I think fish is the best interactive shell. It’s not completely POSIX compatible but it’s close enough for day to day use. I switched from zsh to fish years ago and would recommend anyone using zsh to try it out. Fish provides a customized zsh experience, but out of the box without plugins. It also doesn’t have the compgen performance issues you get with zsh.

For shell scripting I’d stick with POSIX sh or bash.

I switched to Fish from Zsh and never looked back. That said, love the shoutout to scsh, which has the best manpage of all time (also Olin was a great professor, I learned compilers from him)

Bash scripts are ran thorugh bash, not fish…

So if they messed up the shebang, I’d do bash that_script.sh