fix: prevent config overwrite, session history race, and streaming message loss (#663)

Co-authored-by: zuolingxuan <zuolingxuan@bytedance.com>
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

src/stores/chat.ts

@@ -1141,6 +1141,10 @@ export const useChatStore = create<ChatState>((set, get) => ({
 
   switchSession: (key: string) => {
     if (key === get().currentSessionKey) return;
+    // Stop any background polling for the old session before switching.
+    // This prevents the poll timer from firing after the switch and loading
+    // the wrong session's history into the new session's view.
+    clearHistoryPoll();
     set((s) => buildSessionSwitchPatch(s, key));
     get().loadHistory();
   },
@@ -1303,6 +1307,11 @@ export const useChatStore = create<ChatState>((set, get) => ({
 
     const loadPromise = (async () => {
       const applyLoadedMessages = (rawMessages: RawMessage[], thinkingLevel: string | null) => {
+      // Guard: if the user switched sessions while this async load was in
+      // flight, discard the result to prevent overwriting the new session's
+      // messages with stale data from the old session.
+      if (get().currentSessionKey !== currentSessionKey) return;
+
       // Before filtering: attach images/files from tool_result messages to the next assistant message
       const messagesWithToolImages = enrichWithToolResultFiles(rawMessages);
       const filteredMessages = messagesWithToolImages.filter((msg) => !isToolResultRole(msg.role));