Field notes
spec and migration
What each MCP specification revision changed, what it broke, and how to migrate. The 2026-07-28 release is the current wedge: sessions and the handshake gone, three primitives deprecated on a twelve-month clock. These posts track the revisions and the work each one forces on a running server, in the order that work actually happens.
Deprecated in MCP: Roots, Sampling, Logging and the HTTP+SSE transport
Deprecated is not removed. The 2026-07-28 policy guarantees a twelve-month window. What that means for planning, and why "it still works" misleads.
Is your MCP server still on an old spec revision? How to check in 60 seconds
Most teams do not know which revision their MCP server negotiates. Three ways to find out: curl, the Inspector, and the scanner.
What the 2026-07-28 MCP release broke, and how to migrate
The 2026-07-28 revision removed sessions and the handshake and deprecated three primitives. The migration checklist, in the order the work happens.