Being new to merb, I kept getting this error message after generating a basic merb 0.9.5 app: ~ Maybe the site's session_secret_key has changed? - Merb::CookieSession::TamperedWithCookie) /usr/lib/ruby/gems/1.8/gems/merb-core-0.9.5/lib/merb-core/dispatch/session/cookie.rb:162:in `unmarshal' /usr/lib/ruby/gems/1.8/gems/merb-core-0.9.5/lib/merb-core/dispatch/session/cookie.rb:77:in `initialize' /usr/lib/ruby/gems/1.8/gems/merb-core-0.9.5/lib/merb-core/dispatch/session/cookie.rb:14:in `new' /usr/lib/ruby/gems/1.8/gems/merb-core-0.9.5/lib/merb-core/dispatch/session/cookie.rb:14:in `setup_session' What I didn't know was that I needed to uncomment (and set) the :session_id_key in init.rb: [sourcecode="ruby"] # Sets up a custom session id key which is used for the session persistence # cookie name.  If not specified, defaults to '_session_id'. # c[:session_id_key] = '_session_id' [/sourcecode] The comments threw me off since I was expecting a default value. Update: It's hard to find good merb tutorials right now. I wish I had seen the first of these two posts in advance. It specifically says to uncomment the session_id_key:

• http://railsontherun.com/2008/4/5/merb-tips-1
• http://railsontherun.com/2008/4/8/merb-tips-2