We do currently require all threads to be created by one of our own factories, but that's primarily because this grew out of a non-byte weaving approach (where we explicitly replaced our concurrency primitives). Looking at the class now, all of its state could easily be stashed in either global or ThreadLocal variables, so I don't see anything that would stop us working with FJP etc.

> Additionally, modifying application code just track thread creation isn’t ideal.

This would certainly be necessary, but don't you anyway need to rewrite the application to trap synchronised, volatile, atomic accesses etc? It doesn't seem all that different to rewrite calls to Thread::start. The issue of JVM threads is perhaps a little trickier, but I am not averse to some ugly integrations. Just take a look at how we make RNGs deterministic

> So it is worth to give them a try.

Thanks for the tips! I am not sure when I will have time to apply these techniques to our simulator, but they are no doubt valuable for the protocol simulations I am relying on today, so maybe I will have a justification to explore them sometime soon.

Really cool work too. I hope it manages to make its way into more hands, so that this technique can be used more widely.