diff --git a/tools/anaf-monitor/monitor_v2.py b/tools/anaf-monitor/monitor_v2.py
index 6d5742a..4d87c22 100644
--- a/tools/anaf-monitor/monitor_v2.py
+++ b/tools/anaf-monitor/monitor_v2.py
@@ -364,9 +364,16 @@ def main():
     update_dashboard_status(len(all_changes) > 0, len(all_changes), all_changes)
     
     log("=== Monitor complete ===")
-    
+
+    num_changes = len(all_changes)
     print(json.dumps({"changes": all_changes}, ensure_ascii=False, indent=2))
-    return len(all_changes)
+    # GSTACK-CRON marker: contract with Echo-Core scheduler (report_on="changes").
+    # The shell-kind scheduler parses the last line matching
+    # ^GSTACK-CRON: changes=\d+$ to decide whether to forward stdout.
+    # A successful run (even with N>0 changes) must exit 0 — the scheduler
+    # reports non-zero exit codes as errors unconditionally.
+    print(f"GSTACK-CRON: changes={num_changes}")
+    return 0
 
 if __name__ == "__main__":
     exit(main())