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*This model was contributed to Hugging Face Transformers on 2025-08-05.*

<div style="float: right;">
    <div class="flex flex-wrap space-x-1">
        <img alt="FlashAttention" src="https://img.shields.io/badge/%E2%9A%A1%EF%B8%8E%20FlashAttention-eae0c8?style=flat">
        <img alt="Tensor parallelism" src="https://img.shields.io/badge/Tensor%20parallelism-06b6d4?style=flat&logoColor=white">
    </div>
</div>

# GptOss

[GptOss](https://openai.com/index/introducing-gpt-oss/) is a sparse mixture-of-experts (MoE) language model from OpenAI that routes each token to 4 of 128 experts. It uses attention sinks — learnable auxiliary tokens appended to each attention head — and YaRN rotary embeddings for sequences up to 131k tokens.

The example below demonstrates how to generate text with [`Pipeline`] or the [`AutoModelForCausalLM`] class.

<hfoptions id="usage">
<hfoption id="Pipeline">

```python
from transformers import pipeline


pipe = pipeline(
    task="text-generation",
    model="openai/gpt-oss-20b",
)
pipe("Plants create energy through a process known as")
```

</hfoption>
<hfoption id="AutoModelForCausalLM">

```python
from transformers import AutoModelForCausalLM, AutoTokenizer


tokenizer = AutoTokenizer.from_pretrained("openai/gpt-oss-20b")
model = AutoModelForCausalLM.from_pretrained(
    "openai/gpt-oss-20b",
    device_map="auto",
)
input_ids = tokenizer("Plants create energy through a process known as", return_tensors="pt").to(model.device)

output = model.generate(**input_ids, max_new_tokens=50)
print(tokenizer.decode(output[0], skip_special_tokens=True))
```

</hfoption>
</hfoptions>

## Notes

- SDPA is not supported because attention sinks require direct access to the full attention logits before softmax. Use Flash Attention or Flex Attention instead.
- When using Flex Attention, attention sinks require special handling. The `score_mod` function operates on individual score elements rather than the full attention matrix, so sink renormalization is applied after computation using the log-sum-exp (LSE) values returned by Flex Attention.

## GptOssConfig

[[autodoc]] GptOssConfig

## GptOssModel

[[autodoc]] GptOssModel
    - forward

## GptOssForCausalLM

[[autodoc]] GptOssForCausalLM
    - forward

## GptOssForSequenceClassification

[[autodoc]] GptOssForSequenceClassification
    - forward

## GptOssForTokenClassification

[[autodoc]] GptOssForTokenClassification
    - forward
