diff --git a/flake.nix b/flake.nix
index e7ec633..cb0d570 100644
--- a/flake.nix
+++ b/flake.nix
@@ -8,12 +8,35 @@
       system = "x86_64-linux";
       pkgs = nixpkgs.legacyPackages.${system};
 
+      # Custom Python package: garth (not in nixpkgs)
+      garth = pkgs.python3Packages.buildPythonPackage {
+        pname = "garth";
+        version = "0.5.21";
+        src = pkgs.fetchPypi {
+          pname = "garth";
+          version = "0.5.21";
+          sha256 = "sha256-jZeVldHU6iOhtGarSmCVXRObcfiG9GSQvhQPzuWE2rQ=";
+        };
+        format = "pyproject";
+        nativeBuildInputs = [ pkgs.python3Packages.hatchling ];
+        propagatedBuildInputs = with pkgs.python3Packages; [
+          pydantic
+          requests-oauthlib
+          requests
+        ];
+        doCheck = false;
+      };
+
+      # Python with garth for Garmin auth scripts
+      pythonWithGarth = pkgs.python3.withPackages (ps: [ garth ]);
+
       # Common packages for development
-      commonPackages = with pkgs; [
-        nodejs_24
-        pnpm
-        git
-        pocketbase
+      commonPackages = [
+        pkgs.nodejs_24
+        pkgs.pnpm
+        pkgs.git
+        pkgs.pocketbase
+        pythonWithGarth
       ];
     in {
       # Docker image for production deployment