diff --git a/apps/backend/src/index.ts b/apps/backend/src/index.ts
index 34c433a..10246b5 100644
--- a/apps/backend/src/index.ts
+++ b/apps/backend/src/index.ts
@@ -12,6 +12,7 @@ import { registerMessagingHandlers } from './socket/messaging.js';
 import { app } from './app.js';
 import { redis as appRedis } from './lib/redis.js';
 import { setSocketServer } from './lib/socket.js';
+import { setOnline, setOffline, refreshPresence, isOnline } from './services/presence.js';
 import {
   cleanupStaleSockets,
   reconcileBoot,
@@ -106,7 +107,6 @@ io.use(socketAuthMiddleware);
 
 io.on('connection', async (socket: AuthSocket) => {
   const userId = socket.auth!.userId;
-  const deviceId = socket.auth!.deviceId;
   console.log('User connected:', userId, socket.id);
 
   socket.data['userId'] = userId;
@@ -173,12 +173,6 @@ io.on('connection', async (socket: AuthSocket) => {
     await socket.join(m.conversationId);
   }
 
-  const user = await db.query.users.findFirst({
-    where: eq(users.id, userId),
-    columns: { presenceVisible: true },
-  });
-  const presenceVisible = user?.presenceVisible ?? true;
-
   if (appRedis) {
     await registerPresenceSocket(appRedis, userId, deviceId, socket.id);
     await cleanupStaleSockets(io, appRedis, userId, socket.id);
@@ -187,7 +181,12 @@ io.on('connection', async (socket: AuthSocket) => {
     if (becameOnline && presenceVisible) {
       for (const m of memberships) {
         io.to(m.conversationId).emit('user_online', { userId });
-        io.to(m.conversationId).emit('presence_update', { userId, online: true });
+        io.to(m.conversationId).emit('presence_update', {
+          userId,
+          online: true,
+          status: 'online',
+          lastSeen: Date.now(),
+        });
       }
       await recordPresenceForCoMembers(
         userId,
diff --git a/apps/backend/src/services/presence.ts b/apps/backend/src/services/presence.ts
index 80ab847..6c712cd 100644
--- a/apps/backend/src/services/presence.ts
+++ b/apps/backend/src/services/presence.ts
@@ -103,6 +103,22 @@ export async function refreshPresenceSocket(
   await registerPresenceSocket(redis, userId, deviceId, socketId);
 }
 
+export async function setOnline(redis: Redis, userId: string, socketId: string): Promise<boolean> {
+  const key = presenceKey(userId);
+  const debounceKey = `presence_debounce:${userId}`;
+
+  const count = await redis.scard(key);
+  await redis.sadd(key, socketId);
+  await redis.expire(key, PRESENCE_TTL);
+
+  if (count === 0) {
+    const debouncing = await redis.del(debounceKey);
+    if (debouncing === 1) {
+      return false; // Flap detected, don't broadcast online
+    }
+    return true; // First socket connected
+  }
+  return false;
 /**
  * Remove a socket mapping. Returns true when that device has no remaining
  * tracked sockets, so callers may safely remove the device-level presence entry.
diff --git a/apps/web/src/components/conversations/ConversationListSidebar.tsx b/apps/web/src/components/conversations/ConversationListSidebar.tsx
index 46871c8..305d0a0 100644
--- a/apps/web/src/components/conversations/ConversationListSidebar.tsx
+++ b/apps/web/src/components/conversations/ConversationListSidebar.tsx
@@ -241,8 +241,9 @@ export function ConversationListSidebar() {
       handleOffline(data.userId);
     }
 
-    function onPresenceUpdate(data: { userId: string; online: boolean }) {
-      if (data.online) {
+    function onPresenceUpdate(data: { userId: string; online?: boolean; status?: 'online' | 'offline'; lastSeen?: number }) {
+      const isOnline = data.status ? data.status === 'online' : !!data.online;
+      if (isOnline) {
         handleOnline(data.userId);
       } else {
         handleOffline(data.userId);