Kernel panics have traditionally been encountered due to kernel extensions. 3rd party software with access to the kernel and entirely unrestricted access to read/write any portion of memory. Apple phased out kernel extensions in favor of system extensions and kicked all the security vendors out of the kernel and granted them a sandboxed security API to use instead. Ever since Apple made those changes, the odds of a kernel panic being anything but hardware failure would be very unique.
2025-08-25 22:19:18 Kernel Panic (3 times)
First occurrence: 2025-08-25 18:48:15
Details:
panic(cpu 0 caller 0xffffff80025f4c9a): nvme: ". Controller fatal bit
set. Read. fBuiltIn=1 MODEL=APPLE SSD SM0256L FW=CXS7LA0Q CSTS=0x3 US[
1]=0x0 US[0]=0x60 VID=0x144d DID=0xa804 CRITICAL_WARNING=0x0.\
Panicked task 0xffffff91227cc980: 176 threads: pid 0: kernel_task
Looks like a potential SSD hardware failure is imminent. BACKUP YOUR DATA. You may or may not be able to recover this issue by burning a USB flash drive with the macOS Sequoia 15.6.1 installer. Boot from that flash disk. Completely erase the internal SSD storage and re-install macOS. Restoring from Time Machine backup at the same time. This might fix it if the SSD has enough remaining overprovisioned sectors.
Let's say you have a 256GB SSD but in reality it's more like 375 as it has extra flash chips as they do indeed wear out after so many writes. Therefore the drive's firmware will swap out aged sectors for new ones. There is no fragmentation with an SSD each sector can be directly accessed and read and they don't move locations. There is no performance penalty to seek out an available sector. Yes, SSD's do fail and spectularily with little to no warning. At least with an HDD you would hear stuff when the mechnical components failed. Not so with an SSD. It will just up and die all at once or you'll see some warning signs like you've described. Then it fails eventually. FYI - All DISKS DIE it is just a matter of WHEN.
This iMac will be unlikely to run Tahoe 26 shipping next month or soon thereafter. You have about a year before you absolutely need a new Mac to maintain security patches. macOS 27 definitely won't support Intel anymore let alone Tahoe 26 for this particular iMac.
