[skip eval] fix: 回答完成后推荐问题不再闪一下

frontend/src/app/(app)/chat/[chatId]/page.test.tsx

@@ -2418,6 +2418,26 @@ describe('ChatPage 会话切换体验', () => {
     expect(lastMessageListProps?.loadingState).toBeUndefined();
   });
 
+  it('同一会话回答完成后的权威刷新期间保留推荐问题', async () => {
+    conversationsById.set('chat-a', createConversation('chat-a', [textMessage('message-a')]));
+    hydrationById.set('chat-a', { view: 'ready' });
+    suggestedQuestionsState.questions = ['继续问'];
+
+    const { rerender } = render(<ChatPage />);
+
+    await waitFor(() => {
+      expect(screen.getByTestId('message-list')).toHaveAttribute('data-message-ids', 'message-a');
+    });
+
+    hydrationById.set('chat-a', { view: 'loading' });
+    rerender(<ChatPage />);
+
+    const lastMessageListProps = chatMessageListMock.mock.calls.at(-1)?.[0];
+    expect(lastMessageListProps?.loadingState).toBeUndefined();
+    expect(lastMessageListProps?.suggestedQuestions).toEqual(['继续问']);
+    expect(lastMessageListProps?.onSelectQuestion).toEqual(expect.any(Function));
+  });
+
   it('动态 page remount 后切到未加载过的 loading 会话时不显示上一段 ready messages', async () => {
     conversationsById.set('chat-a', createConversation('chat-a', [textMessage('message-a')]));
     hydrationById.set('chat-a', { view: 'ready' });

frontend/src/app/(app)/chat/[chatId]/page.tsx

@@ -1356,10 +1356,12 @@ export default function ChatPage() {
                         ? undefined
                         : handleInspectTrajectory
                     }
-                    suggestedQuestions={shouldKeepPreviousContent || isHydratingWithoutContent ? [] : suggestedQuestions}
-                    isLoadingQuestions={shouldKeepPreviousContent || isHydratingWithoutContent ? false : isLoadingQuestions}
-                    onSelectQuestion={shouldKeepPreviousContent || isHydratingWithoutContent ? undefined : handleSelectQuestion}
-                    onRefreshQuestions={shouldKeepPreviousContent || isHydratingWithoutContent ? undefined : handleRefreshQuestions}
+                    // 保留上一屏的一定是同一会话（回答完成后的权威刷新），推荐问题属于它，
+                    // 照常显示，否则刷新的一瞬间推荐区会消失再出现。
+                    suggestedQuestions={isHydratingWithoutContent ? [] : suggestedQuestions}
+                    isLoadingQuestions={isHydratingWithoutContent ? false : isLoadingQuestions}
+                    onSelectQuestion={isHydratingWithoutContent ? undefined : handleSelectQuestion}
+                    onRefreshQuestions={isHydratingWithoutContent ? undefined : handleRefreshQuestions}
                     completionStateVisible={shouldKeepPreviousContent || isHydratingWithoutContent ? false : showCompletionState}
                     notificationReadEnabled={notificationReadReady && hydrationStatus === 'done' && !shouldKeepPreviousContent && activeSurface === 'chat'}
                     notificationSessionKey={authSessionKey}

frontend/src/components/chat/SuggestedQuestions.test.tsx

@@ -174,6 +174,17 @@ describe('SuggestedQuestions', () => {
     expect(placeholder.querySelectorAll('.h-8')).toHaveLength(3);
   });
 
+  it('fades in questions only when they arrive after the placeholder', () => {
+    const { rerender } = render(
+      <SuggestedQuestions questions={[]} isLoading={true} onSelectQuestion={vi.fn()} />,
+    );
+    rerender(<SuggestedQuestions questions={['后到的问题']} isLoading={false} onSelectQuestion={vi.fn()} />);
+    expect(screen.getByRole('button', { name: /后到的问题/ }).className).toContain('fade-in');
+
+    render(<SuggestedQuestions questions={['已有的问题']} isLoading={false} onSelectQuestion={vi.fn()} />);
+    expect(screen.getByRole('button', { name: /已有的问题/ }).className).not.toContain('fade-in');
+  });
+
   it('uses stronger pending affordance after selecting a question', () => {
     const onSelectQuestion = vi.fn();
 

frontend/src/components/chat/SuggestedQuestions.tsx

@@ -28,6 +28,8 @@ const SuggestedQuestions: React.FC<SuggestedQuestionsProps> = ({
   const [hoveredIndex, setHoveredIndex] = useState<number | null>(null);
   const [isRefreshing, setIsRefreshing] = useState(false);
   const [pendingQuestion, setPendingQuestion] = useState<string | null>(null);
+  // 只有先占位、后到达的问题才淡入；挂载时已有问题（流结束切换渲染分支、刷新页面）直接显示，不重播动画。
+  const [fadeInArrivals] = useState(() => questions.length === 0);
   const { isAuthenticated } = useAppSelector((state) => state.auth);
   const { toast } = useToast();
   const isBusy = isLoading || isRefreshing || pendingQuestion !== null;
@@ -137,7 +139,8 @@ const SuggestedQuestions: React.FC<SuggestedQuestionsProps> = ({
             size="sm"
             className={cn(
               "flex items-center gap-2 w-full text-left rounded-md border border-border/50 bg-transparent px-2.5 py-1.5 text-sm text-foreground transition-colors duration-fast hover:bg-muted/30 hover:border-border",
-              "h-auto justify-start font-normal disabled:opacity-75 animate-in fade-in duration-300 motion-reduce:animate-none",
+              "h-auto justify-start font-normal disabled:opacity-75",
+              fadeInArrivals && "animate-in fade-in duration-300 motion-reduce:animate-none",
               pendingQuestion === question && "border-info-border bg-info-bg text-info"
             )}
             onClick={() => handleQuestionSelect(question)}