MCP stdio servers flash visible CMD windows on Windows (windowsHide not set) #24708

Description

On Windows, every stdio-based MCP server spawns a visible CMD window that briefly flashes on screen during Claude Code startup. This happens for each MCP server configured with type: "stdio".

With 4-5 stdio MCP servers configured, users see multiple CMD windows flash on every claude launch, which is disruptive.

Root Cause

In the MCP StdioClientTransport, the windowsHide option is set conditionally:

windowsHide: process.platform === "win32" && LO9()

Where LO9() checks "type" in process, which always returns false in standard Node.js (it only returns true in Electron where process.type exists).

This means windowsHide is effectively always false on Windows, causing child processes (MCP servers) to spawn with visible console windows.

Expected Behavior

MCP server processes should be hidden on Windows. The fix should be:

windowsHide: process.platform === "win32"

Or simply:

windowsHide: true

(The option is ignored on non-Windows platforms anyway.)

Steps to Reproduce

1. On Windows, configure 2+ stdio MCP servers in ~/.claude.json
2. Run claude from terminal
3. Observe: multiple CMD windows flash briefly during startup

Environment

• OS: Windows 11
• Claude Code: v2.1.37
• Node.js: v24.13.0
• MCP servers: 4 stdio servers (context7, firebase, vercel, github)

Impact

• Every claude startup shows 4+ flashing CMD windows
• Window titles show paths like .bin, .bun which confuse users
• Purely cosmetic but significantly degrades Windows UX