feature: Client support for OAuth

[giridhar-murthy-glean]

Problem Statement

Recent implementations of MCP servers are supporting OAuth based authorization. mcp-go's client fails to connect to such servers, because it receives a HTTP 401 Unauthorized when connecting to such servers.

Proposed Solution

To support connections to such servers, mcp-go's client will need to be able to initiate a full OAuth flow upon receipt of a HTTP 401 Unauthorized response and ensure that users can be authorized correctly.

This issue is primarily a check to see if this work is on the roadmap/under development or if it needs to be worked on. I'm happy to take a stab at this, if there isn't already an effort underway.

MCP Spec Reference

OAuth flow is described here:
https://modelcontextprotocol.io/specification/2025-03-26/basic/authorization#2-authorization-flow

A reference implementation is available as part of the official MCP Typescript SDK

[rwjblue-glean]

I'm not aware of anyone working on this already, @ezynda3 / @pottekkat is this something that one of y'all have in flight (or are aware of)?

[pottekkat]

I'm not working on it either.

But it needs to be worked on. @giridhar-murthy-glean feel free to open a PR.

[ezynda3]

I have not started this, but I can if no one else picks it up.