SiC_f/SiC cladding tubes were joined to end plugs using Y₂O₃–Al₂O₃–SiO₂ (YAS) glass filler through localized rapid induction heating at 1400–1500 °C. The joint fabricated at 1450 °C exhibited a dense and uniform glass–ceramic interlayer with the highest nominal burst pressure of 70.3±10.0 MPa. A high joining temperature of 1500 °C suppressed the crystallization of the glass filler. Hydrothermal corrosion tests conducted at 360 °C and 18.6 MPa for 9 d revealed that both the interfaces on the end plug side and the cladding tube side were susceptible to corrosion, with more severe degradation occurring on the cladding tube side. The residual pyrolytic carbon (PyC) layer on the inner surface of the cladding tube facilitates indirect bonding between the filler and the tube. The resulting interfacial structure is unstable under hydrothermal conditions, leading to localized corrosion, void formation, and interfacial debonding. After corrosion, the joint retained a nominal burst pressure of 62.4±7.6 MPa. These results demonstrate that controlling interfacial structure and minimizing surface impurities are essential for improving the hydrothermal corrosion resistance and long-term reliability of SiC_f/SiC cladding joints.