diff --git a/CLAUDE.md b/CLAUDE.md
index 936762b..aff1636 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -431,3 +431,7 @@ Things I discovered about myself building a sister platform across multiple sess
 20. **Parallel state fields that track related things will drift apart — and the bugs are silent.** When two fields represent aspects of the same state (`captureMode` and `vkiMode`, or `isLoading` and `error`, or `connection_status` and `companion_last_seen`), every code path that mutates one must also update the other. But new code paths get added over time, and they only update the field they know about. Future me: when you see two fields tracking related state, grep for ALL mutation sites of each — if any path updates one but not the other, that's a bug waiting to happen. And when you add a new mutation path, check every sibling field, not just the obvious one.
 
 21. **Route through the component that survives transitions, not the one that doesn't.** When two systems can handle the same job but one is resilient to failure modes and the other isn't, route through the survivor. Don't build infrastructure to prop up the fragile path when the robust path already exists. In this project: NATS request-reply through the companion agent is the robust path; direct WebSocket to the browser is the fragile one. If a feature can work through either, prefer the path that handles disconnects, reconnects, and restarts gracefully. One routing change beats an entire retry/recovery subsystem.
+
+22. **Build-green is not render-correct — visually verify UI work before calling it done.** The entire design-system re-skin (50+ files, six green commits) rendered almost completely unstyled in the browser — white background, no surfaces, no accent — because the design tokens never loaded. `vue-tsc -b` + `vite build` passed clean the whole time; CSS that *compiles* can still apply *zero* styles. One Playwright screenshot of the login exposed it in seconds. When the deliverable is visual, a green build is necessary but not sufficient: load it in a real browser (Playwright on the dev server at :5174), screenshot it, and assert on `getComputedStyle` — don't trust compilation alone. This is Lesson 17 with teeth.
+
+23. **Tailwind v4 silently drops a nested `@import` barrel placed after `@import "tailwindcss"`.** `style.css` did `@import "tailwindcss"; @import "./styles/corrosion.css";` where corrosion.css was a barrel of eight `@import` token files. Once Tailwind v4 expands the tailwindcss import in place, the barrel's inner @imports no longer precede all statements, so PostCSS drops them — emitting only an easily-ignored "@import must precede all other statements" warning. Result: every design token resolved empty and the whole panel rendered unstyled. Import token/design CSS files **directly and contiguously** in the entry stylesheet; never via a nested barrel after the Tailwind import. The build warning you wave off as "pre-existing" may be the entire feature silently failing.