diff --git a/apps/web/.claude/settings.local.json b/apps/web/.claude/settings.local.json
index e62377f3..a352ee6e 100644
--- a/apps/web/.claude/settings.local.json
+++ b/apps/web/.claude/settings.local.json
@@ -32,7 +32,9 @@
       "Bash(git commit -m \"$(cat <<''EOF''\nfeat: add Biome + ESLint linting setup\n\nAdd Biome for formatting and general linting, with minimal ESLint\nconfiguration for React Hooks rules only. This provides:\n\n- Fast formatting via Biome (10-100x faster than Prettier)\n- General JS/TS linting via Biome\n- React Hooks validation via ESLint (rules-of-hooks)\n- Import organization via Biome\n\nConfiguration files:\n- biome.jsonc: Biome config with custom rule overrides\n- eslint.config.js: Minimal flat config for React Hooks only\n- .gitignore: Added Biome cache exclusion\n- LINTING.md: Documentation for the setup\n\nScripts added to package.json:\n- npm run lint: Check all files\n- npm run lint:fix: Auto-fix issues\n- npm run format: Format all files\n- npm run check: Full Biome check\n\n🤖 Generated with [Claude Code](https://claude.com/claude-code)\n\nCo-Authored-By: Claude <noreply@anthropic.com>\nEOF\n)\")",
       "Bash(git commit:*)",
       "Bash(npm run pre-commit:*)",
-      "Bash(npm run:*)"
+      "Bash(npm run:*)",
+      "Bash(git pull:*)",
+      "Bash(git stash:*)"
     ],
     "deny": [],
     "ask": []
diff --git a/apps/web/socket-server.ts b/apps/web/socket-server.ts
index 262ea9b8..0e32d848 100644
--- a/apps/web/socket-server.ts
+++ b/apps/web/socket-server.ts
@@ -1,5 +1,6 @@
 import type { Server as HTTPServer } from 'http'
 import { Server as SocketIOServer } from 'socket.io'
+import type { Server as SocketIOServerType } from 'socket.io'
 import {
   applyGameMove,
   createArcadeSession,
@@ -18,8 +19,19 @@ import { getRoomActivePlayers } from './src/lib/arcade/player-manager'
 import type { GameMove, GameName } from './src/lib/arcade/validation'
 import { matchingGameValidator } from './src/lib/arcade/validation/MatchingGameValidator'
 
+// Global socket.io server instance
+let io: SocketIOServerType | null = null
+
+/**
+ * Get the socket.io server instance
+ * Returns null if not initialized
+ */
+export function getSocketIO(): SocketIOServerType | null {
+  return io
+}
+
 export function initializeSocketServer(httpServer: HTTPServer) {
-  const io = new SocketIOServer(httpServer, {
+  io = new SocketIOServer(httpServer, {
     path: '/api/socket',
     cors: {
       origin: process.env.NEXT_PUBLIC_URL || 'http://localhost:3000',
diff --git a/apps/web/src/app/api/arcade/rooms/[roomId]/join/route.ts b/apps/web/src/app/api/arcade/rooms/[roomId]/join/route.ts
index bc0c5976..ebc5a7c6 100644
--- a/apps/web/src/app/api/arcade/rooms/[roomId]/join/route.ts
+++ b/apps/web/src/app/api/arcade/rooms/[roomId]/join/route.ts
@@ -1,8 +1,9 @@
 import { type NextRequest, NextResponse } from 'next/server'
 import { getRoomById, touchRoom } from '@/lib/arcade/room-manager'
-import { addRoomMember } from '@/lib/arcade/room-membership'
-import { getActivePlayers } from '@/lib/arcade/player-manager'
+import { addRoomMember, getOnlineRoomMembers } from '@/lib/arcade/room-membership'
+import { getActivePlayers, getRoomActivePlayers } from '@/lib/arcade/player-manager'
 import { getViewerId } from '@/lib/viewer'
+import { getSocketIO } from '../../../../../../socket-server'
 
 type RouteContext = {
   params: Promise<{ roomId: string }>
@@ -56,6 +57,34 @@ export async function POST(req: NextRequest, context: RouteContext) {
     // Update room activity to refresh TTL
     await touchRoom(roomId)
 
+    // Broadcast to all users in the room via socket
+    const io = getSocketIO()
+    if (io) {
+      try {
+        const onlineMembers = await getOnlineRoomMembers(roomId)
+        const memberPlayers = await getRoomActivePlayers(roomId)
+
+        // Convert memberPlayers Map to object for JSON serialization
+        const memberPlayersObj: Record<string, any[]> = {}
+        for (const [uid, players] of memberPlayers.entries()) {
+          memberPlayersObj[uid] = players
+        }
+
+        // Broadcast to all users in this room
+        io.to(`room:${roomId}`).emit('member-joined', {
+          roomId,
+          userId: viewerId,
+          onlineMembers,
+          memberPlayers: memberPlayersObj,
+        })
+
+        console.log(`[Join API] Broadcasted member-joined for user ${viewerId} in room ${roomId}`)
+      } catch (socketError) {
+        // Log but don't fail the request if socket broadcast fails
+        console.error('[Join API] Failed to broadcast member-joined:', socketError)
+      }
+    }
+
     // Build response with auto-leave info if applicable
     return NextResponse.json(
       {
diff --git a/apps/web/src/app/api/arcade/rooms/[roomId]/leave/route.ts b/apps/web/src/app/api/arcade/rooms/[roomId]/leave/route.ts
index 8a186718..d9ac0afe 100644
--- a/apps/web/src/app/api/arcade/rooms/[roomId]/leave/route.ts
+++ b/apps/web/src/app/api/arcade/rooms/[roomId]/leave/route.ts
@@ -1,7 +1,9 @@
 import { type NextRequest, NextResponse } from 'next/server'
 import { getRoomById } from '@/lib/arcade/room-manager'
-import { isMember, removeMember } from '@/lib/arcade/room-membership'
+import { getOnlineRoomMembers, isMember, removeMember } from '@/lib/arcade/room-membership'
+import { getRoomActivePlayers } from '@/lib/arcade/player-manager'
 import { getViewerId } from '@/lib/viewer'
+import { getSocketIO } from '../../../../../../socket-server'
 
 type RouteContext = {
   params: Promise<{ roomId: string }>
@@ -31,6 +33,34 @@ export async function POST(_req: NextRequest, context: RouteContext) {
     // Remove member
     await removeMember(roomId, viewerId)
 
+    // Broadcast to all remaining users in the room via socket
+    const io = getSocketIO()
+    if (io) {
+      try {
+        const onlineMembers = await getOnlineRoomMembers(roomId)
+        const memberPlayers = await getRoomActivePlayers(roomId)
+
+        // Convert memberPlayers Map to object for JSON serialization
+        const memberPlayersObj: Record<string, any[]> = {}
+        for (const [uid, players] of memberPlayers.entries()) {
+          memberPlayersObj[uid] = players
+        }
+
+        // Broadcast to all users in this room
+        io.to(`room:${roomId}`).emit('member-left', {
+          roomId,
+          userId: viewerId,
+          onlineMembers,
+          memberPlayers: memberPlayersObj,
+        })
+
+        console.log(`[Leave API] Broadcasted member-left for user ${viewerId} in room ${roomId}`)
+      } catch (socketError) {
+        // Log but don't fail the request if socket broadcast fails
+        console.error('[Leave API] Failed to broadcast member-left:', socketError)
+      }
+    }
+
     return NextResponse.json({ success: true })
   } catch (error) {
     console.error('Failed to leave room:', error)