Qwen models are specifically optimized to perform best within the Qwen-Code harness compared to other coding agent harnesses.

Raschka cites Nvidia's Polar benchmark showing Qwen3.5-4B performs best specifically within the Qwen-Code harness, supporting his choice to pair Qwen models with Qwen-Code. ✦ AI generated

Sebastian Raschka · Ahead of AI · 2026-06-27 · original ↗

Regarding the second point in the list above, that Qwen models work better in Qwen-Code, Nvidia's Polar: Agentic RL on Any Harness at Scale paper (May 2026) has a benchmark showing that the Qwen3.5-4B base model has the best coding performance in said Qwen-Code harness (both before and after their Polar-RL training), which I included below.

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