Rooting the device and then exploring and customizing the every corner of the phone is really a fun. But it is only possible if you can unlock the bootloader. Unfortunately there was no root available for Sony Xperia Z1s until today because its bootloader was locked to T-Mobile.
According to the developers behind this root, jcase and beaups, this root is based on the vulnerability and exploits present in Xperia Z2 and Z2 tablet (which are still waiting for a full root besides the discovery of these exploits).
Sony Xperia Z1s can be rooted only if you are on current kernel. Android Kitkat users will have to wait a little longer until a compatible kernel is provided.
There are a of benefits of rooting and you must know them if you are already in this field. After you have successfully rooted your Z1s device, you could use the root-only applications on your phone and then explore those features which would be still hidden otherwise.
As the root is released today, so we might not see any custom ROM right now but there are a lot of things you could tinker with now on your smartphone.
Where Are Instructions / Step by Step Method for Sony Xperia Z1s T Mobile Root?
If you landed on this page to get the full step by step guide, you’ll have to move to the best place to get the instructions and that is XDA-Developers forum. Besides the instructions you can also find the developers contact details there in order to report any issue to them.
The usual warning is still there for this model as well, that is rooting may void the warranty of your device. So, proceed at your own risk.