Nagstamon Opening Twice on KDE Plasma login

For quite a while I've been having an issue where Nagstamon opens twice on my Fedora laptop ( edit: also just had this problem on my Gentoo desktop ) when I login. I've finally gotten around to investigating it properly and found the cause and a solution.

First of all - the problem: I have Nagstamon set to run on login automatically, and since Nagstamon updated a while ago whenever I logged in I would get a popup with default settings ( no servers configured, the status showing as an overlay instead of in the system tray etc ), as well as the normally configured Nagstamon in my system tray.

Error message showing no servers configured in Nagstamon

I previously tried experimenting by removing the ~/.config/autostart/nagstamon.desktop file, but that just made both instances of Nagstamon stop loading on startup. Manually running nagstamon only opened one instance of Nagstamon, and adding ~/.config/autostart/nagstamon.desktop back in ( or adding it to run on login in system settings ) made one instance start up on the next login, but went back to two on further logins.

I also noticed that the second nagstamon process was being run with different arguments:

pgrep output showing two processes, one of them with a -session argument

and a new directory was being created as ~/-session:

contents of the session directory

This helped me understand the problem - by default Plasma restores the previous session, and seems to run previous commands with an extra argument. Digging around further, I eventually found a Github issue referencing the problem and mentions a code change that likely caused it to suddenly appear one day.

Once I understood this, the solution was simple - either disable restoring of sessions, or just exclude nagstamon from the applications restored.

Plasma settings, add the string nagstamon to the "Don't restore these applications field", or select "Start with an empty session"

And of course add Nagstamon back to being run on login:

Autostart applications in Plasma settings