VTDT0001: Vitest UI Install Failed

Message

Failed to install @vitest/ui: {error}

Cause

The Vitest launcher installs @vitest/ui on demand the first time it is launched in a project that has vitest but not @vitest/ui. This diagnostic is thrown when that install (run via nypm against the project's detected package manager) fails — for example due to network restrictions, a read-only file system, or a package manager error.

Example

Clicking Install @vitest/ui & start in the Vitest dock while offline, so the package manager cannot reach the registry.

Fix

Install @vitest/ui manually with your package manager, then launch again:

npm i -D @vitest/ui
# or: pnpm add -D @vitest/ui
# or: yarn add -D @vitest/ui

Source

• packages/vitest/src/node/plugin.ts — the launcher's onLaunch throws this when addDependency('@vitest/ui', { dev: true }) rejects.