• Install: npm install -D vitest (add @vitest/ui if you want the UI)
• Rename jest.config.js to vitest.config.ts (and probably ask AI to convert it, ChatGPT or Claude can probably do a good job)
• Swap jest.* → vi.* in your tests (use find/replace)
• Update import paths if using custom Jest plugin resolvers
• Run vitest and fix any remaining issues

Most teams complete this in a few hours. Full guide here from Vitest.dev .