I think it's about the stuff that needs to be shared. Like variables for X11 or ssh agent.
If you start server off your graphic session then any new tmux session will get those variables and your ssh agent or graphical app will "just work".
Reading from current one by default might fuck something up if you say have some automation that starts stuff in tmux
There isn't really good way to handle it by default that would make everyone happy, screen had similar "problems".
I just have
tmux new-session -d -s main
in my .Xsessionrc so the main session gets both SSH_AGENT stuff (I use gnupg as agent, for smartcard support) and proper DISPLAY, then just use alias to use that main session
If you start server off your graphic session then any new tmux session will get those variables and your ssh agent or graphical app will "just work".
Reading from current one by default might fuck something up if you say have some automation that starts stuff in tmux
There isn't really good way to handle it by default that would make everyone happy, screen had similar "problems".
I just have
in my .Xsessionrc so the main session gets both SSH_AGENT stuff (I use gnupg as agent, for smartcard support) and proper DISPLAY, then just use alias to use that main session