Arithmetic does not fork across the spaces; the tiebreaker stops at semantics

FIX.org

@@ -615,6 +615,19 @@ The ML share is the part neither model supplies — the type system, the
 options, the exhaustive matching, and whatever a second ML surface would
 eventually add if the deferred syntax question ever reopens.
 
+** Arithmetic semantics do not fork across the two spaces, decided 2026-09-20
+One operator, one meaning, both sides. `/` on integers truncates toward zero
+and `%` is its remainder, sign following the dividend — LLVM's sdiv/srem, the
+x86 backend's cqo/idiv, and flan_dyn.c's arith all already agree, and that
+agreement is now the rule rather than a coincidence. The author's call: this
+sort of semantics is normalized across the dynamic and static spaces, so the
+Clojure tiebreaker above does not reach it. Clojure's flooring `mod` (sign of
+the divisor) is NOT to be added as a dyn-side-only behavior of `%`; if a
+flooring mod is ever wanted it is a second, separately named operation
+available to both spaces, the way Common Lisp keeps `rem` and `mod` side by
+side. Division by zero and INT64_MIN / -1 trap identically on both sides,
+and float `%` is fmod on both backends and in dyn.
+
 ** handler-case, decided 2026-09-19
 Flan has handler-bind, which is the resuming handler: it runs where the
 condition was signalled, with the stack still standing, and carries on by