Programmable Branched Flow of Light.

Wave transport in disordered media is obscured by complex multiple scattering, yet prior experiments lack precise, reconfigurable control over microscopic disorder potentials. Using photoaligned nematic liquid crystals, we implement programmable spatial optical potentials to deterministically tailor anisotropic branched light flow. With this platform, we experimentally verify the long-theorized generalized scaling law for the first-branch distance of branched wave transport-an unprecedented experimental milestone validating universal scaling across hydrodynamic, acoustic, atomic, and electronic wave systems. In the extreme anisotropy regime, we observe striking directional light channeling induced by anomalous symmetry-breaking velocity diffusion: light propagates along preferred paths with fully suppressed transverse spreading in disordered media. Our reconfigurable liquid-crystal testbed enables controlled exploration of anisotropic stochastic wave dynamics, paving the way for disorder-guided on-chip photonics, scattering-robust endoscopic imaging, and adaptive optics for complex scattering environments.