name: frontend description: Use when building React components, optimizing performance, analyzing bundle sizes, scaffolding projects, implementing accessibility, reviewing frontend code quality, performing visual overhauls, or designing UI/UX systems.

Frontend Engineer

Frontend development patterns, performance optimization, accessibility, and distinctive UI design for any framework.

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Step 1: Detect the Stack

Before writing any code, identify the framework and tooling from project signals:

Signal file / pattern	Stack
next.config.*	Next.js (React)
nuxt.config.*	Nuxt (Vue)
svelte.config.*	SvelteKit
astro.config.*	Astro
remix.config.* / @remix-run in package.json	Remix (React)
angular.json	Angular
vite.config.* + React	Vite + React
vite.config.* + Vue	Vite + Vue
tailwind.config.*	Tailwind CSS
styled-components / emotion in package.json	CSS-in-JS

Check: cat package.json, ls -la, cat vite.config.* — whichever applies.

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Step 2: Research Current Practices

Once you know the stack, search before making framework-specific recommendations:

WebSearch: " component patterns best practices 2025" WebSearch: " performance optimization 2025" WebSearch: " bundle size optimization 2025" WebSearch: " accessibility best practices 2025" WebSearch: " best practices 2025"

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Step 3: Design Thinking

When building any UI — component, page, or application — commit to a bold aesthetic direction before writing a line of code:

• Purpose: What problem does this interface solve? Who uses it?
• Tone: Pick an extreme and own it. Brutally minimal, maximalist chaos, retro-futuristic, organic/natural, luxury/refined, playful/toy-like, editorial/magazine, brutalist/raw, art deco/geometric, soft/pastel, industrial/utilitarian — commit to one direction and execute it with precision.
• Differentiation: What makes this unforgettable? What is the one thing someone will remember?
• Constraints: Framework, performance budget, accessibility requirements.

The goal is intentionality, not intensity. Refined minimalism and bold maximalism both work — generic middle ground does not.

Typography

Choose fonts that are beautiful, unique, and characterful. Pair a distinctive display font with a refined body font.

• Avoid: Inter, Roboto, Arial, system fonts, Space Grotesk (overused)
• Prefer: Unexpected choices that elevate the aesthetic and feel designed for the context
• Every font decision should be documented with a reason

Color and Theme

Commit to a cohesive aesthetic. Use CSS variables for consistency.

• Dominant colors with sharp accents outperform timid, evenly-distributed palettes
• Define tokens: primary, surface, text, error, border — never scatter raw hex values
• Vary between light and dark themes — do not default to one
• Check contrast ratios (4.5:1 for body text, 3:1 for large text)

Motion

Use animation for effects and micro-interactions. Prioritize CSS-only for HTML; Motion library for React when available.

• One well-orchestrated page load with staggered reveals creates more delight than scattered micro-interactions
• Use scroll-triggering and hover states that surprise
• Match animation complexity to the aesthetic vision — maximalist designs need elaborate motion, refined designs need restraint

Spatial Composition

• Unexpected layouts: asymmetry, overlap, diagonal flow, grid-breaking elements
• Generous negative space OR controlled density — not the muddled middle
• Visual hierarchy through size contrast, not just color

Backgrounds and Visual Details

Create atmosphere and depth rather than defaulting to solid colors:

• Gradient meshes, noise textures, geometric patterns, layered transparencies
• Dramatic shadows, decorative borders, grain overlays
• Custom cursors, contextual effects that match the overall aesthetic

Aesthetic Anti-Patterns

Never use generic AI-generated aesthetics:

• Overused fonts: Inter, Roboto, Arial, Space Grotesk, system fonts
• Purple gradients on white backgrounds
• Predictable layouts and cookie-cutter component patterns
• Design that lacks context-specific character
• Two consecutive generations that converge on the same choices

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Step 4: Universal Frontend Principles

These apply regardless of framework.

Component Design

• Single responsibility: one component, one job — split when a component does two distinct things
• Props as API: treat component props like a public API — document what is required vs optional
• Co-location: keep styles, tests, and types next to the component they belong to
• Composition over inheritance: prefer passing children/slots over extending base components
• Controlled vs uncontrolled: be intentional — controlled for forms that need validation, uncontrolled for simple inputs

Performance

• Render budget: components should render in under 16ms for 60fps; profile before optimizing
• Lazy loading: code-split at route boundaries; defer below-fold components
• Image optimization: use the framework image component or <picture> + srcset; never serve 2x the display size
• Memoization: only add when profiling shows a problem — premature memoization adds complexity for no gain
• Bundle analysis: regularly audit bundle size; flag dependencies over 50kb that can be replaced or lazy-loaded

Accessibility (a11y)

• Semantic HTML: use the right element (<button> not <div onClick>, <nav> not <div class="nav">)
• Focus management: custom modals/drawers/dropdowns must trap focus and restore it on close
• ARIA: only use ARIA to extend semantics, not replace them; prefer native elements
• Color contrast: 4.5:1 for body text, 3:1 for large text (WCAG AA minimum)
• Keyboard navigation: every interactive element reachable and operable by keyboard
• Screen reader testing: test with NVDA+Firefox or VoiceOver+Safari before shipping

State Management

• Locality first: co-locate state with the component that owns it; lift only when needed
• Server state vs client state: use a data-fetching library for server state (TanStack Query, SWR, Apollo) — do not store it in global store
• Derived state: compute from source of truth — do not sync two pieces of state
• Global store: only for genuinely cross-cutting state (auth user, theme, feature flags)

Forms

• Validation: validate on blur for UX, on submit for correctness; show errors inline
• Accessibility: every input has a <label>; error messages referenced via aria-describedby
• Loading states: disable submit during async; show spinner or progress
• Optimistic UI: apply the mutation locally, rollback on error

Security

• XSS: never set innerHTML/dangerouslySetInnerHTML from user input; sanitize if unavoidable
• CSP: Content-Security-Policy header; avoid unsafe-inline
• Sensitive data: never log tokens, passwords, or PII to the console
• Third-party scripts: audit before adding; every script is a supply chain risk
• Dependency audit: run npm audit regularly; keep dependencies current

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Review Checklist

Before any frontend PR:

• Aesthetic direction chosen and documented before any code was written
• Font choices are distinctive and context-appropriate (not Inter/Roboto/Arial/Space Grotesk)
• Color tokens defined; contrast ratios verified (WCAG AA)
• All component states handled — default, hover, focus, disabled, loading, error, empty
• Components have single, clear responsibility
• No dangerouslySetInnerHTML from unvalidated input
• Every interactive element is keyboard-accessible
• Every input has an associated <label>
• Images have meaningful alt text (or alt="" if decorative)
• Bundle impact assessed for new dependencies
• No console.log of tokens or PII
• Responsive at mobile, tablet, and desktop breakpoints