Point-of-care diagnostics and inline quantitative phase imaging drive the demand for portable, ultra-miniaturized, robust optical imaging and metrology systems. This paper proposes and demonstrates a wavefront sensor integrated into a photonic integrated circuit, enabling single-shot optical phase retrieval. We implemented an integrated wavefront sensor array with a spatial resolution of 17 μm and a high numerical aperture of 0.1. Furthermore, we experimentally demonstrated the reconstruction of wavefronts defined by Zernike polynomials, specifically the first 14 terms (Z1 to Z14), achieving an average root mean square error below 0.07. This advancement paves the way for fully integrated, portable, and robust optical imaging systems, facilitating integrated wavefront sensors in demanding applications such as point-of-care diagnostics, endoscopy, in situ quantitative phase imaging, and inline surface profile measurement.