<p>Leveraging the hyperconnectivity, geographical proximity, and comparative advantages of industrial structures among cities within urban agglomerations to promote cross-city symbiosis offers an effective and affordable approach in facilitating sustainable transition in cities to achieve the Sustainable Development Goals (SDGs). However, the effects of cross-city symbiosis featuring substantial plant diversity remain unknown. Focusing on the typical Beijing-Tianjin-Hebei urban agglomeration in China, our analysis reveals significant spatial mismatch between solid waste generation and co-consumption capacity across cities. The trade-offs among multiple SDGs across 160,875 symbiotic pathways under 322,772 constraints are fully considered to address pollution transfer issues stemming from cross-city symbiosis. Results show that in the optimized strategy, transboundary cooperation can further unlock 26.5% of waste co-consumption ability, contribute an additional 30.6% reduction in CO₂ emissions, avoid 24.7% disease cases from air pollution, and increase 35.5% of economic profits. The benefits vary significantly among cities, with industrial cities benefiting more than service-oriented ones. Even in the optimized strategy, pollution transfer among cities cannot be entirely avoided, highlighting the need for a top-down cross-city compensation mechanism. Subsequently, we propose a locally adapted (city-by-city and plant-by-plant) cross-city symbiosis plan. It provides scientific foundations for promoting refined and actionable symbiosis strategies for urban agglomerations worldwide.</p>