react18-dep-compatibility

# 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 | |---|---|---|--...