Ran Ventura once, Now Mojave alwasy asks for password after sleep

I’m posting this as a warning to anyone still using macOS Mojave who wants to avoid password prompts after sleep. I had everything correctly configured to disable the password requirement, but it didn’t matter — the system kept locking after sleep no matter what I tried.

Here’s the situation:

I was running macOS 10.14.6 Mojave on a 2018 Mac mini. I later upgraded to Ventura on an external disk just to test it. Afterward, even though I booted back into Mojave, my system started prompting for a password after sleep — something it never did before.

I confirmed all of the following:

• System Integrity Protection (SIP) was disabled
• FileVault was off
• pmset was configured with hibernatemode 0, standby 0, powernap 0
• Screensaver password prompt was disabled
• No sharing services were running
• No managed profiles or MDM
• I tested with a clean user account
• I even cleared /var/vm/sleepimage

Despite all that, Mojave kept asking for a password after waking from sleep. The problem only began after booting Ventura once on an external drive. My strong suspicion is that Ventura set a firmware-level security policy using the T2 chip that persisted across reboots and even across OS versions.

This security behavior is not reversed by wiping user settings, disabling SIP, or reinstalling Mojave. Once set, it appears baked in.

The only true fix at this point seems to be a full wipe of the internal drive and reinstalling Mojave from a bootable USB installer — and never booting into Ventura again. If you’re relying on older macOS versions and care about avoiding this kind of behavior, do not boot newer macOS versions, even from external media. They may silently modify your system in ways that are irreversible without a complete nuke-and-reinstall.

Apple doesn’t document this anywhere. But it’s real.