Corrections to flake formatting

flake.nix

@@ -9,8 +9,8 @@
   };
 
   outputs = { self, nixpkgs, nix-bitcoin, nixos-generators, flake-utils, ... }:
-    flake-utils.lib.eachDefaultSystem (system:
     let
+      system = "x86_64-linux";
       pkgs = import nixpkgs { inherit system; };
       modules = [
         nix-bitcoin.nixosModules.default
@@ -19,15 +19,7 @@
         ./nix/modules/btcpay
       ];
     in {
-        devShells.default = pkgs.mkShell {
+      # Top-level nixosConfigurations for proper nixos-rebuild support
-          buildInputs = [
-            nixos-generators.packages.${system}.nixos-generate
-            pkgs.just
-          ];
-          shellHook = ''
-            echo "💚 Devshell ready: nixos-generate, just available."
-          '';
-        };
       nixosConfigurations.btc-pay-server = nixpkgs.lib.nixosSystem {
         system = "x86_64-linux";
         modules = modules ++ [
@@ -51,6 +43,22 @@
           self.nixosModules.btcpay-server
         ];
       };
+
+      # devShells and other per-system outputs, if desired
+      devShells = flake-utils.lib.eachDefaultSystem (system:
+        let
+          pkgs = import nixpkgs { inherit system; };
+        in {
+          default = pkgs.mkShell {
+            buildInputs = [
+              nixos-generators.packages.${system}.nixos-generate
+              pkgs.just
+            ];
+            shellHook = ''
+              echo "💚 Devshell ready: nixos-generate, just available."
+            '';
+          };
         }
       );
+    };
 }