A.X-4.0-Light

A.X 4.0 Light

<p align="center"> <picture> <img src="./assets/A.X_logo_ko_4x3.png" width="45%" style="margin: 40px auto;"> </picture> </p> <p align="center"> <a href="https://huggingface.co/collections/skt/ax-4-68637ebaa63b9cc51925e886">🤗 Models</a> | <a href="https://sktax.chat/chat">💬 Chat</a> | <a href="https://github.com/SKT-AI/A.X-4.0/blob/main/apis/README.md">📬 APIs (FREE!)</a> | <a href="https://github.com/SKT-AI/A.X-4.0">🖥️ Github</a> </p>

A.X 4.0 Family Highlights

SK Telecom released A.X 4.0 (pronounced "A dot X"), a large language model (LLM) optimized for Korean-language understanding and enterprise deployment, on July 03, 2025. Built on the open-source Qwen2.5 model, A.X 4.0 has been further trained with large-scale Korean datasets to deliver outstanding performance in real-world business environments.

• Superior Korean Proficiency: Achieved a score of 78.3 on KMMLU, the leading benchmark for Korean-language evaluation and a Korean-specific adaptation of MMLU, outperforming GPT-4o (72.5).
• Deep Cultural Understanding: Scored 83.5 on CLIcK, a benchmark for Korean cultural and contextual comprehension, surpassing GPT-4o (80.2).
• Efficient Token Usage: A.X 4.0 uses approximately 33% fewer tokens than GPT-4o for the same Korean input, enabling more cost-effective and efficient processing.
• Deployment Flexibility: Offered in both a 72B-parameter standard model (A.X 4.0) and a 7B lightweight version (A.X 4.0 Light).
• Long Context Handling: Supports up to 131,072 tokens, allowing comprehension of lengthy documents and conversations. (Lightweight model supports up to 16,384 tokens length)

Performance

Model Performance

<table><thead> <tr> <th colspan="2">Benchmarks</th> <th>A.X 4.0</th> <th>Qwen3-235B-A22B<br/>(w/o reasoning)</th> <th>Qwen2.5-72B</th> <th>GPT-4o</th> </tr></thead> <tbody> <tr> <td rowspan="6">Knowledge</td> <td>KMMLU</td> <td>78.32</td> <td>73.64</td> <td>66.44</td> <td>72.51</td> </tr> <tr> <td>KMMLU-pro</td> <td>72.43</td> <td>64.4</td> <td>56.27</td> <td>66.97</td> </tr> <tr> <td>KMMLU-redux</td> <td>74.18</td> <td>71.17</td> <td>58.76</td> <td>69.08</td> </tr> <tr> <td>CLIcK</td> <td>83.51</td> <td>74.55</td> <td>72.59</td> <td>80.22</td> </tr> <tr> <td>KoBALT</td> <td>47.30</td> <td>41.57</td> <td>37.00</td> <td>44.00</td> </tr> <tr> <td>MMLU</td> <td>86.62</td> <td>87.37</td> <td>85.70</td> <td>88.70</td> </tr> <tr> <td rowspan="3">General</td> <td>Ko-MT-Bench</td> <td>86.69</td> <td>88.00</td> <td>82.69</td> <td>88.44</td> </tr> <tr> <td>MT-Bench</td> <td>83.25</td> <td>86.56</td> <td>93.50</td> <td>88.19</td> </tr> <tr> <td>LiveBench^2024.11</td> <td>52.30</td> <td>64.50</td> <td>54.20</td> <td>52.19</td> </tr> <tr> <td rowspan="2">Instruction Following</td> <td>Ko-IFEval</td> <td>77.96</td> <td>77.53</td> <td>77.07</td> <td>75.38</td> </tr> <tr> <td>IFEval</td> <td>86.05</td> <td>85.77</td> <td>86.54</td> <td>83.86</td> </tr> <tr> <td rowspan="2">Math</td> <td>HRM8K</td> <td>48.55</td> <td>54.52</td> <td>46.37</td> <td>43.27</td> </tr> <tr> <td>MATH</td> <td>74.28</td> <td>72.72</td> <td>77.00</td> <td>72.38</td> </tr> <tr> <td rowspan="3">Code</td> <td>HumanEval+</td> <td>79.27</td> <td>79.27</td> <td>81.71</td> <td>86.00</td> </tr> <tr> <td>MBPP+</td> <td>73.28</td> <td>70.11</td> <td>75.66</td> <td>75.10</td> </tr> <tr> <td>LiveCodeBench^{2024.10~2025.04}</td> <td>26.07</td> <td>33.09</td> <td>27.58</td> <td>29.30</td> </tr> <tr> <td>Long Context</td> <td>LongBench^&lt;128K</td> <td>56.70</td> <td>49.40</td> <td>45.60</td> <td>47.50</td> </tr> <tr> <td>Tool-use</td> <td>FunctionChatBench</td> <td>85.96</td> <td>82.43</td> <td>88.30</td> <td>95.70</td> </tr> </tbody></table>

Lightweight Model Performance

<table><thead> <tr> <th colspan="2">Benchmarks</th> <th>A.X 4.0 Light</th> <th>Qwen3-8B<br/>(w/o reasoning)</th> <th>Qwen2.5-7B</th> <th>EXAONE-3.5-7.8B</th> <th>Kanana-1.5-8B</th> </tr></thead> <tbody> <tr> <td rowspan="6">Knowledge</td> <td>KMMLU</td> <td>64.15</td> <td>63.53</td> <td>49.56</td> <td>53.76</td> <td>48.28</td> </tr> <tr> <td>KMMLU-pro</td> <td>50.28</td> <td>50.71</td> <td>38.87</td> <td>40.11</td> <td>37.63</td> </tr> <tr> <td>KMMLU-redux</td> <td>56.05</td> <td>55.74</td> <td>38.58</td> <td>42.21</td> <td>35.33</td> </tr> <tr> <td>CLIcK</td> <td>68.05</td> <td>62.71</td> <td>60.56</td> <td>64.30</td> <td>61.30</td> </tr> <tr> <td>KoBALT</td> <td>30.29</td> <td>26.57</td> <td>21.57</td> <td>21.71</td> <td>23.14</td> </tr> <tr> <td>MMLU</td> <td>75.43</td> <td>82.89</td> <td>75.40</td> <td>72.20</td> <td>68.82</td> </tr> <tr> <td rowspan="3">General</td> <td>Ko-MT-Bench</td> <td>79.50</td> <td>64.06</td> <td>61.31</td> <td>81.06</td> <td>76.30</td> </tr> <tr> <td>MT-Bench</td> <td>81.56</td> <td>65.69</td> <td>79.37</td> <td>83.50</td> <td>77.60</td> </tr> <tr> <td>LiveBench</td> <td>37.10</td> <td>50.20</td> <td>37.00</td> <td>40.20</td> <td>29.40</td> </tr> <tr> <td rowspan="2">Instruction Following</td> <td>Ko-IFEval</td> <td>72.99</td> <td>73.39</td> <td>60.73</td> <td>65.01</td> <td>69.96</td> </tr> <tr> <td>IFEval</td> <td>84.68</td> <td>85.38</td> <td>76.73</td> <td>82.61</td> <td>80.11</td> </tr> <tr> <td rowspan="2">Math</td> <td>HRM8K</td> <td>40.12</td> <td>52.50</td> <td>35.13</td> <td>31.88</td> <td>30.87</td> </tr> <tr> <td>MATH</td> <td>68.88</td> <td>71.48</td> <td>65.58</td> <td>63.20</td> <td>59.28</td> </tr> <tr> <td rowspan="3">Code</td> <td>HumanEval+</td> <td>75.61</td> <td>77.44</td> <td>74.39</td> <td>76.83</td> <td>76.83</td> </tr> <tr> <td>MBPP+</td> <td>67.20</td> <td>62.17</td> <td>68.50</td> <td>64.29</td> <td>67.99</td> </tr> <tr> <td>LiveCodeBench</td> <td>18.03</td> <td>23.93</td> <td>16.62</td> <td>17.98</td> <td>16.52</td> </tr> </tbody></table>

🚀 Quickstart

with HuggingFace Transformers

• transformers>=4.46.0 or the latest version is required to use skt/A.X-4.0-Light

pip install transformers>=4.46.0

Example Usage

import torch
from transformers import AutoModelForCausalLM, AutoTokenizer

model_name = "skt/A.X-4.0-Light"
model = AutoModelForCausalLM.from_pretrained(
    model_name,
    torch_dtype=torch.bfloat16,
    device_map="auto",
)
model.eval()
tokenizer = AutoTokenizer.from_pretrained(model_name)

messages = [
    {"role": "system", "content": "당신은 사용자가 제공하는 영어 문장들을 한국어로 번역하는 AI 전문가입니다."},
    {"role": "user", "content": "The first human went into space and orbited the Earth on April 12, 1961."},
]
input_ids = tokenizer.apply_chat_template(messages, add_generation_prompt=True, return_tensors="pt").to(model.device)

with torch.no_grad():
    output = model.generate(
        input_ids,
        max_new_tokens=128,
        do_sample=False,
    )

len_input_prompt = len(input_ids[0])
response = tokenizer.decode(output[0][len_input_prompt:], skip_special_tokens=True)
print(response)
# Output:
# 1961년 4월 12일, 최초의 인간이 우주로 나가 지구를 공전했습니다.

with vLLM

• vllm>=v0.6.4.post1 or the latest version is required to use tool-use function

pip install vllm>=v0.6.4.post1
# if you don't want to activate tool-use function, just commenting out below vLLM option
VLLM_OPTION="--enable-auto-tool-choice --tool-call-parser hermes"
vllm serve skt/A.X-4.0-Light $VLLM_OPTION

Example Usage

from openai import OpenAI

def call(messages, model):
    completion = client.chat.completions.create(
        model=model,
        messages=messages,
    )
    print(completion.choices[0].message)

client = OpenAI(
    base_url="http://localhost:8000/v1",
    api_key="api_key"
)
model = "skt/A.X-4.0-Light"
messages = [{"role": "user", "content": "에어컨 여름철 적정 온도는? 한줄로 답변해줘"}]
call(messages, model)
# Output:
# ChatCompletionMessage(content='여름철 적정 에어컨 온도는 일반적으로 24-26도입니다.', refusal=None, role='assistant', audio=None, function_call=None, tool_calls=[], reasoning_content=None)

messages = [{"role": "user", "content": "What is the appropriate temperature for air conditioning in summer? Response in a single sentence."}]
call(messages, model)
# Output:
# ChatCompletionMessage(content='The appropriate temperature for air conditioning in summer generally ranges from 72°F to 78°F (22°C to 26°C) for comfort and energy efficiency.', refusal=None, role='assistant', audio=None, function_call=None, tool_calls=[], reasoning_content=None)

Examples for tool-use

from openai import OpenAI


def call(messages, model):
    completion = client.chat.completions.create(
        model=model,
        messages=messages,
        tools=tools
    )
    print(completion.choices[0].message)


client = OpenAI(
    base_url="http://localhost:8000/v1",
    api_key="api_key"
)
model = "skt/A.X-4.0-Light"

calculate_discount = {
    "type": "function",
    "function": {
        "name": "calculate_discount",
        "description": "원가격과 할인율(퍼센트 단위)을 입력받아 할인된 가격을계산한다.",
        "parameters": {
            "type": "object",
            "properties": {
                "original_price": {
                    "type": "number",
                    "description": "상품의 원래 가격"
                },
                "discount_percentage": {
                    "type": "number",
                    "description": "적용할 할인율(예: 20% 할인의 경우 20을 입력)"
                }
            },
            "required": ["original_price", "discount_percentage"]
        }
    }
}
get_exchange_rate = {
    "type": "function",
    "function": {
        "name": "get_exchange_rate",
        "description": "두 통화 간의 환율을 가져온다.",
        "parameters": {
            "type": "object",
            "properties": {
                "base_currency": {
                    "type": "string",
                    "description": "The currency to convert from."
                },
                "target_currency": {
                    "type": "string",
                    "description": "The currency to convert to."
                }
            },
            "required": ["base_currency", "target_currency"]
        }
    }
}
tools = [calculate_discount, get_exchange_rate]

### Slot filling ###
messages = [{"role": "user", "content": "우리가 뭘 사야되는데 원래 57600원인데 직원할인 받을 수 있거든? 할인가좀 계산해줘"}]
call(messages, model)
# Output:
# ChatCompletionMessage(content='할인율을 알려주시겠습니까?', refusal=None, role='assistant', audio=None, function_call=None, tool_calls=[], reasoning_content=None)


### Function calling ###
messages = [
    {"role": "user", "content": "우리가 뭘 사야되는데 원래 57600원인데 직원할인 받을 수 있거든? 할인가좀 계산해줘"},
    {"role": "assistant", "content": "할인율을 알려주시겠습니까?"},
    {"role": "user", "content": "15% 할인 받을 수 있어."},
]
call(messages, model)
# Output: 
# ChatCompletionMessage(content=None, refusal=None, role='assistant', audio=None, function_call=None, tool_calls=[ChatCompletionMessageToolCall(id='chatcmpl-tool-7778d1d9fca94bf2acbb44c79359502c', function=Function(arguments='{"original_price": 57600, "discount_percentage": 15}', name='calculate_discount'), type='function')], reasoning_content=None)


### Completion ###
messages = [
    {"role": "user", "content": "우리가 뭘 사야되는데 원래 57600원인데 직원할인 받을 수 있거든? 할인가좀 계산해줘"},
    {"role": "assistant", "content": "할인율을 알려주시겠습니까?"},
    {"role": "user", "content": "15% 할인 받을 수 있어."},
    {"role": "tool", "tool_call_id": "random_id", "name": "calculate_discount", "content": "{\"original_price\": 57600, \"discount_percentage\": 15, \"discounted_price\": 48960.0}"}
]
call(messages, model)
# Output: 
# ChatCompletionMessage(content='57600원의 상품에서 15% 할인을 적용하면, 할인된 가격은 48960원입니다.', refusal=None, role='assistant', audio=None, function_call=None, tool_calls=[], reasoning_content=None)

License

The A.X 4.0 Light model is licensed under Apache License 2.0.

Citation

@article{SKTAdotX4Light,
  title={A.X 4.0 Light},
  author={SKT AI Model Lab},
  year={2025},
  url={https://huggingface.co/skt/A.X-4.0-Light}
}

Contact

• Business & Partnership Contact: [email protected]