On July 28, 2026, the Model Context Protocol published the most significant revision since its launch. MCP is now a stateless protocol. No more session handshakes. No more sticky load balancing. No more shared session stores for horizontal scaling. Every request is self-contained.
I wanted to see if the reality matched the promise, so I spent a day testing the new spec against a live AWS AgentCore Gateway with real Lambda tools behind it. This post is what I found.
A note on perspective: I am writing this as both an AAIF Ambassador and an AWS Community Builder. MCP is an open standard hosted by the Agentic AI Foundation (AAIF) under the Linux Foundation. AgentCore Gateway is AWS's managed implementation of that standard. Testing a managed cloud implementation against the open spec it claims to support felt like exactly the right way to evaluate whether MCP 7-28 delivers what it promises.
Table of Contents
The Seven Breaking Changes
