MCP 2026-07-28 Specification: Transport Shifts to Stateless

Model Context Protocol (MCP) has announced its new version, the 2026-07-28 specification. The core of this update is the shift from the existing bidirectional Stateful approach to a request/response-based Stateless protocol.

The key changes are as follows:

• Introduction of Stateless Core: Session IDs and the handshake process have been abolished. Now all requests are delivered independently and can be routed round-robin to any server instance behind a load balancer, significantly improving scalability.
• Multi Round-Trip Requests (MRTR): When a server needs to request confirmation or additional parameters from a user, instead of keeping the connection open, it adopts an approach where the request is returned and the client retries with the answer included.
• Header-based Routing: Using the Mcp-Method and Mcp-Name HTTP headers, gateways can perform routing and authorization directly at the header level.
• Enhanced Caching and Security: Cache hints are included in list responses to support tool catalog caching on the client side, and security has been strengthened through RFC 9207 compliance and the introduction of Client Metadata Documents (CIMD).

The TypeScript, Python, Go, and C# SDKs have all been updated, and a detailed migration guide is provided for existing developers.