diff --git a/control/internal/service/registry.go b/control/internal/service/registry.go
index 5d18336..3521075 100644
--- a/control/internal/service/registry.go
+++ b/control/internal/service/registry.go
@@ -93,7 +93,10 @@ func (s *RegistryService) startGraphPolling() {
                 onlineDevices = append(onlineDevices, dev)
             }
         }
+        onlineCount := len(onlineDevices)
+        totalCount := len(s.devices)
         s.mu.RUnlock()
+        log.Printf("[graph-poll] tick: total_devices=%d online_devices=%d", totalCount, onlineCount)
 
         for _, dev := range onlineDevices {
             data, _, err := s.agent.Do("GET", dev.IP, dev.AgentPort, "/v1/graphs", nil)