We report on the generation of a multi-octave, phase-stable continuum from the output of a Yb:YAG regenerative amplifier delivering 1-ps pulses with randomly varying carrier-envelope phase (CEP). The intrinsically CEP-stable spectral continuum spans from 450 nm to beyond 2500 nm, covering a spectral range of about 0.6 PHz. The generated coherent broadband light carries an energy of 4 μJ, which can be scaled to higher values if required. The system has been designed and is ideally suited for seeding broadband parametric amplifiers and multichannel synthesizers pumped by picosecond Yb:YAG amplifiers, obviating the need for active timing synchronization required in previous approaches. The presented concept paves the way to cost-effective, reliable all-Yb:YAG single-cycle sources with terawatt peak-power and tens-of-Watts average power.