Stronger models do not always need lighter harnesses. Everyone believes more structured harnesses universally improve reliability, and that …

Stronger models do not always need lighter harnesses. Everyone believes more structured harnesses universally improve reliability, and that higher-capability models need proportionally less structural guidance. Together, that implies a clean inverse relationship between model tier and optimal harness complexity. This new research tests it with a controlled 432-run experiment, six models across four capability tiers crossed with three harness conditions, on a 24-task benchmark with git-based workspace verification. For a frontier chat model, increasing harness verbosity dropped success by 29 to 38 percentage points. They call it the harness-complexity paradox. Paper: https://arxiv.org/abs/2605.26731 Learn to build effective AI agents in our academy: https://academy.dair.ai/

Source: DAIR.AI (X) | 2026-05-27