Two-octave-spanning precision dispersive mirror systems are demonstrated, providing a new enabling technology for pulse-energy and bandwidth scaling of sub-cycle optical waveform synthesizers. We propose and characterize new dispersion management schemes with advanced dielectric coating designs. Based on an analytic dual adiabatic matching structure, we implement a chirped dichroic mirror, to efficiently optimize the beam combining from different spectra, and a double-chirped mirror pair, to avoid unwanted nonlinearity during beam propagation, with custom-tailored dispersion and reflectivity over more than two octaves of bandwidth ranging from 0.49 to 2.3 μm, supporting 1.9-fs-short sub-optical-cycle pulses. The multilayer coating structures can also be applied to the design of chirped-fiber Bragg gratings and general optical filters. The proposed designs and schemes will benefit ultrabroadband applications requiring precise dispersion management, especially enabling the generation of intense sub-optical-cycle light transients