The growing oversupply of PhD graduates in the academic labor market has highlighted concerns about employment outcome inequality among PhD holders. However, the mechanisms underlying such disparities remain poorly understood. This qualitative study employs Careership Theory to investigate these mechanisms by examining differences in horizons for action in career planning between working-class and middle-class PhD students. The study includes 94 mainland Chinese PhD students, comprising both current (n = 72) and former (n = 22) students, from leading universities in mainland China, Hong Kong, and Macau. The findings reveal significant disparities in horizons for action influenced by the participants' habitus and its hysteresis. Specifically, working-class PhD students tended to impose more constraints on their future job choices compared to their middle-class peers. They prioritized jobs that offered respectable salaries, aligned with their expertise, and had a less guanxi-oriented environment. With these constraints, their narrower career horizons often lead to a stronger inclination toward pursuing academic careers. Consequently, working-class PhD students face heightened pressure due to increased competition in the academic job market. The study also underscores the role of meritocratic beliefs in sustaining the habitus of working-class students and influencing their career decisions.