Plugin: can't call before_filter in ApplicationControlle

I expect the problem here is that your plugin init code is running before application.rb is loaded, so you're defining a completely new class. Since this class doesn't descend from ActionController::Base before_filter doesn't exist.

On top of this, I think you'd find that since ApplicationController is defined, rails would then not go and look for the ApplicationController your application defines. You might have better luck if you first require application_controller (forcing it to be loaded, and then fiddle around adding filters to it.