diff --git a/ui/src/views/classroom/RoomDetail.tsx b/ui/src/views/classroom/RoomDetail.tsx
index ad801ff7..172719c5 100644
--- a/ui/src/views/classroom/RoomDetail.tsx
+++ b/ui/src/views/classroom/RoomDetail.tsx
@@ -305,42 +305,35 @@ const RoomDetail: React.FC = () => {
       )
 
       // Existing participants handler
-      signalRServiceRef.current.setExistingParticipantsHandler(async (existing) => {
-        console.log('Existing participants:', existing)
+      signalRServiceRef.current.setParticipantJoinHandler(
+        async (userId: string, name: string, isTeacher: boolean) => {
+          if (userId === user.id) return
 
-        if (webRTCServiceRef.current) {
-          for (const p of existing) {
-            const id = p.userId || p.UserId
-            const name = p.userName || p.UserName
-            const isTeacher = p.isTeacher ?? p.IsTeacher
+          console.log(`Participant joined: ${name}, isTeacher: ${isTeacher}`)
 
-            await webRTCServiceRef.current.createPeerConnection(id)
-
-            // öğrenci → öğretmen
-            if (user.role === 'student' && isTeacher) {
-              const offer = await webRTCServiceRef.current.createOffer(id)
-              await signalRServiceRef.current?.sendOffer(classSession.id, id, offer)
-            }
-
-            // öğretmen → öğrenci
-            if (user.role === 'teacher' && !isTeacher) {
-              const offer = await webRTCServiceRef.current.createOffer(id)
-              await signalRServiceRef.current?.sendOffer(classSession.id, id, offer)
+          if (webRTCServiceRef.current) {
+            // 👇 duplicate connection engelle
+            if (!webRTCServiceRef.current.getPeerConnection(userId)) {
+              await webRTCServiceRef.current.createPeerConnection(userId)
             }
           }
-        }
 
-        setParticipants((prev) => [
-          ...prev,
-          ...existing.map((p) => ({
-            id: p.userId || p.UserId,
-            name: p.userName || p.UserName,
-            isTeacher: p.isTeacher ?? p.IsTeacher,
-            isAudioMuted: classSettings.autoMuteNewParticipants,
-            isVideoMuted: classSettings.defaultCameraState === 'off',
-          })),
-        ])
-      })
+          setParticipants((prev) => {
+            const existing = prev.find((p) => p.id === userId)
+            if (existing) return prev
+            return [
+              ...prev,
+              {
+                id: userId,
+                name,
+                isTeacher,
+                isAudioMuted: classSettings.autoMuteNewParticipants,
+                isVideoMuted: classSettings.defaultCameraState === 'off',
+              },
+            ]
+          })
+        },
+      )
 
       signalRServiceRef.current.setParticipantLeaveHandler((userId) => {
         console.log(`Participant left: ${userId}`)