Hi, In my Firefox Developer install the new tab groups feature seems to now be working like one would expect, but my main Firefox install (Firefox desktop 138.0 (64-bit)) has some issues. I can add tab groups, add tabs to groups, but left mouse clicking the colored tab header does NOT close the tab group, like it does in Developer browser. Mode of tab group clearly changes, as the tab is either dark or light colored after a mouse click. I don't remember changing any other settings lately in about:config, except setting tabs.groups feature to true, and I don't have too many extensions installed, and I also tried disabling all the extensions, but that didn't help.