Building on earlier staging frameworks, the authors highlight challenges in applying transdiagnostic staging models to the diverse and complex presentations commonly seen in young people. They introduce the concept of within-stage heterogeneity, recognising that individuals at the same clinical stage may differ substantially in symptom profiles, functioning, cognitive difficulties, and treatment needs. To address this, they propose the use of stage modifiers, which capture factors related to illness progression and extension, including comorbidities, neurocognitive difficulties, physical health conditions, and psychosocial complexity. Overall, the paper advances a more nuanced and clinically informative staging framework that aims to support personalised care, improve treatment planning, and enhance prediction of illness trajectories in youth mental health.