Postgraduate education is commonly conceptualised as a counter-cyclical investment, with application demand expected to rise during periods of labour market uncertainty. Using a regime-aware diagnostic approach, this study examines whether this relationship remains stable during China’s transition from prolonged expansion to policy-guided recalibration. Drawing on national-level time-series data (2006–2025) and an ex ante policy-regime indicator, the analysis combines descriptive trend examination with out-of-sample forecast diagnostics. The results reveal a pronounced divergence between post-2023 application outcomes and the trajectory implied by expansion-period associations: applications in 2024 and 2025 fall well below the 95% prediction intervals, even as the potential applicant base continues to expand. This pattern indicates a regime-consistent departure from historically observed counter-cyclical dynamics rather than a demographic contraction. While the analysis is diagnostic rather than causal, the findings suggest that the stability of educational investment patterns may be contingent on broader policy environments, underscoring the need for future validation using longer time series or micro-level data.