Absence is the compatibility contract

Fri, 31 Jul 2026 00:00:00 +0000

MCP announced revision 2026-07-28 three days ago. It deletes the initialize handshake and protocol-level sessions. Every request now carries its own protocol version, client identity and capabilities in _meta, and every result carries a resultType. It is the largest breaking change the protocol has had, and the changelog runs long.

I maintain mcp, a CLI that turns MCP servers into terminal commands and can run as a proxy in front of them. That puts me on both sides of the wire at once. To Claude, Cursor and whatever else connects, my proxy is a server. To the backends behind it, npx processes and HTTP endpoints, it is a client. Every one of those backends is on 2025-11-25 or older and will be for a year.

Backwards-Compatibility on Thiago Avelino

Absence is the compatibility contract