Describe the bug
With test.browser.enabled: true, every vitest run prints once:
Plugin "vitest:mocks:interceptor" defines Vite-specific hooks (configureServer) in a plugin returned from applyToEnvironment. These hooks will be ignored.
Cause: @vitest/browser adds interceptorPlugin({ registerWebSocketEvents: false }) (from @vitest/mocker) to the browser contribution, which vitest:browser:loader.applyToEnvironment returns for the client environment. The mocker's interceptorPlugin always defines configureServer (its body returns early when registerWebSocketEvents === false), and Vite 8's resolveEnvironmentPlugins warns for any config / configEnvironment / configureServer / configResolved hook on a plugin returned from applyToEnvironment. Tests and mocking work; the warning is noise on every run.
Suggested fix: attach configureServer only when registerWebSocketEvents !== false (packages/mocker/src/node/interceptorPlugin.ts), or strip the hook in the browser contribution.
I do not plan to submit a PR. Used Claude Code to generate this report.
Reproduction
Link to the GitHub repository with the Reproduction — npm install && npm test.
Bare config: one chromium instance via @vitest/browser-playwright, one passing test, no plugins.
Actual: The warning above is printed once per run.
Expected: no warning. (The same happens in a 200-file production suite; the minimal repo is the stripped-down version.)
System Info
System:
OS: Windows 11 10.0.26200
CPU: (16) x64 Intel(R) Core(TM) Ultra 7 265H
Memory: 6.38 GB / 31.46 GB
Binaries:
Node: 24.20.0 - C:\nvm4w\nodejs\node.EXE
npm: 11.19.1 - C:\nvm4w\nodejs\npm.CMD
Browsers:
Chrome: 152.0.7977.84
Edge: Chromium (147.0.3912.72)
npmPackages:
@vitejs/plugin-react: 6.1.1 => 6.1.1
@vitest/browser-playwright: 5.0.0 => 5.0.0
@vitest/coverage-v8: 5.0.0 => 5.0.0
@vitest/eslint-plugin: 1.6.27 => 1.6.27
@vitest/ui: 5.0.0 => 5.0.0
playwright: 1.63.0 => 1.63.0
vite: 8.3.0 => 8.3.0
vitest: 5.0.0 => 5.0.0
vitest-browser-react: 2.3.0 => 2.3.0Used Package Manager
npm
Validations
Describe the bug
With test.browser.enabled: true, every vitest run prints once:
Plugin "vitest:mocks:interceptor" defines Vite-specific hooks (configureServer) in a plugin returned from applyToEnvironment. These hooks will be ignored.
Cause: @vitest/browser adds interceptorPlugin({ registerWebSocketEvents: false }) (from @vitest/mocker) to the browser contribution, which vitest:browser:loader.applyToEnvironment returns for the client environment. The mocker's interceptorPlugin always defines configureServer (its body returns early when registerWebSocketEvents === false), and Vite 8's resolveEnvironmentPlugins warns for any config / configEnvironment / configureServer / configResolved hook on a plugin returned from applyToEnvironment. Tests and mocking work; the warning is noise on every run.
Suggested fix: attach configureServer only when registerWebSocketEvents !== false (packages/mocker/src/node/interceptorPlugin.ts), or strip the hook in the browser contribution.
I do not plan to submit a PR. Used Claude Code to generate this report.
Reproduction
Link to the GitHub repository with the Reproduction — npm install && npm test.
Bare config: one chromium instance via @vitest/browser-playwright, one passing test, no plugins.
Actual: The warning above is printed once per run.
Expected: no warning. (The same happens in a 200-file production suite; the minimal repo is the stripped-down version.)
System Info
System: OS: Windows 11 10.0.26200 CPU: (16) x64 Intel(R) Core(TM) Ultra 7 265H Memory: 6.38 GB / 31.46 GB Binaries: Node: 24.20.0 - C:\nvm4w\nodejs\node.EXE npm: 11.19.1 - C:\nvm4w\nodejs\npm.CMD Browsers: Chrome: 152.0.7977.84 Edge: Chromium (147.0.3912.72) npmPackages: @vitejs/plugin-react: 6.1.1 => 6.1.1 @vitest/browser-playwright: 5.0.0 => 5.0.0 @vitest/coverage-v8: 5.0.0 => 5.0.0 @vitest/eslint-plugin: 1.6.27 => 1.6.27 @vitest/ui: 5.0.0 => 5.0.0 playwright: 1.63.0 => 1.63.0 vite: 8.3.0 => 8.3.0 vitest: 5.0.0 => 5.0.0 vitest-browser-react: 2.3.0 => 2.3.0Used Package Manager
npm
Validations