diff --git a/DESIGN.md b/DESIGN.md
index fc1b834..c9630a9 100644
--- a/DESIGN.md
+++ b/DESIGN.md
@@ -276,4 +276,9 @@ empty in the model.
   from cached validators and handles a 304 by reusing the cached parse.
   OpenCode (via Cloudflare) currently emits no `ETag` or `Last-Modified` on
   either page, so the slots stay empty and no headers go out. The machinery
-  is idle but correct; it works the day OpenCode adds validators.
\ No newline at end of file
+  is idle but correct; it works the day OpenCode adds validators.
+- Extra billing fields: the Zen page embedded record also streams
+  `reloadAmount`, `reloadTrigger`, `subscriptionPlan`, `monthlyLimit`, and
+  `monthlyUsage`. These do not appear in the rendered DOM. A future `ocd
+  billing` command could expose auto-reload config. Store them by extending
+  the model; keep the scrape module the only place that touches this.
\ No newline at end of file