vercel-react · diff
git:20260518.3fc52ce to git:20260610.36508ae
139 added, 4 removed. Audit A to A.
---
name: vercel-react
description: React/Next.js performance — 70 rules (waterfalls, bundle, re-renders). Use when reviewing or writing React/Next.js code.
group: brana
keywords: [react, nextjs, performance, bundle, server-components, optimization, vercel]
allowed-tools: [Read, Glob, Grep, WebFetch, AskUserQuestion]
status: experimental
source: "https://skills.sh/vercel-labs/agent-skills/vercel-react-best-practices"
acquired: "2026-05-17"
quarantine: false
---
+ # Vercel React Best Practices
- <!-- PROCEDURE_FILE: procedures/vercel-react.md -->
- This skill's full procedure is in a separate file for startup performance (ADR-034).
- Read and execute `system/procedures/vercel-react.md` from the plugin root directory.
- If the path doesn't resolve, use Glob to find `**/procedures/vercel-react.md`.
+ Comprehensive performance optimization guide for React and Next.js applications, maintained by Vercel. Contains 70 rules across 8 categories, prioritized by impact to guide automated refactoring and code generation.
+
+ ## When to Apply
+
+ Reference these guidelines when:
+ - Writing new React components or Next.js pages
+ - Implementing data fetching (client or server-side)
+ - Reviewing code for performance issues
+ - Refactoring existing React/Next.js code
+ - Optimizing bundle size or load times
+
+ ## Rule Categories by Priority
+
+ | Priority | Category | Impact | Prefix |
+ |----------|----------|--------|--------|
+ | 1 | Eliminating Waterfalls | CRITICAL | `async-` |
+ | 2 | Bundle Size Optimization | CRITICAL | `bundle-` |
+ | 3 | Server-Side Performance | HIGH | `server-` |
+ | 4 | Client-Side Data Fetching | MEDIUM-HIGH | `client-` |
+ | 5 | Re-render Optimization | MEDIUM | `rerender-` |
+ | 6 | Rendering Performance | MEDIUM | `rendering-` |
+ | 7 | JavaScript Performance | LOW-MEDIUM | `js-` |
+ | 8 | Advanced Patterns | LOW | `advanced-` |
+
+ ## Quick Reference
+
+ ### 1. Eliminating Waterfalls (CRITICAL)
+
+ - `async-cheap-condition-before-await` - Check cheap sync conditions before awaiting flags or remote values
+ - `async-defer-await` - Move await into branches where actually used
+ - `async-parallel` - Use Promise.all() for independent operations
+ - `async-dependencies` - Use better-all for partial dependencies
+ - `async-api-routes` - Start promises early, await late in API routes
+ - `async-suspense-boundaries` - Use Suspense to stream content
+
+ ### 2. Bundle Size Optimization (CRITICAL)
+
+ - `bundle-barrel-imports` - Import directly, avoid barrel files
+ - `bundle-analyzable-paths` - Prefer statically analyzable import and file-system paths to avoid broad bundles and traces
+ - `bundle-dynamic-imports` - Use next/dynamic for heavy components
+ - `bundle-defer-third-party` - Load analytics/logging after hydration
+ - `bundle-conditional` - Load modules only when feature is activated
+ - `bundle-preload` - Preload on hover/focus for perceived speed
+
+ ### 3. Server-Side Performance (HIGH)
+
+ - `server-auth-actions` - Authenticate server actions like API routes
+ - `server-cache-react` - Use React.cache() for per-request deduplication
+ - `server-cache-lru` - Use LRU cache for cross-request caching
+ - `server-dedup-props` - Avoid duplicate serialization in RSC props
+ - `server-hoist-static-io` - Hoist static I/O (fonts, logos) to module level
+ - `server-no-shared-module-state` - Avoid module-level mutable request state in RSC/SSR
+ - `server-serialization` - Minimize data passed to client components
+ - `server-parallel-fetching` - Restructure components to parallelize fetches
+ - `server-parallel-nested-fetching` - Chain nested fetches per item in Promise.all
+ - `server-after-nonblocking` - Use after() for non-blocking operations
+
+ ### 4. Client-Side Data Fetching (MEDIUM-HIGH)
+
+ - `client-swr-dedup` - Use SWR for automatic request deduplication
+ - `client-event-listeners` - Deduplicate global event listeners
+ - `client-passive-event-listeners` - Use passive listeners for scroll
+ - `client-localstorage-schema` - Version and minimize localStorage data
+
+ ### 5. Re-render Optimization (MEDIUM)
+
+ - `rerender-defer-reads` - Don't subscribe to state only used in callbacks
+ - `rerender-memo` - Extract expensive work into memoized components
+ - `rerender-memo-with-default-value` - Hoist default non-primitive props
+ - `rerender-dependencies` - Use primitive dependencies in effects
+ - `rerender-derived-state` - Subscribe to derived booleans, not raw values
+ - `rerender-derived-state-no-effect` - Derive state during render, not effects
+ - `rerender-functional-setstate` - Use functional setState for stable callbacks
+ - `rerender-lazy-state-init` - Pass function to useState for expensive values
+ - `rerender-simple-expression-in-memo` - Avoid memo for simple primitives
+ - `rerender-split-combined-hooks` - Split hooks with independent dependencies
+ - `rerender-move-effect-to-event` - Put interaction logic in event handlers
+ - `rerender-transitions` - Use startTransition for non-urgent updates
+ - `rerender-use-deferred-value` - Defer expensive renders to keep input responsive
+ - `rerender-use-ref-transient-values` - Use refs for transient frequent values
+ - `rerender-no-inline-components` - Don't define components inside components
+
+ ### 6. Rendering Performance (MEDIUM)
+
+ - `rendering-animate-svg-wrapper` - Animate div wrapper, not SVG element
+ - `rendering-content-visibility` - Use content-visibility for long lists
+ - `rendering-hoist-jsx` - Extract static JSX outside components
+ - `rendering-svg-precision` - Reduce SVG coordinate precision
+ - `rendering-hydration-no-flicker` - Use inline script for client-only data
+ - `rendering-hydration-suppress-warning` - Suppress expected mismatches
+ - `rendering-activity` - Use Activity component for show/hide
+ - `rendering-conditional-render` - Use ternary, not && for conditionals
+ - `rendering-usetransition-loading` - Prefer useTransition for loading state
+ - `rendering-resource-hints` - Use React DOM resource hints for preloading
+ - `rendering-script-defer-async` - Use defer or async on script tags
+
+ ### 7. JavaScript Performance (LOW-MEDIUM)
+
+ - `js-batch-dom-css` - Group CSS changes via classes or cssText
+ - `js-index-maps` - Build Map for repeated lookups
+ - `js-cache-property-access` - Cache object properties in loops
+ - `js-cache-function-results` - Cache function results in module-level Map
+ - `js-cache-storage` - Cache localStorage/sessionStorage reads
+ - `js-combine-iterations` - Combine multiple filter/map into one loop
+ - `js-length-check-first` - Check array length before expensive comparison
+ - `js-early-exit` - Return early from functions
+ - `js-hoist-regexp` - Hoist RegExp creation outside loops
+ - `js-min-max-loop` - Use loop for min/max instead of sort
+ - `js-set-map-lookups` - Use Set/Map for O(1) lookups
+ - `js-tosorted-immutable` - Use toSorted() for immutability
+ - `js-flatmap-filter` - Use flatMap to map and filter in one pass
+ - `js-request-idle-callback` - Defer non-critical work to browser idle time
+
+ ### 8. Advanced Patterns (LOW)
+
+ - `advanced-effect-event-deps` - Don't put `useEffectEvent` results in effect deps
+ - `advanced-event-handler-refs` - Store event handlers in refs
+ - `advanced-init-once` - Initialize app once per app load
+ - `advanced-use-latest` - useLatest for stable callback refs
+
+ ## How to Use
+
+ Read individual rule files for detailed explanations and code examples:
+
+ ```
+ rules/async-parallel.md
+ rules/bundle-barrel-imports.md
+ ```
+
+ Each rule file contains:
+ - Brief explanation of why it matters
+ - Incorrect code example with explanation
+ - Correct code example with explanation
+ - Additional context and references
+
+ ## Full Compiled Document
+
+ For the complete guide with all rules expanded: `AGENTS.md`