`Edit->Preferences->Tools->Terminal`? https://www.geany.org/manual/current/index.html#tool-paths

I just noticed that when I open geany it opens terminal instances repeatedly until geany is closed, with some terminal emulators they close instantly after they pop up, with others they remain open after geany is closed.

I assume you mean it opens a terminal instance each time you do execute, not autonomously :)

The intended operation is that Geany will wait for a terminal to complete before allowing another command so the user can tell Geany to issue a kill to the terminal and thus the process in it if it goes badly wrong (eg infinite loop). That way the user does not have to find the runaway process id and then issue the kill themselves. Then when the user closes the terminal and its process exits Geany gets a signal and returns the execute command to normal.

But some terminal programs open the "terminal" as a tab in a single instance and the terminal process then exits as soon as its communicated with that instance (the way Geany does by default if you open a file from the command line). Since the process it ran exits, Geany no longer has control over the terminal (tab) and it stays open until the user closes it.

You can still use those terminals, you just get different behaviour, or you can add the option that makes it not use a single instance to the command in Geany.

I had same problem. I managed to solve it:

Check default terminal emulator that you using (don't change anything): `sudo update-alternatives --config x-terminal-emulator`

Open Geany and replace the terminal there: `Edit > Preferences > Tools > Terminal`

It should be now: `your-terminal -e "/bin/sh %c"`

@shufuwa the behaviour of terminal emulators varies, without specifying which one you are using your post is not useful to anyone else.