Nice paper from Salesforce on co-evolving harnesses and models. Harness engineering is a hot topic right now. So this is a great read. (bookmark it) Salesforce evolved a harness with a weak model across seven enterprise agent tasks, then trained that model on a stronger expert's full trajectories under the same harness. Performance dropped on all seven tasks, by 4 to 30 points across Qwen3-Coder and Gemma 4. The same fine-tuning helps under the unevolved harness. So the harness is what…