diff --git a/TODO.org b/TODO.org
index c1ee43de..e23add54 100644
--- a/TODO.org
+++ b/TODO.org
@@ -800,6 +800,14 @@ One spelling for one operation; != stays, and not= is refused with a suggestion
 of !=.
 
 * Checker
+** TODO A u64 above the i64 maximum becomes -1 when it crosses into dyn
+=(+ z u)= and =(max u 0 z)= with u = u64 max read u as -1, silently. It should trap at
+the crossing, as a u64 field read through a view already does.
+** TODO A dyn nil past the first pair of a fold is refused at compile time
+=(+ 1 2 (the dyn nil))= says nil has no None at i32, while =(+ (the dyn nil) 1 2)= traps
+at run time. Both should trap at run time.
+** TODO A generic $t beside a dyn operand is refused
+"does not cross into a written type yet"; rule 117 says typed beside dyn gives dyn.
 ** WAIT Checking a wide fold of let operands is slow
 Parked 2026-09-26: design first; remeasure on a quiet machine, it was timed under load 20.
 A 2000-operand (bit-and (let …) …) takes 32 s to check (37 s before the bit operators);