pi: fix python env

home/progs/pi.nix

@@ -119,6 +119,50 @@ let
     };
   };
 
+  # OMP's `eval` tool drives a Jupyter kernel for Python execution. It refuses
+  # ("Python backend is unavailable") unless both `kernel_gateway`
+  # (jupyter-kernel-gateway) and `ipykernel` are importable from the python it
+  # selects. nixpkgs ships ipykernel but not jupyter-kernel-gateway, so we
+  # build it here from the PyPI sdist.
+  jupyter-kernel-gateway = pkgs.python3Packages.buildPythonPackage rec {
+    pname = "jupyter_kernel_gateway";
+    version = "3.0.1";
+    pyproject = true;
+    src = pkgs.python3Packages.fetchPypi {
+      inherit pname version;
+      hash = "sha256-kAaQxMDnloZzVUaNaF9/oc88d3XQjoccFX931l+9bX8=";
+    };
+    nativeBuildInputs = [ pkgs.python3Packages.hatchling ];
+    propagatedBuildInputs = with pkgs.python3Packages; [
+      jupyter-client
+      jupyter-core
+      jupyter-server
+      requests
+      tornado
+      traitlets
+    ];
+    # Upstream test suite hits the network and pulls pytest-jupyter; the import
+    # check is enough to confirm the package wires up correctly.
+    doCheck = false;
+    pythonImportsCheck = [ "kernel_gateway" ];
+    meta = {
+      description = "Jupyter Kernel Gateway: headless web server for Jupyter kernels";
+      homepage = "https://github.com/jupyter/kernel_gateway";
+      license = lib.licenses.bsd3;
+    };
+  };
+
+  # Python env exposed to omp as its "managed venv" at ~/.omp/python-env. omp's
+  # runtime resolver (packages/coding-agent/src/eval/py/runtime.ts) probes that
+  # path before falling back to PATH, so symlinking it here keeps PATH clean
+  # (no conflict with the python313 env in home/profiles/no-gui.nix) while
+  # guaranteeing kernel_gateway + ipykernel are importable without `omp setup
+  # python` ever needing to write to the store.
+  ompPythonEnv = pkgs.python3.withPackages (ps: [
+    ps.ipykernel
+    jupyter-kernel-gateway
+  ]);
+
   # Browser path for the playwright skill body.
   playwrightChromium =
     let
@@ -144,6 +188,9 @@ in
     # main settings: ~/.omp/agent/config.yml (JSON is valid YAML)
     ".omp/agent/config.yml".text = builtins.toJSON ompSettings;
 
+    # see comment above ompPythonEnv definition.
+    ".omp/python-env".source = ompPythonEnv;
+
     # model/provider config: ~/.omp/agent/models.yml
     ".omp/agent/models.yml".text = builtins.toJSON ompModels;