diff --git a/app/services/qualys_service.py b/app/services/qualys_service.py
index d6ec397..e094ca4 100644
--- a/app/services/qualys_service.py
+++ b/app/services/qualys_service.py
@@ -585,6 +585,15 @@ def _refresh_all_agents_impl(db, mode="diff"):
             except Exception:
                 pass
 
+    # Sauve immediatement le timestamp de DEBUT (couvre annulation en cours)
+    if mode == "diff":
+        try:
+            start_iso = datetime.now(timezone.utc).isoformat()
+            set_secret(db, "qualys_last_diff_sync", start_iso, "Timestamp dernier sync Qualys diff (debut)")
+            db.commit()
+        except Exception:
+            pass
+
     qualys_url, qualys_user, qualys_pass, qualys_proxy = _get_qualys_creds(db)
     if not qualys_user:
         return {"ok": False, "msg": "Credentials Qualys non configurés"}