If you use Package._transitional_registerBuildPlugin to run arbitrary code at build time when the package is being deployed inside an app, the first time the handler is being run, the .meteor/local/build folder with the content of the packages is not yet there and the package itself cannot access its own files.

The second time you run meteor, it will work as expected as the files have been copied there at the end of the first run.

If you run meteor reset this happens again as the folder is cleaned up.

Is there a different solution or is it a bug? Is there any workaround?