fix: improve endgame clock and gameplay stability

internal/gameserver/session.go

@@ -35,8 +35,9 @@ type Session struct {
 	stateMu sync.Mutex // serializes packet handlers and hot reload mutations
 	json    *common.FreesrData
 
-	kcpMu sync.Mutex
-	kcp   *kcplib.KCP
+	kcpMu                  sync.Mutex
+	kcp                    *kcplib.KCP
+	levelRewardAwaitingAck bool // guarded by kcpMu
 
 	startTime         time.Time
 	nextSceneSave     int64
@@ -129,6 +130,10 @@ func (s *Session) Consume(data []byte) error {
 		s.kcpMu.Unlock()
 		return err
 	}
+	if s.levelRewardAwaitingAck && s.kcp.PendingSends() == 0 {
+		Log("[KCP] outstanding responses including level rewards acknowledged")
+		s.levelRewardAwaitingAck = false
+	}
 	if err := s.kcp.Update(s.sessionTimeMs()); err != nil {
 		s.kcpMu.Unlock()
 		return err
@@ -141,9 +146,13 @@ func (s *Session) Consume(data []byte) error {
 		if err != nil {
 			break
 		}
-		pkt, err := DecodeNetPacket(buf[:n])
+		// DecodeNetPacket returns slices backed by its input. Keep each frame
+		// independent before the next Recv overwrites the shared buffer.
+		frame := append([]byte(nil), buf[:n]...)
+		pkt, err := DecodeNetPacket(frame)
 		if err != nil {
 			PacketLog(fmt.Sprintf("[ERROR] bad packet: %v", err))
+			Log(fmt.Sprintf("[PACKET] invalid frame: %v", err))
 			continue
 		}
 		packets = append(packets, pkt)
@@ -213,7 +222,14 @@ func (s *Session) SendRaw(pkt *NetPacket) error {
 	if _, err := s.kcp.Send(payload); err != nil {
 		return err
 	}
-	return s.kcp.Flush()
+	if err := s.kcp.Flush(); err != nil {
+		return err
+	}
+	if pkt.CmdType == uint16(goproto.CmdIDByName["GetLevelRewardTakenListScRsp"]) {
+		s.levelRewardAwaitingAck = s.kcp.PendingSends() > 0
+		Log(fmt.Sprintf("[KCP] level rewards response queued; pending segments=%d", s.kcp.PendingSends()))
+	}
+	return nil
 }
 
 // DriveUpdate is called by the gateway ticker to run retransmissions.