Xiaomi has begun rolling out HyperOS 4, based on Android 17, to dozens of smartphones across its three brands—Xiaomi, REDMI, and Poco—in phased, region-by-region releases, with the overall rollout continuing through the end of December. The first wave of upgrades kicked off on November 3, covering the Xiaomi 17 series, the Xiaomi 15, and several entry-level Poco models. The second wave, along with earlier entry-level devices, will follow in succession, and the Xiaomi 13T, released in 2022, is also on the upgrade list. Eligible users can either wait for the update to arrive or manually check for it. HyperOS 4 introduces a "Liquid Glass" visual style, adds extensive lock screen customization options and a large clock widget, improves floating window smoothness and tablet screen orientation handling, and debuts AI optimization tools that can cut app launch times by up to 20%.