My app\'s register and login processes take place on a secure subdomain. For this reason, I have modified config/initializers/session_store.rb to look like
config/initializers/session_store.rb
You need to specify the domain using a more verbose cookie setting method:
cookies[:some_cookie] = { :value => "whatever", :domain => ".app_name.com", :expires => 1.year.from_now.utc }
I haven't found a configuration setting to do this globally yet.