Tessl's Dru Knox on harness engineering: building a software factory where agents write everything
AI Engineer · youtube · 2026-10-06
At AI Engineer World's Fair, Tessl's head of product Dru Knox laid out harness engineering (a.k.a. loop engineering): when agents write everything users get, engineers build the factory instead.
Key points:
- Three metrics define a factory: autonomy, automation, quality — the real payoff is higher quality, not just speed
- Work splits into inner, outer, and meta loops, each improving a different thing
- Why it's hard: the field changes weekly, work is unplanned, and signals are stuck in local logs
- Three layers to build: a control plane, an agent-ready stack, and improvement loops
- Metrics to track: manual takeovers, human PR comments, PRs started without a human
- Showcased Tessl's skills registry, Tessl Agent, and Tessl Launch as a path there
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