Re : CanJS - Default route called when route is not default

Open that pen and watch your console to see what's happening when you click back and forth between the buttons.  When you change the project with

it adds the project param to the current set of route attributes.  The route object changed, but the can.route.attr('route') hasn't been updated, yet.  Once the can.route.attr('route') gets updated to ':project', it works as expected.

When you use 

it adds the project route to the current route's parameters first.  Can.route then checks to see if the new set of params match a known route, then it runs again with the updated route param.

When you change your route, you may want to try replacing the entire route. Using

replaces everything in the route with the passed object and updates the route attr.

replaces the route contents with an empty object (the default route).

http://codepen.io/anon/pen/ztnDj -> Updated to show how it works when replacing all route params.

There's my shot at it.  Hope it helped.