diff --git a/toolbar/hermes_bridge.shelf b/toolbar/hermes_bridge.shelf
index ef8e905..4855ca4 100644
--- a/toolbar/hermes_bridge.shelf
+++ b/toolbar/hermes_bridge.shelf
@@ -149,8 +149,9 @@ class HermesBridgeWindow(QtWidgets.QWidget):
         QtCore.QTimer.singleShot(2000,
             lambda: self.btn_copy.setText("Copy"))
 
-# ── Per SideFX docs: parent to main window to keep alive ──
-win = HermesBridgeWindow(hou.ui.mainQtWindow())
+# ── Store on hou.session to prevent GC (per SideFX docs) ──
+win = HermesBridgeWindow()
+hou.session.hermes_bridge_win = win
 win.show()
 ]]></script>
   </tool>