What were the most significant missing bits?

The worst thing is issues without any visibility.

The other day I was toying with the MCP server (https://github.com/modelcontextprotocol/typescript-sdk). I default to bun these days and the http based server simply did not register in claude or any other client. No error logs, nothing.

After fiddling with my code I simply tried node and it just worked.

It definitely works in bun just fine. I have a production built mcp server with auth running under bun.

Now if you convert the request / response types to native bun server, it can be finicky.

But it works fine using express under bun with the official protocol implementation for typescript.

Actually writing a book about this too and will be using bun for it https://leanpub.com/creatingmcpserverswithoauth

Not sure about the specific underlying apis, but as of my last attempt, Bun still doesn't support PDF.js (pdfjs-dist), ssh2, or playwright.

localAddress is unsupported on sockets, meaning you can not specify an outgoing interface, which is useful if you have multiple network cards.