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

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

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

        pipelineApp = pipeline.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
        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"

            # Run the pre-compiled pipeline escript (org → md, citations transform)
            ${pipelineApp}/bin/pipeline "$NOTES_DIR" \
              --output "$WORK/repo" \
              --content-dir "$WORK/repo/content"

            # Build the static site from within the repo copy so relative paths
            # (e.g. ./package.json in constants.js) resolve correctly.
            # --output is absolute so the result lands in the caller's cwd.
            cd "$WORK/repo"
            node quartz/bootstrap-cli.mjs build \
              --directory "$WORK/repo/content" \
              --output "$ORIG_CWD/public"
          '';
        };
      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.pipeline = pipelineApp;

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