fix: reset-state-on-new-session-click

src/components/app/AppContent.tsx

@@ -44,6 +44,7 @@ function AppContentInner() {
     sidebarOpen,
     isLoadingProjects,
     externalMessageUpdate,
+    newSessionTrigger,
     setActiveTab,
     setSidebarOpen,
     setIsInputFocused,
@@ -194,6 +195,7 @@ function AppContentInner() {
           onNavigateToSession={(targetSessionId: string) => navigate(`/session/${targetSessionId}`)}
           onShowSettings={() => setShowSettings(true)}
           externalMessageUpdate={externalMessageUpdate}
+          newSessionTrigger={newSessionTrigger}
         />
       </div>
 

src/components/chat/hooks/useChatSessionState.ts

@@ -22,6 +22,7 @@ interface UseChatSessionStateArgs {
   sendMessage: (message: unknown) => void;
   autoScrollToBottom?: boolean;
   externalMessageUpdate?: number;
+  newSessionTrigger?: number;
   processingSessions?: Set<string>;
   resetStreamingState: () => void;
   pendingViewSessionRef: MutableRefObject<PendingViewSession | null>;
@@ -95,6 +96,7 @@ export function useChatSessionState({
   sendMessage,
   autoScrollToBottom,
   externalMessageUpdate,
+  newSessionTrigger,
   processingSessions,
   resetStreamingState,
   pendingViewSessionRef,
@@ -131,9 +133,78 @@ export function useChatSessionState({
   const loadAllFinishedTimerRef = useRef<ReturnType<typeof setTimeout> | null>(null);
   const loadAllOverlayTimerRef = useRef<ReturnType<typeof setTimeout> | null>(null);
   const lastLoadedSessionKeyRef = useRef<string | null>(null);
+  /**
+   * Tracks the last processed value from `useProjectsState.newSessionTrigger`.
+   *
+   * The trigger itself is intentionally increment-only and routed via:
+   * useProjectsState -> AppContent -> MainContent -> ChatInterface -> this hook.
+   * We compare values to ensure each explicit New Session click runs exactly one
+   * reset pass in this local chat state domain.
+   */
+  const previousNewSessionTriggerRef = useRef(newSessionTrigger ?? 0);
 
   const createDiff = useMemo<DiffCalculator>(() => createCachedDiffCalculator(), []);
 
+  useEffect(() => {
+    const trigger = newSessionTrigger ?? 0;
+    if (trigger === previousNewSessionTriggerRef.current) {
+      return;
+    }
+    previousNewSessionTriggerRef.current = trigger;
+
+    /**
+     * Consumer-side reset for explicit New Session intent.
+     *
+     * Why this is essential:
+     * - Chat keeps local state that is not fully derived from `selectedSession`:
+     *   `currentSessionId`, `pendingUserMessage`, streaming/status flags, message
+     *   pagination/scroll bookkeeping, and pending session IDs in sessionStorage.
+     * - If the user clicks New Session while already on the same route with no
+     *   selected session, parent state updates can be idempotent and this local
+     *   state would otherwise persist, making the click appear to "do nothing".
+     *
+     * What this reset guarantees:
+     * - A deterministic clean draft state on every New Session click.
+     * - No dependence on route/tab/session-object identity changes.
+     * - No coupling to unrelated external update signals.
+     */
+    resetStreamingState();
+    pendingViewSessionRef.current = null;
+    setClaudeStatus(null);
+    setCanAbortSession(false);
+    setIsLoading(false);
+    setCurrentSessionId(null);
+    setPendingUserMessage(null);
+    sessionStorage.removeItem('pendingSessionId');
+    sessionStorage.removeItem('cursorSessionId');
+    messagesOffsetRef.current = 0;
+    setHasMoreMessages(false);
+    setTotalMessages(0);
+    setTokenBudget(null);
+    setVisibleMessageCount(INITIAL_VISIBLE_MESSAGES);
+    setAllMessagesLoaded(false);
+    allMessagesLoadedRef.current = false;
+    setIsLoadingAllMessages(false);
+    setLoadAllJustFinished(false);
+    setShowLoadAllOverlay(false);
+    setViewHiddenCount(0);
+    setSearchTarget(null);
+    searchScrollActiveRef.current = false;
+    topLoadLockRef.current = false;
+    pendingScrollRestoreRef.current = null;
+    pendingInitialScrollRef.current = true;
+    lastLoadedSessionKeyRef.current = null;
+
+    if (loadAllOverlayTimerRef.current) {
+      clearTimeout(loadAllOverlayTimerRef.current);
+      loadAllOverlayTimerRef.current = null;
+    }
+    if (loadAllFinishedTimerRef.current) {
+      clearTimeout(loadAllFinishedTimerRef.current);
+      loadAllFinishedTimerRef.current = null;
+    }
+  }, [newSessionTrigger, pendingViewSessionRef, resetStreamingState]);
+
   /* ---------------------------------------------------------------- */
   /*  Derive chatMessages from the store                              */
   /* ---------------------------------------------------------------- */

src/components/chat/types/types.ts

@@ -113,6 +113,7 @@ export interface ChatInterfaceProps {
   autoScrollToBottom?: boolean;
   sendByCtrlEnter?: boolean;
   externalMessageUpdate?: number;
+  newSessionTrigger?: number;
   onTaskClick?: (...args: unknown[]) => void;
   onShowAllTasks?: (() => void) | null;
 }

src/components/chat/view/ChatInterface.tsx

@@ -43,6 +43,7 @@ function ChatInterface({
   autoScrollToBottom,
   sendByCtrlEnter,
   externalMessageUpdate,
+  newSessionTrigger,
   onShowAllTasks,
 }: ChatInterfaceProps) {
   const { tasksEnabled, isTaskMasterInstalled } = useTasksSettings();
@@ -123,6 +124,7 @@ function ChatInterface({
     sendMessage,
     autoScrollToBottom,
     externalMessageUpdate,
+    newSessionTrigger,
     processingSessions,
     resetStreamingState,
     pendingViewSessionRef,

src/components/main-content/types/types.ts

@@ -53,6 +53,7 @@ export type MainContentProps = {
   onNavigateToSession: (targetSessionId: string) => void;
   onShowSettings: () => void;
   externalMessageUpdate: number;
+  newSessionTrigger: number;
 };
 
 export type MainContentHeaderProps = {

src/components/main-content/view/MainContent.tsx

@@ -51,6 +51,7 @@ function MainContent({
   onNavigateToSession,
   onShowSettings,
   externalMessageUpdate,
+  newSessionTrigger,
 }: MainContentProps) {
   const { preferences } = useUiPreferences();
   const { autoExpandTools, showRawParameters, showThinking, autoScrollToBottom, sendByCtrlEnter } = preferences;
@@ -145,6 +146,7 @@ function MainContent({
                 autoScrollToBottom={autoScrollToBottom}
                 sendByCtrlEnter={sendByCtrlEnter}
                 externalMessageUpdate={externalMessageUpdate}
+                newSessionTrigger={newSessionTrigger}
                 onShowAllTasks={tasksEnabled ? () => setActiveTab('tasks') : null}
               />
             </ErrorBoundary>

src/hooks/useProjectsState.ts

@@ -261,6 +261,27 @@ export function useProjectsState({
   const [showSettings, setShowSettings] = useState(false);
   const [settingsInitialTab, setSettingsInitialTab] = useState('agents');
   const [externalMessageUpdate, setExternalMessageUpdate] = useState(0);
+  /**
+   * `newSessionTrigger` is an explicit, monotonic intent signal for user-driven
+   * New Session actions.
+   *
+   * It exists because `handleNewSession` can be invoked while the app is already in
+   * the same visible state (`selectedSession === null`, `activeTab === 'chat'`,
+   * route already `/`). In that case, React/router updates are idempotent and no
+   * downstream reset logic runs.
+   *
+   * Usage across the codebase:
+   * 1) Produced here in `handleNewSession` via increment (always changes).
+   * 2) Returned from this hook and threaded through:
+   *    useProjectsState -> AppContent -> MainContent -> ChatInterface.
+   * 3) Consumed in `useChatSessionState` as an effect dependency to forcibly clear
+   *    chat-local state (`currentSessionId`, pending draft message, streaming flags,
+   *    pending session storage keys, pagination/scroll artifacts).
+   *
+   * Keeping this signal dedicated avoids coupling resets to unrelated counters/events
+   * (for example websocket/project refresh updates) that could cause accidental resets.
+   */
+  const [newSessionTrigger, setNewSessionTrigger] = useState(0);
 
   const loadingProgressTimeoutRef = useRef<ReturnType<typeof setTimeout> | null>(null);
   const lastHandledMessageRef = useRef<AppSocketMessage | null>(null);
@@ -587,6 +608,7 @@ export function useProjectsState({
       setSelectedProject(project);
       setSelectedSession(null);
       setActiveTab('chat');
+      setNewSessionTrigger((previous) => previous + 1);
       navigate('/');
 
       if (isMobile) {
@@ -806,6 +828,7 @@ export function useProjectsState({
     showSettings,
     settingsInitialTab,
     externalMessageUpdate,
+    newSessionTrigger,
     setActiveTab,
     setSidebarOpen,
     setIsInputFocused,