  Strings on AdS3xS3xT4 with mixed Ramond-Ramond and
Neveu-Schwarz-Neveu-Schwarz flux are known to be classically integrable. This
is a crucial property of this model, which cannot be studied by conventional
worldsheet-CFT techniques. Integrability should carry over to the quantum
level, and the worldsheet S matrix in the lightcone gauge is known up to the
so-called dressing factors. In this work we study the kinematics of mixed-flux
theories and consider a relativistic limit of the S matrix whereby we can
complete the bootstrap program, including the dressing factors for fundamental
particles and bound states. This provides an important test for the dressing
factors of the full worldsheet model, and offers new insights on the features
of the model when the amount of NSNS flux is low.
