Just like the Windows Insider Program, the Xbox Insider Program allows the Xbox One users to test the preview builds before getting the hands-on official updates. However, the Xbox Insider Program is complicated than the Windows Insiders Program. There are many Preview Rings in the Xbox Insider Program and they receive updates with different features at different time.
Today, Microsoft has started rolling out the first preview update to Xbox One Devices on the Preview Ring 3. Microsoft hasn’t introduced any new features or major changes but there will be some bug fixes included in the update. However, the latest preview build comes with a lot of known issues.
After installing the build version rs_xbox_dev_flight.170308-1900, the party chat will stop functioning when headset audio is switched from Stereo Uncompressed to Windows Sonic while in a party. Furthermore, if you try to enable the Mono output setting in Ease of Access Audio, the settings app would become unresponsive and it will crash. Moreover, when you will try to activate Cortana while playing certain games, Cortana may take a long time to respond.
Microsoft is still rolling out the update, it may or may not be available on your Xbox Device yet. If you are not seeing the update, your device would get upgraded to the current build in the coming weeks. To get the update, you need to go to the System Menu in Settings on Xbox and check for updates.