{
  description = "GlowTrack: reproducible devShell and app build outputs";

  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-25.05";
    flake-utils.url = "github:numtide/flake-utils";
  };

  outputs = { self, nixpkgs, flake-utils }:
    flake-utils.lib.eachDefaultSystem (system:
      let
        pkgs = import nixpkgs { inherit system; };
      in
      {
        # Developer shell with Node.js LTS, pnpm, git, jq
        devShells.default = pkgs.mkShell {
          packages = builtins.attrValues {
            inherit (pkgs) nodejs_20 pnpm git jq;
          };

          # Tip: uncomment Playwright bits below once tests are wired (T007)
          # packages = builtins.attrValues { inherit (pkgs) nodejs_20 pnpm git jq playwright-driver playwright-browsers; };
          # shellHook = ''
          #   export PLAYWRIGHT_BROWSERS_PATH=${pkgs.playwright-browsers}
          # '';
        };

        # Package: static site output from apps/web
        # This derivation copies a prebuilt site (build/ or dist/) from apps/web if present.
        # It does not run networked installs, keeping the build pure. The actual build
        # step is performed via pnpm in the dev shell (see T005/T030 for CI wiring).
        packages.app = pkgs.stdenvNoCC.mkDerivation {
          pname = "glowtrack-app";
          version = "0.0.0";
          src = ./.;

          buildPhase = "true";
          installPhase = ''
            mkdir -p "$out"
            if [ -d apps/web/build ]; then
              cp -r apps/web/build/* "$out/"
            elif [ -d apps/web/dist ]; then
              cp -r apps/web/dist/* "$out/"
            else
              echo "No prebuilt app output detected. After scaffolding (T005), run 'pnpm -C apps/web build' to populate build/ or dist/." > "$out/README.txt"
            fi
          '';
        };

        # Make `.#default` point to the app package for convenience
        packages.default = self.packages.${system}.app;
      }
    );
}