An AI agent in 100 lines of Common Lisp

Category: Agentic coding
Status: discussion
Sources: thebeach.dev, HN discussion
Summary: A write-up implements a working LLM agent in about 100 lines of Common Lisp (SBCL) using only two libraries, dexador for HTTP and shasht for JSON. The agent loop is a recursive function: send the message history to the model, run any tool calls, then recurse with the enriched history. The only tool exposed is eval, so the model writes and runs Lisp directly and uses that to define further capabilities such as web search at runtime instead of drawing from a fixed tool catalog. Conversation memory persists by serializing the message list to JSON. Resurfaced on the front page (162 points).
Why it matters: It reduces the agent loop to its core and shows how a homoiconic language lets one code-execution tool stand in for a design-time tool registry.