React Vendoring
Use this skill for changes touching vendored React, react-server-dom-webpack/*, or react-server layer boundaries.
App Router Vendoring
React is NOT resolved from node_modules for App Router. It's vendored into packages/next/src/compiled/ during pnpm build (task: copy_vendor_react() in taskfile.js). Pages Router resolves React from node_modules normally.
- Two channels: stable (
compiled/react/) and experimental (compiled/react-experimental/). The runtime bundle webpack config aliases to the correct channel viamakeAppAliases({experimental}).
entry-base.ts Boundary
Only entry-base.ts is compiled in rspack's (react-server) layer. ALL imports from react-server-dom-webpack/* (Flight server/static APIs) must go through entry-base.ts. Other files like stream-ops.node.ts or app-render.tsx must access Flight APIs via the ComponentMod parameter (which is the entry-base.ts module exposed through the app-page.ts build template).
Direct imports from react-server-dom-webpack/server.node or react-server-dom-webpack/static in files outside entry-base.ts will fail at runtime with "The react-server condition must be enabled". Dev mode may mask this error, but production workers fail immediately.
Type Declarations
packages/next/types/$$compiled.internal.d.ts contains declare module blocks for vendored React packages. When adding new APIs (e.g. renderToPipeableStream, prerenderToNodeStream), you must add type declarations here. The bare specifier types (e.g. declare module 'react-server-dom-webpack/server') are what source code in src/ imports against.
Adding Node.js-Only React APIs
These exist in .node builds but not in the type definitions. Steps:
- Add type declarations to
$$compiled.internal.d.ts. - Export the API from
entry-base.tsbehind aprocess.envguard. - Access it via
ComponentModin other files.
// In entry-base.ts (react-server layer) only:
/* eslint-disable import/no-extraneous-dependencies */
export let renderToPipeableStream: ... | undefined
if (process.env.__NEXT_USE_NODE_STREAMS) {
renderToPipeableStream = (
require('react-server-dom-webpack/server.node') as typeof import('react-server-dom-webpack/server.node')
).renderToPipeableStream
} else {
renderToPipeableStream = undefined
}
/* eslint-enable import/no-extraneous-dependencies */
// In other files, access via ComponentMod:
ComponentMod.renderToPipeableStream!(payload, clientModules, opts)ESLint Practical Rule
For guarded runtime require() blocks that need import/no-extraneous-dependencies suppression, prefer scoped block disable/enable. If using eslint-disable-next-line, the comment must be on the line immediately before the require() call, NOT before the const declaration. When the const and require() are on different lines, this is error-prone.
Turbopack Remap
react-server-dom-webpack/* is silently remapped to react-server-dom-turbopack/* by Turbopack's import map. Code says "webpack" everywhere, but Turbopack gets its own bindings at runtime. This affects debugging: stack traces and error messages will reference the turbopack variant.
Related Skills
$flags- flag wiring (config/schema/define-env/runtime env)$dce-edge- DCE-safe require patterns and edge constraints$runtime-debug- reproduction and verification workflow