Codepocalypse Now (Age of Agents): Koog vs LangChain4J Agentic

Abstract

Agentic Java is real, today. In this co-presented session we build the same agent — j-claw, a personal assistant that declines speaker-dinner invitations — twice: once in Koog (Kotlin) and once in LangChain4j Agentic (Java). Across four rounds we grow it from a five-line chatbot into a tool-using, MCP-backed, memory-keeping, self-correcting agentic pipeline, and the two apps come out essentially identical — same typed domain model, same per-phase tool slices, same four-phase verify/refine loop. The framework “war” has no loser: whichever side of the arcade cabinet you pick, the winner is the Java developer, because the agent era is open to the JVM right now, no Python required.