<p>Improving carbon emission efficiency is essential for China’s regional green transition, yet existing studies often evaluate digital-intelligence policies separately and pay insufficient attention to their coordinated effects. This study examines whether the joint implementation of the National Big Data Comprehensive Pilot Zones and the Smart City initiative, referred to as the “Dual Pilot” policy, improves urban carbon emission efficiency. Using panel data for 273 Chinese prefecture-level cities from 2006 to 2023, we employ a staggered difference-in-differences design to identify the policy effect and further examine spatial spillovers, mechanisms, heterogeneity, and policy synergy. The results show that the Dual Pilot policy significantly improves carbon emission efficiency, and this finding remains robust across multiple specification checks. The policy also generates positive spatial spillover effects, indicating that neighboring cities benefit from the coordinated digital-intelligence transition. Mechanism analysis suggests that the improvement is mainly achieved through optimized energy utilization, reduced energy consumption intensity, and strengthened industrial agglomeration. Heterogeneity analysis shows that the policy effect is stronger in cities with higher educational attainment, more supportive cultural conditions, and greater digital innovation capacity. Compared with single-policy implementation, the Dual Pilot approach produces additional synergistic gains, confirming the value of coordinated policy design. These findings suggest that local governments should strengthen cross-policy coordination, enhance digital infrastructure and innovation capacity, and tailor green digital strategies to local human-capital and institutional conditions to promote regional low-carbon development.</p>