diff --git a/HANDOFF-x86-abi-marker.md b/HANDOFF-x86-abi-marker.md
index edade72..901f24a 100644
--- a/HANDOFF-x86-abi-marker.md
+++ b/HANDOFF-x86-abi-marker.md
@@ -171,3 +171,9 @@ through the redirect and stays empty until the end; that is not a hang.
   now, not easier: the marker refuses the pair before any of the four `step` functions runs, so anyone who
   wants the answer has to build the crossed module with the marker suppressed on purpose.
 - Items 1, 2 and 5 of `HANDOFF-x86-redef.md`, untouched.
+- A seam worth knowing about before anyone renames a marker. The two strings live in OCaml — `X86.abi_marker`
+  and `Emit.abi_marker` — and the two `abi_mismatch` functions match the same literals in C, with nothing
+  linking the four. Rename one and the refusal still fires, because the symbol is still missing; it just stops
+  being a sentence and reverts to the loader's bare "undefined symbol", which is the failure this lane was
+  about. The crossed tests would catch it — they assert on the marker's name — so the seam is guarded, but it
+  is a seam.