Auto hide tabs when there is only one

[munro]

Is it possible to auto hide the tabs bar if there is only 1 tab?

Here's what I see in firefox:

And here's safari (it hides the tab bar)

This probably isn't helpful, but I had also tried this minimal Firefox theme which says it autohides tab bar—but it didn't work for me: https://gist.github.com/morrolinux/87aa37396432ea5d14a9220bc4892100

[munro]

Hmmm, I hadn't use the install script, but it's still not working!

I also copied the code

#alltabs-button,
#tabbrowser-tabs tab[first-visible-tab="true"][last-visible-tab="true"]:not([pinned]),
#tabbrowser-tabs tab[first-visible-tab="true"][last-visible-tab="true"]:not([pinned]) ~ toolbarbutton,
#tabbrowser-tabs tab[first-visible-tab="true"][last-visible-tab="true"]:not([pinned]) ~ #tabbrowser-arrowscrollbox-periphery {
  visibility: collapse;
}

https://github.com/ideaweb/firefox-safari-style?tab=readme-ov-file#hide-solo-tab

and it's still not working 😢