This issue is related to how rails routes work. By default it allows any endpoint to specify a :format parameter with an optional period. So .html means HTML format, .json means JSON.
about.html is the same as /about (both request the HTML version). However the about.html route doesn’t exist in Ember because we never use routes with the HTML extension, so we get a disagreement from the back and front end. The server returns 200 but the client side then says, no wait that’s not found.
There are ways to fix this. We could refine our rails routes to make sure they don’t support .html but continue supporting .json. I don’t see a way to apply this globally but maybe there’s something I’m unaware of.
Honestly I’m not too excited by this work. Unless there’s a super pressing reason to fix I can’t see, it I think we can live with it.