Microsoft has redesigned the Xbox One Home user interface with a variety of features designed to provide a faster experience. Among the changes, support for the Cortana voice assistant has been dropped.
Announced on the Xbox Wire blog, Microsoft explained that the company intends to shift voice assistant elements away from on-console and into the cloud. This means that, while you can still use voice commands to control your console, you’ll talk to Cortana via a smart device such as an Alexa product with the Cortana skill or a mobile device with an app, rather that via your Xbox headset.
Source: IGN.com Xbox Home Screen Redesign Removes Cortana