vitest-dev/vitest · error · TypeError

The `browser.provider` configuration was changed to accept…

Error message

The `browser.provider` configuration was changed to accept a factory instead of a string. Add an import of "${resolved.browser.provider}" from "${source}" instead. See: https://vitest.dev/config/browser/provider

What it means

In a recent major version the `browser.provider` field changed from a string identifier (`'playwright'`, `'webdriverio'`) to a factory function imported from a dedicated package. Vitest detects the legacy string form and points the user at the correct import. This is a TypeError because the field's runtime type is wrong, not merely a deprecation.

Solutions

Import the provider factory from `@vitest/browser-playwright` (or `-webdriverio`, `-preview`) and pass the call result to `browser.provider`.
Install the matching `@vitest/browser-*` package if it is missing.
Repeat the migration for every workspace project that configures browsers.

Example fix

// before
import { defineConfig } from 'vitest/config'
export default defineConfig({ test: { browser: { provider: 'playwright' } } })
// after
import { defineConfig } from 'vitest/config'
import { playwright } from '@vitest/browser-playwright'
export default defineConfig({ test: { browser: { provider: playwright() } } })

Defensive patterns

Strategy: type-guard

Validate before calling

if (typeof (config.test?.browser as any)?.provider === 'string') {
  throw new TypeError('browser.provider must be a factory; migrate from the string form.')
}

Type guard

function isLegacyStringProvider(provider: unknown): provider is string {
  return typeof provider === 'string'
}

Prevention

Add a post-upgrade codemod that searches for `provider: 'playwright'` and rewrites it.
Keep a single `browserProviders.ts` module that imports and re-exports each factory.

When it happens

Trigger: Carrying over `browser: { provider: 'playwright' }` from a pre-migration config; docs/tutorial still using the string form.

Common situations: Upgrading Vitest across the major version that introduced factory providers; a monorepo where only one app's config was migrated.

Related errors

AI-assisted analysis of vitest-dev/vitest@1fa9837ec2 (2026-08-11). Data as JSON: /api/errors/199e8eeeb863efa4. Report an issue: GitHub.

Appendix: source

Thrown at packages/vitest/src/node/config/resolveConfig.ts:891

    )
  }

  if (resolved.inspector.enabled) {
    resolved.browser.trackUnhandledErrors ??= false
  }

  resolved.browser.viewport ??= {} as any
  resolved.browser.viewport.width ??= 414
  resolved.browser.viewport.height ??= 896

  resolved.browser.locators ??= {} as any
  resolved.browser.locators.testIdAttribute ??= 'data-testid'
  resolved.browser.locators.exact ??= true
  resolved.browser.locators.errorFormat ??= 'all'

  if (typeof resolved.browser.provider === 'string') {
    const source = `@vitest/browser-${resolved.browser.provider}`
    throw new TypeError(
      'The `browser.provider` configuration was changed to accept a factory instead of a string. '
      + `Add an import of "${resolved.browser.provider}" from "${source}" instead. See: https://vitest.dev/config/browser/provider`,
    )
  }

  const isPreview = resolved.browser.provider?.name === 'preview'

  if (!isPreview && resolved.browser.enabled && stdProvider === 'stackblitz') {
    throw new Error(`stackblitz environment does not support the ${resolved.browser.provider?.name} provider. Please, use "@vitest/browser-preview" instead.`)
  }
  if (isPreview && resolved.browser.screenshotFailures === true) {
    console.warn(c.yellow(
      [
        `Browser provider "preview" doesn't support screenshots, `,
        `so "browser.screenshotFailures" option is forcefully disabled. `,
        `Set "browser.screenshotFailures" to false or remove it from the config to suppress this warning.`,
      ].join(''),
    ))

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