- - Introduces React Actions with async support, new hooks (useActionState, useOptimistic, use) and ref‑as‑prop, plus enhanced Suspense pre‑warming, form actions, metadata, stylesheet and async‑script handling, and resource preloading APIs.
- - Adds server‑side prerender APIs and stabilizes React Server Components; many new declarative APIs for streaming and static site generation.
- - Breaking changes include mandatory new JSX transform, removal of propTypes, defaultProps for functions, legacy context APIs, string refs, ReactDOM.render/hydrate, test utils, UMD builds, and other long‑deprecated APIs; deprecates eleme...