.navsearch is a fixed 8rem inside a nowrap flex row, and a flex item defaults to min-width:auto — so it could neither shrink nor drop to its own line, and instead pushed the document wider than the screen. Measured with a chromedriver layout probe (screenshots show THAT something clips, not which element sets the minimum width): 360px document 377 vs viewport 360, sole offender form.navsearch -> 360, none 390px already clean before and after 768 / 1280 unchanged 390px was never affected, so this is narrow-phone only — which is what audit #45 said ("the nav has no flex-wrap and runs off-screen at 360px") before I briefly mis-measured it as a 390px problem via --window-size, which sizes the OS window and not the CSS viewport. The composer control row needed nothing: it already wraps (.controls flex-wrap plus the max-width:640px block). Phase 0 of the visual-parity order. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>