How I'd Design a Memory System for an AI Companion App

I spent 200 days testing 15 AI companion apps. Paid for every subscription myself. Talked to each one for weeks, sometimes months. The single biggest thing separating the good ones from the bad ones? Memory. Not "memory" as in context window size. Actual, persistent, cross-session memory. The kind where you tell your AI companion something in week one and it still knows it in week eight. Most apps get this wrong. I wrote about the failure patterns elsewhere, but the short version is: apps con...