When I try to evaluate (import ./default.nix) { silent = false; } it fails with an evaluation error. At first this was confusing me since the function clearly has such an argument. However the fail happens later in the call of ./support/nix/eval-with-configuration.nix with the same args, which indeed does not have a silent argument.

IME, nothing good has ever come out of @args argument capturing, and some alternative mechanism should be used here instead.