React and Next.js performance guidance for writing, reviewing, and refactoring production UI code.

React and Next.js performance optimization guidelines from Vercel Engineering. This skill should be used when writing, reviewing, or refactoring React/Next.js code to ensure optimal performance patterns. Triggers on tasks involving React components, Next.js pages, data fetching, bundle optimization, or performance improvements.

Build self-contained, double-click-to-open HTML prototypes so the user can vet an interface before it gets built. One file holds several structurally different variants of a page, app screen, component, flow, or terminal/TUI layout (rendered in-browser), plus a draggable Design Deck for flipping between variants, tuning fonts, colors, spacing, shape, motion and 'feel' with live dials, trying vibe presets, checking viewport sizes and light/dark, pinning comments on elements, and an 'Export to LLM' button that copies the chosen variant and every dial value as a handoff block to paste back to the agent. Use this whenever the user wants to prototype, mock up, wireframe, explore options for, or sanity-check a UI (landing page, dashboard, settings page, onboarding, form, mobile screen, component, CLI/TUI layout), or says 'what should this look like', 'show me a few options', 'let me tweak it before we build', 'vet the design'. Also use it when the user pastes a block starting with 'AI-ASSIST

Use this skill for AngularJS unit testing, maintenance, and migration tasks

Automates browser interactions for web testing, form filling, screenshots, and data extraction. Use when the user needs to navigate websites, interact with web pages, fill forms, take screenshots, test web applications, or extract information from web pages.