-normal/arm64/ContentView.1.preview-thunk-launch.o': Operation not permitted