Hi, I did not find an explicit statement about the current status of the implementation of exceptions in JHC. I've looked the source code have some clue. To me it seems that - GRIN backend only supports fatal ioError. The catch function does nothing (probably) because any raise operation will halt the program anyway. - There is an experimental (and disabled) GHC backend which would map JHC catch/raise primps to the corresponding GHC primops. In short the GHC's async exception system is not implemented and JHC's current exception system can only halt the program. Are these assumptions correct? Regards, Csaba Hruska