diff --git a/other/metrics/grafana_seaweedfs.json b/other/metrics/grafana_seaweedfs.json
index 5c04a9992..7b15390a4 100644
--- a/other/metrics/grafana_seaweedfs.json
+++ b/other/metrics/grafana_seaweedfs.json
@@ -5175,8 +5175,8 @@
             "type": "prometheus",
             "uid": "${DS_PROMETHEUS}"
           },
-          "title": "Metadata Subscription Lag",
-          "description": "Seconds since the filer last sent a metadata-subscription event (per client/path); only present with active subscribers",
+          "title": "Time Since Last Subscription Send",
+          "description": "Seconds since the filer last sent to a metadata subscription (real event or idle heartbeat), per client/path. Low for healthy caught-up subscribers; clients that don't request idle heartbeats show time since the last real event.",
           "type": "timeseries",
           "id": 156,
           "gridPos": {
diff --git a/weed/server/filer_grpc_server_sub_meta.go b/weed/server/filer_grpc_server_sub_meta.go
index d1dffb358..678f3629b 100644
--- a/weed/server/filer_grpc_server_sub_meta.go
+++ b/weed/server/filer_grpc_server_sub_meta.go
@@ -564,6 +564,14 @@ func (fs *FilerServer) maybeSendIdleHeartbeat(req *filer_pb.SubscribeMetadataReq
 		glog.V(0).Infof("=> idle heartbeat to %s: %v", req.ClientName, err)
 		return lastHeartbeatNs
 	}
+	// A heartbeat is a send too: advance the freshness gauge so an idle but
+	// healthy subscriber doesn't look stale. The gauge otherwise only moves on
+	// real matching events, which never arrive on a quiet path.
+	var sourceFiler string
+	if fs.option != nil {
+		sourceFiler = fs.option.Host.String()
+	}
+	stats.FilerServerLastSendTsOfSubscribeGauge.WithLabelValues(sourceFiler, req.ClientName, req.PathPrefix).Set(float64(now))
 	return now
 }