jestjs/jest · error · TypeError

Unexpected request from parent process: ${request[0]}

Error message

Unexpected request from parent process: ${request[0]}

What it means

Error "Unexpected request from parent process: ${request[0]}" thrown in jestjs/jest.

Source

Thrown at packages/jest-worker/src/workers/processChild.ts:89

        initialized = true;

        if (main.setup) {
          execFunction(
            main.setup,
            main,
            setupArgs,
            reportSuccess,
            reportInitializeError,
          );
        } else {
          reportSuccess(void 0);
        }
      }
      break;

    default:
      throw new TypeError(
        `Unexpected request from parent process: ${request[0]}`,
      );
  }
};
process.on('message', messageListener);

function reportSuccess(result: unknown) {
  if (!process || !process.send) {
    throw new Error('Child can only be used on a forked process');
  }

  try {
    process.send([PARENT_MESSAGE_OK, result]);
  } catch (error) {
    if (
      isError(error) &&
      // if .send is a function, it's a serialization issue
      !error.message.includes('.send is not a function')

View on GitHub (pinned to f49721c78e)

Solutions

1. Internal Jest error: the parent process sent an unrecognized request type to a forked child. Ensure the parent and child run the same Jest version; if the mismatch persists, upgrade Jest and report the issue.

When it happens

Trigger: Thrown at packages/jest-worker/src/workers/processChild.ts:89 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of jestjs/jest@f49721c78e (2026-08-03). Data as JSON: /data/errors/cb3f829f7b0436d0.json. Report an issue: GitHub.