What is react-best-practices?

A set of rules for building React components and hooks, the reusable building blocks used to create React interfaces. It covers component size, naming, state, effects, lists, and data-fetching boundaries.

It is for designing React components, writing custom hooks, managing shared state, handling lists, and deciding where business logic and data fetching should live.

It helps keep React code easier to understand and reduces common problems such as deeply passed properties, unstable list keys, incomplete effect dependencies, and heavy work during rendering.

react-best-practices — Cursor rule by virastack

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods

npx agentmods add rules/virastack/ai/react-best-practices

Clone the repo

git clone --depth 1 https://github.com/virastack/ai

Made for: Cursor.

Per session 0 Nothing until a file matches its globs; then the whole rule loads.

When invoked 345 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. Scan, not verified.

Origin original No closer match found in the catalogue.

Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

Model	Per session	Once invoked
Fable 5	$0.00000	$0.00345
Opus 5	$0.00000	$0.00172
Sonnet 5	$0.00000	$0.00069
Haiku 4.5	$0.00000	$0.00034

Measured yesterday against content hash dddece490867, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

react-best-practices scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured yesterday.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

templates/core/.cursor/rules/react-best-practices.mdc · 49 lines

What it actually says

React Best Practices

Constraints

SRP: Keep components small (max 200 lines).
Composition: Use children or slots instead of prop drilling.
Naming: Use PascalCase for components, useCamelCase for hooks.
Hooks: Move business logic to custom hooks.
State: Lift state to the nearest common ancestor.
Updates: Use setState(prev => ...) for state updates.
Effects: Use useEffect as a last resort. Prefer event handlers or useMemo.
Keys: Use stable IDs for lists (index is forbidden).

Bans

Prop drilling (>2 levels).
Class components.
Incomplete dependency arrays.
Syncing props to state (use Derived state).
Heavy computations during render.
Data fetching inside components (violation of API rules).

Correct Implementation

Incorrect Implementation

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

yesterday First seen · 49 lines · 0 tokens per session scan A dddece490867

Subscribe to this mod's changes

react-best-practices is a cursor rule published in the GitHub repository virastack/ai (23 stars, last pushed 25d ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 345 tokens. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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