[Freeswitch-users] How to detect close of verto tab?

Our config of FS 10.5 doesn't detect when a verto user closes the tab (or directs the tab to a different url, etc) and the session runs on the server for many minutes (while our virtual agent tries to engage the user, thus defeating our media timeout). Is there a best practice for detecting this per-channel so it can be used to end the conference? Note that browser event beforeunload cannot be relied upon, especially in mobile browsers, as a trigger for hanging-up on the verto end.