Every builder has pasted the same context into a fresh chat. The model answers well once — then the next session forgets the workflow boundaries you carefully explained. Longer prompts are a patch, not a system. What scales is structure: named workflows, clear activities, and cards that carry intent in a form agents can reuse. Dossier exists so that structure lives outside anyone's head — and outside any single thread — so product clarity stays attached to the build as it grows.