DeepSeek, the Chinese AI startup, faced its longest outage, lasting over seven hours on Sunday. Users reported issues starting at 9:35 p.m., with the initial resolution marked two hours later, although performance issues persisted until 10:33 a.m. the next day. The cause remains undisclosed, with DeepSeek previously boasting a 99% operational record since January 2025. The disruption raises concerns about its competitive edge amid rapidly evolving rivals like ChatGPT and Alibaba.