[BUG] Unable to connect to stdio MCP proxies from Windows Terminal

Environment

• Platform (select one):
• [X] Anthropic API
• [ ] AWS Bedrock
• [ ] Google Vertex AI
• [ ] Other: <!-- specify -->
• Claude CLI version: 1.0.53
• Operating System: Windows 11
• Terminal: Terminal App

Bug Description

Unable to launch stdio type MCP proxies from Claude in a Windows Terminal using either Powershell or CMD. Logs are not very helpful, only telling you that it failed to connect. However, if you launch from WSL the mcp proxy works.

Steps to Reproduce

1. Add a stdio MCP proxy (I've tried https://github.com/Tiberriver256/mcp-server-azure-devops and https://github.com/microsoft/azure-devops-mcp with the same result)
2. Attempt to run claude from a Powershell or CMD terminal
3. Observe the failure to connect

Expected Behavior

1. Claude should connect to the MCP and leverage the MCP

Actual Behavior

1. Claude fails to connect immediately when executed from Powershell/CMD
2. Claude succeeds in connecting when launched from WSL

Additional Context

[DEBUG] MCP server "Jira": Starting connection attempt
[DEBUG] MCP server "azure-devops": Starting connection attempt
[DEBUG] AutoUpdaterWrapper: Installation type: unknown, using native: false
[DEBUG] MCP server "azure-devops": Connection attempt completed in 18ms - status: failed
[DEBUG] MCP server "Jira": Returning tokens

[
  {
    "debug": "Starting connection attempt",
    "timestamp": "2025-07-17T21:34:27.418Z",
    "sessionId": "c240a986-18ce-47c1-a3b7-8edd22eb07e1",
    "cwd": "C:\\Users\\Josh\\repos\\smartmoving-cloud\\src"
  },
  {
    "debug": "Connection failed: McpError: MCP error -32000: Connection closed",
    "timestamp": "2025-07-17T21:34:27.656Z",
    "sessionId": "c240a986-18ce-47c1-a3b7-8edd22eb07e1",
    "cwd": "C:\\Users\\Josh\\repos\\smartmoving-cloud\\src"
  },
  {
    "debug": "Error message: MCP error -32000: Connection closed",
    "timestamp": "2025-07-17T21:34:27.658Z",
    "sessionId": "c240a986-18ce-47c1-a3b7-8edd22eb07e1",
    "cwd": "C:\\Users\\Josh\\repos\\smartmoving-cloud\\src"
  },
  {
    "debug": "Error stack: McpError: MCP error -32000: Connection closed\n    at h0A._onclose (file:///C:/ProgramData/nvm/v24.4.1/node_modules/@anthropic-ai/claude-code/cli.js:1201:13174)\n    at _transport.onclose (file:///C:/ProgramData/nvm/v24.4.1/node_modules/@anthropic-ai/claude-code/cli.js:1201:12492)\n    at ChildProcess.<anonymous> (file:///C:/ProgramData/nvm/v24.4.1/node_modules/@anthropic-ai/claude-code/cli.js:1203:1460)\n    at ChildProcess.emit (node:events:507:28)\n    at ChildProcess.emit (node:domain:489:12)\n    at Iw6.A.emit (file:///C:/ProgramData/nvm/v24.4.1/node_modules/@anthropic-ai/claude-code/cli.js:369:144179)\n    at maybeClose (node:internal/child_process:1101:16)\n    at Socket.<anonymous> (node:internal/child_process:457:11)\n    at Socket.emit (node:events:507:28)\n    at Socket.emit (node:domain:489:12)",
    "timestamp": "2025-07-17T21:34:27.659Z",
    "sessionId": "c240a986-18ce-47c1-a3b7-8edd22eb07e1",
    "cwd": "C:\\Users\\Josh\\repos\\smartmoving-cloud\\src"
  },
  {
    "error": "Connection failed: MCP error -32000: Connection closed",
    "timestamp": "2025-07-17T21:34:27.661Z",
    "sessionId": "c240a986-18ce-47c1-a3b7-8edd22eb07e1",
    "cwd": "C:\\Users\\Josh\\repos\\smartmoving-cloud\\src"
  },
  {
    "debug": "Connection attempt completed in 242ms - status: failed",
    "timestamp": "2025-07-17T21:34:27.662Z",
    "sessionId": "c240a986-18ce-47c1-a3b7-8edd22eb07e1",
    "cwd": "C:\\Users\\Josh\\repos\\smartmoving-cloud\\src"
  },
  {
    "debug": "Starting connection attempt",
    "timestamp": "2025-07-17T21:34:27.740Z",
    "sessionId": "c240a986-18ce-47c1-a3b7-8edd22eb07e1",
    "cwd": "C:\\Users\\Josh\\repos\\smartmoving-cloud\\src"
  },
  {
    "debug": "Connection attempt completed in 18ms - status: failed",
    "timestamp": "2025-07-17T21:34:27.759Z",
    "sessionId": "c240a986-18ce-47c1-a3b7-8edd22eb07e1",
    "cwd": "C:\\Users\\Josh\\repos\\smartmoving-cloud\\src"
  }
]