@swflint Thanks. #StarshipPrompt doesn't seem to notice this shell change though, while it does for 'nix-shell -p git-extras --run fish'. Shouldn't be a :fish_shell: #fishShell issue though.
UPDATE: nix-shell sets the IN_NIX_SHELL=[im]pure environment variable (and a whole bunch of others) while nix shell only touches the PATH. Hard to detect for any program that this change happened!
It's been a couple of months since I posted about #FOSSSupport but back at it today with #StarshipPrompt. This beautiful shell prompt is such a pleasure to use. And for being so customizable it's funny how any Starship user can instantly recognize its use in another developer's shell.