I'm sharing a site with a client via valet share which works marvellously except for the control panel. When you login to the backend via the valet share URL (for example http://abc1d234.ngrok.io/cp/) the dashboard page works but if you click on any link (say "pages") the root url changes from http://abc1234.ngrok.io/cp/ to http://mysite.test/cp/ which breaks the site if you were accessing it via ngrok. The front-end works perfect.
I've tried updating the system.yaml under locales to the ngrok.io instance i setup but that doesn't seem to effect it. Is there some secret place where the control panel root url gets defined?