feature: Handle protocol negotiation downgrade for better compatibility

[StarpTech]

Description

Hi, after upgrading to the latest version (0.30.0), we experienced incompatibilities with mcp-remote, a popular tool used to enable SSE in environments where SSE is not yet supported. The same issues have been reproduced in Postman. None of these clients support custom protocol negotiation or have considered SSE as a subset of 2025-03-26, making it impossible to upgrade mcp-go while still supporting the 2024-11-05 protocol version.

It would be great if we could manually specifiy a protocol version or, even better, have the library calculate the version based on the features used. For example, if you opt in to streaming, the version would be 2025-03-26; if not, it remains 2024-11-05.

This would improve ecosystem compatibility until the latest MCP spec has settled.

Logs or Error Messages

Here is a picture when trying to connect against a server that uses mcp-go in version 0.30.0

Environment

• Go version (see go.mod): 1.24.1
• mcp-go version (see go.mod): 0.30.0
• MacOS

[migmartri]

Agreed, same problem here but using claude desktop through mcp-remote

[ezynda3]

I'm thinking we could add logic in the With options that will set the version based on which part of the spec it belongs to. Thoughts?

[StarpTech]

That sounds good to me. Should be obvious, but we need to ensure that once a higher protocol version is opted into, it cannot be downgraded.

[ezynda3]

For now we've added simple version negotiation. We can add a more complex scheme later. Please try https://github.com/mark3labs/mcp-go/releases/tag/v0.30.1 and see if that helps.

[migmartri]

Thank you! I can confirm that it works!