v0.1.0-next.16

Released: 2026-05-29

Features

feat(render): polyfill MessageChannel/setTimeout in the V8 host for React 19 SSR (c9a38d3)

Completes the React island support shipped in next.15 for React 19. React 19’s react-dom/server.browser bundle constructs a MessageChannel at module load (its Fizz scheduler) and references setTimeout in its error-retick path — neither existed in the embedded V8 SSR host, so zfb build with React 19 failed at module load with ReferenceError: MessageChannel is not defined (React 18’s server bundle did not touch MessageChannel, which is why next.15, verified on React 18, missed it). Adds an install-if-absent MessageChannel/MessagePort (Promise/microtask-backed) and setTimeout/clearTimeout to the host polyfills; Preact bundles are byte-unaffected. Verified under React 19 across all four island shapes (basic, Headless UI ssrFallback, in-MDX, ClientRouter head tags); React 18, Preact, and node-free non-regressed. The engine’s own react test baseline is bumped to 19 to guard the class going forward.