This book constitutes the refereed proceedings of the tracks and workshops which complemented the 19th European Conference on Software Architecture, ECSA 2025, held in Limassol, Cyprus, during September 15–19, 2025. The 13 full papers and 19 short papers presented in this volume were carefully reviewed and selected from 56 submissions. They are grouped into the following topics: Tools and Demos; Tutorial; Doctoral Symposium; 1st International Workshop on AI-Assisted Software Architecting (AISA); 5th International Workshop on Agility with Microservices Programming (AMP); 1st International Workshop on Architecting Digital Twin of an Organization (ArchDTO); 12th Workshop on Adaptive and Reconfigurable Systems and Architectures (AROSA); 8th International Workshop on Context-Aware, Autonomous and Smart Architectures (CASA); 1st International Workshop on Software Architecture for Data-Intensive Systems (SADIS).