# Vitest v4.0.9 — Release & Upgrade Intelligence
- **Product:** Vitest (https://vitest.dev)
- **Version:** v4.0.9
- **Released:** Nov 14, 2025
- **Impact Score:** 5/10
- **Breaking Changes:** Not verified
- **Canonical Analysis:** https://changelogs.us/vitest/updates/v4.0.9/

## Executive Summary (TL;DR)
Vitest v4.0.9. Source highlight:    🚀 Experimental Features

## New Features
- **expect**: Add Set support to toBeOneOf &nbsp;-&nbsp; by @tim-we and @sheremet-va in https://github.com/vitest-dev/vitest/issues/8906 <samp>(a415d)</samp>

## Bug Fixes
- **browser**: Add favicon icons to the browser mode ui &nbsp;-&nbsp; by @userquin in https://github.com/vitest-dev/vitest/issues/8972 <samp>(353ee)</samp>
- **forks**: Increase worker start timeout &nbsp;-&nbsp; by @AriPerkkio in https://github.com/vitest-dev/vitest/issues/9027 <samp>(5e750)</samp>
- **jsdom**: Cloned request is an instance of `Request` &nbsp;-&nbsp; by @sheremet-va in https://github.com/vitest-dev/vitest/issues/8985 <samp>(506a9)</samp>
- **ui**: Collect file/suite/test duration correctly &nbsp;-&nbsp; by @userquin in https://github.com/vitest-dev/vitest/issues/8976 <samp>(8016d)</samp>