Urban climate action is essential for achieving global sustainability goals, yet cities face complex implementation challenges when pursuing climate neutrality missions. This study examines how inter-city platforms support municipal climate mission implementation, addressing a gap in mission-oriented innovation literature that has focused primarily on policy design rather than practical implementation support. 

The research investigates two inter-city platforms, NetZeroCities and Viable Cities, through 15 semi-structured interviews with platform coordinators and participating civil servants from Swedish cities. Using inductive thematic analysis, the study identifies significant factors affecting implementation success and platform effectiveness. 

Findings reveal that municipal civil servants encounter organizational silos, multi-level governance tensions, resource limitations, and demands for qualities including patience, bravery, and process facilitation skills in navigating institutional resistance. Inter-city platforms provide critical support through relationship building between cities and supporting cities in mobilizing internal stakeholders. However, platforms must carefully balance providing support with avoiding dependency, manage contextual differences between cities, and avoid overwhelming municipalities with excessive programming. 

These findings advance understanding of how inter-city platforms can support transformative urban sustainability initiatives while providing actionable insights for improving platform design and city implementation strategies.