If you like to manually set your $PATH on macOS, you may have updated /etc/zprofile (for ZSH) or /etc/profile (for Bash) to eliminate calls to path_helper. Unfortunately, macOS will update these files when you install OS updates. I’ve been bitten by this changing my $PATH, so I came up with the following snippet to warn when it happens.

For ZSH, in /etc/zprofile you can add the following to print a red warning when path_helper is enabled:

if [[ $- == *i* ]] && [[ -r /etc/zprofile ]] && grep -E '^\s*eval `/usr/libexec/path_helper' /etc/zprofile > /dev/null; then
  echo "\033[31m!!! WARNING: macOS path_helper enabled in /etc/zprofile !!!\033[m" >&2
fi

If you are using Bash, edit /etc/profile instead and replace zprofile with profile in the snippet.

This has saved me a lot of time troubleshooting issues after installing OS updates. Hope it helps someone else!