test: harden webui and gateway checks

webui/src/components/thread/ThreadShell.tsx

@@ -494,6 +494,7 @@ export function ThreadShell({
     return client.onSessionUpdate((updatedChatId, scope) => {
       if (updatedChatId !== chatId) return;
       if (scope === "metadata") return;
+      viewportRef.current?.cancelAutoScroll();
       pendingCanonicalHydrateRef.current.add(chatId);
       refreshHistory();
     });

webui/src/components/thread/ThreadViewport.tsx

@@ -26,6 +26,7 @@ import type { CliAppInfo, McpPresetInfo, UIMessage } from "@/lib/types";
 
 export interface ThreadViewportHandle {
   jumpToUserPrompt: (promptId: string) => void;
+  cancelAutoScroll: () => void;
 }
 
 interface ThreadViewportProps {
@@ -290,7 +291,14 @@ export const ThreadViewport = forwardRef<ThreadViewportHandle, ThreadViewportPro
     setVisibleMessageCount((count) => Math.max(count, messages.length - index));
   }, [messages]);
 
-  useImperativeHandle(ref, () => ({ jumpToUserPrompt }), [jumpToUserPrompt]);
+  useImperativeHandle(
+    ref,
+    () => ({
+      jumpToUserPrompt,
+      cancelAutoScroll: cancelScheduledBottomScroll,
+    }),
+    [cancelScheduledBottomScroll, jumpToUserPrompt],
+  );
 
   const measureComposerDock = useCallback(() => {
     const el = composerDockRef.current;