The derived symmetries associated to a 3-fold admitting an Atiyah flop may be organised into an action of the fundamental group of a sphere with three punctures, thought of as a stringy Kaehler moduli space. I extend this to general flops of irreducible curves on 3-folds in joint work with M. Wemyss. This uses certain deformation algebras associated to the curve and its multiples, with applications to Gopakumar-Vafa invariants.