From https://modelcontextprotocol.io/specification/2025-03-26/basic/lifecycle#version-negotiation:

In the initialize request, the client MUST send a protocol version it supports. This SHOULD be the latest version supported by the client.

If the server supports the requested protocol version, it MUST respond with the same version. Otherwise, the server MUST respond with another protocol version it supports. This SHOULD be the latest version supported by the server.

Until now, there's only been the one protocol version, so this hasn't been a concern. But trying this out now with clients that don't yet support version 2025-03-26, I'm bumping into this issue.