Sorry for the confusion, I'm to used to `` as code style for markdown, forgot HN doesn't support it. I'm glad Fish doesn't support the backtick syntax :). Like others mention it just drops the dollar from a 'regular' parenthesis expansion.

Fish uses parentheses for command expansion, so backticks aren’t supported and the dollar sign is only for variable substitution.

Fish just uses (cmd), no $.

Ah, which I guess is why no subshell support?

There are other ways to do subshells than using the same syntax, just that the Fish developers never did it, maybe because it's not requested enough. I think it's still the most annoying thing about Fish, and the most convincing reason to switch away again. I frequently drop into bash to do

    (cd subdirectory && command --that might.fail) && run --command-in-original-dir --only-if-subshell-succeeded

... and expect to still be in the original dir when it's done. Any solution in Fish using "&& cd -" at the end of a block AFTER a maybe-failing command is just wrong, and there seriously isn't any way except saving and restoring $PWD every time you want subshell functionality, or using "; cd -" and manually saving the $status, which is equally as frustrating.

There are some non-syntactic suggestions in https://github.com/fish-shell/fish-shell/issues/1439