Working config for fw13 amd

system/nix/default.nix

@@ -0,0 +1,44 @@
+{
+  config,
+  pkgs,
+  inputs,
+  lib,
+  ...
+}: {
+  imports = [
+    ./nh.nix
+    ./nixpkgs.nix
+    ./substituters.nix
+  ];
+
+  # we need git for flakes
+  environment.systemPackages = [pkgs.git];
+
+  nix = let
+    flakeInputs = lib.filterAttrs (_: v: lib.isType "flake" v) inputs;
+  in {
+    package = pkgs.lix;
+
+    # pin the registry to avoid downloading and evaling a new nixpkgs version every time
+    registry = lib.mapAttrs (_: v: {flake = v;}) flakeInputs;
+
+    # set the path for channels compat
+    nixPath = lib.mapAttrsToList (key: _: "${key}=flake:${key}") config.nix.registry;
+
+    settings = {
+      auto-optimise-store = true;
+      builders-use-substitutes = true;
+      experimental-features = ["nix-command" "flakes"];
+      flake-registry = "/etc/nix/registry.json";
+
+      # for direnv GC roots
+      keep-derivations = true;
+      keep-outputs = true;
+
+      trusted-users = ["root" "@wheel"];
+
+      accept-flake-config = false;
+    };
+  };
+  system.stateVersion = "25.05";
+}