Yesod is infamous for being breakage prone. In fact the author now only supports users installing yesod via stackage rather than Hackage, because stackage force

Yesod is infamous for being breakage prone. In fact the author now only supports users installing yesod via stackage rather than Hackage, because stackage forces globally coherent fixed versions for every package in stackage. (Basically that every package should be build able together). If you're doing application dev (rather than lib dev), stackage will help. Or use snap, I've never had build hell with snap. But if yesod works for you, awesome! :-)