Create a React 18 to 19 Upgrade Playbook

Don’t want to set this up manually? Paste a link to this page into a Devin session and ask it to set everything up for you.

Prompt Devin with the React 19 upgrade guide

React 19 introduces breaking changes across ref handling, context usage, TypeScript types, and removed legacy APIs. The official upgrade guide documents every change, but the hard part is mapping those changes to your code. Instead of reading the guide yourself and auditing every component, hand both to Devin and get back a playbook scoped to your actual files.Open a new Devin session from the Devin home page and paste a prompt with the upgrade guide URL and what you need:

Layer in codebase-specific context

Devin uses DeepWiki to understand your repo’s architecture automatically. It can also look up online sources about React 19 — the official upgrade guide, blog posts, library changelogs — and incorporate what it finds directly into the playbook.To make the playbook even sharper, tell Devin about patterns the migration will touch:

“We use forwardRef in 23 components under src/components/ui/ — these are our design system primitives”
“We still have 4 class components in src/legacy/ that use string refs and componentWillMount”
“Check other repos in our org (e.g., acme/design-system, acme/admin-dashboard) to see if they’ve already started the React 19 migration — reuse any patterns they’ve established”

If any dependencies have their own React 19 compatibility guides (e.g., React Router, React Hook Form, or your UI library), paste those URLs into the prompt too — Devin reads them all and cross-references the breaking changes.

Review the codebase-specific playbook

Devin reads the React 19 upgrade guide end-to-end, cross-references every breaking change against your codebase via DeepWiki, and produces a phased playbook with specific files, complexity estimates, and validation steps:

# React 18 → 19 Migration Playbook

## Phase 1: Upgrade to React 18.3 and fix deprecation warnings (S)
- npm install react@18.3 react-dom@18.3
- Run the app and fix all console deprecation warnings:
  - Remove string refs in src/legacy/OldModal.tsx, src/legacy/OldTooltip.tsx
  - Replace ReactDOM.findDOMNode in src/legacy/DropdownMenu.tsx
- Run test suite to confirm no regressions
- Validation: Zero deprecation warnings in dev console, all tests pass

## Phase 2: Migrate forwardRef to ref-as-prop (M)
- Remove forwardRef wrappers from 23 components in src/components/ui/:
  - Button.tsx, Input.tsx, Select.tsx, TextArea.tsx (high usage)
  - Modal.tsx, Popover.tsx, Tooltip.tsx (medium usage)
  - +16 more components (full list below)
- Pass ref as a regular prop instead of wrapping in forwardRef
- Update TypeScript types: change RefObject<T> to RefObject<T> | null
- Update src/types/refs.d.ts to match new React 19 ref semantics
- Validation: All ref-forwarding components render, focus management works

## Phase 3: Remove deprecated APIs (M)
- Replace legacy Context (contextTypes/getChildContext) in:
  - src/legacy/ThemeProvider.tsx → already uses createContext (no change)
  - src/legacy/LocaleContext.tsx → convert to createContext pattern
- Remove propTypes from 12 files (TypeScript handles validation)
- Remove defaultProps from function components (use JS defaults)
- Validation: Context values propagate correctly, no runtime warnings

## Phase 4: Update data fetching and Suspense patterns (L)
- Review Suspense boundaries in src/components/layouts/
- Update any components relying on fallback behavior changes
- Test lazy-loaded routes in src/routes/ with new Suspense semantics
- Validation: All lazy routes load, loading states render correctly

## Phase 5: Install React 19 and adopt new features (M)
- npm install react@19 react-dom@19
- Replace useFormState with useActionState in src/hooks/useFormField.ts
- Update react-dom imports: ReactDOM.render → already using createRoot
- Enable the new JSX transform if not already active
- Validation: Full test suite passes, app runs without errors

## Phase 6: Update third-party libraries (L)
- react-hook-form → upgrade to v8 (React 19 compatible)
- @radix-ui/react-* → upgrade to latest (ref-as-prop support)
- react-router-dom → verify v6.4+ compatibility
- Validation: Forms submit correctly, UI primitives render, routing works

## Risks
- forwardRef removal is highest-volume change — 23 components, many
  consumed by other teams
- TypeScript ref type changes may surface null-safety issues
- react-hook-form v8 has its own breaking changes — test form
  validation thoroughly

The playbook is a plan, not an executed migration. Review it with your team, adjust the phasing or scope, then decide how to execute.

Execute and scale

Once the playbook looks right, save it and attach it to a session to execute phase by phase:Scale across repos — If you have multiple React apps that need the same upgrade, ask Devin to run the saved playbook across all of them in parallel using managed Devins.