This study reports the generation of high-energy proton beams with a spectrally separated high-energy component up to 150 MeV using a petawatt laser and solid-density plastic foil targets. The laser pulses, with ultrashort durations and high intensity, heat the target, leading to relativistically induced transparency. This enables the laser to penetrate the initially opaque target and trigger proton acceleration through a cascade of mechanisms, as confirmed by 3D particle-in-cell simulations. The transmitted laser light, linked to target transparency, serves as a feedback parameter for optimizing laser and target conditions to enhance plasma accelerator stability. Laser-driven ion accelerators offer a compact alternative to conventional accelerators, but achieving sufficient energy levels for applications like radiation therapy remains challenging. This research demonstrates that by matching the initial target thickness to laser parameters, multiple shots under optimal conditions can produce proton beams with energies exceeding 100 MeV. The results show that the maximum proton energy scales with the square root of the laser energy in one direction and linearly in another, indicating different acceleration mechanisms in different directions. The study highlights the role of prompt electrons in facilitating efficient energy transfer from the ultra-intense laser to protons, both during and after the interaction. The identification of target transparency as a simple control parameter for determining the high-performance domain is crucial for future automated laser and target optimization. The results emphasize the potential of compact petawatt-class laser systems to further scale laser-driven ion acceleration to unprecedented energy levels. The findings pave the way for practical applications of laser-driven ion sources in various demanding fields.This study reports the generation of high-energy proton beams with a spectrally separated high-energy component up to 150 MeV using a petawatt laser and solid-density plastic foil targets. The laser pulses, with ultrashort durations and high intensity, heat the target, leading to relativistically induced transparency. This enables the laser to penetrate the initially opaque target and trigger proton acceleration through a cascade of mechanisms, as confirmed by 3D particle-in-cell simulations. The transmitted laser light, linked to target transparency, serves as a feedback parameter for optimizing laser and target conditions to enhance plasma accelerator stability. Laser-driven ion accelerators offer a compact alternative to conventional accelerators, but achieving sufficient energy levels for applications like radiation therapy remains challenging. This research demonstrates that by matching the initial target thickness to laser parameters, multiple shots under optimal conditions can produce proton beams with energies exceeding 100 MeV. The results show that the maximum proton energy scales with the square root of the laser energy in one direction and linearly in another, indicating different acceleration mechanisms in different directions. The study highlights the role of prompt electrons in facilitating efficient energy transfer from the ultra-intense laser to protons, both during and after the interaction. The identification of target transparency as a simple control parameter for determining the high-performance domain is crucial for future automated laser and target optimization. The results emphasize the potential of compact petawatt-class laser systems to further scale laser-driven ion acceleration to unprecedented energy levels. The findings pave the way for practical applications of laser-driven ion sources in various demanding fields.