It's, as I said, that programs should use line terminators, but we cannot mandate that all programs do use line terminators, so it's still the responsibility of

It's, as I said, that programs should use line terminators, but we cannot mandate that all programs do use line terminators, so it's still the responsibility of the shell to deal with this. Specifically, it's a reaction to > First of all, that's a hack zsh really shouldn't have to do. In an ideal world, zsh wouldn't need a hack, but it would still need to send a signal to the terminal emulator to say "please ensure the cursor is at the beginning of a line; if it's not, mark this somehow so the user understands". Slightly less ideally, a simple way to say "am I at the beginning of a line?" (this is less ideal only in that now the terminal can't be smart about copying program output). But either way, it's still the responsibility of the shell to ensure its prompt ends up starting at column 0 without overwriting the previous program's output. Because no matter what conventions you establish, there will be programs that exit without printing a line terminator (even the best-behaved of programs can still do this if they use unbuffered output and you send a signal to kill the process in the middle of a line).