diff --git a/plugin/server/store.go b/plugin/server/store.go
index 0c04f32..9a0ac72 100644
--- a/plugin/server/store.go
+++ b/plugin/server/store.go
@@ -146,6 +146,18 @@ func (s *Store) CleanStaleSessions(staleThresholdMs, expireThresholdMs int64) (c
 			lastUpdate = session.StartTimeMs
 		}
 		if lastUpdate == 0 {
+			// No timestamps at all (pre-cleanup era orphan) — treat as expired immediately.
+			// Delete non-active sessions; mark active ones as interrupted so they get
+			// picked up on the next cleanup cycle with a real timestamp.
+			if session.Status == "active" {
+				session.Status = "interrupted"
+				session.LastUpdateMs = now
+				_ = s.SaveSession(session.SessionKey, session)
+				cleaned++
+			} else {
+				_ = s.DeleteSession(session.SessionKey)
+				expired++
+			}
 			continue
 		}
 		age := now - lastUpdate