I Built a Mini Claude Code from Scratch. Here's What I Learned
A few months ago I went down a rabbit hole: reading OpenCode's GitHub repo, studying screenshots of Claude Code's behavior, reverse engineering the flows. I wanted to understand how these terminal coding agents actually work under the hood, not just use them, but build one. This post is about what I built, the real technical challenges I hit, and what I'm planning next.
What I Built
A CLI-based AI coding agent. You open your terminal, run it inside a project, describe a task, and the agent autonomously reads files, edits them, runs commands, searches the web, and commits to Git. This happens all while asking for your approval before changing any of your code.
I started it as a simple sidequest, to read and implement things side by side. It's built in TypeScript, runs on Bun, uses Vercel's AI SDK (Agents, Tools and Loop Control), and uses Google Gemini 2.5 Flash as the model (because it has a free tier, lol), and the terminal UI is built with Ink, I used it because it is very similar to writing frontends in React.
