The MCP 2026-07-28 release candidate is the largest major specification revision since MCP launched. It is also a compatibility test for everyone building clients, servers, SDKs, gateways, and developer tools around the protocol.
The release candidate was locked on May 21, 2026. The final specification is scheduled for July 28, 2026. This window is the time to test real implementations and find migration pain points.
1. Check your transport assumptions
The biggest change is that MCP is now stateless at the protocol layer.
If your current Streamable HTTP implementation depends on initialize, initialized, or Mcp-Session-Id, you have migration work. In the release candidate, each request carries the protocol version, client info, and capabilities in _meta. The new server/discover method covers cases where a client needs server capabilities up front.
