diff --git a/server/src/agents/pool/start/spawn.rs b/server/src/agents/pool/start/spawn.rs
index 938857fd..525aa47c 100644
--- a/server/src/agents/pool/start/spawn.rs
+++ b/server/src/agents/pool/start/spawn.rs
@@ -248,6 +248,11 @@ pub(super) async fn run_agent_spawn(
         );
     }
 
+    match &session_id_to_resume_owned {
+        Some(sess_id) => slog!("[agent:{sid}:{aname}] spawn mode=warm session_id={sess_id}"),
+        None => slog!("[agent:{sid}:{aname}] spawn mode=cold"),
+    }
+
     // Build the effective prompt and determine resume session.
     //
     // When resuming a previous session, discard the full rendered prompt