When you’ve tried all the logical solutions, restarted, had a go in Safe mode, and still can’t solve a problem, you may need to bring the big guns to bear on it. These are radical fixes that carry a risk of going further than you want, but are all you’ve got left. You might have been recommended them by someone who seems to know best, or, as we saw last week, by an AI. This article looks at the state of those big guns in Tahoe 26.1, and which you should consider seriously.

Reset NVRAM and SMC

Although quick and simple to use, resetting the NVRAM and SMC are well known for fixing all sorts of problems. They’re still valuable in Intel Macs, but you can forget them in Apple silicon, as the SMC resets with each startup, and the NVRAM is protected from user access. The only way you could reset an Apple silicon Mac’s NVRAM is by Restoring it in DFU mode, which almost certainly isn’t something you want to do at this stage.

Reset TCC

TCC is the subsystem responsible for implementing privacy protection, and is notorious for its mystifying misbehaviour. Before convincing yourself that doing anything with TCC is going to help a problem, you should really look for a pattern of misbehaviour that points to one of the resources that it controls access to. If possible, tie this to a single app and use
sudo tccutil reset All com.apple.clock
for example to reset just that one app’s privacy settings.

TCC is also a popular recommendation in solutions that lack a firm logical basis, where there’s no attempt to target one app, but go for the lot with
sudo tccutil reset All
The effect of that is to empty every section (apart from Location Services) in Privacy & Security settings. That’s certain to stop many apps from working properly, and you’ll end up adding them back one by one over the following days or weeks. In some cases, even that doesn’t prove sufficient, and deleting TCC’s database seems the only way forward. That and other issues are discussed here.

tccutil doesn’t appear to have changed in any significant way in Tahoe.

Delete LaunchServices’ database

LaunchServices handles many features including opening apps, populating their Open Recent menu commands, and handling much of the integration of apps with their documents. To achieve that, it maintains an extensive database of apps and other executable components.

Access to LaunchServices’ database and control over it is provided in the lsregister command, buried deep in /System/Library/Frameworks/CoreServices.framework/Versions/A/Frameworks/LaunchServices.framework/Versions/A/Support, although there’s a public lsappinfo tool that provides different features and is seldom used. Earlier this year I gave an account of its use in Sequoia, but its most popular option to kill the LaunchServices database has been removed from Tahoe “because it was dangerous and no longer useful”, a fair assessment.

Repair permissions

I have recently reexamined the various forms of repairing permissions. If anyone or anything recommends you run
sudo /usr/libexec/repair_packages --verify --standard-pkgs
you shouldn’t listen to another word they say, as that form went out with El Capitan, and isn’t even possible with a modern version of macOS.

The more modern replacement, initiated by the command repairHomePermissions in Recovery mode, may once have had a purpose, but is now grossly disruptive, as it locks the user out of most of the contents of their Home folder by removing them as their owner.

It would take you hours to restore your Mac to a usable state after performing that ‘repair’. If anyone recommends that you try it, ask them when they last used it successfully.

Clean install

Tahoe does provide convenient methods for clean installing macOS, as described here. One of the simplest is to Erase All Content and Settings using the EACAS option in Transfer or Reset, in General settings. That renders all your data inaccessible by securely erasing its encryption key, then you can migrate from your latest backup when setting up your currently installed version of macOS afresh.

If you want to go back to fresh firmware and macOS as well, then the simplest way is to Restore in DFU mode, as explained here. That also gives you the choice of using any compatible IPSW, making it possible to perform a full downgrade to an earlier version of macOS if you wish. Remember that Apple silicon Macs can’t run a version of macOS that was released before that model shipped. If in doubt, consult Mactracker’s database for the original version shipped with that model.

Summary for Apple silicon Macs:

• Resetting SMC and NVRAM is not possible (still available for Intel).
• Resetting TCC is still available.
• Killing the LaunchServices database is no longer available (but still in Sequoia).
• Repairing permissions is grossly disruptive and should be avoided.
• Clean install can be confined to the Data volume, or include firmware and macOS.

Whatever you choose, I wish you success.