Vercel Functions' Bun runtime now supports Bun.serve as entrypoint

Vercel Functions' Bun runtime now supports Bun.serve() as a function entrypoint. Servers run locally with Bun can be deployed as-is without wrapping them in a separate framework, and it is enabled by setting "bunVersion": "1.x" in vercel.json.

In server.ts at the project root, you can define static, dynamic, and wildcard routes using the routes map. WebSocket connections are also handled when using the websocket handler together with server.upgrade(request).

WebSocket connections are subject to Fluid compute and Active CPU pricing, meaning costs are incurred only for message processing time, not idle connection time. Connections are pinned to a single function instance for their lifetime, and an external data store must be used for message coordination across multiple instances.