This paper presents a unification of interface automata and modal specifications, two radically dissimilar models for interface theories. Interface automata is a game-based model, which allows to make assumptions on the environment and propose an optimistic view for composition : two components can be composed if there is an environment where they can work together. Modal specification is a language theoretic account of a fragment of the modal mu-calculus logic that is more complete but which does not allow to distinguish between the environment and the component. Partial unifications of these two frameworks have been explored recently. A first attempt by Larsen et al. considers modal interfaces, an extension of modal specifications that deals with compatibility issues in the composition operator. However, this composition operator is incorrect. A second attempt by Raclet et al. gives a different perspective …