diff --git a/all-modules.nix b/all-modules.nix
index bc194a5..f6e508c 100644
--- a/all-modules.nix
+++ b/all-modules.nix
@@ -2,9 +2,12 @@
 {
   imports = [
     ./modules/checks.nix
+    ./modules/darwinModules.nix
     ./modules/devShell.nix
     ./modules/flake.nix
     ./modules/legacyPackages.nix
+    ./modules/nixosModules.nix
+    ./modules/overlay.nix
     ./modules/packages.nix
     ./modules/perSystem.nix
   ];
diff --git a/modules/darwinModules.nix b/modules/darwinModules.nix
new file mode 100644
index 0000000..fb3df5b
--- /dev/null
+++ b/modules/darwinModules.nix
@@ -0,0 +1,27 @@
+{ config, self, lib, flake-modules-core-lib, ... }:
+let
+  inherit (lib)
+    filterAttrs
+    mapAttrs
+    mkOption
+    optionalAttrs
+    types
+    ;
+  inherit (flake-modules-core-lib)
+    mkSubmoduleOptions
+    ;
+in
+{
+  options = {
+    flake = mkSubmoduleOptions {
+      darwinModules = mkOption {
+        type = types.lazyAttrsOf types.unspecified;
+        default = { };
+        apply = mapAttrs (k: v: { _file = "${toString self.outPath}/flake.nix#darwinModules.${k}"; imports = [ v ]; });
+        description = ''
+          Nix-darwin modules.
+        '';
+      };
+    };
+  };
+}
diff --git a/modules/devShell.nix b/modules/devShell.nix
index 4f347c3..b4154ac 100644
--- a/modules/devShell.nix
+++ b/modules/devShell.nix
@@ -36,6 +36,10 @@ in
       options = {
         devShell = mkOption {
           type = types.package;
+          # We don't have a way to unset devShell in the flake without computing
+          # the root of each allSystems module, so to improve laziness, the best
+          # choice seems to be to require a devShell and give the opportunity
+          # to unset it manually.
           default = throw "The default devShell was not configured for system ${system}. Please set it, or if you don't want to use the devShell attribute, set flake.devShell = lib.mkForce {};";
           description = ''
             A derivation that nix develop bases its environment on.
diff --git a/modules/nixosModules.nix b/modules/nixosModules.nix
new file mode 100644
index 0000000..e26d040
--- /dev/null
+++ b/modules/nixosModules.nix
@@ -0,0 +1,27 @@
+{ config, self, lib, flake-modules-core-lib, ... }:
+let
+  inherit (lib)
+    filterAttrs
+    mapAttrs
+    mkOption
+    optionalAttrs
+    types
+    ;
+  inherit (flake-modules-core-lib)
+    mkSubmoduleOptions
+    ;
+in
+{
+  options = {
+    flake = mkSubmoduleOptions {
+      nixosModules = mkOption {
+        type = types.lazyAttrsOf types.unspecified;
+        default = { };
+        apply = mapAttrs (k: v: { _file = "${toString self.outPath}/flake.nix#nixosModules.${k}"; imports = [ v ]; });
+        description = ''
+          NixOS modules.
+        '';
+      };
+    };
+  };
+}
diff --git a/modules/overlay.nix b/modules/overlay.nix
new file mode 100644
index 0000000..88405ae
--- /dev/null
+++ b/modules/overlay.nix
@@ -0,0 +1,32 @@
+{ config, lib, flake-modules-core-lib, ... }:
+let
+  inherit (lib)
+    mkOption
+    types
+    ;
+  inherit (flake-modules-core-lib)
+    mkSubmoduleOptions
+    ;
+in
+{
+  options = {
+    flake = mkSubmoduleOptions {
+      overlay = mkOption {
+        # uniq should be ordered: https://github.com/NixOS/nixpkgs/issues/147052
+        # also update description when done
+        type = types.uniq (types.functionTo (types.functionTo (types.lazyAttrsOf types.unspecified)));
+        # This eta expansion exists for the sole purpose of making nix flake check happy.
+        apply = f: final: prev: f final prev;
+        default = _: _: { };
+        defaultText = lib.literalExpression or lib.literalExample ''final: prev: {}'';
+        description = ''
+          An overlay.
+
+          Note that this option's type is not mergeable. While overlays can be
+          composed, the order of composition is significant, but the module
+          system does not guarantee deterministic definition ordering.
+        '';
+      };
+    };
+  };
+}