Plugins » Discovery

config/routes.rb matches hosts#architecture_selected and other routes as GET. These routes are POST in Foreman core, so when javascript contacts 'GET architecture_selected_discovered_hosts', Foreman 404s.
The solution is simple, just actually match the requests as POST. I am guessing this worked before Rails 4 because it used the method of the matched route.

I'd say this one is important as currently provisioning a discovered system isn't possible unless you select a hostgroup with the OS/media/etc.