MCP's 2026-07-28 release candidate drops sessions so any server instance can answer any request

Under 2025-11-25, a client cannot call a tool until it has opened a session with an initialize request. The server answers with an Mcp-Session-Id that every later request must carry. That pins the client to the instance that issued it ^[9]. In the post's own example, a first tool call takes two requests under that version and one under 2026-07-28, which any instance can handle ^[12][10]. The post lists what a remote server previously needed because of the pin: sticky sessions, a shared session store and deep packet inspection at the gateway ^[13].

The pitch is a plain load balancer. The work is whatever the server kept per session. The post says state stays possible: a server that needs state across calls can have a tool issue a handle, a basket_id or browser_id for instance, which the model then hands back like any other argument ^[7]. Its authors wrote that they have found the pattern "to be more than just a workable substitute for session state" ^[8]. The post does not include measurements behind that. Whether a given model threads a handle through a long task is something a team can learn from its own transcripts before cutover.

In our view the sensible order is staging first and production after the final text. The post calls this the largest revision of the protocol since launch ^[2], and the final specification ships July 28, 2026 ^[1]. Waiting delays the gateway savings. Moving early means building against a candidate.

To stage the work, sort each server by two facts taken from its code, not from a deck: whether it keeps per-session state, and whether it ever sends a request to the client when no client request is in flight.

- Neither: the handshake and per-request `_meta` changes are the migration ^[4][5]. - Session state only: redesign those tools to mint and accept handles ^[7]. - Outbound requests only: tie each server request to a client call that is still being processed ^[6]. - Both: the longest list of changes, so these servers set the schedule.