Although this blog post is tagged "open source" I couldn't find the source for Sapienz. It's also short on details. Apparently Facebook has "acqui-hired" the three people of a startup called Majicke, where Ke Mao, the author of above blog post, was the CTO.
I mainly use the iOS app but I find that it’s rather buggy. I get bugs maybe a few times a week.
The actual website is such a performance mess. I have a chrome book and that can watch YouTube videos, twitch, etc just fine. But load the Facebook page and it grinds to a stop. Even on my actual laptop the fans spin up to max speed when on the website.
In other articles they mention tools such as SapFix or GetaFix https://engineering.fb.com/developer-tools/getafix-how-faceb... but I couldn't find any code, too - apart from a GitHub repo by Ke Mao that contains (the readme of) an obsolete prototype.