A harness sits at L0/L4 (Meta/Orchestration) and is the assembled agent bundle: model + tools + memory + orchestration + policy. It defines how work is done, not just what to do. It wraps an agent or pipeline with lifecycle controls — sequencing steps, enforcing context budgets, persisting checkpoints, and triggering stop conditions. Examples include execution harnesses (GSD, BMAD), test harnesses (Superpowers), and CI/CD harnesses (Harness.io). Not to be confused with the agent or the tools it calls — the harness is the governing scaffold around them.
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