Nobody knows which agent broke the multi-agent system.

arXiv 2607.07989 formalizes failure localization as its own research problem: identifying which agent is responsible and the exact step where the trajectory became irreversibly misdirected. Anyone running a fan-out of research or coding agents has lived this. The output is bad. The trace is 40,000 tokens. There's no obvious fault line. Treating this as a first-class problem rather than a debugging afterthought is overdue.