[BUG] MCP servers using `npx` fail silently in VS Code extension (no TTY) — workaround included

Description

MCP servers configured with npx commands work in the CLI but fail silently in the VS Code extension. This is because the VS Code panel/sidebar has no TTY (process.stdin.isTTY is false), and npx (especially on Windows, where it's a .cmd wrapper) fails without one.

This is NOT a config file mismatch — both the CLI and VS Code extension read from the same ~/.claude.json. The servers are seen but fail to spawn.

Related issues

This is the same symptom reported in:

• #24770 (macOS)
• #19054 (macOS)
• #3321 (macOS)

This report adds the root cause analysis and a working solution.

Root cause

1. The VS Code extension runs Claude Code in panel/sidebar mode, which has no TTY
2. npx (and on Windows, npx.cmd) requires a TTY to work reliably — it fails silently when spawned without one
3. The servers appear in config but never connect, so no MCP tools are available to the agent

Steps to reproduce

1. Configure an MCP server in ~/.claude.json using npx:

``json
"mcpServers": {
"github": {
"type": "stdio",
"command": "npx",
"args": ["-y", "@modelcontextprotocol/server-github"],
"env": { "GITHUB_PERSONAL_ACCESS_TOKEN": "..." }
}
}
``

1. Run claude mcp list in terminal → github: ✓ Connected
2. Open Claude Code in VS Code → server tools are not available

Workaround (confirmed working)

Replace npx with node + direct paths to the installed package entry points.

Option A: Global install + wrapper scripts

1. Install packages globally: npm install -g @modelcontextprotocol/server-github
2. Create a wrapper .mjs file (e.g. ~/.claude/mcp-wrappers/github.mjs):

``js
import "file:///C:/Users/YourUser/AppData/Roaming/npm/node_modules/@modelcontextprotocol/server-github/dist/index.js";
``

1. Configure in ~/.claude.json:

``json
"github": {
"type": "stdio",
"command": "node",
"args": ["C:/Users/YourUser/.claude/mcp-wrappers/github.mjs"],
"env": { "GITHUB_PERSONAL_ACCESS_TOKEN": "..." }
}
``

Option B: Direct node path to globally installed package

"github": {
  "type": "stdio",
  "command": "node",
  "args": [
    "C:/Users/YourUser/AppData/Roaming/npm/node_modules/@modelcontextprotocol/server-github/dist/index.js"
  ],
  "env": { "GITHUB_PERSONAL_ACCESS_TOKEN": "..." }
}

For mcp-remote (e.g. Linear):

"linear": {
  "type": "stdio",
  "command": "node",
  "args": [
    "C:/Users/YourUser/AppData/Roaming/npm/node_modules/mcp-remote/dist/proxy.js",
    "https://mcp.linear.app/mcp"
  ],
  "env": {}
}

Result after workaround

All 5 MCP servers (GitHub, Puppeteer, Chrome DevTools, Linear, Maestro) connect and provide tools in VS Code extension.

Expected behavior

npx-based MCP server commands should work in the VS Code extension, or Claude Code should automatically resolve npx to the underlying node command when running without a TTY.

Environment

• Claude Code CLI: v2.1.x (latest)
• VS Code Extension: latest
• OS: Windows 10 (likely affects all platforms based on #24770 and #19054 on macOS)
• Node: v24.13.0

🤖 Generated with Claude Code