[en] Modular transformations of string theory (including the well-known stringy dualities) play a crucial role in the discussion of discrete flavor symmetries in the Standard Model. They are at the origin of $\mathcal{CP}$-transformations and provide a unification of $\mathcal{CP}$ with traditional flavor symmetries. Here, we present a novel, fully systematic method to reliably compute the unified flavor symmetry of the low-energy effective theory, including enhancements from the modular transformations of string theory. The unified flavor group is non-universal in moduli space and exhibits the phenomenon of “Local Flavor Unification” where different sectors of the theory can be subject to different flavor structures.