React Guide

Establish the installed react/react-dom versions, supported consumers, and rendering path: client rendering, server rendering, or hydration. Inspect package/lockfile and entry-point evidence when available. If versions or inputs are missing, continue investigation and version-independent explanation; defer only choices that depend on the missing facts. Do not assume every React 19 minor exposes the same APIs.

Treat existing defects, incomplete cleanup, and failed checks as diagnosis and repair work. Ask for a decision only when an unresolved product or compatibility choice changes the solution. Migration evidence can come from current source and diagnostics; a prior-stage report is not required.

Route

Start with the closest reference, then read related references directly as the task crosses topics. Use their inputs and checks selectively for the requested explanation, implementation, or review.