diff --git a/CLAUDE.md b/CLAUDE.md
index 43effeb0e..52ba615d8 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -15,3 +15,4 @@
 - Never use `localStorage` for user settings or preferences. All settings must be stored server-side (via WebSocket messages or REST API) so they persist across devices and browsers.
 - Client modules (`lib/public/modules/`): state goes in store.js (zustand-like), WS via ws-ref.js, functions via direct import. Never use `var _ctx = null` / `initXxx(ctx)`. See [docs/guides/CLIENT_MODULE_DEPS.md](docs/guides/CLIENT_MODULE_DEPS.md).
 - Reserve `clay-*` for Clay-only skills. Bundle built-ins in `lib/bundled-skills/` and install optional skills under the owner/project `.clay/skills/`. Never put them in generic vendor/project skill discovery folders or register their bridges globally; expose them only through Clay-owned queries. Apply this rule to every future Clay-specific skill.
+- For Clay UI design, implementation, and review, use `clay-design-skill` from the owner's `.clay/skills/clay-design-skill/SKILL.md` (current installation: `/Users/chad/.clay/skills/clay-design-skill/SKILL.md`). Read its principles and relevant visual references before changing UI. Preserve Clay's existing compact proportions and product behavior; do not use `frontend-design` for Clay design work. If the skill is unavailable, report the missing reference rather than silently substituting another design skill.