Chrome adds a stylesheet of its own to extension pages that sets the font on body. Tailwind 4 puts its classes in a cascade layer, and a rule outside any layer wins over them, so font-mono lost and Chrome drew the popup in the system font. body now carries font-mono!, which marks the class important. Both end-to-end suites check the popup's font. The same stylesheet also makes Chrome draw the popup's text at 12px rather than text-sm's 14px; that is unchanged here and filed as issue 456. Model: opus-5-5