In this paper, we showcase a method of identifying opportunities during the lesson where the communicational patterns go beyond the mathematics of the moment, namely beyond the boundaries of the curriculum. Drawing on the literature around Horizon Content Knowledge and building on the Theory of Commognition, we look at a lesson from one teacher and study instances where her communication with the students goes beyond the mathematics of the moment. Our analysis identifies three types of opportunities (manifested, potentials of the discussion and potentials of the task). Further analysis of manifested opportunities indicates that intersubjectivity is a characteristic of the discourse of the teacher at the mathematical horizon.