The complex moisture–oxygen environment in air places stringent demands on surface passivation for air-processed perovskite solar cells. However, most conventional ammonium ligand-based passivation, which binds to the perovskite surface through a terminal site, often induces ligand intercalation, elevates interfacial resistance, and compromises environmental stability, thereby limiting efficient device fabrication under ambient conditions. In this study, we report a robust, ligand-based, intermediate-site anchoring strategy for nonlayered interfacial passivation using a series of choline derivatives. The thioacyl sulfur coordinates strongly with under-coordinated Pb2+ sites, while iodide counter-anions assist in halide vacancy healing, collectively forming a thermally robust and electronically homogeneous top interface. The surface passivation homogenizes surface potential, optimizes band alignment, relaxes residual strain, and suppresses trap-assisted recombination and halide migration. Consequently, the resulting perovskite solar cells achieve a power conversion efficiency (PCE) of 26.54%, the highest value for air-processed n–i–p PSCs reported so far. These devices also retained over 90% PCE after 2000 h at 65°C and 90% under continuous maximum power point tracking for 1000 h (AM 1.5G, 40°C ± 1°C), with projected T80 lifetimes of ∼9800 h under illumination and ∼11 000 h under thermal aging, among the most stable air-processed perovskite solar cells reported to date.