diff --git a/docs/source/_static/theme-override.css b/docs/source/_static/theme-override.css
index 460812aca4..24b5c0273a 100644
--- a/docs/source/_static/theme-override.css
+++ b/docs/source/_static/theme-override.css
@@ -78,4 +78,9 @@ tbody tr:hover {
     .container:has(#left-sidebar) {
         grid-template-columns: 310px minmax(0, 1fr);
     }
-}
\ No newline at end of file
+}
+
+/* Always enable scrollbar in left TOC to prevent layout shifts when expanding */
+#left-sidebar {
+    overflow-y: scroll;
+}