The full installer failed in exactly the same way as the two normal updates. On Apple Silicon, "Install macOS…app" uses the same update mechanism (UpdateBrain → patchd), so it hit the same wall. The new crash-report folder did its job, though: /Library/Logs/CrashReporter/OTAUpdate-2026-10-27-07-19-11.ips holds the full installer log, and it shows where things go wrong.
What the log shows:
- Installing 27.2 works. The system volume is patched and sealed, and the new startup files are written to Preboot under manifest 38D0D4C9…. A new security policy (LocalPolicy) for 27.2, 0F12B055…, is created at 06:58.
- patchd deliberately doesn't switch to the new policy itself. It skips ff_commit_local_policy_nonce "on condition (ctx->do_postupgrade_boot)" and leaves that to a "post-upgrade" boot.
- Then the bless step (marking what to start next) prepares that boot: bless2_boot_with_args() … "boot_once" = 1 reading blessed macOS local policy …/LocalPolicy/…94.img4 ← B8B2…7894, the OLD 30-Sep policy bootpolicy_get_