fix: keep scroll position when switching between cached conversations

src/renderer/src/App.test.tsx

@@ -4777,9 +4777,16 @@ describe("App", () => {
     });
     expect(messageRenderProbe).not.toHaveBeenCalled();
     expect(firstPane?.querySelectorAll(".message")).toHaveLength(160);
+    const paneOrder = (): string[] =>
+      [...container.querySelectorAll<HTMLElement>(".chat-history-pane")].map(
+        (pane) => pane.dataset.conversationId ?? "",
+      );
+    const warmPaneOrder = paneOrder();
     fireEvent.click(screen.getByText("第一段长会话").closest("button")!);
 
     expect(await screen.findByText("第一段历史 001")).toBeInTheDocument();
+    // Chromium resets scrollTop when React moves a kept pane; jsdom does not.
+    expect(paneOrder()).toEqual(warmPaneOrder);
     const restoredFirstPane = container.querySelector<HTMLElement>(
       `[data-conversation-id="${firstConversationId}"]`,
     );

src/renderer/src/App.tsx

@@ -3594,18 +3594,26 @@ function App(): React.JSX.Element {
     () => new Set(cachedWorkspaceViews.map((entry) => entry.key)),
     [cachedWorkspaceViews],
   );
+  // Kept panes must keep a stable DOM order. Reordering keyed siblings makes
+  // React detach and reinsert scroll containers, which resets their scrollTop.
+  const conversationPaneOrderRef = useRef<string[]>([]);
   const cachedConversations = useMemo(() => {
     const conversationById = new Map(
       conversations.map((conversation) => [conversation.id, conversation]),
     );
-    const cachedIds = [
-      activeId,
-      ...cachedConversationViews.map((entry) => entry.key),
-    ].filter(
-      (conversationId, index, values) =>
-        conversationId && values.indexOf(conversationId) === index,
+    const cachedIds = new Set(
+      [activeId, ...cachedConversationViews.map((entry) => entry.key)].filter(
+        Boolean,
+      ),
     );
-    return cachedIds.flatMap((conversationId) => {
+    const paneOrder = conversationPaneOrderRef.current.filter((id) =>
+      cachedIds.has(id),
+    );
+    cachedIds.forEach((id) => {
+      if (!paneOrder.includes(id)) paneOrder.push(id);
+    });
+    conversationPaneOrderRef.current = paneOrder;
+    return paneOrder.flatMap((conversationId) => {
       const conversation = conversationById.get(conversationId);
       return conversation ? [conversation] : [];
     });

src/renderer/src/ChatHistoryPane.tsx

@@ -108,6 +108,7 @@ export const ChatHistoryPane = memo(function ChatHistoryPane({
   const pinnedToBottomRef = useRef(scrollSnapshot?.pinnedToBottom ?? true);
   const latestScrollSnapshotRef = useRef(scrollSnapshot);
   const restorePendingRef = useRef(true);
+  const wasActiveRef = useRef(false);
   const prependScrollPositionRef = useRef<
     | {
         scrollHeight: number;
@@ -234,12 +235,15 @@ export const ChatHistoryPane = memo(function ChatHistoryPane({
 
   useLayoutEffect(() => {
     if (!active) {
+      wasActiveRef.current = false;
       return;
     }
     const scrollContainer = scrollRef.current;
     if (!scrollContainer) {
       return;
     }
+    const activated = !wasActiveRef.current;
+    wasActiveRef.current = true;
     if (restorePendingRef.current) {
       restorePendingRef.current = false;
       if (scrollSnapshot && !scrollSnapshot.pinnedToBottom) {
@@ -247,6 +251,14 @@ export const ChatHistoryPane = memo(function ChatHistoryPane({
         scrollContainer.scrollTop = scrollSnapshot.scrollTop;
         return;
       }
+    } else if (activated && !pinnedToBottomRef.current) {
+      // Hidden panes may lose scrollTop when the browser detaches or re-lays
+      // them out; restore the reader's last position instead of the top.
+      const saved = latestScrollSnapshotRef.current;
+      if (saved && !saved.pinnedToBottom) {
+        scrollContainer.scrollTop = saved.scrollTop;
+        return;
+      }
     }
     if (pinnedToBottomRef.current) {
       scrollContainer.scrollTo({