# Harness Engineering 101

> Building AI agents from first principles with a simple harness model.
- Title: Harness Engineering 101 · GitHub | Shortify
- Summary: Building AI agents from first principles with a simple harness model. Harness engineering creates AI agents by patching a stateless JSON array loop with…
- Keywords: harness engineering, ai agents, llm, json array, python, open source, code, technology, startups, Harness, Engineering, 101
- Source: GitHub — https://github.com/IsuruMaduranga/harness-engineering-101
- Read time: 1 min
- Topics: harness engineering, ai agents, llm, json array, python, open source, code, technology, startups
## The LLM is the brain
The LLM is the brain. The harness is the body.
## Version 1.0, September 2026
Version 1.0, September 2026. A blog series about building AI agents from first principles, published as a book.
## Stateless LLM API
An LLM API is stateless. Every turn, you send the entire conversation as a JSON array and get text back.
## The Harness
A harness is the program that builds, maintains, and protects that array. Everything the field calls 'agents' is a set of patches to that one loop.
## 16 chapters
This series develops that one idea across 16 chapters, growing a ~300-line toy agent in plain Python as it goes.
## One Code
The patterns here are developed in full in One Code, an open-source coding agent built on pi.
## Key takeaway

Harness engineering creates AI agents by patching a stateless JSON array loop with minimal, concrete fixes.