<p>The rapid advancement of the thin-film lithium niobate (LiNbO₃) platform has established it as a premier choice for high-performance photonics integrated circuits. However, the scalability and cost-efficiency of this platform are hindered by the reliance on chip-level fabrication and integration for passive and active components, necessitating a robust wafer-level LiNbO₃ heterogeneous integration platform. Despite its critical role in enabling ultrahigh-speed optical interconnects, as well as optical mmWave/THz sensing and communication, the realization of ultrahigh-speed photodiodes and optical coherent receivers on the LiNbO₃ platform remains an unresolved challenge. This is primarily due to the challenges associated with the large-scale integration of direct-bandgap materials. To address these challenges, we have developed a scalable, high-speed InP-LiNbO₃ wafer-level heterogeneous integration platform. This platform facilitates the fabrication of ultrahigh-speed photodiodes with a bandwidth of 140 GHz, capable of receiving high-quality 100-Gbaud pulse amplitude modulation (PAM4) signals. Moreover, we demonstrate a seven-channel, single-polarization I–Q coherent receiver chip with an aggregate receiving capacity of 3.584 Tbit s^-1. This coherent receiver exhibits a balanced detection bandwidth of 60 GHz and a common mode rejection ratio (CMRR) exceeding 20 dB. It achieves receiving capacities of 600 Gbit s^-1 λ^-1 with a 100-Gbaud 64-QAM signal and 512 Gbit s^-1 λ^-1 with a 128-Gbaud 16-QAM signal. Furthermore, energy consumption as low as 9.6 fJ bit^-1 and 13.5 fJ bit^-1 is achieved for 200 Gbit s^-1 and 400 Gbit s^-1 capacities, respectively. Our work provides a viable pathway toward enabling Pbps hyperscale data center interconnects, as well as optical mmWave/THz sensing and communication.</p>