• MS-SOFCs emerge as Gen-III architecture targeting 500–700°C operation, balancing high performance and mechanical robustness.
• Integration of multiscale simulations with experiments establishes benchmarks for thin electrolytes, MIEC cathodes, and corrosion-resistant metal substrates.
• Key degradation mechanisms such as chromium poisoning and interfacial instability are addressed via plasma spraying and in situ sintering.
• System-level priorities—thermal management, gas transport, and scalable fabrication—are critical for sub-600°C commercial deployment.