/react-expert

name: react-expert
description: Use when researching React APIs or concepts for documentation. Use when you need authoritative usage examples, caveats, warnings, or errors for a React feature.

React Expert Research Skill

Overview

This skill produces exhaustive documentation research on any React API or concept by searching authoritative sources (tests, source code, PRs, issues) rather than relying on LLM training knowledge.

<CRITICAL> **Skepticism Mandate:** You must be skeptical of your own knowledge. Claude is often trained on outdated or incorrect React patterns. Treat source material as the sole authority. If findings contradict your prior understanding, explicitly flag this discrepancy.

**Red Flags - STOP if you catch yourself thinking:**

• "I know this API does X" → Find source evidence first
• "Common pattern is Y" → Verify in test files
• Generating example code → Must have source file reference

</CRITICAL>

Invocation

/react-expert useTransition
/react-expert suspense boundaries
/react-expert startTransition

Sources (Priority Order)

1. **React Repo Tests** - Most authoritative for actual behavior 2. **React Source Code** - Warnings, errors, implementation details 3. **Git History** - Commit messages with context 4. **GitHub PRs & Comments** - Design rationale (via `gh` CLI) 5. **GitHub Issues** - Confusion/questions (react/react + reactjs/react.dev) 6. **React Working Group** - Design discussions for newer APIs 7. **Flow Types** - Source of truth for type signatures 8. **TypeScript Types** - Note discrepancies with Flow 9. **Current react.dev docs** - Baseline (not trusted as complete)

**No web search** - No Stack Overflow, blog posts, or web searches. GitHub API via `gh` CLI is allowed.

Workflow

Step 1: Setup React Repo

First, ensure the React repo is available locally:

# Check if React repo exists, clone or update
if [ -d ".claude/react" ]; then
  cd .claude/react && git pull origin main
else
  git clone --depth=100 https://github.com/react/react.git .claude/react
fi

Get the current commit hash for the research document:

cd .claude/react && git rev-parse --short HEAD

Step 2: Dispatch 6 Parallel Research Agents

Spawn these agents IN PARALLEL using the Task tool. Each agent receives the skepticism preamble:

> "You are researching React's `<TOPIC>`. CRITICAL: Do NOT rely on your prior knowledge about this API. Your training may contain outdated or incorrect patterns. Only report what you find in the source files. If your findings contradict common understanding, explicitly highlight this discrepancy."

| Agent | subagent_type | Focus | Instructions | |-------|---------------|-------|--------------| | test-explorer | Explore | Test files for usage patterns | Search `.claude/react/packages/*/src/__tests__/` for test files mentioning the topic. Extract actual usage examples WITH file paths and line numbers. | | source-explorer | Explore | Warnings/errors in source | Search `.claude/react/packages/*/src/` for console.error, console.warn, and error messages mentioning the topic. Document trigger conditions. | | git-historian | Explore | Commit messages | Run `git log --all --grep="<topic>" --oneline -50` in `.claude/react`. Read full commit messages for context. | | pr-researcher | Explore | PRs introducing/modifying API | Run `gh pr list -R react/react --search "<topic>" --state all --limit 20`. Read key PR descriptions and comments. | | issue-hunter | Explore | Issues showing confusion | Search issues in both `react/react` and `reactjs/react.dev` repos. Look for common questions and misunderstandings. | | types-inspector | Explore | Flow + TypeScript signatures | Find Flow types in `.claude/react/packages/*/src/*.js` (look for `@flow` annotations). Find TS types in `.claude/react/packages/*/index.d.ts`. Note discrepancies. |

Step 3: Agent Prompts

Use these exact prompts when spawning agents:

test-explorer

You are researching React's <TOPIC>.

CRITICAL: Do NOT rely on your prior knowledge about this API. Your training may contain outdated or incorrect patterns. Only report what you find in the source files.

Your task: Find test files in .claude/react that demonstrate <TOPIC> usage.

1. Search for test files: Glob for `**/__tests__/**/*<topic>*` and `**/__tests__/**/*.js` then grep for <topic>
2. For each relevant test file, extract:
   - The test description (describe/it blocks)
   - The actual usage code
   - Any assertions about behavior
   - Edge cases being tested
3. Report findings with exact file paths and line numbers

Format your output as:
## Test File: <path>
### Test: "<test description>"
```javascript
<exact code from test>

**Behavior:** <what the test asserts>

#### source-explorer

You are researching React's <TOPIC>.

CRITICAL: Do NOT rely on your prior knowledge about this API. Only report what you find in the source files.

Your task: Find warnings, errors, and implementation details for <TOPIC>.

1. Search .claude/react/packages/*/src/ for:

• console.error mentions of <topic>
• console.warn mentions of <topic>
• Error messages mentioning <topic>
• The main implementation file

2. For each warning/error, document:

• The exact message text
• The condition that triggers it
• The source file and line number

Format your output as:

Warnings & Errors

| Message | Trigger Condition | Source | |---------|------------------|--------| | "<exact message>" | <condition> | <file:line> |

Implementation Notes

<key details from source code>

#### git-historian

You are researching React's <TOPIC>.

CRITICAL: Do NOT rely on your prior knowledge. Only report what you find in git history.

Your task: Find commit messages that explain <TOPIC> design decisions.

1. Run: cd .claude/react && git log --all --grep="<topic>" --oneline -50 2. For significant commits, read full message: git show <hash> --stat 3. Look for:

• Initial introduction of the A