Vitest v4.0.17 — 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

✨ Features 2 🔧 Bug Fixes 6

⚡ Executive Summary (TL;DR)

Vitest v4.0.17. Source highlight:    🚀 Experimental Features

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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.

✨ New Features & Capabilities (2)

Support openTelemetry for browser mode  -  by @hi-ogawa in https://github.com/vitest-dev/vitest/issues/9180 <samp>(1ec3a)</samp>
Support TRACEPARENT and TRACESTATE environment variables for OpenTelemetry context propagation  -  by @Copilot, **hi-ogawa** and @hi-ogawa in https://github.com/vitest-dev/vitest/issues/9295 <samp>(876cb)</samp>

🔧 Bug Fixes & Patches (6)

Improve asymmetric matcher diff readability by unwrapping container matchers  -  by @Copilot, **sheremet-va**, **hi-ogawa** and @hi-ogawa in https://github.com/vitest-dev/vitest/issues/9330 <samp>(b2ec7)</samp>
Improve runner error when importing outside of test context  -  by @sheremet-va in https://github.com/vitest-dev/vitest/issues/9335 <samp>(2dd3d)</samp>
Replace crypto.randomUUID to allow insecure environments (fix #9…  -  by @plusgut in https://github.com/vitest-dev/vitest/issues/9339 and https://github.com/vitest-dev/vitest/issues/9 <samp>(e6a3f)</samp>
Handle null options in `addEventHandler` #9371  -  by @ThibautMarechal in https://github.com/vitest-dev/vitest/issues/9372 and https://github.com/vitest-dev/vitest/issues/9371 <samp>(40841)</samp>
Typo in browser.provider error  -  by @deammer in https://github.com/vitest-dev/vitest/issues/9394 <samp>(4b67f)</samp>
Fix `process.env` and `import.meta.env` defines in inline project  -  by @hi-ogawa in https://github.com/vitest-dev/vitest/issues/9239 <samp>(b70c9)</samp>

📄 View Raw Release Notes (Original Developer Log)

###    🚀 Experimental Features - Support openTelemetry for browser mode  -  by @hi-ogawa in https://github.com/vitest-dev/vitest/issues/9180 [<samp>(1ec3a)</samp>](https://github.com/vitest-dev/vitest/commit/1ec3a8b68) - Support TRACEPARENT and TRACESTATE environment variables for OpenTelemetry context propagation  -  by @Copilot, **hi-ogawa** and @hi-ogawa in https://github.com/vitest-dev/vitest/issues/9295 [<samp>(876cb)</samp>](https://github.com/vitest-dev/vitest/commit/876cb84c2) ###    🐞 Bug Fixes - Improve asymmetric matcher diff readability by unwrapping container matchers  -  by @Copilot, **sheremet-va**, **hi-ogawa** and @hi-ogawa in https://github.com/vitest-dev/vitest/issues/9330 [<samp>(b2ec7)</samp>](https://github.com/vitest-dev/vitest/commit/b2ec724a8) - Improve runner error when importing outside of test context  -  by @sheremet-va in https://github.com/vitest-dev/vitest/issues/9335 [<samp>(2dd3d)</samp>](https://github.com/vitest-dev/vitest/commit/2dd3dd839) - Replace crypto.randomUUID to allow insecure environments (fix #9…  -  by @plusgut in https://github.com/vitest-dev/vitest/issues/9339 and https://github.com/vitest-dev/vitest/issues/9 [<samp>(e6a3f)</samp>](https://github.com/vitest-dev/vitest/commit/e6a3f8cc7) - Handle null options in `addEventHandler` #9371  -  by @ThibautMarechal in https://github.com/vitest-dev/vitest/issues/9372 and https://github.com/vitest-dev/vitest/issues/9371 [<samp>(40841)</samp>](https://github.com/vitest-dev/vitest/commit/40841ff00) - Typo in browser.provider error  -  by @deammer in https://github.com/vitest-dev/vitest/issues/9394 [<samp>(4b67f)</samp>](https://github.com/vitest-dev/vitest/commit/4b67fc25a) - **browser**: - Fix `process.env` and `import.meta.env` defines in inline project  -  by @hi-ogawa in https://github.com/vitest-dev/vitest/issues/9239 [<samp>(b70c9)</samp>](https://github.com/vitest-dev/vitest/commit/b70c96121) - Fix upload File instance  -  by @hi-ogawa in https://github.com/vitest-dev/vitest/issues/9294 [<samp>(b6778)</samp>](https://github.com/vitest-dev/vitest/commit/b67788c69) - Fix invalid project token for artifacts assets  -  by @hi-ogawa in https://github.com/vitest-dev/vitest/issues/9321 [<samp>(caa7d)</samp>](https://github.com/vitest-dev/vitest/commit/caa7d73d4) - Log `ErrorEvent.message` when unhandled `ErrorEvent.error` is null  -  by @hi-ogawa in https://github.com/vitest-dev/vitest/issues/9322 [<samp>(5d84e)</samp>](https://github.com/vitest-dev/vitest/commit/5d84eeb91) - Support `fileParallelism` on an instance  -  by @sheremet-va in https://github.com/vitest-dev/vitest/issues/9328 [<samp>(15006)</samp>](https://github.com/vitest-dev/vitest/commit/150065459) - **coverage**: - Remove unnecessary `istanbul-lib-source-maps` usage  -  by @AriPerkkio in https://github.com/vitest-dev/vitest/issues/9344 [<samp>(b0940)</samp>](https://github.com/vitest-dev/vitest/commit/b09405375) - Apply patch from istanbuljs/istanbuljs#837  -  by @AriPerkkio and **sapphi-red** in https://github.com/vitest-dev/vitest/issues/9413 and https://github.com/vitest-dev/vitest/issues/837 [<samp>(e05ce)</samp>](https://github.com/vitest-dev/vitest/commit/e05cedbf4) - **fsModuleCache**: - Don't store importers in cache  -  by @sheremet-va in https://github.com/vitest-dev/vitest/issues/9422 [<samp>(75136)</samp>](https://github.com/vitest-dev/vitest/commit/751364eec) - Add importers alongside importedModules  -  by @sheremet-va in https://github.com/vitest-dev/vitest/issues/9423 [<samp>(59f92)</samp>](https://github.com/vitest-dev/vitest/commit/59f92d403) - **mocker**: - Fix mock transform with class  -  by @hi-ogawa in https://github.com/vitest-dev/vitest/issues/9421 [<samp>(d390e)</samp>](https://github.com/vitest-dev/vitest/commit/d390eb527) - **pool**: - Validate environment options when reusing the worker  -  by @sheremet-va in https://github.com/vitest-dev/vitest/issues/9349 [<samp>(a8a88)</samp>](https://github.com/vitest-dev/vitest/commit/a8a8836e3) - Handle worker start failures gracefully  -  by @AriPerkkio in https://github.com/vitest-dev/vitest/issues/9337 [<samp>(200da)</samp>](https://github.com/vitest-dev/vitest/commit/200dadb32) - **reporter**: - Report test module if it failed to run  -  by @sheremet-va in https://github.com/vitest-dev/vitest/issues/9272 [<samp>(c7888)</samp>](https://github.com/vitest-dev/vitest/commit/c78882985) - **runner**: - Respect nested test.only within describe.only  -  by @Ujjwaljain16 in https://github.com/vitest-dev/vitest/issues/9021 and https://github.com/vitest-dev/vitest/issues/9213 [<samp>(55d5d)</samp>](https://github.com/vitest-dev/vitest/commit/55d5dad69) - **typecheck**: - Improve error message when tsc outputs help text  -  by @Ujjwaljain16 in https://github.com/vitest-dev/vitest/issues/9214 [<samp>(7b10a)</samp>](https://github.com/vitest-dev/vitest/commit/7b10ab4cd) - **ui**: - Detect gzip by magic numbers instead of Content-Type header in html reporter  -  by @Copilot, **hi-ogawa** and @hi-ogawa in https://github.com/vitest-dev/vitest/issues/9278 [<samp>(dd033)</samp>](https://github.com/vitest-dev/vitest/commit/dd0331632) - **webdriverio**: - Fall back to WebDriver Classic #9244  -  by @JustasMonkev in https://github.com/vitest-dev/vitest/issues/9373 and https://github.com/vitest-dev/vitest/issues/9244 [<samp>(c23dd)</samp>](https://github.com/vitest-dev/vitest/commit/c23dd11bd) #####     [View changes on GitHub](https://github.com/vitest-dev/vitest/compare/v4.0.16...v4.0.17)

← Older Version Vitest v4.0.16 Newer Version → Vitest v4.0.18