You can use gpt-oss-120b and gpt-oss-20b with Transformers. If you use the Transformers chat template, it will automatically apply the harmony response format. If you use model.generate directly, you need to apply the harmony format manually using the chat template or use our openai-harmony package.
To get started, install the necessary dependencies to setup your environment:
pip install -U transformers kernels torch
Once, setup you can proceed to run the model by running the snippet below:
from transformers import pipeline
import torch
model_id = "openai/gpt-oss-120b"
pipe = pipeline(
"text-generation",
model=model_id,
torch_dtype="auto",
device_map="auto",
)
messages = [
{"role": "user", "content": "Explain quantum mechanics clearly and concisely."},
]
outputs = pipe(
messages,
max_new_tokens=256,
)
print(outputs[0]["generated_text"][-1])
Alternatively, you can run the model via Transformers Serve to spin up a OpenAI-compatible webserver:
transformers serve
transformers chat localhost:8000 --model-name-or-path openai/gpt-oss-120b
Learn more about how to use gpt-oss with Transformers.
vLLM
vLLM recommends using uv for Python dependency management. You can use vLLM to spin up an OpenAI-compatible webserver. The following command will automatically download the model and start the server.
uv pip install --pre vllm==0.10.1+gptoss \
--extra-index-url https://wheels.vllm.ai/gpt-oss/ \
--extra-index-url https://download.pytorch.org/whl/nightly/cu128 \
--index-strategy unsafe-best-match
vllm serve openai/gpt-oss-120b
Learn more about how to use gpt-oss with vLLM.
PyTorch / Triton
To learn about how to use this model with PyTorch and Triton, check out our reference implementations in the gpt-oss repository.
Ollama
If you are trying to run gpt-oss on consumer hardware, you can use Ollama by running the following commands after installing Ollama.
# gpt-oss-120b
ollama pull gpt-oss:120b
ollama run gpt-oss:120b
Learn more about how to use gpt-oss with Ollama.
LM Studio
If you are using LM Studio you can use the following commands to download.
# gpt-oss-120b
lms get openai/gpt-oss-120b
Check out our awesome list for a broader collection of gpt-oss resources and inference partners.
Download the model
You can download the model weights from the Hugging Face Hub directly from Hugging Face CLI:
# gpt-oss-120b
huggingface-cli download openai/gpt-oss-120b --include "original/*" --local-dir gpt-oss-120b/
pip install gpt-oss
python -m gpt_oss.chat model/
Reasoning levels
You can adjust the reasoning level that suits your task across three levels:
- Low: Fast responses for general dialogue.
- Medium: Balanced speed and detail.
- High: Deep and detailed analysis.
The reasoning level can be set in the system prompts, e.g., "Reasoning: high".
The gpt-oss models are excellent for:
- Web browsing (using built-in browsing tools)
- Function calling with defined schemas
- Agentic operations like browser tasks
Fine-tuning
Both gpt-oss models can be fine-tuned for a variety of specialized use cases.
This larger model gpt-oss-120b can be fine-tuned on a single H100 node, whereas the smaller gpt-oss-20b can even be fine-tuned on consumer hardware.
Citation
@misc{openai2025gptoss120bgptoss20bmodel,
title={gpt-oss-120b & gpt-oss-20b Model Card},
author={OpenAI},
year={2025},
eprint={2508.10925},
archivePrefix={arXiv},
primaryClass={cs.CL},
url={https://arxiv.org/abs/2508.10925},
}
