diff --git a/TODO.org b/TODO.org
index 468c389d..95258123 100644
--- a/TODO.org
+++ b/TODO.org
@@ -633,6 +633,12 @@ generic binding — saying =$= marks a
 type variable and naming the bare spelling. A =defn= parameter was already
 refused, as a type in a name slot.
 
+** NEXT A container parameter the function grows is warned at
+Decided 2026-09-25: Odin's behaviour stays — a Vec or Map passed by value is a
+copy of its header, so growth inside the callee does not reach the caller. A
+parameter the function grows (push, put, reserve, anything that can reallocate)
+gets a warning at the parameter suggesting (Ptr ...).
+
 * Checker
 
 ** DONE The ownership flow analysis is repealed