diff --git a/src/components/room/DiscordChannelSidebar.tsx b/src/components/room/DiscordChannelSidebar.tsx
index f1ef110..8337e37 100644
--- a/src/components/room/DiscordChannelSidebar.tsx
+++ b/src/components/room/DiscordChannelSidebar.tsx
@@ -13,6 +13,7 @@ import {
   PointerSensor,
   useSensor,
   useSensors,
+  useDroppable,
   type DragEndEvent,
   type UniqueIdentifier,
 } from '@dnd-kit/core';
@@ -141,6 +142,9 @@ const ChannelGroup = memo(function ChannelGroup({
 }) {
   const ids: UniqueIdentifier[] = rooms.map((r) => `${DRAG_PREFIX}${r.id}`);
 
+  // Make the category header a droppable zone so rooms can be dragged onto it
+  const { setNodeRef: setHeaderRef, isOver: isOverHeader } = useDroppable({ id: categoryName });
+
   return (
     <div
       className="discord-channel-category"
@@ -148,7 +152,8 @@ const ChannelGroup = memo(function ChannelGroup({
       onDrop={canReceiveDrops ? () => undefined /* handled by DnD */ : undefined}
     >
       <button
-        className={cn('discord-channel-category-header w-full', isCollapsed && 'collapsed')}
+        ref={setHeaderRef}
+        className={cn('discord-channel-category-header w-full', isCollapsed && 'collapsed', isOverHeader && 'ring-1 ring-accent')}
         onClick={onToggle}
         title={isCollapsed ? 'Expand' : 'Collapse'}
       >
@@ -309,25 +314,30 @@ export const DiscordChannelSidebar = memo(function DiscordChannelSidebar({
     [onMoveRoomToCategory],
   );
 
-  // Group rooms by category
+  // Group rooms by category — empty categories still show as collapsible groups
   const uncategorized = useMemo(
-    () => rooms.filter((r) => !r.category_info?.name),
+    () => rooms.filter((r) => !r.category),
     [rooms],
   );
   const categorized = useMemo(
-    () => rooms.filter((r) => r.category_info?.name),
+    () => rooms.filter((r) => r.category),
     [rooms],
   );
 
   const categoryMap = useMemo(() => {
+    // Start with ALL categories (including empty ones), then merge in rooms
     const map = new Map<CatName, RoomWithCategory[]>();
+    for (const cat of categories) {
+      if (!map.has(cat.name)) map.set(cat.name, []);
+    }
     for (const room of categorized) {
-      const name = room.category_info!.name;
-      if (!map.has(name)) map.set(name, []);
-      map.get(name)!.push(room);
+      const catName = room.category_info?.name;
+      if (catName && map.has(catName)) {
+        map.get(catName)!.push(room);
+      }
     }
     return map;
-  }, [categorized]);
+  }, [categorized, categories]);
 
   return (
     <div className="discord-channel-sidebar flex flex-col h-full">
diff --git a/src/components/room/DiscordChatPanel.tsx b/src/components/room/DiscordChatPanel.tsx
index d174650..d4c2c95 100644
--- a/src/components/room/DiscordChatPanel.tsx
+++ b/src/components/room/DiscordChatPanel.tsx
@@ -59,6 +59,7 @@ export function DiscordChatPanel({ room, isAdmin, onClose, onDelete, onToggleCha
     refreshThreads,
     roomAiConfigs,
     presence,
+    typingUsers,
   } = useRoom();
 
   const messagesEndRef = useRef<HTMLDivElement>(null);
@@ -352,6 +353,35 @@ export function DiscordChatPanel({ room, isAdmin, onClose, onDelete, onToggleCha
             onCreateThread={handleCreateThread}
           />
 
+          {/* Typing indicator — show who is typing */}
+          {(() => {
+            const roomTyping = typingUsers?.[room.id] ?? {};
+            const typingList = Object.entries(roomTyping);
+            if (typingList.length === 0) return null;
+            const names = typingList.map(([, v]) => v.username);
+            const label = names.length === 1
+              ? `${names[0]} is typing...`
+              : names.length === 2
+              ? `${names[0]} and ${names[1]} are typing...`
+              : `${names[0]} and ${names.length - 1} others are typing...`;
+            return (
+              <div className="px-4 py-1 text-xs text-muted-foreground animate-pulse flex items-center gap-1.5">
+                <span className="flex gap-0.5">
+                  {[0, 1, 2].map((i) => (
+                    <span
+                      key={i}
+                      className="w-1.5 h-1.5 rounded-full bg-muted-foreground"
+                      style={{
+                        animation: `typing-bounce 1.2s infinite ${i * 0.2}s`,
+                      }}
+                    />
+                  ))}
+                </span>
+                {label}
+              </div>
+            );
+          })()}
+
           <MessageInput
             ref={messageInputRef}
             roomName={room.room_name ?? 'room'}
diff --git a/src/components/room/message/MessageActions.tsx b/src/components/room/message/MessageActions.tsx
index fdc99c0..abba4ef 100644
--- a/src/components/room/message/MessageActions.tsx
+++ b/src/components/room/message/MessageActions.tsx
@@ -13,6 +13,8 @@ import type { MessageWithMeta } from '@/contexts';
 import { useCallback, useState } from 'react';
 import { toast } from 'sonner';
 
+const QUICK_EMOJIS = ['👍', '❤️', '😂', '🎉', '😮'];
+
 interface MessageActionsProps {
   message: MessageWithMeta;
   isOwner: boolean;
@@ -52,7 +54,26 @@ export function MessageActions({
 
   return (
     <div className="flex items-start gap-0.5 opacity-0 transition-opacity group-hover:opacity-100">
-      {/* Add reaction */}
+      {/* Quick reaction bar — Slack-style hover reveal */}
+      {QUICK_EMOJIS.map((emoji) => {
+        const reacted = message.reactions?.find((r) => r.emoji === emoji)?.reacted_by_me;
+        return (
+          <Button
+            key={emoji}
+            variant="ghost"
+            size="sm"
+            onClick={() => handleReaction(emoji)}
+            className={`size-6 p-0 text-sm hover:bg-accent transition-transform hover:scale-125 ${
+              reacted ? 'bg-accent' : ''
+            }`}
+            title={emoji}
+          >
+            {emoji}
+          </Button>
+        );
+      })}
+
+      {/* Add more reaction — opens full picker */}
       <Popover open={reactionPickerOpen} onOpenChange={setReactionPickerOpen}>
         <PopoverTrigger
           render={
diff --git a/src/components/room/message/MessageInput.tsx b/src/components/room/message/MessageInput.tsx
index 2f8ca58..dca8727 100644
--- a/src/components/room/message/MessageInput.tsx
+++ b/src/components/room/message/MessageInput.tsx
@@ -53,6 +53,22 @@ export const MessageInput = forwardRef<MessageInputHandle, MessageInputProps>(fu
     { id: 'code-review', label: '/code-review', description: 'Request AI code review', type: 'command' as const },
   ];
 
+  // Special mention items — @here (online), @channel (all members)
+  const SPECIAL_MENTIONS = [
+    {
+      id: '__here__',
+      label: 'here',
+      description: 'Notify online members',
+      type: 'special_here' as const,
+    },
+    {
+      id: '__channel__',
+      label: 'channel',
+      description: 'Notify all members',
+      type: 'special_channel' as const,
+    },
+  ];
+
   // Transform room data into MentionItems — memoized to prevent IMEditor re-creation
   const mentionItems = useMemo(() => ({
     users: members.map((m) => ({
@@ -64,6 +80,7 @@ export const MessageInput = forwardRef<MessageInputHandle, MessageInputProps>(fu
     channels: [] as { id: string; label: string; type: 'channel'; avatar?: string }[],
     ai: [] as { id: string; label: string; type: 'ai'; avatar?: string }[],
     commands: SLASH_COMMANDS,
+    specialMentions: SPECIAL_MENTIONS,
   }), [members]);
 
   // File upload handler — POST to /rooms/{room_id}/upload
diff --git a/src/components/room/message/MessageList.tsx b/src/components/room/message/MessageList.tsx
index 157e17e..25b6add 100644
--- a/src/components/room/message/MessageList.tsx
+++ b/src/components/room/message/MessageList.tsx
@@ -108,10 +108,13 @@ export const MessageList = memo(function MessageList({
     const result: MessageRow[] = [];
     let lastDateKey: string | null = null;
     let lastSenderKey: string | null = null;
+    let lastMessageTime: number | null = null;
+    const GROUP_GAP_MS = 5 * 60 * 1000; // 5 minutes
 
     for (const message of messages) {
       const dateKey = getDateKey(message.send_at);
       const senderKey = getSenderKey(message);
+      const msgTime = new Date(message.send_at).getTime();
 
       if (dateKey !== lastDateKey) {
         result.push({
@@ -121,9 +124,14 @@ export const MessageList = memo(function MessageList({
         });
         lastDateKey = dateKey;
         lastSenderKey = null;
+        lastMessageTime = null;
       }
 
-      const grouped = senderKey === lastSenderKey;
+      // Group if: same sender AND within 5-minute gap (Discord-style)
+      const sameSender = senderKey === lastSenderKey;
+      const withinTimeGap = lastMessageTime !== null && (msgTime - lastMessageTime) < GROUP_GAP_MS;
+      const grouped = sameSender && withinTimeGap;
+
       result.push({
         type: 'message',
         message,
@@ -132,6 +140,7 @@ export const MessageList = memo(function MessageList({
         key: message.id,
       });
       lastSenderKey = senderKey;
+      lastMessageTime = msgTime;
     }
     return result;
   }, [messages, replyMap]);
diff --git a/src/components/room/message/editor/IMEditor.tsx b/src/components/room/message/editor/IMEditor.tsx
index 916dc2d..f742e0b 100644
--- a/src/components/room/message/editor/IMEditor.tsx
+++ b/src/components/room/message/editor/IMEditor.tsx
@@ -26,6 +26,7 @@ export interface IMEditorProps {
         channels: MentionItem[];
         ai: MentionItem[];
         commands: MentionItem[];
+        specialMentions?: MentionItem[];
     };
     onUploadFile?: (file: File) => Promise<{ id: string; url: string }>;
     placeholder?: string;
@@ -185,6 +186,10 @@ function MentionDropdown({
     p: Palette;
     query: string;
 }) {
+    const SPECIAL_TYPES = ['special_here', 'special_channel'];
+    const specialItems = items.filter((item) => SPECIAL_TYPES.includes(item.type));
+    const regularItems = items.filter((item) => !SPECIAL_TYPES.includes(item.type));
+
     return (
         <div
             className="absolute left-0 z-50 overflow-hidden"
@@ -203,14 +208,49 @@ function MentionDropdown({
                 </div>
             ) : (
                 <div className="py-1 max-h-60 overflow-y-auto">
-                    {items.map((item, i) => {
+                    {/* Special mentions section */}
+                    {specialItems.length > 0 && regularItems.length > 0 && (
+                        <div className="px-3 py-1 text-[10px] font-semibold uppercase tracking-wide" style={{color: p.textSubtle}}>
+                            Notify
+                        </div>
+                    )}
+                    {specialItems.map((item) => {
+                        const realIndex = items.indexOf(item);
+                        const icon = item.type === 'special_here' ? '📍' : '📢';
+                        return (
+                            <button
+                                key={item.id}
+                                onClick={() => onSelect(item)}
+                                className="w-full flex items-center gap-3 px-3 py-2.5 transition-colors text-left cursor-pointer"
+                                style={{background: realIndex === selectedIndex ? p.popupSelected : 'transparent'}}
+                            >
+                                <span className="w-7 h-7 rounded-full shrink-0 flex items-center justify-center text-base">
+                                    {icon}
+                                </span>
+                                <span className="flex-1 truncate text-sm font-medium" style={{color: p.text}}>
+                                    @{item.label}
+                                </span>
+                                {item.description && (
+                                    <span className="text-[10px] text-muted-foreground mr-1">
+                                        {item.description}
+                                    </span>
+                                )}
+                            </button>
+                        );
+                    })}
+                    {specialItems.length > 0 && regularItems.length > 0 && (
+                        <div className="mx-3 my-1 border-t border-border" />
+                    )}
+                    {/* Regular mentions section */}
+                    {regularItems.map((item) => {
+                        const realIndex = items.indexOf(item);
                         const badge = getBadge(item.type);
                         return (
                             <button
                                 key={item.id}
                                 onClick={() => onSelect(item)}
                                 className="w-full flex items-center gap-3 px-3 py-2.5 transition-colors text-left cursor-pointer"
-                                style={{background: i === selectedIndex ? p.popupSelected : 'transparent'}}
+                                style={{background: realIndex === selectedIndex ? p.popupSelected : 'transparent'}}
                             >
                                 {item.avatar ? (
                                     <img src={item.avatar} alt={item.label} className="w-7 h-7 rounded-full shrink-0"/>
@@ -261,6 +301,7 @@ export const IMEditor = forwardRef<IMEditorHandle, IMEditorProps>(function IMEdi
     const wrapRef = useRef<HTMLDivElement>(null);
 
     const allItems = [
+        ...(mentionItems.specialMentions ?? []),
         ...mentionItems.users,
         ...mentionItems.channels,
         ...mentionItems.ai,
diff --git a/src/contexts/room-context.tsx b/src/contexts/room-context.tsx
index fe8994f..ee4dc0a 100644
--- a/src/contexts/room-context.tsx
+++ b/src/contexts/room-context.tsx
@@ -18,6 +18,8 @@ import {
   type RoomPinResponse,
   type RoomResponse,
   type RoomThreadResponse,
+  categoryList as restCategoryList,
+  roomList as restRoomList,
 } from '@/client';
 import {
   createRoomWsClient,
@@ -159,6 +161,9 @@ interface RoomContextValue {
   /** Room AI configs for @ai: mention suggestions */
   roomAiConfigs: RoomAiConfig[];
   aiConfigsLoading?: boolean;
+
+  /** Typing users in the active room: roomId -> userId -> { username, avatar_url } */
+  typingUsers: Record<string, Record<string, { username: string; avatar_url?: string; timeoutId?: ReturnType<typeof setTimeout> }>>;
 }
 
 const RoomContext = createContext<RoomContextValue | null>(null);
@@ -224,6 +229,15 @@ export function RoomProvider({
   const [categories, setCategories] = useState<RoomCategoryResponse[]>([]);
   const [categoriesLoading, setCategoriesLoading] = useState(false);
 
+  // Merge category_info into rooms whenever either changes
+  const roomsWithCategory = useMemo<RoomWithCategory[]>(() => {
+    const catMap = new Map(categories.map((c) => [c.id, c]));
+    return rooms.map((r) => ({
+      ...r,
+      category_info: r.category ? (catMap.get(r.category) ?? null) : null,
+    }));
+  }, [rooms, categories]);
+
   const [activeRoom, setActiveRoomState] = useState<RoomResponse | null>(null);
 
   const [messages, setMessages] = useState<MessageWithMeta[]>([]);
@@ -413,6 +427,9 @@ export function RoomProvider({
   // User presence map: user_id -> status
   const [presence, setPresence] = useState<PresenceMap>({});
 
+  // Typing users map: roomId -> Map<userId, { username, avatar_url, timeoutId }>
+  const [typingUsers, setTypingUsers] = useState<Record<string, Record<string, { username: string; avatar_url?: string; timeoutId?: ReturnType<typeof setTimeout> }>>>({});
+
   const [streamingContent, setStreamingContent] = useState<Map<string, string>>(new Map());
 
   // Project repos for @repository: mention suggestions
@@ -638,6 +655,41 @@ export function RoomProvider({
           if (payload.room_id !== activeRoomIdRef.current) return;
           setPresence((prev) => ({ ...prev, [payload.user_id]: payload.status }));
         },
+        onTypingStart: (payload) => {
+          if (payload.room_id !== activeRoomIdRef.current) return;
+          if (payload.user_id === user?.uid) return; // Don't show self
+          setTypingUsers((prev) => {
+            const roomMap = prev[payload.room_id] ?? {};
+            // Clear existing timeout for this user
+            const existing = roomMap[payload.user_id];
+            if (existing?.timeoutId) clearTimeout(existing.timeoutId);
+            const timeoutId = setTimeout(() => {
+              setTypingUsers((p) => {
+                const rm = { ...p[payload.room_id] };
+                delete rm[payload.user_id];
+                return { ...p, [payload.room_id]: rm };
+              });
+            }, 4000);
+            return {
+              ...prev,
+              [payload.room_id]: {
+                ...roomMap,
+                [payload.user_id]: { username: payload.username, avatar_url: payload.avatar_url, timeoutId },
+              },
+            };
+          });
+        },
+        onTypingStop: (payload) => {
+          if (payload.room_id !== activeRoomIdRef.current) return;
+          setTypingUsers((prev) => {
+            const roomMap = prev[payload.room_id] ?? {};
+            const existing = roomMap[payload.user_id];
+            if (existing?.timeoutId) clearTimeout(existing.timeoutId);
+            const newRoomMap = { ...roomMap };
+            delete newRoomMap[payload.user_id];
+            return { ...prev, [payload.room_id]: newRoomMap };
+          });
+        },
         onStatusChange: (status) => {
           setWsStatus(status);
           if (status === 'closed' || status === 'error') {
@@ -682,16 +734,20 @@ export function RoomProvider({
   }, []);
 
   const fetchRooms = useCallback(async () => {
-    const client = wsClientRef.current;
-    if (!projectName || !client) {
+    if (!projectName) {
       setRooms([]);
       return;
     }
     setRoomsLoading(true);
     setRoomsError(null);
     try {
-      const resp = await client.roomList(projectName);
-      setRooms(resp.map((r) => ({ ...r, category_info: null })));
+      const resp = await restRoomList({ path: { project_name: projectName } });
+      const data = resp.data?.data;
+      if (Array.isArray(data)) {
+        setRooms(data.map((r) => ({ ...r, category_info: null })));
+      } else {
+        setRooms([]);
+      }
     } catch (err) {
       setRoomsError(err instanceof Error ? err : new Error('Failed to load rooms'));
     } finally {
@@ -704,12 +760,12 @@ export function RoomProvider({
   }, [fetchRooms]);
 
   const fetchCategories = useCallback(async () => {
-    const client = wsClientRef.current;
-    if (!projectName || !client) return;
+    if (!projectName) return;
     setCategoriesLoading(true);
     try {
-      const resp = await client.categoryList(projectName);
-      setCategories(resp);
+      const resp = await restCategoryList({ path: { project_name: projectName } });
+      const data = resp.data?.data;
+      setCategories(Array.isArray(data) ? data : []);
     } catch (error) {
       handleRoomError('Load categories', error);
     } finally {
@@ -1236,7 +1292,7 @@ export function RoomProvider({
       wsClient: wsClientRef.current,
       connectWs,
       disconnectWs,
-      rooms,
+      rooms: roomsWithCategory,
       roomsLoading,
       roomsError,
       refreshRooms: fetchRooms,
@@ -1283,6 +1339,7 @@ export function RoomProvider({
       reposLoading,
       roomAiConfigs,
       aiConfigsLoading,
+      typingUsers,
     }),
     [
       wsStatus,
@@ -1290,7 +1347,7 @@ export function RoomProvider({
       connectWs,
       disconnectWs,
       wsClientRef.current,
-      rooms,
+      roomsWithCategory,
       roomsLoading,
       roomsError,
       fetchRooms,
@@ -1336,6 +1393,7 @@ export function RoomProvider({
       reposLoading,
       roomAiConfigs,
       aiConfigsLoading,
+      typingUsers,
     ],
   );