This study examines whether Smart Food Safety Management System practices help convert critical success factors into carbon neutral and broader sustainability gains in export oriented agri food firms. We surveyed 243 manufacturers in China and Viet Nam and analysed the data with confirmatory factor analysis and structural equation modelling. Results show two patterns. Critical success factors such as leadership support, skilled people, infrastructure, and supply chain integration improve sustainability outcomes. They also foster deeper SMART FSMS routines that further raise environmental, social, and economic performance. The evidence supports a partial mediation in which SMART FSMS carries part of the effect from the enablers to performance. Integration with trading partners shows the strongest association with carbon related gains, while early infrastructure spending can weigh on margins in the short run. The study reframes SMART FSMS as a digital capability in the TOE lens and offers clear steps for managers and policymakers that align safety audits with low carbon goals.