# Which Agent's Skill Should Change? Group-Relative Credit Assignment for Evolving Multi-Agent Teams > Source: > Published: 2026-10-22 02:00:27+00:00 Cooperative language-model agents can improve without weight updates by revising reusable skills, but only if a shared team reward is traced to the responsible agent and skill. Existing methods credit the skills present in each trajectory, yet presence is not responsibility: a harmful skill active i