The State of Memory in Java AI Agents (April 2026)

This post was originally published on jamjet.dev. TL;DR If you're building AI agents in Java today, your options for persistent memory range from "store the last 20 chat messages in Postgres" to "run a Python service in a sidecar container and call it over HTTP." There is no Java-native equivalent to Mem0, Zep, or Letta — the libraries Python developers reach for when they need real memory. This post is a tour of every option a Java developer has in April 2026, why most of them stop at chat history, what "real memory" should actually mean, and one library we shipped to fill the gap. The scenario every Java AI developer recognises You're building an AI agent in Spring Boot. Maybe it's a customer support copilot, maybe it's a coding assistant, maybe it's a research agent. You wire up Spring AI or LangChain4j, write a few tools, and the first conversation works. Then your user comes back the next day. The agent doesn't remember them. It doesn't remember they're allergic to peanuts. It doe