diff --git a/internal/proto/analytics/connections_log.proto b/internal/proto/analytics/connections_log.proto
index e2e194c7..68c1f0d0 100644
--- a/internal/proto/analytics/connections_log.proto
+++ b/internal/proto/analytics/connections_log.proto
@@ -63,6 +63,9 @@ message ConnectionsLog {
 
     // Zero or more StrategySessions.
     repeated StrategySession strategy_session = 2;
+
+    // The client session flow id.
+    optional int64 client_flow_id = 3 /* type = ST_SESSION_ID */;
   }
 
   // One round of a particular Strategy done by a client.