theme styles change didn't get applied on page content (because of iframe I guess?).

For example, if I change the --uip-body-font-family to Geist Sans, the change didn't reflect on content page (because I guess it uses iframe internally to load the content)

But I confirmed that the change did change on the sidebar and the taskbar, only the content frame that still use the default font (Inter, system-apple-ui, bla bla bla)

How do I fix this?