# Vitest v4.1.5 — Release & Upgrade Intelligence
- **Product:** Vitest (https://vitest.dev)
- **Version:** v4.1.5
- **Released:** Apr 21, 2026
- **Impact Score:** 5/10
- **Breaking Changes:** Not verified
- **Canonical Analysis:** https://changelogs.us/vitest/updates/v4.1.5/

## Executive Summary (TL;DR)
Vitest v4.1.5. Source highlight:    🚀 Experimental Features

## New Features
- **coverage**: Istanbul to support `instrumenter` option &nbsp;-&nbsp; by @BartWaardenburg and @AriPerkkio in https://github.com/vitest-dev/vitest/issues/10119 <samp>(0e0ff)</samp>

## Bug Fixes
- --project negation excludes browser instances &nbsp;-&nbsp; by @felamaslen in https://github.com/vitest-dev/vitest/issues/10131 <samp>(9423d)</samp>
- Project color label on html reporter &nbsp;-&nbsp; by @hi-ogawa in https://github.com/vitest-dev/vitest/issues/10142 <samp>(596f7)</samp>
- Fix `vi.defineHelper` called as object method &nbsp;-&nbsp; by @hi-ogawa in https://github.com/vitest-dev/vitest/issues/10163 <samp>(122c2)</samp>
- Alias `agent` reporter to `minimal` &nbsp;-&nbsp; by @sheremet-va in https://github.com/vitest-dev/vitest/issues/10157 <samp>(663b9)</samp>
- Respect diff config options in soft assertions &nbsp;-&nbsp; by @Copilot, **sheremet-va** and @sheremet-va in https://github.com/vitest-dev/vitest/issues/8696 <samp>(9787d)</samp>
- Respect diff config options in soft assertions " &nbsp;-&nbsp; by @sheremet-va in https://github.com/vitest-dev/vitest/issues/8696 <samp>(7dc6d)</samp>