We also see this issue, interestingly when Xcode cloud shows the call to run the generated script, the surrounding sandbox-exec does seem to say that writing to this directory should be allowed, yet it still fails: Swift/ErrorType.swift:200: Fatal error: Error raised at top level: Error Domain=NSCocoaErrorDomain Code=513 "You don’t have permission to save the file “String+TransactionsAccessors.swift” in the folder “StringsGeneratorPlugin”." UserInfo={NSURL=file:///Volumes/workspace/DerivedData/SourcePackages/plugins/SampleApp.output/SampleApp/StringsGeneratorPlugin/String+TransactionsAccessors.swift, NSUserStringVariant=Folder, NSUnderlyingError=0x600003104330 {Error Domain=NSPOSIXErrorDomain Code=1 "Operation not permitted"}} then in the call to sandbox-exec /Volumes/workspace/DerivedData/Build/Intermediates.noindex/SampleApp.build/Debug-iphonesimulator/SampleApp.build/Script-7981050304838536995.sh: line 17: 12085 Illegal instruction: 4 /usr/bin/sandbox-exec -p "(version 1) (deny default) (import \"system.sb\") (allow file-read*) (allow process*) (allow file-write* (subpath \"/private/tmp\") (subpath \"/private/var/folders/22/cm0mxjnn4zg5l2rs2l3b51qr0000gn/T\") ) (deny file-write* (subpath \"/Volumes/workspace/repository/SampleApp\") ) (allow file-write* (subpath \"/Volumes/workspace/DerivedData/SourcePackages/plugins/SampleApp.output/SampleApp/StringsGeneratorPlugin\") )