Hm...
I just use the "default" fish as home-service and it's set as my user's shell... I will try to change them both to bash and try again. Maybe that's a "non standard-shell" issue.
Will update later.

чт, 16 дек. 2021 г. в 21:29, Maxime Devos <maximedevos@telenet.be>:
Grigory Shepelev schreef op do 16-12-2021 om 20:46 [+0300]:
> guix pull fails for a 4 days at least with the same error:
>
> fish: Unknown command: nix
> fish:
> nix show-derivation "/home/shegeley/.cache/.fr-
> sqOEpp/273vsd5gv1ch73ayih504s5wcxvysq-module-import-compiled.drv"

That's an error message from fish, not from guix.

Why is fish trying to run nix on Guix System?
Maybe you configured fish to interpret output lines containing ".drv"?

Greetings,
Maxime.