Notwithstanding the earlier suggestion which it is claimed has been 'implemented' (Poorly, half-heartedly implemented)
. . there is still fartoolittlecontrastbetweenthetabs in dark mode, both between individual tabs (a faint and indistinguishable vertical line) and more essentially between active tab and the rest. Personally I would like to see a clearer base to tabs as well, and a wider, otherwise emphasized pinned tab.
Finding the active tab is further obscured by colourful site icons, which produce far greater contrast than the essential tab delineation.
Please consider that you are inconveniencing those with sight difficulties - this is a disability discrimination issue.
Myself I have to crane forward to the screen to see which tab is active, and it is barely discernible.
Optimally, a user would be able to set their own choice of colour depth for active and hover-selected tab, and to be able to emphasize the tab edge (and base) according to their own requirements.
Why be so stingy and parsimonious over this?
(Additionally there should be a minimum tab width setting, and a better way to manipulate groups of tabs, but that is a separate issue. The whole mess needs a thorough review and fresh thinking.)