If doing greenfield work, planning sounds nice, but if you're integrating with crusty / legacy systems that are poorly documented (if at all) planning is a wast

If doing greenfield work, planning sounds nice, but if you're integrating with crusty / legacy systems that are poorly documented (if at all) planning is a waste of time; you'll end up saying "Library X will do Y" a lot only to find out none of that works the way you thought. So for brownfield, I may have a plan (written down or not) but it's mostly code (some throwaway) just to uncover how things actually work.