vitest-dev/vitest · error · Error

Vitest standalone mode requires --watch

Error message

Vitest standalone mode requires --watch

What it means

Standalone mode keeps Vitest's server alive so other tools (e.g. an editor) can attach and trigger runs; it is meaningless without watch because there would be no re-run trigger and the process would just exit. The guard at resolveConfig.ts:344 forces --watch whenever --standalone is set.

Source

Thrown at packages/vitest/src/node/config/resolveConfig.ts:345

    const [indexString, countString] = options.shard.split('/')
    const index = Math.abs(Number.parseInt(indexString, 10))
    const count = Math.abs(Number.parseInt(countString, 10))

    if (Number.isNaN(count) || count <= 0) {
      throw new Error('--shard <count> must be a positive number')
    }

    if (Number.isNaN(index) || index <= 0 || index > count) {
      throw new Error(
        '--shard <index> must be a positive number less then <count>',
      )
    }

    resolved.shard = { index, count }
  }

  if (resolved.standalone && !resolved.watch) {
    throw new Error(`Vitest standalone mode requires --watch`)
  }

  if (resolved.mergeReports && resolved.watch) {
    throw new Error(`Cannot merge reports with --watch enabled`)
  }

  if (resolved.maxWorkers) {
    resolved.maxWorkers = resolveInlineWorkerOption(resolved.maxWorkers)
  }

  // `browser.fileParallelism` was replaced by the top-level `fileParallelism`. Map
  // it (only when browser is enabled, since it was a browser-only option) so
  // existing configs keep working instead of being silently ignored.
  const browserOptions = options.browser as { enabled?: boolean; fileParallelism?: boolean } | undefined
  const browserFileParallelism = browserOptions?.enabled ? browserOptions.fileParallelism : undefined
  if (browserFileParallelism !== undefined) {
    logger.deprecate('`browser.fileParallelism` is deprecated. Use the top-level `fileParallelism` option instead.')
  }

View on GitHub (pinned to d568f8ce37)

Solutions

1. Always pair standalone with watch: `vitest --standalone --watch`.
2. If you do not need a persistent server, drop --standalone and run vitest normally.
3. Configure your editor plugin to pass both flags.

Example fix

# before
vitest --standalone
# after
vitest --standalone --watch

function assertStandaloneHasWatch(opts: { standalone?: boolean; watch?: boolean }) {
  if (opts.standalone && !opts.watch) throw new Error('--standalone requires --watch')
}

When it happens

Trigger: Run `vitest --standalone` without --watch, or set `standalone: true` while `watch: false`.

Common situations: Trying standalone in a CI one-shot context; editor integration that forgot to enable watch.

Related errors

• You cannot use --shard option with enabled watch
• Cannot merge reports with --watch enabled
• --shard <count> must be a positive number
• --shard <index> must be a positive number less then <count>
• You cannot use ${inspectOption} without "--no-file-paralleli

AI-assisted analysis of vitest-dev/vitest@d568f8ce37 (2026-08-03). Data as JSON: /data/errors/1848b3f2ad775ad3.json. Report an issue: GitHub.