[BUG] VSCode extension spawns duplicate MCP servers - config cache loader starts unnecessary MCP connections

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?

When opening Claude Code in VSCode, the extension spawns two Claude processes:
One for "Loading config cache" (resume: undefined)
One for the actual conversation session (resume: <session-id>)
Both processes independently initialize all configured MCP servers, resulting in duplicate server instances (e.g., two Serena servers on ports 24282 and 24283).

What Should Happen?

Only one instance of each MCP server should be started. Actual behavior: Two instances of each MCP server are started - one by the config cache loader process, one by the conversation process.

Error Messages/Logs

14:48:42.392 Loading config cache by launching Claude...
14:48:42.392 Spawning Claude - resume: undefined
14:48:43.174 MCP server "serena": Starting connection...
14:48:44.260 Serena dashboard started at http://127.0.0.1:24282

14:48:42.476 Spawning Claude - resume: f4618329-...
14:48:43.498 MCP server "serena": Starting connection...
14:48:44.376 Serena dashboard started at http://127.0.0.1:24283

Steps to Reproduce

Configure an MCP server in .mcp.json (e.g., Serena)
Kill all MCP server processes
Reload VSCode window
Start Claude Code in VSCode

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.0.76

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

Claude Code extension version: 2.0.75
OS: macOS (darwin-arm64)