Overview
Model quality is only one component of agent performance. An excellent model with poor instructions, missing tools, unmanaged context, or unsafe permissions can still perform badly. Conversely, a well-designed harness can reduce wasted search, expose capabilities the model would otherwise overlook, and make long-running work more reliable.
The harness also determines the system's risk profile. Terminal access, browser control, file deletion, network access, and autonomous execution can create significant leverage, but each capability expands the consequences of a mistake. Permission design is therefore not a separate concern from productivity. It is part of the harness itself.