[BUG] Windows: "Connection closed" error when using LSP tools despite "Connected" status

[PsypraxDesign]

Environment

• OS: Windows 10/11
• Node.js: [deine Version - node --version]
• cclsp: latest (via npx)
• Claude Code: 2.1.1

Problem

cclsp shows "✓ Connected" in claude mcp list, but all LSP tool calls fail with:

Error: MCP error -32000: Connection closed

Steps to Reproduce

1. Install cclsp: npm install -g cclsp
2. Run setup: cclsp setup --user
3. Configure for Python (pyright) and TypeScript
4. Add to Claude: claude mcp add cclsp -s user cmd /c npx cclsp@latest
5. Verify connection: claude mcp list shows "✓ Connected"
6. In Claude Code, request: "get LSP diagnostics for [file].py"
7. Error: "Connection closed"

Additional Info

• npx pyright-langserver --stdio works correctly in terminal
• npx typescript-language-server --stdio works correctly in terminal
• The language servers start and respond, but cclsp seems to lose connection when Claude calls the tools

cclsp.json config

{
  "servers": [
    {
      "extensions": ["js", "ts", "jsx", "tsx"],
      "command": ["npx", "--", "typescript-language-server", "--stdio"],
      "rootDir": "."
    },
    {
      "extensions": ["py", "pyi"],
      "command": ["npx", "--", "pyright-langserver", "--stdio"],
      "rootDir": "."
    }
  ]
}

[andrew-harness]

In windows update your command from npx to npx.cmd

{
  "servers": [
    {
      "extensions": ["js", "ts", "jsx", "tsx"],
      "command": ["npx.cmd", "--", "typescript-language-server", "--stdio"],
      "rootDir": "."
    }
  ]
}

Or look at: #29 (comment)