How We Built Chat Memory That Actually Works — Lessons from Shipping to 100K+ Users

How We Built Chat Memory That Actually Works — Lessons from Shipping to 100K+ Users Most AI chatbots forget you exist after a few messages. Here's how we built a memory system that doesn't. I've been building EchoMelon — a roleplay and companion chat platform — for a while now. Early on, the most common complaint we got was brutal in its simplicity: "Why doesn't my character remember what happened last week?" Fair question. You'd pour hours into building a relationship with an AI character, share secrets, go on adventures, name things together — and then the character would just... blank on all of it. Because under the hood, all it sees is the last handful of messages. This post is a deep dive into how we solved that. No hand-wavy theory. Actual patterns, actual trade-offs, actual scars. The Problem: Context Windows Are a Lie Every LLM has a context window — the amount of text it can "see" at once. Claude gives you 200K tokens. Gemini offers a million. Sounds like a lot, right? It's no