Steps to reproduce:
Open or close a tab while using horizontal tabs mode.
The usual tab animations should show the tab smoothly opening or closing in the tab bar. Instead, no animation is present (the tab opens or closes properly, but there is no animation). Animations work as normal in vertical tabs mode.
Orion, OS version; hardware type:
Orion RC 0.99.124.1.1-rc
macOS Monterey 12.6.5 (21G531)
2020 Macbook Air M1