Coding Agent Harness: Same Model, 2x the Cost
Everyone compares coding agents by asking which model is better. Three independent studies published in the first half of September suggest that is the wrong question. The bigger lever is the harness, and accepting the default can double your bill for the same result, or worse. All three landed within 10 days: HarnessTax from UC Berkeley and Arena (September 16), a 43-page arXiv paper (September 17), and an independent benchmark running nine harnesses against a local model on a laptop (September 10). They agree with each other. ...