[BUG] MCP servers requiring OAuth authentication don't expose tools - no browser auth flow triggered

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?

Environment:

• Claude Code version: 2.0.37
• Node.js version: v25.1.0
• OS: Windows (win32)
• MCP Server: @azure-devops/mcp v2.2.2

Description:
MCP servers that require OAuth/browser-based authentication show as "Connected" in claude mcp list but
their tools are never exposed to Claude in the session. The OAuth authentication flow (browser popup) that
should trigger on first tool use never happens.

Actual Behavior:

• claude mcp list shows server as "✓ Connected"
• No MCP tools are exposed to Claude (no mcp__azure-devops__* tools available)
• No authentication flow is triggered
• Direct JSON-RPC testing shows the server works and returns tools:

echo '{"jsonrpc":"2.0","id":1,"method":"tools/list"}' | npx -y @azure-devops/mcp <me>
# Returns full list of 40+ tools successfully

Verification:
Testing the MCP server directly via JSON-RPC confirms it's functional but unauthenticated:
echo
'{"jsonrpc":"2.0","id":2,"method":"tools/call","params":{"name":"core_list_projects","arguments":{}}}' |
npx -y @azure-devops/mcp <me>
Returns:
{"result":{"content":[{"type":"text","text":"Error fetching projects: TF400813: The user
'9cb29f7d-c1a8-4ac5-a300-a4a9bcd9a4be' is not authorized to access this
resource."}],"isError":true},"jsonrpc":"2.0","id":2}

This proves:

1. The MCP server is responding correctly
2. It's returning tools via the MCP protocol
3. Authentication never happened (authorization error when calling tools)
4. Claude Code isn't loading the tools into the session

Configuration:
From ~/.claude.json:
"mcpServers": {
"azure-devops": {
"type": "stdio",
"command": "npx",
"args": ["-y", "@azure-devops/mcp", "<me>"],
"env": {}
}
}

Impact:
This makes it impossible to use any MCP servers that require OAuth authentication (Azure DevOps,
potentially Slack, Google services, etc.) with Claude Code.

Additional Context:

• Tested after multiple restarts of Claude Code
• Server shows as connected but tools never appear
• Azure DevOps MCP documentation states: "the first time an ADO tool is executed browser will open

prompting to login with your Microsoft account" - this never happens in Claude Code

What Should Happen?

Expected Behavior:

• MCP tools should be available in the session as mcp__azure-devops__* tools
• On first tool use, browser should open for Microsoft authentication (per Azure DevOps MCP docs)
• After authentication, tools should work normally

Error Messages/Logs

Steps to Reproduce

Steps to Reproduce:

1. Add the Azure DevOps MCP server:
2. Verify it shows as connected:

claude mcp list

1. Start a Claude Code session and try to use MCP tools:

User: "use the ado mcp and tell me what projects you have access to"
Claude: Error: No such tool available: mcp__azure-devops__core_list_projects

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.0.37

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

_No response_