diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 13ab7f7..f5c300d 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -1,3 +1,5 @@
 # infra-tools — CONTRIBUTING
 
 (Initial — see git history.)
+
+# update 13 (2026-04)