MCP 2.0 drops the handshake and sessions from the protocol

The MCP working group shipped release candidate 2026-07-28, billed as the largest revision of the protocol since launch. The connection model is gone: no initialize, no Mcp-Session-Id, no held-open stream — version, capabilities and clientInfo now travel in _meta on every request, with state moved into explicit handles.

• initialize, notifications/initialized and Mcp-Session-Id removed
• Version and capabilities now sent in _meta on each request
• Mcp-Method and Mcp-Name headers enable routing without body parsing
• Server-to-client calls use InputRequiredResult without an open stream