Coding agents from first principles

Build The Loop_

A minimal, practical blog about building a coding agent from scratch: the message loop, tools, permissions, memory, evals, and the engineering that makes the magic look ordinary.

Abstract dark illustration of a coding agent tool-calling loop.

Post 01

The Smallest Coding Agent Loop

At the center of every coding agent is a tiny primitive: send messages, run requested tools, feed the result back, and repeat until the model stops.