@@ -61,10 +61,12 @@ # Uv2nix can only work with what it has, and uv.lock is missing essential metadata to perform some builds.
         # This is an additional overlay implementing build fixups.
         # See:
         # - https://pyproject-nix.github.io/uv2nix/FAQ.html
-        pyprojectOverrides = _final: _prev: {
-          # Implement build fixups here.
-          # Note that uv2nix is _not_ using Nixpkgs buildPythonPackage.
-          # It's using https://pyproject-nix.github.io/pyproject.nix/build.html
+        pyprojectOverrides = final: prev: {
+          toml-dataclass = prev.toml-dataclass.overrideAttrs (old: {
+            nativeBuildInputs = (old.nativeBuildInputs or [ ]) ++ final.resolveBuildSystem {
+              setuptools = [ ];
+            };
+          });
         };
 
         # Construct package set
@@ -89,8 +91,10 @@ };
 
         devShells = {
           default = pkgs.mkShell {
-            packages = with pkgs; [
+            packages = (with pkgs; [
               uv
+            ]) ++ [
+              python
             ];
             inputsFrom = [ self.packages.${pkgs.system}.default ];
             env =
@@ -119,6 +123,8 @@ cfg = config.services.mycal;
             pkg = cfg.venv;
             python = self.packages.${pkgs.system}.python;
 
+            settingsFormat = pkgs.formats.toml { };
+
             inherit (lib) mkEnableOption mkOption mkIf types;
           in
           {
@@ -149,41 +155,56 @@ Mycal virtual environment package
                 '';
               };
 
-              timezone = mkOption {
-                type = types.str;
-                default = "Europe/Berlin";
+              settings = mkOption {
+                default = { };
                 description = ''
-                  Default timezone for the calendar.
+                  Additional settings for Mycal.
                 '';
-              };
-
-              name = mkOption {
-                type = types.str;
-                description = ''
-                  Name of person for whom this calendar is created.
-                '';
-              };
+                type = types.submodule {
+                  freeformType = settingsFormat.type;
 
-              calendar = mkOption {
-                default = { };
-                type = types.submodule {
                   options = {
-                    file = mkOption {
-                      type = with types; nullOr str;
-                      default = null;
-                      example = "/path/to/calendar/file";
+                    name = mkOption {
+                      type = types.str;
                       description = ''
-                        Path to the calendar file. Preferred over URL.
+                        Name of person for whom this calendar is created.
                       '';
                     };
-                    url = mkOption {
-                      type = with types; nullOr str;
-                      default = null;
-                      example = "https://example.com/calendar.ics";
+
+                    timezone = mkOption {
+                      type = types.str;
+                      default = "Europe/Berlin";
                       description = ''
-                        URL to the calendar file.
+                        Default timezone for the calendar.
                       '';
                     };
+
+                    calendar = mkOption {
+                      default = { };
+                      description = ''
+                        Configuration for the calendar. Either a file or a URL must be provided.
+                      '';
+                      type = types.submodule {
+                        options = {
+                          file = mkOption {
+                            type = types.str;
+                            default = "";
+                            example = "/path/to/calendar/file";
+                            description = ''
+                              Path to the calendar file. Preferred over URL.
+                            '';
+                          };
+                          url = mkOption {
+                            type = types.str;
+                            default = "";
+                            example = "https://example.com/calendar.ics";
+                            description = ''
+                              URL to the calendar file.
+                            '';
+                          };
+                        };
+                      };
+                    };
                   };
                 };
               };
@@ -194,11 +215,8 @@ systemd.services.mycal = {
                 description = "Mycal Calendar Service";
 
                 environment = {
-                  TZ = cfg.timezone;
-                  NAME = cfg.name;
-                  CALENDAR_FILE = cfg.calendar.file;
-                  CALENDAR_URL = cfg.calendar.url;
                   PYTHONPATH = "${python.pkgs.makePythonPath pkg.propagatedBuildInputs}:${pkg}/${python.sitePackages}";
+                  CONFIG_FILE = settingsFormat.generate "mycal-config.toml" cfg.settings;
                 };
 
                 serviceConfig = {