On here https://github.com/cakephp/app/blob/5.x/config/bootstrap.php#L169 , it throws an Exception if debug is false. However, if debug is false, we cannot see the Exception, which leads to seeing the site in debug mode with no warnings or errors, but then seeing only a blank screen if debug is off. It should either show the warning if debug is on so I can expect why I no longer see it when debug is off, or show something in the logs.