In July 2026, the MCP spec got a new protocol revision: 2026-07-28 . If you migrated an MCP server to the new era recently — or you're about to — here's the uncomfortable part: nothing in your own toolchain will tell you whether it took. We noticed the pattern in the official SDK's issue tracker ( typescript-sdk#2977 ), built a probe, and pointed it at fixtures and real servers to see how widespread it is. The results surprised us more than the bug report did. The failure shape...