{
  description = "Quartz org-roam dev shell and build app";

  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
    flake-utils.url = "github:numtide/flake-utils";
    org-garden.url = "path:./org-garden";
  };

  outputs = { self, nixpkgs, flake-utils, org-garden }:
    flake-utils.lib.eachDefaultSystem (system:
      let
        pkgs = import nixpkgs { inherit system; };
        fs = pkgs.lib.fileset;

        orgGardenApp = org-garden.packages.${system}.default;

        # Pre-fetched npm dependency tree (node_modules).
        # src is filtered to only package.json + package-lock.json so that
        # edits to Quartz source files do not invalidate this derivation.
        quartzDeps = pkgs.buildNpmPackage {
          pname = "quartz-deps";
          version = "4.5.2";
          src = fs.toSource {
            root = ./.;
            fileset = fs.unions [
              ./package.json
              ./package-lock.json
            ];
          };
          npmDepsHash = "sha256-7u+VlIx44B3/ivM9vLMIOn+e4TL4eS6B682vhS+Ikb4=";
          dontBuild = true;
          installPhase = ''
            mkdir -p $out
            cp -r node_modules $out/node_modules
          '';
        };

        # The build application wrapper script (one-shot build)
        buildApp = pkgs.writeShellApplication {
          name = "build";
          runtimeInputs = [ pkgs.nodejs_22 ];
          text = ''
            NOTES_DIR="''${1:?Usage: build <path-to-notes-dir>}"
            NOTES_DIR=$(realpath "$NOTES_DIR")
            ORIG_CWD=$(pwd)

            # Set up a writable working copy of the repo in a temp dir
            WORK=$(mktemp -d)
            trap 'rm -rf "$WORK"' EXIT
            cp -r ${self}/. "$WORK/repo"
            chmod -R u+w "$WORK/repo"

            # Drop in pre-built node_modules
            ln -s ${quartzDeps}/node_modules "$WORK/repo/node_modules"

            # Pass paths via environment for org-garden
            export QUARTZ_PATH="$WORK/repo"
            export NODE_PATH="${pkgs.nodejs_22}/bin/node"

            # Run org-garden build (org → md → static site)
            ${orgGardenApp}/bin/org-garden build "$NOTES_DIR" \
              --output "$WORK/repo" \
              --content-dir "$WORK/repo/content"

            # Copy public output to caller's cwd
            cp -r "$WORK/repo/public" "$ORIG_CWD/public"
          '';
        };

        # Development server with watch + live reload
        notesApp = pkgs.writeShellApplication {
          name = "notes";
          runtimeInputs = [ pkgs.nodejs_22 orgGardenApp ];
          text = ''
            NOTES_DIR="''${1:?Usage: notes <notes-dir>}"
            NOTES_DIR=$(realpath "$NOTES_DIR")

            # Set up writable working copy
            WORK=$(mktemp -d)
            trap 'rm -rf "$WORK"' EXIT
            cp -r ${self}/. "$WORK/repo"
            chmod -R u+w "$WORK/repo"
            ln -s ${quartzDeps}/node_modules "$WORK/repo/node_modules"

            # Pass paths via environment
            export QUARTZ_PATH="$WORK/repo"
            export NODE_PATH="${pkgs.nodejs_22}/bin/node"

            # org-garden reads these internally
            org-garden serve "$NOTES_DIR" \
              --output "$WORK/repo" \
              --content-dir "$WORK/repo/content"
          '';
        };
      in
      {
        devShells.default = pkgs.mkShell {
          buildInputs = [
            pkgs.nodejs_22
            pkgs.elixir
            pkgs.mcp-nixos
          ];

          shellHook = ''
            echo "Node $(node --version) / npm $(npm --version)"
            elixir --version 2>/dev/null | head -1 || true
          '';
        };

        packages.default = buildApp;
        packages.build = buildApp;
        packages.notes = notesApp;
        packages.org-garden = orgGardenApp;

        apps.default = { type = "app"; program = "${buildApp}/bin/build"; };
        apps.build = { type = "app"; program = "${buildApp}/bin/build"; };
        apps.notes = { type = "app"; program = "${notesApp}/bin/notes"; };
      });
}