A.X LLM Series
SK Telecom’s proprietary Korean-specialized large language models
A.X LLM is a series of Korean-specialized large language models independently developed by SK Telecom. A.X K1, A.X 4.0, and A.X 3.1 are publicly available as open source and can be freely used for academic research and commercial purposes.
Project Information
- Developer: SK Telecom
- License: Apache-2.0
- GitHub:
- Hugging Face:
Key Features
A.X K1 Series
- 519B-A33B Sparse MoE: A large-scale Mixture-of-Experts model with 519B total parameters and 33B active parameters per token
- Hybrid Reasoning Control: Think / Non-Think modes allow users to choose between deeper reasoning and lower latency
- Long-context support: Supports a 131,072-token context length
- Multilingual and code tokenizer: BBPE-based tokenizer optimized for Korean, English, Chinese, Japanese, Spanish, and code data
A.X 4.0 Series
- 72B model: Optimized for large-scale Korean language processing
- 7B Light Model: Efficient lightweight model
- Korean token efficiency: ~33% improvement over GPT-4o
- Real-world deployment: Used in SK Telecom’s A. call summary service
A.X 3.1 Series
- 34B model: Independently developed sovereign AI model
- Light Model: Lightweight version
- Significantly enhanced coding and mathematical reasoning capabilities
- KMMLU benchmark: 69.20 points (~88% of A.X 4.0 performance)
A.X 4.0-VL-Light
- Vision-Language model: Integrated image and text processing
- Multimodal AI: Capable of understanding and analyzing visual information
Technical Achievements
Korean Language Processing Capabilities
- Excellent performance on KMMLU (Korean Massive Multitask Language Understanding)
- Specialized in Korean conversation, document understanding, and summarization
- Optimized for Korean business environments
Model Architecture
- A.X K1: A from-scratch 519B-A33B proprietary Sparse MoE model
- A.X 3 series: Sovereign AI developed from scratch
- A.X 4 series: Open-source models enhanced with CPT (Continual Pre-Training) using large-scale Korean data
Use Cases
SK Telecom Internal Services
- A. call summary service (since May 2025)
- Customer service chatbots
- Internal document analysis and search
Potential Applications
- Korean conversational AI services
- Text generation and summarization
- Translation and sentiment analysis
- Code generation and mathematical problem solving
- Korean content creation
Benchmark Performance
| Model | Parameters | KMMLU Score | Features |
|---|---|---|---|
| A.X K1 | 519B-A33B | 80.2 (Thinking Mode) | Sparse MoE, long context |
| A.X 4.0 | 72B | 78.3 | High performance |
| A.X 3.1 | 34B | 69.2 | Independently developed |
| A.X 4.0 Light | 7B | - | Efficiency |
| A.X 3.1 Light | - | - | Lightweight |
Resources
- A.X K1: GitHub / Hugging Face
- A.X K1 Technical Report: arXiv:2601.09200
- Hugging Face: SKT-AI Organization
- GitHub: SKT-AI
- Official News: SK Telecom Newsroom
- Contact: a.x@sk.com
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