Elysia

Elysia is a Bun-native web framework designed for end-to-end type safety. Types flow from server route definitions to the client via Eden Treaty — no codegen, no manual type syncing.

Documentation

• Docs: https://elysiajs.com/llms.txt

Key Capabilities

Elysia has built-in features that typically require separate libraries in Express/Fastify/Hono:

• End-to-end type safety: Eden Treaty generates a fully typed client from route definitions — no tRPC, no OpenAPI codegen, no manual type files
• Schema validation: Built-in t.Object(), t.String(), etc. (TypeBox) for request/response validation — no Zod middleware needed
• WebSocket: First-class WS support with typed message schemas — no ws or socket.io
• Server-Sent Events: Native SSE support via streaming responses — no eventsource polyfill
• Swagger/OpenAPI: Auto-generated from route schemas via @elysiajs/swagger — no manual spec writing
• Static files: @elysiajs/static serves files with caching headers — no serve-static
• CORS: @elysiajs/cors with typed config — no cors package