There are several ways, actually. One can be directly reading what the engine reports on TraceStream and ErrorStream, by explicitly using their Read() method. The easiest way I have found (it's time consuming, though) is to clips.DebugConfig.WatchAll() to activate all trace output and clips.DebugConfig.DribbleOn("my_trace.log"). When an error occurs in CLIPS, everything about it will be written to the file specified in DebugConfig.DribbleOn(), and it becomes easier to spot it correctly.