“Day 14: A functional replica of Slack’s core product, built by Nathan using LLM agents.” What does that even mean? What are “core features”? Just a chat room? That’s trivial compared to what a real system like Slack actually does: handling millions of messages at scale, ensuring consistency across clients, maintaining high availability, storing and serving media (videos, audio, images), managing backups, and more. Building a simple chat app that mimics Slack’s UI isn’t impressive. That was a few hours of work even 20 years ago, long before LLMs. Calling that a “replica of Slack’s core product” is, at best, misleading.