[BUG] Claude Code launch mcp process even if it's not using them

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?

I have defined many mcp server for Claude code. Every time I start claude, even if it not using an mcp tool, it already start the process for that mcp. This would eat up local machine memory quickly when we need to run multiple instance of claude code.

What Should Happen?

Better start these mcp tool on-demand

Error Messages/Logs

Steps to Reproduce

Define some npx mcp server.
Launch claude
the mcp servers started

Claude Model

None

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

2.0.32 (Claude Code)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Other

Additional Information

_No response_