At the moment, flakes is an evaluation-time thing (thus client-side) so no restart of nix-daemon is technically required. However, if you are upgrading from 2.3

At the moment, flakes is an evaluation-time thing (thus client-side) so no restart of nix-daemon is technically required. However, if you are upgrading from 2.3 to 2.4+ it's best to restart the daemon, otherwise other things like build log output can be messed up if you try to mix client-daemon versions.