githubcopilot-react18-dep-compatibility

name	githubcopilot-react18-dep-compatibility
description	React 18.3.1 and React 19 dependency compatibility matrix.

React Dependency Compatibility Matrix

Minimum versions required for React 18.3.1 and React 19 compatibility.

Use this skill whenever checking whether a dependency supports a target React version, resolving peer dependency conflicts, deciding whether to upgrade or use legacy-peer-deps, or assessing the risk of a react-router v5 to v6 migration.

Review this matrix before running npm install during a React upgrade and before accepting an npm dependency conflict resolution, especially where concurrent mode compatibility may be affected.

Core Upgrade Targets

Package	React 17 (current)	React 18.3.1 (min)	React 19 (min)	Notes
react	17.x	18.3.1	19.0.0	Pin exactly to 18.3.1 for the R18 orchestra
react-dom	17.x	18.3.1	19.0.0	Must match react version exactly

Testing Libraries

Package	React 18 Min	React 19 Min	Notes
@testing-library/react	14.0.0	16.0.0	RTL 13 uses ReactDOM.render internally - broken in R18
@testing-library/jest-dom	6.0.0	6.0.0	v5 works but v6 has React 18 matcher updates
@testing-library/user-event	14.0.0	14.0.0	v13 is sync, v14 is async - API change required
jest	27.x	27.x	jest 27+ with jsdom 16+ for React 18
jest-environment-jsdom	27.x	27.x	Must match jest version

Apollo Client

Package	React 18 Min	React 19 Min	Notes
@apollo/client	3.8.0	3.11.0	3.8 adds useSyncExternalStore for concurrent mode
graphql	15.x	16.x	Apollo 3.8+ peer requires graphql 15 or 16

Read references/apollo-details.md for concurrent mode issues and MockedProvider changes.

Emotion

Package	React 18 Min	React 19 Min	Notes
@emotion/react	11.10.0	11.13.0	11.10 adds React 18 concurrent mode support
@emotion/styled	11.10.0	11.13.0	Must match @emotion/react version
@emotion/cache	11.10.0	11.13.0	If used directly

React Router

Package	React 18 Min	React 19 Min	Notes
react-router-dom	v6.0.0	v6.8.0	v5 → v6 is a breaking migration - see details below
react-router-dom v5	5.3.4 (workaround)	❌ Not supported	See legacy peer deps note

react-router v5 → v6 is a SEPARATE migration sprint. Read references/router-migration.md.

Redux

Package	React 18 Min	React 19 Min	Notes
react-redux	8.0.0	9.0.0	v7 works on R18 legacy root only - breaks on concurrent mode
redux	4.x	5.x	Redux itself is framework-agnostic - react-redux version matters
@reduxjs/toolkit	1.9.0	2.0.0	RTK 1.9 tested against React 18

Other Common Packages

Package	React 18 Min	React 19 Min	Notes
react-query / @tanstack/react-query	4.0.0	5.0.0	v3 doesn't support concurrent mode
react-hook-form	7.0.0	7.43.0	v6 has concurrent mode issues
formik	2.2.9	2.4.0	v2.2.9 patched for React 18
react-select	5.0.0	5.8.0	v4 has peer dep conflicts with R18
react-datepicker	4.8.0	6.0.0	v4.8+ added React 18 support
react-dnd	16.0.0	16.0.0	v15 and below have R18 concurrent mode issues
prop-types	any	any	Standalone - unaffected by React version

---

Conflict Resolution Decision Tree

npm ls shows peer conflict for package X
         │
         ▼
Does package X have a version that supports React 18?
  YES → npm install X@[min-compatible-version]
  NO  ↓
         │
Is the package critical to the app?
  YES → check GitHub issues for React 18 branch/fork
      → check if maintainer has a PR open
      → last resort: --legacy-peer-deps (document why)
  NO  → consider removing the package

--legacy-peer-deps Rules

Only use --legacy-peer-deps when:

• The package has no React 18 compatible release
• The package is actively maintained (not abandoned)
• The conflict is only a peer dep declaration mismatch (not actual API incompatibility)

Document every --legacy-peer-deps usage in a comment at the top of package.json or in a MIGRATION.md file explaining why it was necessary.