[BUG]

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Title: GitHub MCP server fails with "Incompatible auth server: does not support dynamic client registration"

Description:
The GitHub MCP server (@modelcontextprotocol/server-github) was working ~48 hours ago and now fails to load with this error in /mcp:

SDK auth failed: Incompatible auth server: does not support dynamic client registration
This happens with both @latest and pinned version 0.6.2, and with both npx and a globally installed binary. The server starts correctly when run manually in terminal with the PAT env var set. The issue appears to be Claude Code's MCP client trying to do an OAuth handshake that GitHub's auth server doesn't support.

Environment:

Claude Code VS Code extension
macOS
Node v24.14.0
Steps to reproduce:

Add @modelcontextprotocol/server-github to ~/.claude/mcp.json with GITHUB_PERSONAL_ACCESS_TOKEN set
Restart Claude Code
Open /mcp — server shows the auth error
Expected: Server loads and GitHub tools are available

Actual: Auth failure, server doesn't load

What Should Happen?

Claude should be able to connect to my MCP easily, it was connected for months before it deleted it this morning

Error Messages/Logs

Steps to Reproduce

{
"mcpServers": {
"github": {
"command": "/Users/lucascecere/.npm-global/bin/mcp-server-github",
"args": [],
"env": {
"GITHUB_PERSONAL_ACCESS_TOKEN": "your-token-here"
}
}
}
}

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

2 days ago I had my MCP working great

Claude Code Version

VS Code extension, version unknown

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_