When running Vitest (I assume in Browser Mode), you see a console message like

Browser runner started by playwright at http://localhost:5173/

There is a number of places the configuration is done:

• browser.api for serving code to browser;
• api for the Vitest own test API;
• Test runner, i.e. playwright or webdriverio having their own stuff, can be configured at Vitest-level by using browser.providerOptions