Harness Engineering: How to Build a Software Factory — Dru Knox, Tessl

In a software factory, agents write everything your users get. Your engineers build the factory. Dru Knox, head of product and design at Tessl, explains harness engineering (some now call it loop engineering), the discipline that takes a team from using coding agents to running a software factory. He defines a factory by three metrics: autonomy, automation and quality. He breaks the work into inner, outer and meta loops, and explains why harness engineering is hard: the field changes weekly, the work is unplanned, and the signals you need are stuck in local logs. Then he lays out three layers to build, a control plane, an agent-ready stack and improvement loops, and shows how Tessl's skills registry, Tessl Agent and Tessl Launch help you get there one workflow at a time. In this talk: • What a software factory is, and why the real payoff is higher quality, not just speed • Inner, outer and meta loops, and what each one improves • The three layers: control plane, agent-ready infrastructure, improvement loops • Metrics to track: manual takeovers, human PR comments, PRs started without a human SPEAKER Dru Knox, Head of Product & Design, Tessl LinkedIn: https://www.linkedin.com/in/dru-knox-6b57b830/ X: https://x.com/drufball GitHub: https://github.com/drufball LINKS Tessl: https://tessl.io Tessl on X: https://x.com/tessl_io CHAPTERS 0:00 Intro 0:43 Who this talk is for 2:03 What is a software factory? 2:58 Autonomy, automation, quality 4:33 The payoff: higher quality 6:13 Harness engineering 6:43 Inner, outer and meta loops 9:08 Why harness engineering is hard 11:13 The three layers 11:33 Layer 1: the control plane 12:47 Layer 2: making your stack agent-ready 14:22 Layer 3: improvement loops 15:32 How Tessl helps 17:37 Tessl Agent 18:47 Tessl Launch 19:37 Metrics to track Recorded at the AI Engineer World's Fair 2026 in San Francisco. Subscribe for more talks from the engineers building with AI. AI Engineer: https://ai.engineer YouTube: https://www.youtube.com/@aiDotEngineer X: https://x.com/aiDotEngineer LinkedIn: https://www.linkedin.com/company/aidotengineer/ #HarnessEngineering #CodingAgents #AIEngineer