The largest MCP revision changes how you run it, not what it does
How we build
The 2026-07-28 specification release candidate (Model Context Protocol)
Lead maintainers David Soria Parra and Den Delimarsky call it “the largest revision of the protocol since launch”. The protocol becomes stateless. Two proposals remove the initialize handshake (SEP-2575) and the Mcp-Session-Id header (SEP-2567), so that any request can now land on any instance. A server that “previously needed sticky sessions, a shared session store, and deep packet inspection at the gateway can now run behind a plain round-robin load balancer”. State does not vanish. It becomes explicit, in that a tool mints a handle such as a basket_id and the model passes it back as an ordinary argument, which “makes the state visible to the model rather than hidden away”. There are new required headers, so that a gateway can route and rate-limit on the operation without reading the body, and list results now carry a cache lifetime modelled on the one HTTP already has. Authorisation is hardened to match the way that OAuth 2.0 and OpenID Connect are actually deployed, which reduces a class of mix-up attack that the single-client, many-server pattern had made likelier. Tasks becomes an extension and drops tasks/list, which “can’t be scoped safely without sessions”. MCP Apps lets a server render an interface in a sandboxed frame, where every action “goes through the same audit and consent path as a direct tool call”. Roots, Sampling and Logging are formally deprecated, under a new lifecycle policy that keeps them working for at least a year. The final version shipped on 28 July, with breaking changes.
Architecture: almost none of this makes an agent more capable. The model did not move; the plumbing did. A protocol that needed specialist deployment now runs on commodity infrastructure, gains a deprecation contract a platform team can plan against, and routes every agent action through one audit path. The cost is stated plainly: breaking changes and a migration with numbered proposals, from the Tasks lifecycle to a changed error code. That migration is not a model upgrade anyone downloads. It is planned engineering and governance work, owned by whoever runs the servers, and it is the kind of effort that decides whether a firm gets value from its agents or merely installs them.
Find out who in your organisation owns the MCP servers your agents call, and whether the 28 July migration is on anyone’s plan. If no name comes back, the answer is that your agent estate has no maintainer.