diff --git a/vehicle-data-platform/apps/api/internal/platform/mock_store.go b/vehicle-data-platform/apps/api/internal/platform/mock_store.go
index 2800c218..ccd1f140 100644
--- a/vehicle-data-platform/apps/api/internal/platform/mock_store.go
+++ b/vehicle-data-platform/apps/api/internal/platform/mock_store.go
@@ -239,6 +239,10 @@ func (m *MockStore) VehicleServiceSummary(ctx context.Context) (VehicleServiceSu
 				summary.IdentityRequiredVehicles++
 			}
 		}
+		onlineByProtocol := map[string]bool{}
+		for _, status := range row.SourceStatus {
+			onlineByProtocol[status.Protocol] = status.Online
+		}
 		for _, protocol := range row.Protocols {
 			current := protocolCounts[protocol]
 			if current == nil {
@@ -246,7 +250,7 @@ func (m *MockStore) VehicleServiceSummary(ctx context.Context) (VehicleServiceSu
 				protocolCounts[protocol] = current
 			}
 			current.Total++
-			if row.Online {
+			if onlineByProtocol[protocol] {
 				current.Online++
 			}
 		}
diff --git a/vehicle-data-platform/apps/api/internal/platform/service_test.go b/vehicle-data-platform/apps/api/internal/platform/service_test.go
index 43b4e95c..c0b18ec8 100644
--- a/vehicle-data-platform/apps/api/internal/platform/service_test.go
+++ b/vehicle-data-platform/apps/api/internal/platform/service_test.go
@@ -64,3 +64,22 @@ func TestVehicleServiceOverviewsUsesBatchDataPath(t *testing.T) {
 		t.Fatalf("batch overview should avoid per-keyword store calls, vehicles=%d realtime=%d", store.vehiclesCalls, store.vehicleRealtimeCalls)
 	}
 }
+
+func TestVehicleServiceSummaryCountsProtocolOnlineByProtocolSlot(t *testing.T) {
+	service := NewService(NewMockStore())
+	summary, err := service.VehicleServiceSummary(context.Background())
+	if err != nil {
+		t.Fatalf("VehicleServiceSummary returned error: %v", err)
+	}
+	byProtocol := map[string]ProtocolStat{}
+	for _, protocol := range summary.Protocols {
+		byProtocol[protocol.Protocol] = protocol
+	}
+	gb32960 := byProtocol["GB32960"]
+	if gb32960.Total != 2 {
+		t.Fatalf("expected two GB32960 source slots, got %+v", gb32960)
+	}
+	if gb32960.Online != 1 {
+		t.Fatalf("GB32960 online count must use GB32960 source status only, got %+v", gb32960)
+	}
+}