We demonstrate an optical hitless bypass switch based on nanomechanical proximity perturbation for high-bitrate transparent networks. Embedded in a single-level pi-imbalanced Mach-Zehnder interferometer, the two nanomechanical-based Deltabeta-directional couplers permit broadband signal rerouting on-chip, while the selected wavelength remains unaffected at all times for optical filter reconfiguration. The optical hitless switch is implemented in the silicon nanophotonics platform, with experimental measurements matching well with numerical and theoretical modeling.