Also facing the same situation. I'd like to run a script that generates code (the script is in the package directory, and the generated code should also end up in the package directory). Using a buildTool plugin, I can get the plugin to run before each build, but cannot get it to save files outside of DerivedData directory, which is the issue @benkai is hitting. If I change it to a command() plugin, I can get it to write to the package directory, but can't figure out how to run it without manually typing swift package <command>. Has anyone discovered if it's possible to do both: Run a script before each package build (like a .buildTool plugin) Write to the package directory (like a command plugin) How can I just give my buildTool plugin permission to write anywhere?