July 11, 2026
Lisp Is Back, Baby?
An agent in 100 lines of Lisp
Coder says old-school Lisp can run an AI helper — commenters are very not calm
TLDR: A developer argued that a modern AI helper can be built with a tiny amount of old-school Lisp code, reviving a language many thought was long past its moment. Commenters instantly split between “neat simplicity” and “this proves nothing,” with extra snark over the writing style and the Lisp hype.
A programmer dusted off a language he learned in college 25 years ago and made a bold little flex: an artificial intelligence “agent” — basically a chatbot helper that can call tools and keep going — in about 100 lines of Lisp, with the core loop squeezed into just a few lines. His big revelation? Maybe the magical modern AI assistant is, under the hood, just a very simple repeat-until-done routine wearing expensive clothes. Nostalgic? Absolutely. Revolutionary? Well, the comments were not ready to hand over the crown.
The loudest reaction was a giant “cool story, but so what?” One commenter flat-out asked how this is different from just letting a bot run a one-line Python command, basically puncturing the big reveal with a hiss. Another went for the jugular with the brutally short review, “Littered with AI writing tells,” which is the internet equivalent of throwing a drink in someone’s face. Ouch. Meanwhile, Lisp fans and skeptics started their own side quest: is this actually a win for Lisp, or just a basic idea dressed in nostalgic academic robes? One commenter said they love Lisp “with a passion” but still didn’t buy the argument.
And then, because the internet never misses a chance to get weird, one person casually dropped that they built an interpreted Lisp, stuffed its syntax tree into Postgres, and hooked it up with htmx — a sentence so gloriously niche it became the thread’s accidental comedy gold. The vibe: part retro comeback, part eye-roll fest, part programmer talent show.
Key Points
- •The article recounts the author’s experience learning Lisp in an AI course at the University of Guelph around 2000.
- •It describes Lisp as historically associated with symbolic AI, including expert systems and theorem provers.
- •The author contrasts earlier AI education with modern AI technologies such as transformers, CUDA, and PyTorch.
- •The article argues that an AI agent loop can be reduced to a simple pattern of sending messages to a model, handling tool calls, and repeating.
- •It provides a short Common Lisp example that implements an agent loop recursively by appending tool outputs to message history until no tool call remains.