A Coding Agent's Harness Can Triple Its Cost Without Making It More Accurate, Study Finds
VentureBeat, Friday, October 23rd, 2026
Study of Claude Code, OpenCode and mini-SWE-agent on fixed models finds harnesses change cost up to 3x with little accuracy difference.
Shandong University researchers held models fixed and compared three coding harnesses on 492 SWE-bench Verified tasks, finding Claude Code and the minimalist mini-SWE-agent statistically equivalent while OpenCode trailed by up to 9 points.
On the hardest tasks, switching harnesses flipped about 13% of outcomes, roughly the same as simply rerunning a setup.
Cost per task varied up to threefold, largely from fixed context overhead of 16,581 tokens in Claude Code versus 829 in mini-SWE-agent, repeated on every step.
The authors advise running baselines twice, trimming system prompts and tool schemas, and tuning reasoning budgets per model-harness pair.