A synthesis of hard-won lessons from Claude Code, OpenHands, SWE-agent, GoClaw, Nanobot, PicoClaw, and the emerging discipline of harness engineering . This is the guide we wish existed when we started building agents.

The goal: an AI agent that is fast, scalable, capable, reliable, efficient, and secure — not by accident, but by design.

📖 How to read this guide

Read top-to-bottom for the full mental model. Each section builds on the previous one.

Skim the boxes if you only want the takeaways — every section ends with an Actionable rules box.

Jump to Part 14 — The Build-Your-Own Roadmap if you already know the theory and want a sequenced plan.

Bookmark Part 15 — Anti-Patterns for design reviews.

📋 Table of Contents

⚡ Part 0 — The Core Equation

🧠 Part 1 — Mental Model: What an AI Agent Actually Is

🔄 Part 2 — The Agent Loop (the Kernel)

🛠️ Part 3 — Tools: The Agent's Hands

💭 Part 4 — Context Engineering

💾 Part 5 — Memory (Long-Term Knowledge)

⚡ Part 6 — Concurrency & Multi-Agent…