Today, the Model Context Protocol (MCP) published its 2026-07-28 specification, the largest revision since its launch, making MCP a stateless protocol that scales on ordinary HTTP infrastructure. This version introduces a governed extensions system, strengthens authorization by aligning with enterprise practices for OAuth 2.0 and OpenID Connect, and establishes lifecycle guarantees to limit future breakage. Users can start using the protocol on AgentCore Gateway, a capability of Amazon Bedrock AgentCore, by calling UpdateGateway with the list of versions. Existing clients keep working exactly as before, with no per-target step. The release contains backward-incompatible changes, but upgrading is opt-in; nothing changes until both you and your clients act. AgentCore Gateway advertises protocol versions through a single configuration field, and clients select a version on every request. Adding 2026-07-28 to a gateway that also advertises 2025-11-25 does not change anything for clients requesting the older version. In prior versions, every Streamable HTTP interaction began with an initialize/initialized handshake, and the server issued an Mcp-Session-Id header that every subsequent request was required to carry, pinning the client to that server. By removing that session requirement, the new protocol addresses scaling challenges with enterprise deployments.