diff --git a/CLAUDE.md b/CLAUDE.md
index 6009428..2e2dc80 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -191,6 +191,12 @@ of `PATCH` on notifications, a dropped guest refresh token). Read the contract f
 `python manage.py spectacular --file schema.yaml --format openapi` and check shapes
 against a running server. `content/tests_frontend_contract.py` is the backend-side guard.
 
+**Android app (WebView shell in the frontend repo, `android/`):** the installed APK lags the code. What the
+next build must carry (vibrate bridge, in-app Zarinpal with `paysInApp()`, media-gesture setting), what to
+check on a phone, and who owns signing (MH-W90) are in `~/Desktop/MathApp_frontend/android/README.md`
+(«نسخه‌ی بعدیِ APK»). Until then payment from the app goes through the frontend's `pay.html`, because
+Zarinpal refuses StartPay without our domain as Referer (checked live 2026-10-10).
+
 **Content the frontend shows but nobody has filled in yet:** `Unit.blurb`,
 `Plan.features`/`badge`, `Lesson.example`/`steps`. All optional, all editable from the
 admin panel.