Decisions that outlive the session
Coding agents remember little from one session to the next. The code tells them what a system does, but not why, and not which ideas were already tried and dropped. A decision log fills that gap: one file per decision, an index, a short section in the agent's instructions, and a check. How it worked while agents built a 3D space game, where it helped, where it hurt, and the instructions to copy into your own project.