I've encountered a similar issue building an app with a package, MyPackage, that has a single MyPackage target using a FooPlugin build tool plugin from the Foo package. Everything works as expected when building locally, but I encounter an error on Xcode Cloud due to insufficient permissions: === BUILD TARGET MyPackage OF PROJECT MyPackage WITH CONFIGURATION Debug === ... WriteAuxiliaryFile /Volumes/workspace/DerivedData/Build/Intermediates.noindex/MyPackage.build/Debug-iphonesimulator/MyPackage.build/Script-8495445145755076753.sh (in target 'MyPackage' from project 'MyPackage') cd /Volumes/workspace/repository/Packages/MyPackage write-file /Volumes/workspace/DerivedData/Build/Intermediates.noindex/MyPackage.build/Debug-iphonesimulator/MyPackage.build/Script-8495445145755076753.sh PhaseScriptExecution Foo /Volumes/workspace/DerivedData/Build/Intermediates.noindex/MyPackage.build/Debug-iphonesimulator/MyPackage.build/Script-8495445145755076753.sh (in target 'MyPackage' from project 'MyPackage') cd /Volumes/workspace/repository/Packages/MyPackage /bin/sh -c /Volumes/workspace/DerivedData/Build/Intermediates.noindex/MyPackage.build/Debug-iphonesimulator/MyPackage.build/Script-8495445145755076753.sh Error: You don’t have permissio n to save the file “Foo.swift” in the folder “FooPlugin” . Command PhaseScriptExecution failed with a nonzero exit code Result bundle written to path: /Volumes/workspace/resultbundle.xcresult ** TEST BUILD FAILED ** For reference, the output from the earlier Process build tool plug-in results is: Apply build tool plug-in “FooPlugin” to target “MyPackage” in package “mypackage” Process build tool plug-in results package: <IDESwiftPackageCore.IDESwiftPackage:0x7f9c1c2069e0 path:'/Volumes/workspace/repository/Packages/mypackage'> target: MyPackage prebuildOutputPaths: [] buildCommands: [SwiftPM.SPMCustomBuildCommand(displayName: Optional("Foo"), executable: "/${BUILD_DIR}/${CONFIGURATION}/Foo", arguments: ["--input", "/Volumes/workspace/repository/Packages/MyPackage/Sources/MyPackage/Resources/en.lproj/Localizable.strings", "--output", "/Volumes/workspace/DerivedData/SourcePackages/plugins/mypackage.output/MyPackage/FooPlugin/Foo.swift"], environment: [:], workingDir: nil, inputPaths: ["/Volumes/workspace/repository/Packages/MyPackage/Sources/MyPackage/Resources/en.lproj/Localizable.strings"], outputPaths: ["/Volumes/workspace/DerivedData/SourcePackages/plugins/mypackage.output/MyPackage/FooPlugin/Foo.swift"], sandboxProfile: Optional(SwiftPM.SPMSandboxProfile(strictness: Basics.Sandbox.Strictness.writableTemporaryDirectory, writableDirectories: [<AbsolutePath:"/Volumes/workspace/DerivedData/SourcePackages/plugins/mypackage.output/MyPackage/FooPlugin">], readOnlyDirectories: [<AbsolutePath:"/Volumes/workspace/repository/Packages/MyPackage">])))] allDerivedOutputPaths: ["/Volumes/workspace/DerivedData/SourcePackages/plugins/mypackage.output/MyPackage/FooPlugin/Foo.swift"] I have been unable to fix this.