["Behavioral Sciences &the Law, EarlyView. ", "\nABSTRACT\nJuvenile cybercrime is a salient governance challenge in digitalizing societies, yet scholarship concentrates on ex post sanction and under‐theorizes the interaction among platform design, the digital risk environment, and minors' developmental vulnerability. Drawing on K.G.M. v. Meta Platforms, this study develops a “front‐end governance” framework anchored in the best‐interests‐of‐the‐child principle and articulated through three doctrinal pillars, the platform duty of risk mitigation, the regulation of harmful design and risky digital environments, and the foreseeability of risk. An empirical component, based on a cross‐sectional survey in China, examines institutional support for prevention. Endorsement is broad, 92% for strengthened market regulation, 91% for cyber‐law education, 84% for technical firewalls, and 83% for internet classification and digital curfews. On responsibility allocation, 76% prioritize tri‐partite collaborative governance involving families, schools, and society. Multinomial logistic regression indicates occupational positioning is the only significant predictor of priority orientation; regional, income, and educational variation are non‐significant once controls are applied, a null pattern we read as suggestive rather than confirmatory. The findings support a shift from ex post sanction to ex ante risk governance, organized around platform accountability, age‐appropriate design, rule‐of‐law education, and graded content ecosystems.\n"]