Session message handler are able to received messages.
It is either Session not sending system.perspective.sendMessage or view not listening to "Session" Scope.
-- but view session scope is working, when messages are sent from view.
@diamond are you doing system.perspective.sendMessage from your session?
I just tried and it works just fine.
As Michael asked: Are you trying this when the view is opened ? It needs to be opened for the message handler to be active.
Session messages sent with system.util.sendMessage() can only be caught by message handlers defined on the session. Component message handlers can only catch messages sent with system.perspective.sendMessage().
in perspective I call system.util.sendMessage for session's message handler.
In session message handler I call system.perspective.sendMessage for view's message Handler.
But in my case, view's message handler does not receive the message.
I don't have to time to troubleshoot, as this is urgent, so I reverted back to 8.1.37.