fix(web): summarize session titles, sort by activity, and paginate history (BUG-553)

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/src/components/app-sidebar.tsx

@@ -40,6 +40,7 @@ import {
 import { ThemePreferenceMenu } from "@/components/theme-preference-menu";
 import { UserAvatar } from "@/components/user-avatar";
 import type { BeamAvatar } from "@/lib/beam-avatar";
+import { groupSessionsByRecency } from "@/lib/session-groups";
 
 export type SidebarAccount = {
   name: string;
@@ -106,12 +107,25 @@ export function AppSidebar({
   const { isMobile, setOpen, setOpenMobile, state, viewport } = useSidebar();
   const firstSessionRef = useRef<HTMLButtonElement>(null);
   const historyHeadingRef = useRef<HTMLElement>(null);
+  const loadMoreRef = useRef<HTMLDivElement>(null);
   const isCollapsedDesktop = state === "collapsed" && !isMobile;
   const showExpandedContent = !isCollapsedDesktop;
   const menuPlacement = `${viewport}:${state}`;
   const previousMenuPlacement = useRef(menuPlacement);
   const favoriteSessions = sessions.filter((session) => session.pinned);
   const historySessions = sessions.filter((session) => !session.pinned);
+  const historyGroups = groupSessionsByRecency(historySessions);
+
+  useEffect(() => {
+    if (!sessionControls.hasMore || !sessionControls.onLoadMore) return;
+    const node = loadMoreRef.current;
+    if (!node) return;
+    const observer = new IntersectionObserver((entries) => {
+      if (entries.some((entry) => entry.isIntersecting)) sessionControls.onLoadMore?.();
+    });
+    observer.observe(node);
+    return () => observer.disconnect();
+  }, [historySessions.length, sessionControls.hasMore, sessionControls.onLoadMore]);
 
   useEffect(() => {
     if (previousMenuPlacement.current !== menuPlacement && accountMenuOpen) {
@@ -259,7 +273,16 @@ export function AppSidebar({
                 <SidebarGroupContent className="sidebar-nested">
                   {historySessions.length === 0 ? <p className="sidebar-empty">暂无对话，点上方「新建对话」开始</p> : (
                     <SidebarMenu className="session-list">
-                      {historySessions.map((session, index) => renderSession(session, favoriteSessions.length + index))}
+                      {historyGroups.map((group) => (
+                        <div key={group.key}>
+                          <p className="sidebar-group-label">{group.label}</p>
+                          {group.sessions.map((session) => renderSession(
+                            session,
+                            favoriteSessions.length + historySessions.findIndex((item) => item.id === session.id),
+                          ))}
+                        </div>
+                      ))}
+                      {sessionControls.hasMore ? <div ref={loadMoreRef} aria-hidden className="session-list-sentinel" /> : null}
                     </SidebarMenu>
                   )}
                 </SidebarGroupContent>

frontend/src/components/sidebar-session-row.tsx

@@ -19,13 +19,17 @@ import { sessionMutationMenuVisible } from "@/lib/chat-session-persistence";
 export type SidebarSession = {
   readonly id: string;
   readonly title: string;
+  readonly subtitle?: string | null;
   readonly pinned: boolean;
   readonly archived: boolean;
+  readonly updatedAt: number;
 };
 
 export type SidebarSessionControls = {
   readonly archivedCount: number;
   readonly showingArchived: boolean;
+  readonly hasMore?: boolean;
+  readonly onLoadMore?: () => void;
   readonly menuSessionId: string | null;
   readonly disabled: boolean;
   readonly onToggleArchivedView: () => void;
@@ -96,6 +100,7 @@ export const SidebarSessionRow = forwardRef<HTMLButtonElement, SidebarSessionRow
             <span className="truncate">{session.title}</span>
             {opening ? <span className="session-opening-note">{RECTIFICATION_SIDEBAR_OPENING_NOTE}</span> : null}
           </span>
+          {session.subtitle ? <small className="session-subtitle">{session.subtitle}</small> : null}
         </SidebarMenuButton>
         <Menu.Trigger
           className="session-menu-trigger"