  Angle-twisting engineering has emerged as a powerful tool for modulating
electronic properties in van der Waals heterostructures. Recent theoretical
works have predicted the modulation of spin texture in graphene-based
heterostructures by twist angle, although an experimental verification is
missing. Here, we demonstrate the tunability of the spin texture and associated
spin-charge interconversion with twist angle in WSe$_2$/graphene
heterostructures by using spin precession experiments. For specific twist
angles, we experimentally detect a spin component radial with the electron's
momentum, in addition to the standard orthogonal component. Our results show
that the helicity of the spin texture can be reversed by angle twisting,
highlighting its critical role on the spin-orbit properties of WSe$_2$/graphene
heterostructures and paving the way for the development of novel
spin-twistronic devices.
