Its not 100% nodejs compatible. I see enough non-green dots in their own official report https://bun.com/docs/runtime/nodejs-compat

And even in packages with full support you can find many github issues that bun behaves directly which leads to some bugs.

Not saying it’s 100%, there’s still the repl missing but all of node’s API is available in the sense that it’s ABI compatible (or will be very near term).