I built this because existing Ruby options for MCP either don't handle persistent connections properly (MCP servers bind sessions to TCP connections) or couple you to a specific LLM framework.

Manceps is a pure protocol client. Two transports (Streamable HTTP and stdio), built-in auth (bearer, API key, experimental OAuth 2.1 with PKCE), and full 2025-11-25 spec support including protocol negotiation, elicitation, structured output, and notifications.

It uses httpx under the hood for connection persistence. No LLM opinions -- just MCP.

Ruby >= 3.4, MIT licensed.