SK Telecom unveiled its 688 billion-parameter (688B) scale model ‘A.X K2’ on Hugging Face on the 29th, ahead of the government’s second evaluation for its homegrown AI foundation model project. Compared to the previous model A.X K1 (519B), the new model expanded parameters to enhance mathematical and scientific reasoning, knowledge related to Korea, and long-text inference capabilities. The average score across 14 domestic and international benchmarks increased by 32.2 percentage points compared to K1, achieving results comparable to Qwen3.5 and DeepSeek-V4. Performance improvement was driven by the self-developed structure ‘SGA.’ A.X K2 will be sequentially applied to industrial sites, including a manufacturing-specialized AI agent with KG Steel and Connex in the second half of the year. With the Ministry of National Defense, three lightweight models based on K1 were developed for high-security defense environments. In partnership with SK Biopharmaceuticals, AI reduced the initial research period for targeted treatments of intractable cancers from 1–2 years to five months. The lightweight version of A.X K2 has been integrated into the AI secretary ‘A.Dot’ for call summarization and schedule extraction. SK Telecom will provide its AI models via API to government AI competition participants and startups, and join the Ministry of Science and ICT’s “AI for All” project.