How can I enter some kind of "private" zsh shell session where none of my commands will be recorded in the on-disk history?
I know there is an option for adding a space character before any/each command to avoid it being recorded in the history, however, I'm looking for a solution that is not requiring adding a space in front of each command.
Launch a new zsh shell and disable history within it.
zsh unset HISTFILE ...secret commands... exit The secret commands won't be stored in the history file.
zsh fc -p ...secret commands... exit The fc -p will switch zsh to a in-memory history that will be discarded when you exit.
The downside: the previous history (commands entered before the private session started) will not be available.
echo $SHELL from zsh returns /bin/bash. I believe it points to login shell rather than current shell $SHELL then, to avoid any confusion.