MCP deleted protocol sessions and the handshake in July

MCP's maintainers deleted protocol-level sessions and the initialization handshake in the July 28 spec release, per an August 22 roadmap post. Servers no longer hold per-client state, which is what lets them scale horizontally. It's one of five structural changes in that release, authored by David Soria Parra and Den Delimarsky. If you wrote a server before July and it still compiles, you're running a removed protocol version, not a deprecated one.

That release also added server/discover, so clients negotiate capabilities before any other call. List results became cacheable through ttlMs and cacheScope. Tasks moved out of the core spec into its own extension. And server-initiated requests got replaced by Multi Round-Trip Requests, the mechanism elicitation now depends on.

Three groups are already forming for the next cycle. A Transports WG wants Streamable HTTP as the single binding. Right now every HTTP feature needs a second stdio-specific design, so SDKs maintain two pipelines. A Core Primitives WG is redesigning tools/call, since letting responses carry both content and structuredContent produced diverging implementations. It's also starting experimental progressive tool discovery, so clients stop loading a server's full catalog upfront. The Agent Identity WG carries the real stakes. MCP's authorization model still assumes a human with a browser, not a cloud workload or sub-agent acting without one. It's finalizing DPoP and Workload Identity Federation to close that gap.

Two days before the roadmap post, Google Cloud handed A2A to the Linux Foundation's Agentic AI Foundation, the same body that now runs MCP. AWS, Anthropic, Microsoft and OpenAI are listed as platinum signatories.

Check which spec revision your server declares before the next deploy. Microsoft's Agent Framework already shipped a breaking migration to the new Tasks extension in dotnet-1.19.0.