CheckMCP
Last audit 2026-09-03

3 of 37 MCP servers have moved to 2026-07-28.

The 2026-07-28 revision is the largest change to the Model Context Protocol since it launched: it removes the initialize handshake and protocol-level sessions, and requires every server to implement server/discover. We probed every server in the CheckMCP directory to find out who had actually followed.

3
negotiate 2026-07-28
and still answer initialize
34
handshake-only
unchanged from 2025-11-25
0
modern-only
nothing has dropped the old path yet

The 3 that moved

They are dual-era: they answer server/discover and still accept initialize. That is what the specification recommends during the transition, and it is why nothing has broken yet.

  • Context7https://mcp.context7.com/mcp
  • huggingface.co/mcphttps://huggingface.co/mcp
  • docs-ai-searchhttps://docs.mcp.cloudflare.com/sse

Why this matters before it hurts

The specification's own compatibility matrix is blunt: a client built for the old handshake, talking to a server that has dropped it, fails with 400 Bad Request — the request is missing headers the new revision requires. Today that costs nothing, because every migrated server above still answers the old way. The day the first modern-only server ships, every legacy client stops working against it, with no fall-forward path.

We know because it happened to us. This site's own audit probe was a legacy client, and a failed handshake scores zero here. It would have started grading the most standards-conformant servers on the market as failures. The probe now tries server/discover first and falls back only on an error that is not a recognised modern one.

Method, and what this number is not

  • — Figures are read from each server's last CheckMCP audit — most recent 2026-09-03. The audit sends a server/discover call carrying the required MCP-Protocol-Version, Mcp-Method and Mcp-Name headers, then an initialize call, to classify each one as dual-era, modern or legacy.
  • — An UnsupportedProtocolVersionError (−32022) counts as modern: it is a server refusing our version, not a server that has never heard of the revision.
  • — 37 servers is the CheckMCP live-probe corpus. It is not the whole ecosystem, and this page does not extrapolate a percentage from it.
  • — The count follows the audits: when a server is re-probed and negotiates the new revision, it moves here on its own. No figure on this page is entered by hand.

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