vercel/next.js · error

Invalid response ${mocked.res.statusCode}

Error message

Invalid response ${mocked.res.statusCode}

What it means

Thrown in NextNodeServer's on-demand revalidation path after it builds a mocked request/response pair and runs the real request handler against the page. The revalidation is only considered successful when the response is 200, carries the x-nextjs-cache: REVALIDATED header, or is a 404 while unstable_onlyGenerated is set. Any other status code reaches this guard, meaning the page handler rejected the revalidation request.

Source

Thrown at packages/next/src/server/next-server.ts:1368

  }) {
    const mocked = createRequestResponseMocks({
      url: urlPath,
      headers,
    })

    const handler = this.getRequestHandler()
    await handler(
      new NodeNextRequest(mocked.req),
      new NodeNextResponse(mocked.res)
    )
    await mocked.res.hasStreamed

    if (
      mocked.res.getHeader('x-nextjs-cache') !== 'REVALIDATED' &&
      mocked.res.statusCode !== 200 &&
      !(mocked.res.statusCode === 404 && opts.unstable_onlyGenerated)
    ) {
      throw new Error(`Invalid response ${mocked.res.statusCode}`)
    }
  }

  public async render(
    req: NodeNextRequest | IncomingMessage,
    res: NodeNextResponse | ServerResponse,
    pathname: string,
    query?: NextParsedUrlQuery,
    parsedUrl?: NextUrlWithParsedQuery,
    internal = false
  ): Promise<void> {
    return super.render(
      this.normalizeReq(req),
      this.normalizeRes(res),
      pathname,
      query,
      parsedUrl,
      internal

View on GitHub (pinned to 43273a1d21)

Solutions

1. Ensure the mocked/handled response has a valid HTTP status code; check custom server or middleware response handling.

When it happens

Trigger: A mocked handler produced an invalid response status.

Common situations: Internal invariant when a mock request result has an unexpected status code.

AI-assisted analysis of vercel/next.js@43273a1d21 (2026-08-19). Data as JSON: /api/errors/b3234129b09c0b6d. Report an issue: GitHub.