Aligning climate and air quality goals demands early VOC control for China's ozone pollution.

Global surface ozone (O3), intensified by climate change, poses increasing health and ecosystem threats. Despite stringent air policies, China's persistent O3 pollution exemplifies a global challenge intertwined with climate actions reshaping emission pathways. Optimal mitigation remains contentious, primarily due to inconsistent conclusions regarding the sensitivity of summer regional O3 formation. Here we show the path dependency in O3 mitigation strategies for synergistic clean air and climate action goal achievement over multidecade scales. This path dependence is validated by observed concurrent plateaus (2020-2023) in deweathered O3 concentrations and sensitivity trends across Chinese megacity clusters. Leveraging this understanding of path dependency, we quantitatively reveal that the optimal future strategy involves prioritizing early volatile organic compound reductions, as their high effectiveness for regional O3 mitigation gradually diminishes towards 2050. This challenges prevailing nitrogen oxides priority paradigms. Our work reframes O3 control, providing a paradigm for resilient air quality-climate governance.