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