[BUG] Local stdio MCP servers not loaded on native Windows

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?

Description

Local stdio MCP servers configured in ~/.mcp.json, ~/.claude/settings.json, and project-level .mcp.json are
completely ignored by Claude Code on native Windows. The /mcp command does not list them at all — they are absent, not errored. Cloud-hosted claude.ai MCP servers (Miro, Egnyte, Figma, Asana, Microsoft 365) load and work
correctly.

The same configuration works correctly when running Claude Code under WSL on the same machine.

Environment

• OS: Windows 11 Enterprise 10.0.26100 (native, not WSL)
• Claude Code model: claude-opus-4-6
• MCP server tested: @octopusdeploy/mcp-server, @azure-devops/mcp

Actual Behavior

• /mcp only shows cloud-hosted claude.ai servers
• Local stdio servers are completely absent — not errored, just missing
• No error messages displayed

Verification

• The MCP server starts fine manually: cmd /c npx -y @octopusdeploy/mcp-server --version → 1.1.0
• Sending initialize JSON-RPC over stdio returns valid response with tool capabilities
• Same config works in WSL on the same computer

Configurations Attempted

• "command": "npx" and "command": "cmd" with ["/c", "npx", ...] wrapper
• All three config file locations
• Multiple Claude Code restarts
• No managed policies found at C:\Program Files\ClaudeCode\ blocking local servers

_This summary was prepared by claude after trying for a few hours to make this work_

What Should Happen?

Expected Behavior

Local stdio MCP servers should appear in the /mcp list, connect, and register their tools.

Error Messages/Logs

There are no errors

Steps to Reproduce

Steps to Reproduce

1. Configure a local stdio MCP server in any supported config location (~/.mcp.json, ~/.claude/settings.json, or

project .mcp.json)

1. Start Claude Code on native Windows
2. Run /mcp

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.72

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

_No response_