What hidden symmetries live at the edges of spacetime?

BF theory is a topological framework for understanding gravity and gauge fields. This work reveals the quantum structure that emerges at the corners and edges of spacetime regions—analogous to finding hidden symmetries at a boundary. In the abelian (simplest) case, the corner algebras match familiar oscillator patterns; in the non-abelian case, the picture is more complex and reveals obstructions in constructing the full set of physical states.