For one thing, our solution is open source and has been described in an academic paper. Also, Chronon cannot record Scala or Groovy programs. ChroniclerJ has no such issues as it operates through byte code rewriting. Moreover, the technique we have implemented can be easily ported to other VMs such as the .Net CLR. Chronon does not execute code during replay so I am not sure how they are guaranteeing that the state of the program when it crashed can be reproduced. Chronicler records sources of nondeterminism while allowing execution of the deterministic parts of the program and thus guarantees that you will get to the exact state at which the program crashed.