diff --git a/tests/vectors/ref-list-drift/README.md b/tests/vectors/ref-list-drift/README.md
index 639bf6d5..6b3ea9da 100644
--- a/tests/vectors/ref-list-drift/README.md
+++ b/tests/vectors/ref-list-drift/README.md
@@ -8,3 +8,9 @@ payload is an array of key strings. Its layout is copied from a real 1.0.x-writt
 
 Hand-written by a script outside the runtime under test; never regenerated by CultCache. A change to this file is a
 reviewed commit.
+
+`v1-0-60-written.cc` is the same shape written by CultLib itself: `OldWriterRefListProbe` (in
+`tests/vectors/document-variants-c2a/old-writer-probes/`), compiled into a checkout of `cultlib-unity-v1.0.60` (45c2f400) and run
+as `old-reader-refusal.sh gate csharp`, which stages that tree and writes the store through `CultCache` and
+`SingleFileMessagePackBackingStore`. It is `cultcache.store.v1` with records `alpha`, `beta` and `list` (`Items = [alpha, beta]`).
+The runtime under test never regenerates it; `RefListDriftTests.A_1_0_60_Written_Store_Opens_Like_2_0_1` reads it.
diff --git a/tests/vectors/ref-list-drift/v1-0-60-written.cc b/tests/vectors/ref-list-drift/v1-0-60-written.cc
new file mode 100644
index 00000000..c2084e8b
Binary files /dev/null and b/tests/vectors/ref-list-drift/v1-0-60-written.cc differ