Vercel react best practices

Skill coco-research/coco/skills/vercel-react-best-practices

Meet Coco. A superintelligent agent framework powered by an advisory board of 389 world-class minds. Scale your AI assistant into a complete engineering department with 142 skills, 277 commands, and persistent state. Universal compatibility. Local privacy. Free and open source.

Install

npx -y skills add coco-research/coco --skill vercel-react-best-practices

Assembled from the repository path, not quoted from the project. Check it against their README if it does not work.

One thing to look at

no licenseNo license file was found in the repository. Code published without one is not open source by default, so using it at work is a question for whoever answers licensing questions where you are.

What its author says it does

Copied from the file, not written here

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.

The file declares its own license as MIT. That is the author’s claim about this one file, and it is not the same thing as the license GitHub reports for the repository, which is listed with the other numbers below.

SKILL.md

6.0 KB, ~1.4k tokens by cl100k_base, as published. Nobody here has run it

Vercel React Best Practices

Comprehensive performance optimization guide for React and Next.js applications, maintained by Vercel. Contains 57 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-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-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-serialization - Minimize data passed to client components
server-parallel-fetching - Restructure components to parallelize fetches
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-move-effect-to-event - Put interaction logic in event handlers
rerender-transitions - Use startTransition for non-urgent updates
rerender-use-ref-transient-values - Use refs for transient frequent values

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

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

8. Advanced Patterns (LOW)

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

Gives 1 of the 12 instructions most performance cost skills give in ~1.4k tokens

Counted across 803 of the 1,058 authors here whose files we hold, read 2026-08-06

keep skill files under 500 linesin 82 of 803, across 17 files
use imperative form in instructionsin 81 of 803, across 10 files
draft assertions while test runs are in progressin 75 of 803, across 9 files
create two to three realistic test promptsin 74 of 803, across 8 files
write skill descriptions to be pushyin 72 of 803, across 7 files
save test cases to evals jsonin 72 of 803, across 6 files
ask questions about edge cases and input formatsin 71 of 803, across 6 files
save timing data immediately when runs completein 70 of 803, across 5 files
include all trigger conditions in the skill descriptionin 69 of 803, across 3 files
launch all test runs in a single turnin 69 of 803, across 3 files
capture intent before writing a skillin 67 of 803, across 1 file
import directly instead of barrel fileshere, and in 52 of 803, across 15 files

Grouped from the skills themselves: near-identical wordings counted once, and counted by distinct author, so one author publishing three of these counts once. Length counted with cl100k_base; the agent that loads this file may tokenize it differently.