In dark mode the active workspace tab was hard to tell from the others:
its background is the page colour (the tab flows into the page), which
measured 1.07:1 against the strip and its neighbours (1.09:1 in light),
with the same text colour and weight. It now carries a 2px accent line
along its top edge (inset box-shadow): 4.85:1 / 5.20:1 in dark, 5.70:1 /
5.24:1 in light, against the strip and the tab.
A survey of every selected-state control with siblings, across 12 pages
in both themes, found three tab-like segmented toggles failing the same
way (background steps of 1.05-1.16:1): the item pane's Rich / Markdown
toggle, the tag page's view toggle and the Insights window selector. Each
selected segment gets a 1px inset accent ring (>= 4.47:1). Underline tab
bars (item pane, settings, library, admin) already met 3:1 and are
unchanged.
The e2e pins the requirement for the tab bar in both colour schemes: the
active tab's indicator reaches 3:1 against an inactive tab and the strip.
Red on the old build (no indicator) and on a mutant drawing the line in
the border grey.
Claude-Session: https://claude.ai/code/session_01Q9WssCjFuHjSfLABoW4tmS
xarmian
d39cb9f00a