HTC's One A9 is the luckiest Android but non-Nexus non-Android One phone on the planet these days. It keeps getting updates sooner than most other OEM smartphones and is even receiving the monthly security patches faster than all of them too. The unlocked version of the device received Marshmallow 6.0.1 at the end of 2015 and now, one month later, the Sprint carrier version is ready for this update too.
Version 1.57.651.1 of the software brings the A9 all of the new Android 6.0.1 emojis with plenty of improvements that HTC details in its changelog below.
This software upgrade available for your HTC One provides the following key enhancements:
· Android 6.0.1 Marshmallow update
· Battery life improvements
· Camera feature improvements
· Addition of Wi-Fi Calling Functionality
· System enhancements
The OTA should have already started rolling to Sprint One A9 devices, but if you don't see the notification yet, be patient because it's probably on a slow release. Or you can grab the 1.86GB RUU file (.exe warning) and flash it manually. You'll likely lose all of your data though so proceed with caution.
Source: HTC Support