  Using the ${\mathcal N}=1$ supersymmetric, spinning worldline quantum field
theory formalism we compute the conservative spin-orbit part of the momentum
impulse $\Delta p_i^\mu$, spin kick $\Delta S_i^\mu$ and scattering angle
$\theta$ from the scattering of two spinning massive bodies (black holes or
neutron stars) up to fourth post-Minkowskian (PM) order. These three-loop
results extend the state-of-the-art for generically spinning binaries from 3PM
to 4PM. They are obtained by employing recursion relations for the integrand
construction and advanced multi-loop Feynman integral technology in the causal
(in-in) worldline quantum field theory framework to directly produce classical
observables. We focus on the conservative contribution (including tail effects)
and outline the computations for the dissipative contributions as well. Our
spin-orbit results agree with N$^3$LO post-Newtonian and test-body data in the
respective limits. We also re-confirm the conservative 4PM non-spinning
results.
