Whole-set language pass (owner doctrine: language gets its OWN pass). Fresh single-navigation iframe per template — race-free, mirroring responsive-overflow.html — then __dcSetProps(root,{language:"Tiếng Việt"}), settle, and measure. Fails if VN introduces document horizontal overflow (over) or clips text inside a fixed-height/nowrap box (clip — the real VN risk: diacritics + longer strings). ⚑ = VN did not apply (no Language tweak reached). ◇ = canvas deck/social (scrolls inside .cs-canvas-desk; 0 document overflow).