[BUG] ArchicadTapir MCP server consistently fails to connect on startup with "Could not attach to MCP server ArchicadTapir"

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?

Version: Claude 1.11187.4 (584005), Windows 11, MSIX package

Issue: ArchicadTapir MCP server consistently fails to connect on startup with
"Could not attach to MCP server ArchicadTapir" even though the server initializes
successfully in ~10 seconds.

Root cause: Claude Desktop spawns 2-3 instances of the MCP server simultaneously
at startup. They compete, causing all instances to miss the connection window.
The server logs show successful initialization but Claude has already timed out.

Reproduction:

1. Configure any MCP server that takes >5 seconds to initialize
2. Launch Claude Desktop
3. MCP server shows "Could not attach" error every time

Workaround: File → Exit and relaunch Claude Desktop (sometimes works on 2nd try)

Request: Make spawn timeout configurable, and fix the multiple simultaneous
spawn issue on Windows.

Related issue: #64671

What Should Happen?

"Claude Desktop should connect to the MCP server reliably on every startup. Only one instance of the MCP server should be spawned at a time, and the spawn timeout should be configurable so servers that take longer than 5 seconds to initialize can still connect successfully."

Error Messages/Logs

2026-06-10 16:11:45,281 - INFO - root - MCP Server Lifespan: Initializing...
2026-06-10 16:11:45,404 - INFO - multiconn_archicad.actions.refresh - Refreshing - Open ports: 1, Closed ports: 20
2026-06-10T20:12:04.213Z [ArchicadTapir] [info] Client transport closed
2026-06-10T20:13:05.572Z [ArchicadTapir] [info] Message from client: {"jsonrpc":"2.0","method":"notifications/cancelled","params":{"requestId":0,"reason":"McpError: MCP error -32001: Request timed out"}}

Steps to Reproduce

1. Install Claude Desktop (Windows, MSIX/Microsoft Store version)

1. Add the following to claude_desktop_config.json

(located at %LOCALAPPDATA%\Packages\Claude_pzs8sxrjxfjjc\LocalCache\Roaming\Claude\):

{
"mcpServers": {
"ArchicadTapir": {
"command": "C:\\Users\\<username>\\AppData\\Roaming\\uv\\tools\\tapir-archicad-mcp\\Scripts\\archicad-server.exe"
}
}
}

1. Install the tapir-archicad-mcp package:

uv tool install --python 3.12 tapir-archicad-mcp

1. Launch Claude Desktop

1. Observe "Could not attach to MCP server ArchicadTapir" error

Expected: Single MCP server instance spawns and connects successfully
Actual: 2-3 instances spawn simultaneously, all compete and timeout

Notes:

• Server takes ~10 seconds to initialize
• MCP server logs confirm successful initialization AFTER Claude times out
• Timeout appears hardcoded at ~60 seconds but multiple simultaneous spawns

cause all instances to miss the connection window

• Issue occurs every startup and whenever any connector is toggled
• Server shows "running" in Settings → Developer even after the error

Claude Model

None

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

n/a

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

_No response_