Complexity in Health, Education, and Social Support for Children and Young People With Life-limiting Conditions.

Children and young people (CYP) with life-limiting conditions represent a growing population with complex care needs that span health, education, and social care systems. These children often have multiple diagnoses, rely on medical technologies, and experience prolonged trajectories of illness. Despite this, care remains fragmented, services are poorly integrated, and definitions of "complexity" are variable, inconsistent, and inadequately reflect the lived experience of families and the perspectives of professionals. The CHESS (Complexity in Health, Education, and Social Support) study aims to develop a shared, evidence-informed understanding of "complexity" in the context of CYP with life-limiting conditions. The study will be delivered by a multi-disciplinary, multisectoral research team and is funded by a National Institute for Health and Care Research (NIHR) Programme Development Grant. This research will provide the foundational work to inform the design and implementation of a future NIHR Programme Grant focused on the development and testing of a child-centred, nationally applicable case mix classification system to support integrated multisector care and resource allocation. This qualitative study involves two stages. Stage 1 consists of semi-structured interviews with (i) CYP aged 5-17 years with a life-limiting condition, (ii) parents/carers (including bereaved parents and parents of children aged under 5 years), and (iii) professionals across healthcare, social care, and education sectors. These interviews aim to elicit stakeholder understandings of "complexity," how it is experienced and enacted in care, and the implications for service access, coordination, and outcomes. Stage 2 comprises a series of stakeholder workshops to review, refine, and synthesise findings from Stage 1 and a parallel realist review. Using consensus methods including the Nominal Group Technique, the workshops will co-develop a cross-sectoral conceptual definition of "complex