Tuning a Local Qwen Coding Agent: What Changed, What Still Fails

On eight development coding cases repeated three times, a local Qwen3.8-27B agent went from 5/24 to 23/24 functional and delivered successes across sequential output-budget and reasoning rounds. That is promising development evidence. It does not establish generalization or show that xhigh alone caused the difference. The next experiment was less encouraging: lowering temperature to 0.8 on two selected difficult cases preserved 5/6 functional successes but reduced delivered successes to 4/6. The reused temperature-1.0 controls scored 5/6 on both metrics.