I didn't know much about Jai, and started reading it, and it really has (according to the article) some exciting features, but this caught my eye:

"... Much like how object oriented programs carry around a this pointer all over the place when working with objects, in Jai, each thread carries around a context stack, which keeps track of some cross-functional stuff, like which is the default memory allocator to ..."

It reminds me of GoLang's context, and it should've existed in any language dealing with multi-threading, as a way of carrying info about parent thread/process (and tokens) for trace propagation, etc.

The Odin programming language uses an implicit context pointer like Jai, and is freely available and open source.