However, it is important to note that version 0.9.5013 does come with some limitations. While it supports iOS 8, after every reboot you must respring before Cydia Substrate will load extensions. Saurik notes that he is working with the Pangu team to roll out a stable fix for this respring issue.
In short, on iOS 8: after every reboot, you need to respring before Substrate will load extensions in SpringBoard.
Substrate version 0.9.5013 supports iOS 8, but because of limitations in Pangu (versions 1.0 through 1.0.1 so far tested), Substrate won't work immediately after the device boots - it will only work after the first respring. You can respring by SSHing to your device and typing killall backboardd
This happens because Pangu loads Substrate after other processes have already loaded, causing Substrate to not work until the next time backboardd and SpringBoard restart.
We are coordinating closely with the Pangu team to make certain the best possible fix for this is deployed.
Note that Pangu has not bundled Cydia with their iOS 8 jailbreak yet, so we recommend holding off until the team releases a new version of the jailbreak. We'll be posting step-by-step tutorials so be sure to follow iClarified on Twitter, Facebook, Google+, or RSS for updates.