Elysia Bun

Elysia is the Bun-native web framework that prioritizes performance and end-to-end type safety above all else — it is among the fastest Node/Bun HTTP frameworks in benchmarks. The Eden treaty client generates a fully typed API client from the server definition, eliminating client-server type drift. Schema validation is automatic from TypeBox definitions. Strong fit for teams building high-throughput API backends on Bun. Confidence is docs-derived.

Bun runtime required. bun add elysia. const app = new Elysia().get("/", () => "Hello"). app.post("/predict", ({ body }) => runModel(body), { body: t.Object({prompt: t.String()}) }). Eden treaty: import {treaty} from "@elysiajs/eden"; const api = treaty<App>("http://localhost:3000"). Plugin system: app.use(cors(), swagger()). TypeBox for schema validation (t.Object, t.String, etc.).

No Elysia API key — open-source library. Auth: app.use(jwt({secret})) via @elysiajs/jwt plugin. Session, CORS, and auth plugins available. Open-source MIT license. Bun-specific runtime — not portable to Node.js or Cloudflare Workers (unlike Hono).

Type validation errors return 422 with validation details by default. Lifecycle hooks: onRequest, onError, afterHandle for cross-cutting concerns. Bun's stable runtime underpins Elysia's reliability. Active GitHub (elysiajs/elysia). Bun-only limitation means runtime failures track Bun's stability.

elysiajs.com/quick-start covers installation, routing, validation, Eden treaty, and plugins. Getting started: bun add elysia, first endpoint in under 5 minutes. Open-source MIT (GitHub: elysiajs/elysia). Community via Elysia Discord. Growing ecosystem of plugins for auth, swagger, websockets.