I have the same issue and didn't even close my browser. I closed a tab group, and they're ''gone''. I've always used ''warn me when closing multiple tabs''; why didn't it prevent this? I dutifully updated to 6.0.1 (Win7 Pro 64bit SP1) today, and saw "''Tabs, meet groups''." I played briefly with a group and then clicked (x). While exploring the UI, I had assumed I was manipulating a filter rather than the actual tabs. No reason to suspect this would close an entire window's worth. The "restore tab group" button suggested I'd merely ungrouped the tabs. No biggie; new feature playtime is over for now. The background blur was still present, so again no worry that my six or eight tabs were about to be annihilated. The recently closed window list includes three pages from yesterday. Naturally the recently closed tabs ''from the other window'' aren't here. My full history is sorted by visit date; why isn't each tab added to today's list after a restart? Now I'll search the entire history to ensure I'm not forgetting one. Tab groups are likely quite nifty, but for now I'm irritated with 'em. '''Why didn't "''warn me when closing multiple tabs''" kick in''' to alert me?! SUGGESTION: '''''Warning:''' The 'tabs group' feature does not care if you've checked "warn me on closing multiple tabs." If you click the (x), you're hosed.''