• • The combined treatment of Klebsiella aerogenes Wn and hydroxyapatite (8 g·kg−1 HAP + 3.75×10^9 cfu·kg−1 Wn) reduced soil available Cd by 40.2%, demonstrating a significant enhancement over single treatments.
• • Rice grain Cd content decreased to 0.0699 mg·kg−1, which is 65% below the national food safety limit (GB 2762-2022, 0.2 mg·kg−1), ensuring safe crop production.
• • The treatment increased soil available phosphorus by 4%–67% and maintained pH in the range of 5.8–6.7, which are optimal for Cd immobilization and soil health.
• • The formation of a stable cadmium hydroxyapatite mineral [Ca3.9(Ca4.7Cd0.7)(PO4)6(OH)1.8] was confirmed, indicating long-term Cd sequestration potential due to its extremely low solubility (Ksp ~10^-64.62).