In production AI, the language model is a commodity; the real differentiation lies in the scaffolding. Harness engineering is the discipline of building the infrastructure that wraps, controls, and guides agents—especially on long-horizon tasks. We’ll explore how harnesses work under the hood—covering context management, safety guardrails, automated backpressure, and memory—and share hands-on techniques in Google Antigravity using AGENTS.md, modular skills, and hooks. Learn how harness engineering can make agentic workflows predictable, debuggable, and safe.