Bun is designed as a drop-in replacement for Node.js. It natively implements hundreds of Node.js and Web APIs, including fs, path, Buffer and more.
The goal of Bun is to run most of the world's server-side JavaScript and provide tools to improve performance, reduce complexity, and multiply developer productivity.
If it can replace node and pnpm at the same time then this sounds quite good actually.
While Vite currently works with Bun, it has not been heavily optimized, nor has Vite been adapted to use Bun's bundler, module resolver, or transpiler.