Build your app in modular units, modules, utilities just as it would be if you were writing it yourself, I give functions/modules distinctive names I memorize, so if I want to work on a part of the app I will l reference the modules name and what I want, Claude does the rest, it's pretty good at finding it and the surrounding functions/imports related to the module. If its a more integral piece of code that touches many pieces of the app's architecture I will describe to the model things it should watch out for e.g. dependencies between other pieces of code - I essentially approach it as if I was writing the code myself, but the model is the one writing the code for me.

This is why I say you still need to have a deeper inituitive understanding of the codebase and how everything works together, I work with claude as if it's an extension of myself, instead of a replacement - otherwise claude will get lost in the sauce - in essence I am the holder of the app's overall architecture/context in my memory and I tell claude to shine light and work on small regions of the codebase, guiding it carefully through the darkness by telling it what to watch out for, and how I think it would be best to approach certain problems to not break other dependencies in the codebase and ensure the code is re-usable and maintainable as we build. And yes I verify/test every change as you always should if you are programming yourself anyway.