The iOS 7 jailbreak released by the evad3rs team has updated its Mobile Substrate software to be compatible with A7 (64 bit) devices like the iPhone 5S, iPad Air, and iPad Mini Retina, but the update isn’t automatic. Users must first jailbreak their devices using the evasi0n7 jailbreak and then download the update, CydiaSubstrate, from Cydia.
Mobile Substrate is a very critical piece of software for jailbroken iPhones. Many tweaks require the Mobile Substrate architecture to work. Additionally, Mobile Substrate offers a “Safe Mode” which allows users to reboot their devices without any tweaks active. This is critical, for sometimes tweaks make one’s device unusable, and without a Safe Mode, there would be no way to turn these problematic tweaks off.
It is risky business to install tweaks, hoping they work, without this Substrate update. One bad move and your device will require a complete factory restore.
Fortunately, the CydiaSubstrate download will avoid most of these problems.