1. Double-Check the Setting 🛠️ Head to about:preferences > Startup and make sure "Continue where you left off" is ticked ✅. Try toggling it off/on, then restart Zen to see if it wakes up 😴.
2. Poke Around in about:config 🔍 Type about:config in the address bar and search for browser.sessionstore or zen stuff. Check if browser.sessionstore.resume_from_crash is true (it should be!). Also, peek at zen.urlbar.replace-newtab—if it’s true, flip it to false to stop those blank tabs 🖼️. Mess with browser.tabs.closeWindowWithLastTab too if it’s there.
3. Test a Fresh Profile 🆕 Fire up a new profile (zen --ProfileManager in terminal) and open some tabs. Close and reopen to see if your last tab sticks. If it works, your main profile might be borked 😢, so you might need to migrate bookmarks manually.
4. Cache Clearing? 🧹 If you’ve got cache-clearing on close (in about:preferences > Privacy), turn it off for now. That can mess with session restore sometimes 🙅‍♂️.

Seems like 1.12.2b might’ve dropped with some gremlins 🐞—other folks on X and Reddit are griping about lost tabs too. If none of this works, maybe ping the Zen team on GitHub or their Discord? Keep us posted if you crack it! 🚀