TL;DR There is no single model of harness engineering. OpenAI builds repository-centered harnesses, Anthropic focuses on agent cognitive continuity, while companies like Stripe, Shopify, and Airbnb develop vertical harnesses built around compliance, context, and action verification. Harness engineering is becoming a domain-specific discipline, shaped by the type of risk each company needs to control. Why There Is No Single Harness: Stripe, Shopify, Airbnb, and the Industrial Fragmentation of Agent Engineering After observing OpenAI's repository harness and Anthropic's runtime harness (if you haven't done so already, read my articles: OpenAI and the New Cognitive Architecture of Software Repositories e Anthropic and the Runtime Harness for Persistent Agents ), one might expect the industry to be converging toward a fairly clear formula: define memory, tools, feedback loops, constraints, and let the agents work.…