CaSPER: A programming environment for development and integration of constraint solvers. CaSPER is a C++ library for generic constraint solving which aims to be efficient, extensible and easy to understand. It currently features: A clean implementation of the set of idioms proved useful for constraint solving such as event-driven execution, callback scheduling, garbage collection, trail-aware generic data structures, etc. Full control over many aspects of the solving process such as propagator scheduling, search strategies, low-level domain implementation selection, and more. Powerful interface for adding new constraints due to efficient domain delta information availability (information about what has changed in the variable’s domains). Powerful interface for adding new reasoning domains. Constructs for modeling search available directly in C++ (a la OPL). Builtin modules for finite domain variables, finite set domain variables, graph domain variables, generic (possibly real-valued) interval-based reasoning and for 3d space reasoning. A black-box solver for problems expressed in CSPXML. Competitive performance compared with other state-of-the-art solvers.