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.
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Install
Works with every agent the skills CLI supports.
npx skills add https://github.com/github/awesome-copilot --skill react18-batching-patterns- 01
Install
Run the command in your project. The CLI asks which agents to install for.
- 02
Describe the task
Ask your agent for something this skill covers. It loads react18-batching-patterns automatically when relevant.
- 03
Review the result
The agent follows the SKILL.md steps, scripts and references bundled with the skill.
SKILL.md
The instructions your agent reads when the skill is triggered.
React 18 Automatic Batching Patterns
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 codereferences/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.
FAQ
What does the react18-batching-patterns skill do?
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.
How do I install react18-batching-patterns?
Run npx skills add https://github.com/github/awesome-copilot --skill react18-batching-patterns in your project. The skills CLI detects the agents you use and copies the skill into the right folder. For Claude Code you can also place the skill folder at ~/.claude/skills/react18-batching-patterns/ (personal) or .claude/skills/react18-batching-patterns/ (project).
Which AI agents can use react18-batching-patterns?
Any agent that supports the open Agent Skills format (a folder with a SKILL.md file), including Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, Windsurf, Cline, OpenCode and more.
Is react18-batching-patterns safe to install?
No partner security audit is available yet. Skills can run commands and scripts, so read the SKILL.md and any bundled files before installing.
Who maintains react18-batching-patterns?
It is published by github in github/awesome-copilot, and it is an official skill from the maker of the technology it covers. It has 754 recorded installs.
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