Enterprise toolkit for migrating React 18 codebases to React 19. Includes five specialized agents and three skills targeting the specific challenges of upgrading to React 19's modern API surface.

Installation

copilot plugin install react19-upgrade@awesome-copilot

What's Included

Agents

react19-commander Master orchestrator that coordinates the entire migration pipeline through audit, dependencies, source code migration, and test verification phases.
react19-auditor Deep-scan specialist that identifies every React 19 breaking change and deprecated pattern:
- Removed APIs: ReactDOM.render, ReactDOM.hydrate, unmountComponentAtNode, findDOMNode, createFactory, react-dom/test-utils exports
- Legacy Context API (contextTypes, childContextTypes, getChildContext)
- String refs (this.refs.x)
- Deprecated patterns: forwardRef, defaultProps on function components, useRef() without initial value
- Test-specific issues: act import location, Simulate usage, StrictMode changes
react19-dep-surgeon Dependency upgrade specialist that upgrades to react@19, handles @testing-library/react@16+, resolves all peer conflicts, and returns GO/NO-GO confirmation.
react19-migrator Source code migration engine that rewrites required React 19 changes and can apply optional modernizations for deprecated patterns:
- ReactDOM.render → createRoot
- ReactDOM.hydrate → hydrateRoot
- unmountComponentAtNode → root.unmount()
- findDOMNode → direct refs
- Optional modernization: forwardRef → ref as direct prop
- defaultProps → ES6 defaults
- Legacy Context → createContext
- String refs → createRef
- useRef() → useRef(null)
- propTypes → documentation comments
react19-test-guardian Test suite fixer that handles:
- act import fixes (react-dom/test-utils → react)
- Simulate → fireEvent migrations
- StrictMode spy call count deltas (no more double-invoke in React 19)
- useRef shape updates
- Custom render helper verification
- Error boundary test updates
- Runs tests until zero failures

Skills

react19-concurrent-patterns Deep patterns for React 19 concurrent features including Suspense, use() Hook, Server Components integration, and concurrent batching.
react19-source-patterns Migration patterns for source API changes including DOM/root APIs, refs, and context updates.
react19-test-patterns Comprehensive test migration guide covering act() semantics, error boundary testing, and StrictMode behavioral changes.

Quick Start

Ask: "Start implementing React 19 migration for my codebase"

The react19-commander will guide you through:

Audit → identify all breaking changes
Deps → upgrade to react@19 + compatible libraries
Migrate → fix all deprecated APIs and patterns
Tests → migrate test suite and run to green

Breaking Changes from React 18

Removed APIs

ReactDOM.render() use createRoot()
ReactDOM.hydrate() use hydrateRoot()
ReactDOM.unmountComponentAtNode() use root.unmount()
ReactDOM.findDOMNode() use direct refs
React.createFactory() use JSX
react-dom/test-utils exports
Legacy Context API
String refs

Deprecated Patterns (Still work but should migrate)

forwardRef ref is now a direct prop
defaultProps on function components use ES6 defaults
useRef() without initial value pass null

Behavioral Changes

StrictMode no longer double-invokes effects (affects test call count assertions)
propTypes runtime validation removed (keep for documentation, but no runtime checks)

Key Features

✅ Comprehensive removal of 8+ deprecated React APIs
✅ Handles complex patterns: legacy context, forwardRef, defaultProps
✅ Memory-based resumable pipeline survive interruptions
✅ Zero tolerance for incomplete migrations run to full success
✅ StrictMode-aware test fixes
✅ Testing-library v16+ compatibility verification
✅ Error boundary and async test pattern updates

Prerequisite

This plugin assumes you're migrating from React 18 codebases. If you're on React 16/17, use the react18-upgrade plugin first to reach React 18.3.1, then use this plugin for the React 19 final upgrade.

Source

This plugin is part of Awesome Copilot.

License

MIT