diff --git a/TODO.org b/TODO.org
index e1553910..3cedcb26 100644
--- a/TODO.org
+++ b/TODO.org
@@ -654,6 +654,10 @@ Decided 2026-09-26: ~grid[r c]~ and ~grid[(r + 1) (c - 1)]~ read like a vector's
 space-separated single values; commas always work; an index with a bare operator
 needs them, ~grid[r + 1, c]~.
 
+** NEXT not is a prefix word
+Decided 2026-09-26: .fln writes ~not x~ (binding like F#'s ~not~, tighter than
+~and~/~or~, looser than comparisons); ~not(x)~ keeps working as a call.
+
 ** NEXT A let takes several bindings on indented lines
 Decided 2026-09-26: lines indented under a ~let~ that are ~name = v~ or ~name: T = v~ are
 more bindings of the same let; anything else there stays refused. flan convert writes