Hi Quinn, The image list is a good suggestion. I was just using that other day. I'll try that, and see what lldb reports. This is pure C++, no Swift or ObjC usage. For some of our users, the dylib hotloads and for others not. It's a mix of people mostly on 10.15.7 and XCode 12.2/3. I did the implementation mentioned above of renaming the lib, but it seems like we have a partial reload. So some code hotloads fine, and other code is still pointing to the old lib. Some code at init of the dylib where we crash (with renaming) is reporting the previous numbered dylib in the debugger. This may be an artifact of how Xcode loads the sources once at launch, but when I do hotload, my breakpoints show the new sources. By ODR, do you mean on-demand-resource? We did have those a while back, but I think they're disabled currently. it’s definitely not there after dlclose() on my system. But my system works. Others don't. So I'll get some more info on the machines that don't hotload. after dlopen() (lldb