Issue Description My Mac originally had macOS 26.2, and I updated it to macOS 26.6. After using Safari normally for 2–3 days, Safari suddenly crashed. After the crash, when I open Safari again, it sometimes launches as a new/empty Safari instance instead of opening my existing Safari profile. My bookmarks, history, tabs, and other Safari profile data are not available in this new instance. While investigating the issue, I found a folder under my Mac's Library whose name appears to be my Mac's serial number/hardware identifier. This folder contains Safari-related files. I believe this serial-number-named folder may be related to the problem. My concern is that this folder may be causing Safari to create or open another Safari instance/profile after Safari crashes. If this folder is incorrectly created or recreated, it may explain why a new Safari instance appears and why my original Safari profile is not loaded. I have already contacted Apple Support and tried the following: Created and tested with a new macOS user Tested in Safe Mode Cleared Safari cache and cookies and checked Safari Library data Restarted the Mac multiple times Reinstalled macOS Completely erased the internal drive Performed a fresh macOS installation Updated macOS to the latest available version The issue still occurs even after completely erasing the drive and performing a clean macOS installation. I am also currently seeing two different Safari icons/appearances on my Mac: one appears to be the newer macOS 27 Safari icon, while another appears to be the older macOS 26 Safari icon. Request to Apple Please investigate the serial-number-named folder specifically and determine: Why this folder is created. Which macOS or Safari process creates it. What its purpose is. Whether it is related to Safari profiles, containers, application registration, or Safari instances. Whether this folder can cause Safari to launch as a new/empty instance after a crash. Why the folder or related Safari state can appear again even after a completely clean macOS installation. Why two different Safari icons/appearances are currently present. I believe identifying the source and purpose of this serial-number-named folder may help identify the root cause of the Safari issue. I do not want to delete or modify this folder without Apple's confirmation because it may be a system-managed folder. Please investigate this as a possible macOS/Safari system-level issue and escalate it to the Safari/macOS engineering team if necessary. I can provide the exact folder path, screenshots, Safari crash reports, system logs, and Terminal output showing the Safari application locations and related folders.