Hi Guys, thank you for your feedback and taking your time to help me! I identified the issue.
It looks like I am spawning st with tmux (e.g. st -e tmux), and the issue is that tmux is reparenting the process id to tmux's daemon. Example: tmux | \_newsbeuter | \_vim st.c It is not an issue with xmonad after all, and I can confirm that the issue happens on urxvt as well (e.g. urxvt -e tmux). I did not find any tmux option to disable this reparenting behaviour, so I guess I'll have to find another way to scroll the screen with st. :( Since this is described on st's page on suckless.org as a viable way to have scrolling can we at least update it to warn about this? Thanks, Amadeus.