AbstractThe common formal methods workflow consists of formalising a model followed by applying model checking and proof techniques. Once an appropriate level of certainty is reached, code generators are used in order to gain executable code. In this paper, we propose a different approach: instead of generating code from formal models, it is also possible to embed a model checker or animator into applications in order to use the formal models themselves at runtime. We present a Java API to the ProB animator and model checker. We describe several case studies that use this API as enabling technology to interact with a formal specification at runtime.