A general aim of this project is to set-up a new software framework that can be extended in phases with existing and new functionalities. FCC-ee will serve as the basis to evaluate the key requirements for such a framework and identify potential bottlenecks in the simulations. Two key challenges will be addressed in parallel, each needing input from the other, in order to help understand how they can be addressed efficiently in a single framework. The concept of the software framework should be developed in a sustainable way, providing a modular structure and extendibility in a collaborative approach. Open source software projects have demonstrated collaboration of a large number of developers in a systematic and very successful manner. The framework should allow easy utilization of modern computer science developments, in particular parallelization of numerical computations, advanced optimization techniques and scripting capabilities. The framework is aimed to be a tool for accelerator design work with a broad range of applications. The basic functionality that shall be implemented from the start includes beam-beam effects and 6D particle tracking simulations. This will allow to address the physics goals relevant for FCC-ee and mentioned in the second part of this project description, in particular radiation effects, beam-beam interactions and lattice non-linearities.