Cities are searching for unarmed approaches to disorder and crime. Colombia is a leader here. Police are a national institution, and mayors have limited control over police staffing and operations. Thus, many cities have developed large civilian apparatuses for dispute resolution, family problems, and street disorder—an approach commonly called convivencia (coexistence). Researchers worked with Medellín’s municipal government to identify 80 typical neighborhoods and experimentally evaluate this approach. In half, the city intensified their civilian apparatus for 20 months, assigning full-time liaisons to help communities organize to improve public order, foster communication with the government, and connect residents to dispute resolution and family/social services. A centralized task force ensured city agencies fulfilled these roles. This represented a 60-fold increase in street-level presence, plus increased city agency attention. To the researchers' surprise, Operación Convivencia had no average treatment effect on reported governance, legitimacy, or crime. Anticipating that impacts could diverge by neighborhood, however, the researchers prespecified heterogeneity analyses by initial state presence. This proved revealing. In neighborhoods where the state began weak, the task force and city agencies worked sporadically, and opinions of governance fell. In neighborhoods where the state began relatively strong, the liaisons and task force delivered, and there are indications this raised state legitimacy and reduced crime and emergency calls. The divergent results suggest the importance of existing state capacity, plus the dangers of over-promising and under-delivering. This may be especially important in Latin America, where cities like Medellín compete with gangs for local problem-solving and legitimacy.