The Model Stayed Frozen. The Agent Got Better.
TL;DR for operators Designer-RSI shifts one production decision: improving an agent does not always require improving its foundation model. The paper keeps the model, tools, renderer, and evaluator frozen and instead changes an external library of reusable operating procedures. The strongest evidence is not simply that the library grows. On a fixed 200-brief ablation, adding new procedures alone produced a 49.4% win rate against the base agent, while rewriting existing procedures reached 48.6%. Combining both reached 58.5%, with completeness rising to 74.04. The operational lesson is that continual adaptation looks less like accumulating prompts and more like maintaining a system with separate processes for coverage, repair, retrieval, testing, and release. ...