jestjs/jest · error · Error

Both --${key} and --watchAll were specified, but cannot be u

Error message

Both --${key} and --watchAll were specified, but cannot be used together. Try the --watch option which reruns only tests related to changed files.

What it means

The `check` function loops over the change-detection flags (`onlyChanged`, `lastCommit`, `changedFilesWithAncestor`, `changedSince`) and throws if any is combined with `--watchAll` (packages/jest-cli/src/args.ts:22). `--watchAll` reruns every test on any file change, which contradicts the 'only run tests for changed files' semantics. The message points users to `--watch`, which reruns only tests related to changed files.

Source

Thrown at packages/jest-cli/src/args.ts:29

export function check(argv: Config.Argv): true {
  if (
    argv.runInBand &&
    Object.prototype.hasOwnProperty.call(argv, 'maxWorkers')
  ) {
    throw new Error(
      'Both --runInBand and --maxWorkers were specified, only one is allowed.',
    );
  }

  for (const key of [
    'onlyChanged',
    'lastCommit',
    'changedFilesWithAncestor',
    'changedSince',
  ]) {
    if (argv[key] && argv.watchAll) {
      throw new Error(
        `Both --${key} and --watchAll were specified, but cannot be used ` +
          'together. Try the --watch option which reruns only tests ' +
          'related to changed files.',
      );
    }
  }

  if (argv.onlyFailures && argv.watchAll) {
    throw new Error(
      'Both --onlyFailures and --watchAll were specified, only one is allowed.',
    );
  }

  if (argv.findRelatedTests && argv._.length === 0) {
    throw new Error(
      'The --findRelatedTests option requires file paths to be specified.\n' +
        'Example usage: jest --findRelatedTests ./src/source.js ' +
        './src/index.js.',

View on GitHub (pinned to f49721c78e)

Solutions

1. Replace `--watchAll` with `--watch` — `--watch` already implies change-detection scoping and composes with onlyChanged/changedSince.
2. If you truly want to rerun ALL tests on every change, drop the changed-files flag instead.

Example fix

# before
jest --onlyChanged --watchAll

# after
jest --onlyChanged --watch

const CHANGED_FLAGS = ['onlyChanged','lastCommit','changedFilesWithAncestor','changedSince'] as const;
function validateWatchFlags(argv: any): void {
  if (argv.watchAll && CHANGED_FLAGS.some(k => argv[k])) {
    throw new Error('Use --watch (not --watchAll) with change-detection flags');
  }
}

const usesChangedFiles = (a: any) =>
  Boolean(a.onlyChanged || a.lastCommit || a.changedFilesWithAncestor || a.changedSince);

When it happens

Trigger: `jest --onlyChanged --watchAll`, `jest -o --watchAll`, `jest --changedSince=main --watchAll`, or `jest --lastCommit --watchAll`.

Common situations: Wanting watch mode plus change-scoping and reaching for the broader `--watchAll`; copy-pasting a watch script and adding a changed-files flag; IDE integrations that default to watchAll.

Related errors

• Both --onlyFailures and --watchAll were specified, only one
• The --maxWorkers (-w) option requires a number or string to
• Both --runInBand and --maxWorkers were specified, only one i
• The --findRelatedTests option requires file paths to be spec
• The --selectProjects option requires the name of at least on

AI-assisted analysis of jestjs/jest@f49721c78e (2026-08-03). Data as JSON: /data/errors/5349ed6a0dd967ea.json. Report an issue: GitHub.