diff --git a/backend/src/index.js b/backend/src/index.js
index e92ee7c..3736d98 100644
--- a/backend/src/index.js
+++ b/backend/src/index.js
@@ -194,7 +194,23 @@ io.on('connection', (socket) => {
   websocketConnections.inc();
   trackUniqueUser(user.jiraAccountId);
   trackUniqueTenant(user.jiraCloudId);
-  socket.on('disconnect', () => { websocketConnections.dec(); });
+  socket.on('disconnect', async () => {
+    websocketConnections.dec();
+    for (const room of socket.rooms) {
+      if (!room.startsWith('poker:')) continue;
+      const sessionId = room.slice(6);
+      try {
+        await leaveSession({
+          sessionId,
+          tenantCloudId: socket.user.jiraCloudId,
+          userKey: socket.user.jiraAccountId
+        });
+        await emitSessionState(sessionId, socket.user.jiraCloudId);
+      } catch {
+        // best-effort cleanup
+      }
+    }
+  });
   const throttled = socketThrottle(socket);
 
   throttled('poker:join', async ({ sessionId }) => {