{
  description = "Westgate Urban Foundation MVP — Blender 4.0.2 tileset generator kit";

  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
    # Reuse the machine's pinned Blender 4.0.2 + NWN toolchain via the repo overlay.
    theorem.url = "git+file:///nix/nixos";
  };

  outputs =
    {
      self,
      nixpkgs,
      theorem,
    }:
    let
      system = "x86_64-linux";
      pkgs = import nixpkgs {
        inherit system;
        overlays = [ theorem.overlays.default ];
      };
      blender = pkgs.blender-402-bin; # /bin/blender-4.0.2 (NWN needs 4.0.x, not 5.x)
      py = pkgs.python3.withPackages (ps: [ ps.mcp ]);

      gen = ./generator; # whole dir so tiles.py sits beside each script for import

      build = pkgs.writeShellApplication {
        name = "wgt-build";
        runtimeInputs = [ blender ];
        text = ''
          out="''${1:-westgate_urban_foundation_mvp.blend}"
          exec blender-4.0.2 --background --python ${gen}/build.py -- "$out"
        '';
      };

      mkset = pkgs.writeShellApplication {
        name = "wgt-set";
        runtimeInputs = [ py ];
        text = ''exec python ${gen}/make_set.py "$@"'';
      };

      mkwok = pkgs.writeShellApplication {
        name = "wgt-wok";
        runtimeInputs = [ py ];
        text = ''exec python ${gen}/make_wok.py "$@"'';
      };

      # Real .mdl + .wok export via the Neverblender addon (must be enabled in
      # this Blender's user config — confirmed working headless).
      mkmdl = pkgs.writeShellApplication {
        name = "wgt-export";
        runtimeInputs = [ blender ];
        text = ''
          blend="''${1:?usage: wgt-export <blend> <outdir> [CODE...]}"
          outdir="''${2:-mdl}"
          shift 2 || true
          exec blender-4.0.2 --background "$blend" --python ${gen}/export_mdl.py \
            --python-exit-code 1 -- "$outdir" "$@"
        '';
      };
    in
    {
      packages.${system}.default = build;

      apps.${system} = {
        default = {
          type = "app";
          program = "${build}/bin/wgt-build";
        };
        build = {
          type = "app";
          program = "${build}/bin/wgt-build";
        };
        set = {
          type = "app";
          program = "${mkset}/bin/wgt-set";
        };
        wok = {
          type = "app";
          program = "${mkwok}/bin/wgt-wok";
        };
        export = {
          type = "app";
          program = "${mkmdl}/bin/wgt-export";
        };
      };

      devShells.${system}.default = pkgs.mkShell {
        packages = [
          blender
          py
          pkgs.neverwinter-nim
          pkgs.cleanmodels
        ];
        shellHook = ''
          export BLENDER_BIN=${blender}/bin/blender-4.0.2
          echo "wgt01 dev shell — build: blender-4.0.2 --background --python generator/build.py -- out.blend" >&2
        '';
      };
    };
}