Hi to all.
To reproduce the bug you need to open the page "Getting Started" on mobile device. Here is my screenshot:

Related to screen width? I'm not sure.
Reproduced on my iPhone ...
But it looks fine in Chrome's simulator... don't know why

@stevenjoezhang reproduced in simulator responsive mode, drag screen...
Ah... need to update this file: https://github.com/theme-next/hexo-theme-next/blob/master/source/css/_common/components/tags/tabs.styl
to make tabs more responsive
Flex:

Block:

And other borders & marigns in this file...
But I think about that and it seems will be better somehow to determine tabs width & counts and if width of this values longer then viewport width → set tabs as block; if not → stay as is, in flex style.
How about tabs like this:

Using float: left

Or vertical? 😹
Referenced:https://getbootstrap.com/docs/4.3/components/navs/#vertical
Example: https://www.dnocm.com/more/tools/
Code:https://raw.githubusercontent.com/JiangTJ/blog/master/source/more/tools/index.md
Just a joke. Ignore it. 😉
How about tabs like this:
Usingfloat: left
Seems good too. Need just to fix this bug.
Most helpful comment
How about tabs like this:

Using
float: left