vitest-dev/vitest · error · TypeError

Tag " ": retry.condition function cannot be used inside a…

Error message

Tag "${tag.name}": retry.condition function cannot be used inside a config file. Use a RegExp pattern instead, or define the function in your test file.

What it means

A tag's `retry.condition` may not be a function when defined in a config file, because config files are serialized/shared across worker boundaries where functions cannot travel. Vitest detects `typeof tag.retry === 'object' && typeof tag.retry.condition === 'function'` and throws a `TypeError`, asking the user to use a RegExp pattern or move the function into the test file.

Solutions

Replace the function with a RegExp pattern over the error message if the config supports it.
Move the conditional retry into the test file where the function executes in-process.
If a RegExp is insufficient, narrow the retry scope to specific tests instead of a tag.

Example fix

// before — vitest.config.ts
export default defineConfig({ test: { tags: [{
  name: 'flaky',
  retry: { condition: (e: Error) => /timeout/.test(e.message) },
}] } })

// after — use a RegExp pattern in config
export default defineConfig({ test: { tags: [{
  name: 'flaky',
  retry: { condition: /timeout/ },
}] } })
// or move the function into the test file and attach retry there

Defensive patterns

Strategy: validation

Validate before calling

type RetryConfig = { condition?: RegExp; limit?: number }
function assertConfigSafeRetry(retry: unknown): void {
  if (retry && typeof retry === 'object'
      && 'condition' in (retry as any)
      && typeof (retry as any).condition === 'function') {
    throw new TypeError('retry.condition cannot be a function in a config file; use a RegExp')
  }
}

(rawTags ?? []).forEach(t => assertConfigSafeRetry(t.retry))

Type guard

function isConfigSafeRetry(r: unknown): r is RetryConfig {
  if (r == null) return true
  if (typeof r !== 'object') return false
  const cond = (r as any).condition
  return cond === undefined || cond instanceof RegExp
}

Prevention

Use RegExp patterns for `retry.condition` in config files.
Move function-based conditions into the test file where they run in-process.
Lint configs for function-valued properties on serialisable config shapes.

When it happens

Trigger: `test.tags: [{ name: 'flaky', retry: { condition: (err) => err.message.includes('timeout') } }]` in `vitest.config.ts`. The same shape is fine when declared inside a test file via the runner API, because that code runs in-process.

Common situations: Migrating per-test retry conditions into shared config; reusing a function from a config preset; refactoring that moves logic from test files into config.

Related errors

AI-assisted analysis of vitest-dev/vitest@1fa9837ec2 (2026-08-11). Data as JSON: /api/errors/ccfd85d4a28784bb. Report an issue: GitHub.

Appendix: source

Thrown at packages/vitest/src/node/config/resolveConfig.ts:305

  const definedTags = new Set<string>()
  resolved.tags.forEach((tag) => {
    if (!tag.name || typeof tag.name !== 'string') {
      throw new Error(`Each tag defined in "test.tags" must have a "name" property, received: ${JSON.stringify(tag)}`)
    }
    if (definedTags.has(tag.name)) {
      throw new Error(`Tag name "${tag.name}" is already defined in "test.tags". Tag names must be unique.`)
    }
    if (/\s/.test(tag.name)) {
      throw new Error(`Tag name "${tag.name}" is invalid. Tag names cannot contain spaces.`)
    }
    if (/[!()*|&]/.test(tag.name)) {
      throw new Error(`Tag name "${tag.name}" is invalid. Tag names cannot contain "!", "*", "&", "|", "(", or ")".`)
    }
    if (/^\s*(?:and|or|not)\s*$/i.test(tag.name)) {
      throw new Error(`Tag name "${tag.name}" is invalid. Tag names cannot be a logical operator like "and", "or", "not".`)
    }
    if (typeof tag.retry === 'object' && typeof tag.retry.condition === 'function') {
      throw new TypeError(`Tag "${tag.name}": retry.condition function cannot be used inside a config file. Use a RegExp pattern instead, or define the function in your test file.`)
    }
    if (tag.priority != null && (typeof tag.priority !== 'number' || tag.priority < 0)) {
      throw new TypeError(`Tag "${tag.name}": priority must be a non-negative number.`)
    }
    definedTags.add(tag.name)
  })

  resolved.name = typeof options.name === 'string'
    ? options.name
    : (options.name?.label || '')

  resolved.color = typeof options.name !== 'string' ? options.name?.color : undefined

  if (resolved.environment === 'browser') {
    throw new Error(`Looks like you set "test.environment" to "browser". To enable Browser Mode, use "test.browser.enabled" instead.`)
  }

  resolved.benchmark = {

View on GitHub (pinned to 1fa9837ec2)