Calling Intialize with Procol version 2026-07-28 returns success

[dawid-nowak]

Describe the bug
When calling MCP Initialize with protocol version "2026-07-28", the MCP SDK returns a successful response, but no MCP-Session-id.

To Reproduce
Send following Initialize with curl or other tool:

{"method":"initialize","params":{"protocolVersion":"2026-07-28","capabilities":{},"clientInfo":{"name":"inspector-client","version":"0.21.1"}},"jsonrpc":"2.0","id":0}

curl -H "Content-type:application/json" -H "Accept: application/json,text/event-stream" -d '{"method":"initialize","params":{"protocolVersion":"2026-07-28","capabilities":{},"clientInfo":{"name":"inspector-client","version":"0.21.1"}},"jsonrpc":"2.0","id":0}' 127.0.0.1:6666/mcp

Expected behavior
Initialize is not supported in the latest version of the protocol, so an error 404 should is expected.

Additional context
Running against main and the counter example.