facebook/react · critical · Error

The React Server Writer cannot be used outside a react-serve

Error message

The React Server Writer cannot be used outside a react-server environment. You must configure Node.js using the `--conditions react-server` flag.

What it means

react-server-dom-turbopack/server resolves to the Flight writer only under the react-server Node export condition; this npm fallback stub throws at import time to keep the server-only writer out of non-react-server processes (client bundles, plain Node).

Source

Thrown at packages/react-server-dom-turbopack/npm/server.js:3

'use strict';

throw new Error(
  'The React Server Writer cannot be used outside a react-server environment. ' +
    'You must configure Node.js using the `--conditions react-server` flag.'
);

View on GitHub (pinned to eafeac097b)

Solutions

Run Node with --conditions react-server when the process imports the writer
Keep writer imports inside modules only ever loaded in the react-server condition branch
Teach bundlers/test runners the react-server condition so the real entry resolves

Example fix

# before
$ node server.js   # import of react-server-dom-turbopack/server throws

# after
$ node --conditions react-server server.js

Defensive patterns

Strategy: validation

Validate before calling

const args = process.execArgv.join(' ');
if (!args.includes('react-server')) {
  throw new Error('Server writer requires --conditions react-server');
}
const {renderToPipeableStream} = require('react-server-dom-turbopack/server.node');

Prevention

Run writer-importing processes with --conditions react-server
Keep server imports in modules only loaded from the react-server branch
Propagate the condition through bundlers and test runners

When it happens

Trigger: Importing react-server-dom-turbopack/server in a Node process launched without --conditions react-server, or a bundler resolving the conditionless fallback export into a client/server-hybrid graph.

Common situations: Running the server entry with plain `node`; jest/vitest without condition propagation; isomorphic code that imports both client and server entries unconditionally.

Related errors

AI-assisted analysis of facebook/react@eafeac097b (2026-08-21). Data as JSON: /api/errors/c7ab40d5ef98f26d. Report an issue: GitHub.