When tabs can't fit horizontally into page, they're wrapped to new line. But since the first, and the last tab borders are rounded this looks little bit odd:
I zoomed an image to show the issue more clearly.
The design of this component will be revisited at some point. Prior to our recent changes that introduce wrapping, horizontal scrolling would be forced. I'd argue this is a much better alternative to that.
Our future design will need to be able to wrap without feeling awkward. In the meantime, we may look into killing rounded corners at the smallest breakpoint. But, it's possible this component could wrap well before the smallest breakpoint.
Oh, responsive design, heheh