Smart home PSA: Apple's "new architecture" for Home app becomes mandatory today
In 2022, Apple announced it was adopting a "new Home architecture" for its smart home ecosystem to improve its performance and reliability and make it possible to support different kinds of accessories. Although it was mostly an invisible update when it worked properly, some users who attempted to switch to the new architecture when it first rolled out in iOS 16.2 ran into slow or unresponsive devices and other problems, prompting Apple to pause the rollout and re-release it as part of iOS 16.4.
If you put off transitioning to the new architecture because of those early teething problems or for some other reason, Apple is forcing the issue starting today: You'll need to update to the new Home architecture if you want to continue using the Home app, and older iOS and macOS versions that don't support the new architecture will no longer be able to control your smart home devices. The old version of the Home app and the old Home/HomeKit architecture are no longer supported.
If you're like me, you hit an "upgrade" button in your Home app years ago and then mostly forgot about it—if you open the Home app on a modern iPhone, iPad, or Mac and don't see an update prompt, it means you're already using the updated architecture and don't need to worry about it.