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A.X-K2

docs/source/en/model_doc/axk2.md

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This model was contributed to Hugging Face Transformers on 2026-07-24.

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A.X-K2

A.X-K2 is SK Telecom's flagship large language model. It is a Mixture-of-Experts decoder built on the DeepSeek-V3.2 architecture — Multi-head Latent Attention (MLA) with DeepSeek Sparse Attention (DSA) — plus three SK Telecom modifications:

  • Sparse Gated Attention (SGA): every layer runs a lightweight lightning indexer that scores each query against the keys and keeps only the top-index_topk positions, which become an additive sparse mask folded into the MLA attention. The indexer maintains its own key cache alongside the main KV cache (DynamicIndexedLayer / StaticIndexedLayer).
  • Gated RMSNorm: input_layernorm (every layer) and post_attention_layernorm (MoE layers) are wrapped with a low-rank input-dependent sigmoid gate, RMSNorm(x) * sigmoid(gate_mlp(RMSNorm(x))).
  • Attention output gate: the attention output is multiplied by an input-dependent sigmoid gate (g_proj) before the output projection. In the released checkpoint this gate is fused into q_b_proj (vLLM layout) and split back out at load time by the weight converter.

Routing is plain (non-grouped) sigmoid top-k with a correction bias; the first layer is dense and the rest are MoE (with a shared expert).

[!TIP] A.X-K2 relies on an explicit additive sparse mask, so it runs under the eager and sdpa attention implementations (attn_implementation="sdpa" is the default and recommended backend).

The example below shows how to generate text with [Pipeline] or the [AutoModel].

<hfoptions id="usage"> <hfoption id="Pipeline">
python
from transformers import pipeline

pipe = pipeline(task="text-generation", model="skt/A.X-K2")

print(pipe("대한민국의 수도는", max_new_tokens=32)[0]["generated_text"])
</hfoption> <hfoption id="AutoModel">
python
from transformers import AutoModelForCausalLM, AutoTokenizer

tokenizer = AutoTokenizer.from_pretrained("skt/A.X-K2")
model = AutoModelForCausalLM.from_pretrained("skt/A.X-K2", device_map="auto")

inputs = tokenizer("대한민국의 수도는", return_tensors="pt").to(model.device)
outputs = model.generate(**inputs, max_new_tokens=32, do_sample=False)
print(tokenizer.decode(outputs[0], skip_special_tokens=True))
</hfoption> </hfoptions>

AXK2Config

[[autodoc]] AXK2Config

AXK2Model

[[autodoc]] AXK2Model - forward

AXK2ForCausalLM

[[autodoc]] AXK2ForCausalLM - forward

AXK2ForSequenceClassification

[[autodoc]] AXK2ForSequenceClassification - forward

AXK2ForTokenClassification

[[autodoc]] AXK2ForTokenClassification - forward