Vitest v4.0.4 — Release Notes & Engineering Impact

Source available — automated, not human-reviewed

Component: vitest · Channel: stable. Automated analysis, not a compatibility certification. How this works.

Analysis updated: 2026-11-01.

Compatibility not verified — check source notes

📄 .MD

⚡ Improvements 1 🔧 Bug Fixes 6

⚡ Executive Summary (TL;DR)

Vitest v4.0.4. Source highlight:    🐞 Bug Fixes

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Who Does This Impact? (Role-Based Analysis)

💻 Software Engineers & Devs

Check the source notes against the package and APIs you use before upgrading.

📊 Product & Engineering Leads

Use the documented changes to assess relevance to your product; release frequency alone is not a quality measure.

⚙️ DevOps & Security

Verify the target version, runtime requirements and rollback procedure in the official documentation.

⚡ Performance & Enhancements (1)

**utils**: Optimized reducer to avoid creating new objects  -  by @Connormiha in https://github.com/vitest-dev/vitest/issues/8818 <samp>(d19ce)</samp>

🔧 Bug Fixes & Patches (6)

Correct typo  -  by @benmccann in https://github.com/vitest-dev/vitest/issues/8796 <samp>(ede1f)</samp>
Publish a missing context file for webdriverio  -  by @sheremet-va in https://github.com/vitest-dev/vitest/issues/8824 <samp>(7c7b6)</samp>
Support mocking builtins without `node:` prefix  -  by @sheremet-va in https://github.com/vitest-dev/vitest/issues/8829 <samp>(06208)</samp>
Runner's error listener causing `MaxListenersExceededWarning`  -  by @AriPerkkio in https://github.com/vitest-dev/vitest/issues/8820 <samp>(d1bff)</samp>
Capture workers `stdio` to logger  -  by @AriPerkkio in https://github.com/vitest-dev/vitest/issues/8809 <samp>(fb95f)</samp>
Allow classes in `vi.mocked` utility  -  by @sheremet-va in https://github.com/vitest-dev/vitest/issues/8839 <samp>(f8756)</samp>

📄 View Raw Release Notes (Original Developer Log)

###    🐞 Bug Fixes - **browser**: - Correct typo  -  by @benmccann in https://github.com/vitest-dev/vitest/issues/8796 [<samp>(ede1f)</samp>](https://github.com/vitest-dev/vitest/commit/ede1f39d6) - Publish a missing context file for webdriverio  -  by @sheremet-va in https://github.com/vitest-dev/vitest/issues/8824 [<samp>(7c7b6)</samp>](https://github.com/vitest-dev/vitest/commit/7c7b6f0b1) - **mocker**: - Support mocking builtins without `node:` prefix  -  by @sheremet-va in https://github.com/vitest-dev/vitest/issues/8829 [<samp>(06208)</samp>](https://github.com/vitest-dev/vitest/commit/06208d30b) - **pool**: - Runner's error listener causing `MaxListenersExceededWarning`  -  by @AriPerkkio in https://github.com/vitest-dev/vitest/issues/8820 [<samp>(d1bff)</samp>](https://github.com/vitest-dev/vitest/commit/d1bff3bb3) - Capture workers `stdio` to logger  -  by @AriPerkkio in https://github.com/vitest-dev/vitest/issues/8809 [<samp>(fb95f)</samp>](https://github.com/vitest-dev/vitest/commit/fb95fc736) - **spy**: - Allow classes in `vi.mocked` utility  -  by @sheremet-va in https://github.com/vitest-dev/vitest/issues/8839 [<samp>(f8756)</samp>](https://github.com/vitest-dev/vitest/commit/f87568d64) - **worker**: - Rpc listener leak when `isolate: false`  -  by @AriPerkkio in https://github.com/vitest-dev/vitest/issues/8821 [<samp>(573dc)</samp>](https://github.com/vitest-dev/vitest/commit/573dc06fe) ###    🏎 Performance - **utils**: Optimized reducer to avoid creating new objects  -  by @Connormiha in https://github.com/vitest-dev/vitest/issues/8818 [<samp>(d19ce)</samp>](https://github.com/vitest-dev/vitest/commit/d19cece3a) #####     [View changes on GitHub](https://github.com/vitest-dev/vitest/compare/v4.0.3...v4.0.4)

← Older Version Vitest v4.0.3 Newer Version → Vitest v4.0.5