We are using discourse with SSO and it works great.
However, I am running into an odd situation.
We are leveraging Discourse private messaging links on our external site (paddling.com) to spawn a new private message on discourse (forums.paddling.com).
If the user is logged in to the forums, it works exactly as expected.
If the user logs in to paddling.com (but doesn’t go to the forums first) when the user clicks on the link to spawn a new message, it simply opens the forums (without spawning a new message)
If the user clicks on the message link a second time, then the message works.
It seems to me that the issue is that while the user is logged in to paddling.com, they are not logged into the forums until they view a page on forums.paddling.com.
I just re-read my previous reply. What I had meant to write was that the approach outlined in this topic should work: Create an SSO login link. This is how our WordPress plugin creates links that automatically log users into Discourse. What I haven’t tested is using this approach with a pre-filled message URL set for the return_path.