diff --git a/obi/obi.nix b/obi/obi.nix
new file mode 100644
index 0000000..e7a2a87
--- /dev/null
+++ b/obi/obi.nix
@@ -0,0 +1,50 @@
+# nix-build obi.nix
+
+# not callPackage because we need a very new nixpkgs for numpy2
+with import (builtins.fetchTarball {
+  name = "nixos-unstable-2025-10-05";
+  url = "https://github.com/nixos/nixpkgs/archive/e06e469c8e2d893f1f0dcb55bbd9de8904ee0cf5.tar.gz";
+  sha256 = "sha256:174gj7nxcmj4l5dr1iqfr67cl14x1aw3hxqzg716pw0g1qrmjs4w";
+}) {};
+
+python3.pkgs.buildPythonApplication {
+  name = "open-beam-interface";
+  src = fetchFromGitHub {
+    owner = "q3k";
+    repo = "Open-Beam-Interface";
+    rev = "7076782325fe04f146e6c3d126a4a1fe1ff9da8f";
+    hash = "sha256-3Tu2nFx3V5XIgyRb0da/28CxkY7Lscln0F4T98PGyHY=";
+  };
+  pyproject = true;
+
+  nativeBuildInputs = [
+    python3.pkgs.pdm-backend
+  ];
+
+  nativeCheckInput = [
+    python3.pkgs.unittestCheckHook
+  ];
+
+  propagatedBuildInputs = [
+    glasgow
+    yosys
+    nextpnr
+    icestorm
+  ] ++ (with python3.pkgs; [
+    numpy
+    tifffile
+    pillow
+    tomlkit
+    pyqtgraph
+    pyqt6
+    qasync
+  ]);
+
+  check = false;
+
+  preBuild = ''
+    export PDM_BUILD_SCM_VERSION=1.0
+    cd software
+  '';
+}
+