The stateless MCP spec is now the current protocol — every request carries its own version

The Model Context Protocol’s 2026-07-28 revision is now marked Current on the specification site, landing the stateless move that shipped as a release candidate in May. Every request declares its protocol version in its own _meta field (and, on Streamable HTTP, in an MCP-Protocol-Version header), and the server accepts or rejects each request independently instead of negotiating once at handshake; a new mandatory server/discover call returns a server’s supported versions, capabilities and identity in a single round trip, and an UnsupportedProtocolVersionError lists what a server will accept. Clients and servers built to the handshake-based 2025-11-25 and earlier revisions are covered by a documented backward-compatibility path, and deprecated features must now stay in the spec at least twelve months (ninety days under an expedited exception) before removal.

What it means Anything hosting or consuming a remote tool server can version per request and drop sticky sessions — but a handshake-era client needs the compatibility path, not a version bump.