  MWC 758 is a young star hosting a spiral protoplanetary disk. The spirals are
likely companion-driven, and two previously-identified candidate companions
have been identified -- one at the end the Southern spiral arm at ~0.6 arcsec,
and one interior to the gap at ~0.1 arcsec. With JWST/NIRCam, we provide new
images of the disk and constraints on planets exterior to ~1". We detect the
two-armed spiral disk, a known background star, and a spatially resolved
background galaxy, but no clear companions. The candidates that have been
reported are at separations that are not probed by our data with sensitivity
sufficient to detect them -- nevertheless, these observations place new limits
on companions down to ~2 Jupiter-masses at ~150 au and ~0.5 Jupiter masses at
~600 au. Owing to the unprecedented sensitivity of JWST and youth of the
target, these are among the deepest mass-detection limits yet obtained through
direct imaging observations, and provide new insights into the system's
dynamical nature.
