China's Nuclear Modernisation and the Dynamics of the Stability–Instability Paradox in U.S.–China Strategic Competition

China's rapid nuclear modernisation is reshaping crisis dynamics in East Asia in ways that reflect a contemporary form of the stability–instability paradox. As Beijing moves toward a more diverse and survivable second-strike capability, strategic nuclear stability with the United States may become firmer in relative terms, even as coercive pressure and grey-zone activity around Taiwan intensify. This paper situates China within competing interpretations of the paradox, contrasting the classic Snyder–Jervis model with arguments that some states deliberately manipulate nuclear risk, as seen in Pakistan and in Russia's conduct during the Ukraine war. The analysis does not claim that nuclear modernisation initiates coercion, which has older roots, but that improving retaliatory survivability can condition how coercion is sustained, calibrated, and risk-managed under heightened escalation stakes. China is pursuing neither open brinkmanship nor a static form of minimal deterrence. Instead, it is building a nuclear backstop that supports prolonged competition below the threshold of major war. Evidence from China's missile expansion, silo construction, sea-based forces, and regional military behaviour shows how a firmer nuclear ceiling can coexist with recurrent lower level instability. The paper concludes with implications for U.S. crisis management and regional deterrence in the Taiwan Strait.