The model context protocol spec of july 28 went stateless, dropping protocol level sessions and…
the model context protocol spec of july 28 went stateless, dropping protocol level sessions and replacing the sse endpoint with a single message endpoint. the standard that wired agents to tools just removed the state from the wire.
the session memory did not disappear, it moved into the application where nobody can see it.
Context
The MCP changelog for the 2026-07-28 revision, and the MCP blog post of 28 July 2026, say the revision removes protocol-level sessions and the Mcp-Session-Id header from Streamable HTTP, with servers that need cross-call state minting explicit handles passed as ordinary tool arguments. It removes the initialize handshake, so each request carries the protocol version and client capabilities. It removes SSE stream resumability, replaces the HTTP GET endpoint and resources/subscribe with subscriptions/listen, a long-lived POST-response stream, and officially deprecates the legacy HTTP+SSE transport with a year-long offramp.
Dropping protocol-level sessions matches the changelog. A single message endpoint is not a phrase in the text read: the GET endpoint is replaced by a subscriptions/listen POST stream and the legacy HTTP+SSE transport is deprecated, so the note's wording is a partial match. The blog says the handle is passed back by the model and that the model can see it, which cuts against nobody can see it, though the application still holds the underlying state. State moving where nobody can see it is the author's opinion.
Watch next
- SDK migration notes for session users and the deprecation windows.
Sources
- MCP specification changelog, 2026-07-28modelcontextprotocol.io
- MCP blog, 28 Jul 2026blog.modelcontextprotocol.io
Provenance
The note above is reproduced unedited from the original post, first published on Threads on 19 September 2026 at 02:17 IST. Sources are the papers and datasets the note draws on.
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