Elysia.js: Type-Safe APIs Without the Mess

Elysia.js is a TypeScript-first API framework for Bun that addresses Next.js API route organization issues by allowing all routes to be defined in a single file using a chaining syntax. It provides end-to-end type safety through the Eden companion library, eliminating the need for code generation while maintaining standard HTTP endpoints. The framework uses TypeBox for inline schema validation that doubles as TypeScript type generation, and follows the WinterTC standard for cross-runtime deployment compatibility.