MCP Just Went Stateless: What the 2026 Spec Actually Changes for Your Servers
For its first two years, MCP was a protocol that assumed it was talking to a process on your laptop. That assumption was baked in deep, and nowhere deeper than in the session.
Every connection started with a handshake. The client sent initialize, the server replied with its capabilities, the client sent initialized, and from that point on the two sides shared a session identified by an MCP-Session-Id header. It was a reasonable design for a local subprocess. It was a nightmare for anyone trying to run MCP as a real service.
The 2026-07-28 spec - now the current official version, released on July 28, 2026 and superseding 2025-11-25 - throws that model out. It is the biggest structural change MCP has made since it launched, and if you run a server, it will break things. Let me walk through what happened and why.
Why the session had to die
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