quarkus-chat-ui (2): The Actor Design Behind LLM-to-LLM Conversation
· 8 min read
In a previous post I introduced POJO-actor — a lightweight actor-model library for Java that needs no framework, no annotation processor, and no external runtime. Just plain Java 21.
This post is about how I actually use it in quarkus-chat-ui, a Quarkus-based LLM chat UI that connects to Claude Code CLI, vLLM, and other backends. The application manages stateful LLM sessions, streams responses via SSE, handles concurrent MCP requests, and supports a /btw command for side questions — all without a single synchronized block.
The three actors that make this work are ChatActor, BtwActor, and QueueActor. This post focuses on the first two and the design principle behind them.