How do I install the React18 Batching Patterns skill?

Run npx skillmds@latest add fluxonlab/react18-batching-patterns in your terminal (requires Node.js), paste this page's agent-chat prompt into Claude, Cursor, or any MCP-connected agent, or download the SKILL.md file and copy it into your agent's skills directory.

Is React18 Batching Patterns safe to use?

This skill has not completed SkillMD's automated safety review yet. SkillMD never runs a skill's scripts for you; review the SKILL.md before installing.

Which AI agents work with React18 Batching Patterns?

This skill is tagged as working with Claude Code, Claude.ai, OpenAI Codex. SKILL.md is an open format, so most agents that read a skills directory can load it too.

Is React18 Batching Patterns free to use?

Yes. Installing skills from SkillMD is free, and the skill stays under its author's original license.

Who published React18 Batching Patterns?

FluxonLab (@fluxonlab) published this skill. Their other Agent Skills are listed on their SkillMD profile.

React18 Batching Patterns by fluxonlab

Name: React18 Batching Patterns
Author: FluxonLab

React18 Batching Patterns

Provides exact patterns for diagnosing and fixing automatic batching regressions in React 18 class components. Use this skill whenever a class component has multiple setState calls in an async method, inside setTimeout, inside a Promise .then() or .catch(), or in a native event handler. Use it before writing any flushSync call - the decision tree here prevents unnecessary flushSync overuse. Also use this skill when fixing test failures caused by intermediate state assertions that break after React 18 upgrade.

FluxonLab 63c3255 3 files · 10.7 KB Updated Sep 17, 2026

File contents

React 18 Automatic Batching Patterns

Vendor skill (source: github-awesome-copilot). Imported 2026-05-31.

Reference for diagnosing and fixing the most dangerous silent breaking change in React 18 for class-component codebases.

The Core Change

Location of setState	React 17	React 18
React event handler	Batched	Batched (same)
setTimeout	Immediate re-render	Batched
Promise .then() / .catch()	Immediate re-render	Batched
async/await	Immediate re-render	Batched
Native addEventListener callback	Immediate re-render	Batched

Batched means: all setState calls within that execution context flush together in a single re-render at the end. No intermediate renders occur.

Quick Diagnosis

Read every async class method. Ask: does any code after an await read this.state to make a decision?

Code reads this.state after await?
  YES → Category A (silent state-read bug)
  NO, but intermediate render must be visible to user?
    YES → Category C (flushSync needed)
    NO → Category B (refactor, no flushSync)

For the full pattern for each category, read:

references/batching-categories.md - Category A, B, C with full before/after code
references/flushSync-guide.md - when to use flushSync, when NOT to, import syntax

The flushSync Rule

Use flushSync sparingly. It forces a synchronous re-render, bypassing React 18's concurrent scheduler. Overusing it negates the performance benefits of React 18.

Only use flushSync when:

The user must see an intermediate UI state before an async operation begins
A spinner/loading state must render before a fetch starts
Sequential UI steps have distinct visible states (progress wizard, multi-step flow)

In most cases, the fix is a refactor - restructuring the code to not read this.state after await. Read references/batching-categories.md for the correct approach per category.

---name: react18-batching-patternsdescription: Provides exact patterns for diagnosing and fixing automatic batching regressions in React 18 class components. Use this skill whenever a class component has multiple setState calls in an async method, inside setTimeout, inside a Promise .then() or .catch(), or in a native event handler. Use it before writing any flushSync call - the decision tree here prevents unnecessary flushSync overuse. Also use this skill when fixing test failures caused by intermediate state assertions that break after React 18 upgrade.---# React 18 Automatic Batching Patterns> _Vendor skill (source: github-awesome-copilot). Imported 2026-05-31._Reference for diagnosing and fixing the most dangerous silent breaking change in React 18 for class-component codebases.## The Core Change| Location of setState | React 17 | React 18 ||---|---|---|| React event handler | Batched | Batched (same) || setTimeout | **Immediate re-render** | **Batched** || Promise .then() / .catch() | **Immediate re-render** | **Batched** || async/await | **Immediate re-render** | **Batched** || Native addEventListener callback | **Immediate re-render** | **Batched** |**Batched** means: all setState calls within that execution context flush together in a single re-render at the end. No intermediate renders occur.## Quick DiagnosisRead every async class method. Ask: does any code after an `await` read `this.state` to make a decision?```Code reads this.state after await? YES → Category A (silent state-read bug) NO, but intermediate render must be visible to user? YES → Category C (flushSync needed) NO → Category B (refactor, no flushSync)```For the full pattern for each category, read:- **`references/batching-categories.md`** - Category A, B, C with full before/after code- **`references/flushSync-guide.md`** - when to use flushSync, when NOT to, import syntax## The flushSync Rule**Use `flushSync` sparingly.** It forces a synchronous re-render, bypassing React 18's concurrent scheduler. Overusing it negates the performance benefits of React 18.Only use `flushSync` when:- The user must see an intermediate UI state before an async operation begins- A spinner/loading state must render before a fetch starts- Sequential UI steps have distinct visible states (progress wizard, multi-step flow)In most cases, the fix is a **refactor** - restructuring the code to not read `this.state` after `await`. Read `references/batching-categories.md` for the correct approach per category.

Frequently asked questions