## Deforming Holomorphic Chern-Simons at Large N

We describe the coupling of holomorphic Chern-Simons theory at large N with Kodaira-Spencer gravity. This gives a complete description of open-closed string field theory in the topological B-model. We explain an anomaly cancellation mechanism at all loops in perturbation theory in this model. At one loop this anomaly cancellation is analogous to the Green-Schwarz mechanism. This is joint work with Kevin Costello.