This mini-symposium aims to provide a focused platform for presenting recent advances and fostering discussion around computational multiphysics using open-source software frameworks. Emphasis is placed on contributions that not only demonstrate progress in physical modeling and numerical algorithms but also provide insights into the design and implementation of robust, extensible, and high-performance software infrastructures. A central objective of the mini-symposium is to showcase developments in established open-source multiphysics platforms—such as OpenFOAM, Alya, Sparselizard, Yales2 among others—and to provide a forum for the communities behind these tools to exchange experiences and ideas. Topics of interest include, but are not limited to, novel coupling strategies for multiphysics problems, algorithmic improvements in time integration and solver technology, and methodological advances in partitioned and monolithic approaches. Particular attention will be given to the challenges of maintaining accuracy, stability, and scalability in strongly coupled systems. In addition to numerical methods, the mini-symposium invites contributions on software engineering practices that enable maintainable and reusable code bases. This includes discussions on modular software architectures, data structures optimized for coupled solvers, integration workflows, and the role of community governance in sustainable development of scientific software. Contributions highlighting the use of open standards, reproducible research workflows, and interfaces for user extensibility are especially welcome. Application-oriented presentations are encouraged, particularly where they highlight the use of open-source multiphysics tools in complex, real-world scenarios. Examples may include fluid–structure interaction, conjugate heat transfer, magneto-hydrodynamics, or coupled processes in biomechanics, geophysics, or energy systems. Submissions that illustrate full simulation pipelines—from geometry and meshing to solver execution and data analysis—are of particular interest when they provide insight into practical bottlenecks or innovative solutions. By bringing together developers, methodologists, and advanced users, this mini-symposium seeks to promote exchange across communities and strengthen collaboration in the open-source multiphysics ecosystem. The session aims to advance shared understanding of current capabilities and identify future directions in the dev