Before shipping, test a production build rather than relying only on development mode. Verify responsive layouts, keyboard navigation, focus visibility, contrast, form errors, dark mode, and reduced-motion behavior. Check that all important content is available without hover and that hidden elements do not create confusing keyboard paths.

Keep utilities consistent through a documented scale and reusable components where they add value. Remove dead custom CSS, avoid broad global selectors that unexpectedly affect third-party components, and document non-obvious arbitrary values or design tokens.