Function tab 

pub fn tab(
    theme: &Theme,
    key: impl Into<SharedString>,
    label: Label,
    state: State,
) -> Stateful<Div>

One tab, up to the ×: pass the same key to close and chain the result on as a child.

key names both the element and the hover group Close::OnHover reads, so the two are derived from one string rather than written twice.

Every tab but a State::Focused one takes its own hover, and gpui panics on a second one: reach for Close::OnHover’s group, or a group_hover of your own, rather than chaining .hover(..) onto what this returns.