Current Limitations

The adapter intentionally keeps its dependency surface and transport behavior small.

Not implemented

• stateful MCP sessions
• resumable SSE streams
• server-initiated requests
• inferred multipart or file uploads
• automatic model-controlled credential or filesystem access

Transport scope

GET SSE provides a minimal connected event and closes. DELETE can acknowledge a session deletion request, but no server-side session state is retained.

Route discovery

Route inspection uses Elysia's current public app.routes and router history shapes. That compatibility boundary is isolated in src/route-inspector.ts so future Elysia changes do not spread through the adapter.

Framework dependency

The package does not depend on the official MCP TypeScript SDK. It implements the required JSON-RPC surface directly to keep transport abstractions thin and avoid translating TypeBox schemas through Zod.

Output constraints

Text and structured output default to 256 KiB limits. Binary output fails unless explicitly set to base64. These limits are safeguards, not streaming controls.