Qwen3-4B-SafeRL / README.md
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---
library_name: transformers
license: apache-2.0
license_link: https://huggingface.co/Qwen/Qwen3-4B-SafeRL/blob/main/LICENSE
pipeline_tag: text-generation
base_model:
- Qwen/Qwen3-4B
---
# Qwen3-4B-SafeRL
## Model Overview
**Qwen3-4B-SafeRL** is a safety-aligned version of the [Qwen3-4B](https://huggingface.co/Qwen/Qwen3-4B) model. It has been trained using Reinforcement Learning (RL) with a reward signal from **Qwen3Guard-Gen** to enhance its robustness against harmful or adversarial prompts. This process aims to ensure strong safety guarantees without leading to overly simplistic or evasive refusal behaviors, thereby maintaining a positive user experience.
For more details on the safety alignment process, please refer to the [Qwen3Guard Technical Report](https://github.com/QwenLM/Qwen3Guard/blob/main/Qwen3Guard_Technical_Report.pdf).
### Reinforcement Learning with Hybrid Reward
To prevent the model from defaulting to refusal across all prompts in an attempt to remain safe, we introduce a hybrid reward function that jointly optimizes three key objectives:
- **Safety Maximization:** Penalizes the generation of unsafe content, as detected by [Qwen3Guard-Gen-4B](https://huggingface.co/Qwen/Qwen3Guard-Gen-4B).
- **Helpfulness Maximization:** Rewards responses that are genuinely helpful, as evaluated by the [WorldPM-Helpsteer2](https://huggingface.co/Qwen/WorldPM-72B-HelpSteer2) model.
- **Refusal Minimization:** Applies a moderate penalty for unnecessary refusals, also identified by [Qwen3Guard-Gen-4B](https://huggingface.co/Qwen/Qwen3Guard-Gen-4B).
### Performance
| Mode | Model | Safety Rate (Qwen3-235B) | Safety Rate (WildGuard) | Refusal (WildGuard) | ArenaHard-v2 (Winrate vs GPT-4.1) | AIME25 (Pass@1) | LCB-v6 (Pass@1) | GPQA (Pass@1) |
|-------------|-------------------------|--------------------------|--------------------------|---------------------|-----------------------------------|-----------------|-----------------|---------------|
| **Non-Think** | Qwen3-4B | 47.5 | 64.7 | 12.9 | 9.5 | **19.1** | 26.4 | **41.7** |
| | Qwen3-4B-SafeRL | **86.5** | **98.1** | **5.3** | **10.7** | 18.2 | **27.7** | 40.8 |
| **Think** | Qwen3-4B | 43.8 | 59.0 | 6.5 | 13.7 | **65.6** | **48.4** | **55.9** |
| | Qwen3-4B-SafeRL | **83.4** | **97.4** | **6.2** | **16.6** | 63.5 | 47.5 | 51.2 |
## Quickstart
Qwen3-4B-SafeRL is used in the same way as Qwen3-4B, preserving the ability of hybrid thinking modes. The code of Qwen3 has been in the latest Hugging Face `transformers` and we advise you to use the latest version of `transformers`.
With `transformers<4.51.0`, you will encounter the following error:
```
KeyError: 'qwen3'
```
The following contains a code snippet illustrating how to use the model generate content based on given inputs.
```python
from transformers import AutoModelForCausalLM, AutoTokenizer
model_name = "Qwen/Qwen3-4B-SafeRL"
# load the tokenizer and the model
tokenizer = AutoTokenizer.from_pretrained(model_name)
model = AutoModelForCausalLM.from_pretrained(
model_name,
torch_dtype="auto",
device_map="auto"
)
# prepare the model input
prompt = "Give me a short introduction to large language model."
messages = [
{"role": "user", "content": prompt}
]
text = tokenizer.apply_chat_template(
messages,
tokenize=False,
add_generation_prompt=True,
enable_thinking=True # Switches between thinking and non-thinking modes. Default is True.
)
model_inputs = tokenizer([text], return_tensors="pt").to(model.device)
# conduct text completion
generated_ids = model.generate(
**model_inputs,
max_new_tokens=32768
)
output_ids = generated_ids[0][len(model_inputs.input_ids[0]):].tolist()
# parsing thinking content
try:
# rindex finding 151668 (</think>)
index = len(output_ids) - output_ids[::-1].index(151668)
except ValueError:
index = 0
thinking_content = tokenizer.decode(output_ids[:index], skip_special_tokens=True).strip("\n")
content = tokenizer.decode(output_ids[index:], skip_special_tokens=True).strip("\n")
print("thinking content:", thinking_content)
print("content:", content)
```
For deployment, you can use `sglang>=0.4.6.post1` or `vllm>=0.8.5` or to create an OpenAI-compatible API endpoint:
- SGLang:
```shell
python -m sglang.launch_server --model-path Qwen/Qwen3-4B-SafeRL --reasoning-parser qwen3
```
- vLLM:
```shell
vllm serve Qwen/Qwen3-4B-SafeRL --enable-reasoning --reasoning-parser deepseek_r1
```
For local use, applications such as Ollama, LMStudio, MLX-LM, llama.cpp, and KTransformers have also supported Qwen3.
For more usages, please refer to the modelcard of [Qwen3-4B](https://huggingface.co/Qwen/Qwen3-4B).
## Citation
If you find our work helpful, feel free to give us a cite.
```
@misc{qwen3guard,
title={Qwen3Guard Technical Report},
author={Qwen Team},
year={2025},
url={http://arxiv.org/abs/2510.14276},
}
```