diff --git a/bec_widgets/applications/launch_window.py b/bec_widgets/applications/launch_window.py
index 4eae81a4..50f8e3b1 100644
--- a/bec_widgets/applications/launch_window.py
+++ b/bec_widgets/applications/launch_window.py
@@ -660,20 +660,35 @@ class LaunchWindow(BECMainWindow):
         Check if the launcher is the last widget in the application.
         """
 
-        # get all parents of connections
         for connection in connections.values():
-            try:
-                parent = connection.parent()
-                if parent is None and connection.objectName() != self.objectName():
-                    logger.info(
-                        f"Found non-launcher connection without parent: {connection.objectName()}"
-                    )
-                    return False
-            except Exception as e:
-                logger.error(f"Error getting parent of connection: {e}")
+            if not self._connection_belongs_to_launcher(connection):
                 return False
         return True
 
+    def _connection_belongs_to_launcher(self, connection: QObject) -> bool:
+        """
+        Check whether a registered connection is the launcher itself or part of its Qt hierarchy.
+
+        Registered top-level windows such as BECMainWindowNoRPC are expected when another GUI is
+        open. They are not launcher children, but they are also not an error condition.
+        """
+        try:
+            if connection is self or getattr(connection, "gui_id", None) == self.gui_id:
+                return True
+            if connection.objectName() == self.objectName():
+                return True
+
+            parent = connection.parent()
+            while parent is not None:
+                if parent is self:
+                    return True
+                parent = parent.parent()
+        except Exception as e:
+            logger.error(f"Error checking launcher ownership of connection: {e}")
+            return False
+
+        return False
+
     def _turn_off_the_lights(self, connections: dict):
         """
         If there is only one connection remaining, it is the launcher, so we show it.
diff --git a/tests/unit_tests/test_launch_window.py b/tests/unit_tests/test_launch_window.py
index 44df9022..90b942f4 100644
--- a/tests/unit_tests/test_launch_window.py
+++ b/tests/unit_tests/test_launch_window.py
@@ -153,6 +153,17 @@ def test_gui_server_turns_off_the_lights(bec_launch_window, connection_names, hi
             mock_set_quit_on_last_window_closed.assert_called_once_with(True)
 
 
+def test_launcher_detects_external_main_window_without_info_log(bec_launch_window):
+    connection = mock.MagicMock()
+    connection.parent.return_value = None
+    connection.objectName.return_value = "BECMainWindowNoRPC"
+
+    with mock.patch("bec_widgets.applications.launch_window.logger.info") as mock_info:
+        assert not bec_launch_window._launcher_is_last_widget({"window": connection})
+
+    mock_info.assert_not_called()
+
+
 @pytest.mark.parametrize(
     "connection_names, close_called",
     [