The strip's rule is an inset shadow painted in the container's last pixel
row, and full-height tabs covered it — so each tab read as overhanging
the bar by 1px. Inactive tabs compensated with their own border, stacking
a second translucent line that darkened the seam.
Inactive tabs now stop 1px short and draw no bottom border, leaving the
container as the sole owner of one continuous rule; the active tab keeps
full height so it alone cuts through. Hover also darkens rather than
lightens, since lightening moved a hovered tab toward the active
surface's look.
Brooklyn Nicholson
f2ac03196f