Official MCP reference servers hit v2.0.0 on the 2026-07-28 spec, and now need Node 24
The filesystem, memory, sequential-thinking, and everything servers move to TypeScript SDK v2 and the 2026-07-28 spec while still answering older clients, and the Python fetch, git, and time servers (2026.10.19) now return a JSON-RPC -32602 error for unknown tools instead of an isError result. The TypeScript servers require Node 24 or later, and v1.0.0 (Oct 11) was the final legacy-era release, so pin it if you can't upgrade yet.