nix develop -c $SHELL

I built my development flake for this website with the FlakeHub CLI. That flake uses pkgs.mkShell to load in binary dependencies to the development environment. I run zsh defined and configured by nix-darwin, so it was pretty jarring getting thrown into a plain bash shell when running nix develop. Luckily the fix is simple. Rather than just running nix develop, run:

nix develop -c $SHELL

and your normal shell will be run instead of the default bash shell.

(via this discussion)