It’s loaded in via .zshrc or .bashrc (didn’t read the fish docs, but I assume it’s similar), so catches commands you enter in an interactive shell.

Commands within a shell script won’t be handled by it.

Similarly cron jobs don’t typically run with a full user environment, unless you’ve gone out of your way to make them, so would be safe.

shellfirm not execute the command. it's just get interrupt when you run the command, check the pattern and prompt your a verification. your shell is the executer