High CPU usage only when using browser-harness via CDP

[AClon314]

env

OS: Windows 10
Chrome: v125.0.6422.142 (x64) (Maybe because this version too old, and get latest version will solve this problem)
browser-harness: (2026-5-6 in UTC-8 commit)

problem

very lag on browser-harness controlled tab with "🟢" or "⚪" prefix
chrome://tracing shows that:
CPU usage high relevance to CrBrowserMain with:

title: MessagePumpForUIDispatchMessage
Category: base,toplevel
User Friendly Category other
Wall Duration: 1.135 ms
CPU Duration: 1.135 ms
Args:
  - chrome_message_pump_for_ui {message_id: 1024}

about MessagePumpForUIDispatchMessage