AI Agent Memory Part 2: The Case for Intelligent Forgetting

Introduction After publishing Part 1 , a comment came in that changed how I think about agent memory entirely. "One thing that's missing from the comparison space: memory decay. All the tools you've listed treat memory as an append-only store." That one line exposed a quiet assumption baked into every tool I covered — Mem0, LangMem, AWS AgentCore, and even the manual implementation. They all append. None of them forget. This post is about fixing that. Why Never Forgetting Is Actually a Bug Imagine a customer support agent that has been running for 6 months. Every conversation, every user preference, every trivial question — all stored forever. Here is what starts to go wrong: Problem What Happens Stale context User changed their stack from React to Vue 3 months ago. Agent still recommends React. Retrieval noise Searching "user's project" returns 50 results — half of them outdated. Conflicting memories User said they are a beginner in January. They are now a senior dev. Agent still trea