Is dmenu messing with PS1?
It seems that if I start a process with i3-msg "exec blabla", PS1 has the value from /etc/profile. However, if I start the process via dmenu (i3-msg "exec dmenu_run", and then type blabla into the dmenu prompt), PS1 is set to a mere \s-\v\$.
Why is that? I grepped for PS1 in the dmenu sources, but could not find anything.
(When trying to reproduce any of this, make sure to completely terminate your terminal emulator, so that i3-sensible-terminal is actually starting a new terminal and not just telling an existing terminal process to open another window).