Is your feature request related to a problem? Please describe.
When we connect to a MCP server, we may get a 401 with a www-authenticate header. For example:

$ curl https://mcp.linear.app/mcp -I -X POST
HTTP/2 401
date: Wed, 30 Jul 2025 14:21:02 GMT
content-type: application/json
content-length: 79
www-authenticate: Bearer realm="OAuth", error="invalid_token", error_description="Missing or invalid access token"
server: cloudflare
cf-ray: 96758008190efa52-SJC
alt-svc: h3=":443"; ma=86400

However, its not possible to act on this from an MCP client using the SDK.

We will get a rmcp::transport::worker worker quit with fatal: Client error: received status code 401 Unauthorized, when send initialize request error, but the original error is lost (at

The same issue occurs at another part of the code in serve_client_with_ct where we lose context and only get connection closed: initialize response

There may additional be problems that the initialize is in a spawn