Hello. I was wondering if anyone could point me to or otherwise suggest some best practices for working on Kernel code. Iâm futzing about with the Duration class (in the interest of fixing 13215) and have discovered that itâs really easy to crash Pharo if I break that class. I assume there are other classes that would exhibit the same behavior. I suppose I could just be really cautious and save my image after every change but that seems so error prone that Iâm hoping that there are idiomatic ways of working on kernel code (beyond just save ones image early and often) so I donât lose work. Iâm asking because the naive solution (copy the original class, modify it to suit, delete the original and rename the new class to the original) of course doesnât work. TIA for any suggestions or assistance and apologies in advance if this is RTFM, I didnât see anything (didnât look very hard either though). âRick