Vouch request: mtsmfm

[mtsmfm]

What do you want to work on?

I want to fix #4331 because the port stays open after the server process exits

Why this change?

This bug affects my sandbox env, because when an E2E test boots and shuts down web server, it can't be observed as stopped.

Checklist

• I wrote this request myself (not AI-generated)
• I have read CONTRIBUTING.md