test: Isolation jupyter env

runtime/src/runtime/process.py

@@ -64,6 +64,14 @@ JUPYTER_MAX_LIFETIME_SECONDS = int(
     os.environ.get("JUPYTER_MAX_LIFETIME_SECONDS", str(24 * 3600))
 )
 
+# Jupyter Server no longer lives in /app/.venv (the runtime's own venv).
+# It is provisioned in a dedicated Python 3.12 venv by runtime/Dockerfile,
+# which also registers the Python 3.8 / 3.10 kernelspecs under that venv's
+# share/jupyter/kernels tree. The runtime only launches the server here;
+# user code runs in the per-kernel venv the user picks in the Notebook UI.
+JUPYTER_PY312_VENV = os.environ.get("JUPYTER_PY312_VENV", "/opt/venv/python3.12")
+JUPYTER_BIN = os.path.join(JUPYTER_PY312_VENV, "bin", "jupyter")
+
 # Sidecar metadata file written next to the workspace directory. Holds
 # the runtime state we need to reconstruct the in-memory map after a
 # crash. We intentionally store only the bits that are safe to recover:
@@ -196,7 +204,7 @@ async def start_workspace(ws_id: str) -> dict:
         base_path = f"/jupyter/{ws_id}/"
 
         cmd = [
-            "jupyter",
+            JUPYTER_BIN,
             "notebook",
             f"--port={port}",
             "--ip=0.0.0.0",
@@ -214,11 +222,22 @@ async def start_workspace(ws_id: str) -> dict:
             "--NotebookApp.disable_check_xsrf=True",
         ]
 
+        # Isolate the Jupyter subprocess inside the dedicated Python 3.12
+        # venv. VIRTUAL_ENV makes `python` / `pip` resolve against it; PATH
+        # prepended so its `bin/` wins over the runtime's /app/.venv.
+        jupyter_env = os.environ.copy()
+        jupyter_env["VIRTUAL_ENV"] = JUPYTER_PY312_VENV
+        jupyter_env["PATH"] = (
+            os.path.join(JUPYTER_PY312_VENV, "bin")
+            + os.pathsep
+            + jupyter_env.get("PATH", "")
+        )
+
         try:
             process, log_file = start_process(
                 cmd,
                 WORKSPACES_ROOT,
-                env={"PATH": f"/app/.venv/bin:{os.environ.get('PATH', '')}"},
+                env=jupyter_env,
             )
         except Exception as e:
             logger.error(f"Failed to start Jupyter for {ws_id}: {e}")