Harness vs. Loop Engineering: The Two Distinct Problems in Building Reliable AI Agents
goyalshaliniuk · x · 2026-10-04
The author argues that building reliable AI agents requires distinguishing two engineering layers:
- Harness Engineering: focuses on the environment of a single agent run — providing the right context, prompts, tools, sub-agents, constraints, tests, observability, and verification so one execution is reliable and repeatable.
- Loop Engineering: operates one level up, across repeated runs — defining a goal, checking progress after each execution, evaluating completion, watching time and token budgets, retrying, updating state, and deciding whether to continue or stop.
Core takeaway: getting an agent to complete a task is easy; making it keep working, self-check, recover, and know when to stop is a fundamentally different engineering problem that the two disciplines address separately.
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