The next Model Context Protocol specification, 2026-07-28, is the largest revision since the protocol launched. The release candidate locked on May 21, 2026, and the final spec publishes on July 28. It contains breaking changes to transport, authorization, and how tool schemas are handled.
A server that is correct against 2025-11-25 today is not broken. Nothing here is a present-tense vulnerability. But several of these changes are security properties, not just compatibility ones — request routing integrity, cross-user cache scope, and schema-driven fetch behavior all move under this revision. This checklist walks the changes a server operator needs to handle before July 28, and calls out the security implication wherever there is one.
Everything below describes the release candidate. Treat specifics as subject to change until the July 28 final, and validate against the official spec before shipping.
Transport: the stateless core
This is the headline change. MCP becomes stateless at the protocol layer, and most of the migration work lives here.
