minor fixes

app.py

@@ -4,11 +4,13 @@ import os
 # Set headless rendering environment variables BEFORE any VTK/pyvista imports
 os.environ.setdefault("VTK_DEFAULT_RENDER_WINDOW_OFFSCREEN", "1")
 os.environ.setdefault("LIBGL_ALWAYS_SOFTWARE", "1")
-os.environ.setdefault("MESA_LOADER_DRIVER_OVERRIDE", "llvmpipe")
 os.environ.setdefault("MESA_GL_VERSION_OVERRIDE", "3.3")
 # Use dummy DISPLAY value instead of empty string to avoid X server connection attempts
 if "DISPLAY" not in os.environ or os.environ.get("DISPLAY") == "":
-    os.environ["DISPLAY"] = ":99"
+    # Disable all X11 attempts
+    os.environ["DISPLAY"] = ":0"
+    os.environ["VTK_USE_X"] = "NO"
+
 os.environ.setdefault("PYVISTA_OFF_SCREEN", "True")
 
 import sys