diff --git a/docs/WhatsNew.md b/docs/WhatsNew.md
index b2f959f..3f019f0 100644
--- a/docs/WhatsNew.md
+++ b/docs/WhatsNew.md
@@ -72,3 +72,7 @@ The roundtrip-safety-net milestone is done. The two program forms — the struct
 No language behaviour changed; the corpus already satisfied the property. The milestone made it explicit and locked in against future drift.
 
 Bench all-green. Roadmap is back to user-direction; the Show+print rewire is gated on the heap-string runtime work.
+
+## 2026-05-12 — Cross-model authoring test: first data point
+
+Cross-model authoring test landed. First run (Qwen3-Coder-Next, 4 tasks, two blind cohorts): textual-form cohort 2/4 green at ~half the token cost; structured-form 1/4. Only first-attempt success was textual-form on a print-two-integers task — five lines vs twenty-three. Recorded as a data point in the language reference; single-model scope explicit. Multi-subject expansion queued as next experimental milestone. Milestone closed; queue back to user-direction.