DarwinX: Evolving Agent Harnesses Through Natural Selection

Treats agent self-evolution as selection over a population of harnesses (prompts, tools, skills, control flow) with the model weights frozen, using a natural-selection-style loop to evolve the harness rather than the underlying model. Frames agent capability as a function of both weights and harness, and demonstrates harness-only evolution as a model-agnostic self-improvement lever.