Repository boundary: advisory design guidance only

Downstream adaptation for Issue #841. This reference provides design advice, not execution authority. Current main canonical documents, CLAUDE Hard rules, existing components and their behavior, src/styles/tokens.css, i18n, security rules and the user's actual permissions take precedence. Preserve the incumbent design and authorized scope. Missing design documents do not imply a greenfield project. Do not create or replace PRODUCT.md, DESIGN.md, sidecars or other project documentation automatically. Review requests and visual selections do not authorize applying changes, installing tools, replacing dependencies, downloading fonts/assets, changing settings, or publishing. Any implementation needs its own applicable authorization. No external engine, hook, launcher, helper agent or operational fallback is enabled by these files. Generic examples illustrate design concepts; adapt their values to existing tokens and their copy to i18n. Accessibility suggestions do not waive repo tests, independent review or release gates.

Picking The Right Library

How to use this

1. Identify the task, not the library the user named. "I need to show a dropdown" is a UI-primitives task (base-ui), even if they asked about something else.
2. Check what's already installed. Look at package.json first. If the project already uses a listed library, use it. If it uses a competitor (e.g. react-window instead of Virtuoso), flag the recommendation but don't churn the dependency without being asked.
3. Recommend one library, state what it's for in one sentence, and describe how it fits existing components; installation and implementation remain separately scoped. Don't present a menu of options when the list has a clear answer.
4. If the task isn't covered by the list, say so explicitly and recommend from your own knowledge — but be clear you've left the curated list.

The list

UI components & primitives

Task	Library
Unstyled, accessible UI components (dialogs, popovers, menus, selects…)	base-ui
Command menus (⌘K palettes)	cmdk
Toasts / notifications	Sonner
One-time password / verification code inputs	input-otp
Customizable GUIs / control panels	Leva — dialkit is an alternative

Motion & visuals

Task	Library
General-purpose animation (springs, layout animations, enter/exit)	motion (Framer Motion)
Animating numbers (counters, prices, stats)	NumberFlow
Animated text components	torph
3D globes	Cobe
Dynamic OG images (HTML/CSS → SVG/PNG)	Satori
Syntax highlighting	shiki

Reach for motion when you need springs, layout animations, exit animations, or gesture-driven values. A simple hover or fade doesn't need it — plain CSS transitions are the right tool there.

Charts

Task	Library
Real-time / streaming charts	Liveline
General charts (static or interactive dashboards)	recharts

The split: if data points arrive live and the chart scrolls with time, use Liveline. Everything else is recharts.

Interaction & performance

Task	Library
Drag and drop	dnd kit
Virtualization (long lists, large tables)	Virtuoso

State & styling

Task	Library
State management	zustand
Constructing className strings conditionally	clsx
Type-safe, variant-driven styling for Tailwind	cva
Theme switching / dark mode (no flash on load)	next-themes

The styling split: clsx for ad-hoc conditional classes; cva when a component has real variants (size, intent, state) that deserve a typed API. They compose — cva uses clsx-style inputs internally.

Common mismatches to catch

• Toasts built by hand or with a modal library → Sonner exists for exactly this.
• A <div>-based dropdown/dialog with manual focus handling → base-ui, which handles accessibility, focus trapping, and dismissal.
• Animating a number by re-rendering text → NumberFlow handles digit transitions properly.
• Rendering a 1,000+ row list directly → Virtuoso before reaching for pagination hacks.
• A useState-per-component web of props for shared state → zustand.
• Template-literal className ternaries three conditions deep → clsx (or cva if it's variant-shaped).