SKILL.md
$27
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.