  We identify the auxiliary fields in the hypermultiplets of type IIB string
theory compactified on a Calabi-Yau manifold, using a combination of worldsheet
and supergravity techniques. The SUSY-breaking squark and gaugino masses in
type IIB models depend on these auxiliary fields, which parametrize
deformations away from a pure Calabi-Yau compactification to one with NS-NS
3-form flux and SU(3) x SU(3) structure. Worldsheet arguments show that such
compactifications are generically globally nongeometric. Our results, combined
with earlier results for type IIA compactifications, imply that these
deformations are the mirrors of NS-NS 3-form flux, in accord with work from the
supergravity point of view. Using the worldsheet current algebra, we explain
why mirror symmetry may continue to hold in the presence of fluxes breaking the
symmetries (e.g., (2,2) SUSY) on which mirror symmetry is typically taken to
depend. Finally, we give evidence that nonperturbative worldsheet effects (such
as worldsheet instantons) provide important corrections to the supergravity
picture in the presence of auxiliary fields for Kahler moduli.
