Model Overview
Model Features
Model Capabilities
Use Cases
🚀 Qwen3-4B
Qwen3-4B is a powerful large language model in the Qwen series. It offers advanced reasoning, multilingual support, and excellent agent capabilities, providing high - quality text generation services.
🚀 Quick Start
The code of Qwen3 has been integrated into the latest Hugging Face transformers
. We strongly recommend using the latest version of transformers
.
If you use transformers<4.51.0
, you will encounter the following error:
KeyError: 'qwen3'
The following code snippet demonstrates how to use the model to generate content based on given inputs:
from transformers import AutoModelForCausalLM, AutoTokenizer
model_name = "Qwen/Qwen3-4B"
# 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
to create an OpenAI - compatible API endpoint:
- SGLang:
python -m sglang.launch_server --model-path Qwen/Qwen3-4B --reasoning-parser qwen3
- vLLM:
vllm serve Qwen/Qwen3-4B --enable-reasoning --reasoning-parser deepseek_r1
For local use, applications such as Ollama, LMStudio, MLX - LM, llama.cpp, and KTransformers have also supported Qwen3.
✨ Features
Qwen3 Highlights
Qwen3 is the latest generation of large language models in the Qwen series, offering a comprehensive suite of dense and mixture - of - experts (MoE) models. Based on extensive training, Qwen3 has made groundbreaking advancements in reasoning, instruction - following, agent capabilities, and multilingual support, with the following key features:
- Unique seamless switching: It supports seamless switching between thinking mode (for complex logical reasoning, math, and coding) and non - thinking mode (for efficient, general - purpose dialogue) within a single model, ensuring optimal performance across various scenarios.
- Enhanced reasoning capabilities: There is a significant enhancement in its reasoning capabilities, surpassing previous QwQ (in thinking mode) and Qwen2.5 instruct models (in non - thinking mode) on mathematics, code generation, and commonsense logical reasoning.
- Superior human preference alignment: It has superior human preference alignment, excelling in creative writing, role - playing, multi - turn dialogues, and instruction following, to deliver a more natural, engaging, and immersive conversational experience.
- Expert agent capabilities: It has expertise in agent capabilities, enabling precise integration with external tools in both thinking and unthinking modes and achieving leading performance among open - source models in complex agent - based tasks.
- Multilingual support: It supports 100+ languages and dialects with strong capabilities for multilingual instruction following and translation.
Model Overview
Qwen3 - 4B has the following features:
Property | Details |
---|---|
Model Type | Causal Language Models |
Training Stage | Pretraining & Post - training |
Number of Parameters | 4.0B |
Number of Paramaters (Non - Embedding) | 3.6B |
Number of Layers | 36 |
Number of Attention Heads (GQA) | 32 for Q and 8 for KV |
Context Length | 32,768 natively and 131,072 tokens with YaRN |
For more details, including benchmark evaluation, hardware requirements, and inference performance, please refer to our blog, GitHub, and Documentation.
⚠️ Important Note
If you encounter significant endless repetitions, please refer to the Best Practices section for optimal sampling parameters, and set the
presence_penalty
to 1.5.
💻 Usage Examples
Basic Usage
The basic usage of Qwen3 - 4B has been shown in the Quick Start section.
Advanced Usage
Switching Between Thinking and Non - Thinking Mode
enable_thinking=True
By default, Qwen3 has thinking capabilities enabled, similar to QwQ - 32B. This means the model will use its reasoning abilities to enhance the quality of generated responses. For example, when explicitly setting enable_thinking=True
or leaving it as the default value in tokenizer.apply_chat_template
, the model will engage its thinking mode.
text = tokenizer.apply_chat_template(
messages,
tokenize=False,
add_generation_prompt=True,
enable_thinking=True # True is the default value for enable_thinking
)
In this mode, the model will generate think content wrapped in a <think>...</think>
block, followed by the final response.
⚠️ Important Note
For thinking mode, use
Temperature = 0.6
,TopP = 0.95
,TopK = 20
, andMinP = 0
(the default setting ingeneration_config.json
). DO NOT use greedy decoding, as it can lead to performance degradation and endless repetitions. For more detailed guidance, please refer to the Best Practices section.
enable_thinking=False
We provide a hard switch to strictly disable the model's thinking behavior, aligning its functionality with the previous Qwen2.5 - Instruct models. This mode is particularly useful in scenarios where disabling thinking is essential for enhancing efficiency.
text = tokenizer.apply_chat_template(
messages,
tokenize=False,
add_generation_prompt=True,
enable_thinking=False # Setting enable_thinking=False disables thinking mode
)
In this mode, the model will not generate any think content and will not include a <think>...</think>
block.
⚠️ Important Note
For non - thinking mode, we suggest using
Temperature = 0.7
,TopP = 0.8
,TopK = 20
, andMinP = 0
. For more detailed guidance, please refer to the Best Practices section.
Advanced Usage: Switching Between Thinking and Non - Thinking Modes via User Input
We provide a soft switch mechanism that allows users to dynamically control the model's behavior when enable_thinking=True
. Specifically, you can add /think
and /no_think
to user prompts or system messages to switch the model's thinking mode from turn to turn. The model will follow the most recent instruction in multi - turn conversations.
Here is an example of a multi - turn conversation:
from transformers import AutoModelForCausalLM, AutoTokenizer
class QwenChatbot:
def __init__(self, model_name="Qwen/Qwen3-4B"):
self.tokenizer = AutoTokenizer.from_pretrained(model_name)
self.model = AutoModelForCausalLM.from_pretrained(model_name)
self.history = []
def generate_response(self, user_input):
messages = self.history + [{"role": "user", "content": user_input}]
text = self.tokenizer.apply_chat_template(
messages,
tokenize=False,
add_generation_prompt=True
)
inputs = self.tokenizer(text, return_tensors="pt")
response_ids = self.model.generate(**inputs, max_new_tokens=32768)[0][len(inputs.input_ids[0]):].tolist()
response = self.tokenizer.decode(response_ids, skip_special_tokens=True)
# Update history
self.history.append({"role": "user", "content": user_input})
self.history.append({"role": "assistant", "content": response})
return response
# Example Usage
if __name__ == "__main__":
chatbot = QwenChatbot()
# First input (without /think or /no_think tags, thinking mode is enabled by default)
user_input_1 = "How many r's in strawberries?"
print(f"User: {user_input_1}")
response_1 = chatbot.generate_response(user_input_1)
print(f"Bot: {response_1}")
print("----------------------")
# Second input with /no_think
user_input_2 = "Then, how many r's in blueberries? /no_think"
print(f"User: {user_input_2}")
response_2 = chatbot.generate_response(user_input_2)
print(f"Bot: {response_2}")
print("----------------------")
# Third input with /think
user_input_3 = "Really? /think"
print(f"User: {user_input_3}")
response_3 = chatbot.generate_response(user_input_3)
print(f"Bot: {response_3}")
⚠️ Important Note
For API compatibility, when
enable_thinking=True
, regardless of whether the user uses/think
or/no_think
, the model will always output a block wrapped in<think>...</think>
. However, the content inside this block may be empty if thinking is disabled. Whenenable_thinking=False
, the soft switches are not valid. Regardless of any/think
or/no_think
tags input by the user, the model will not generate think content and will not include a<think>...</think>
block.
Agentic Use
Qwen3 excels in tool - calling capabilities. We recommend using [Qwen - Agent](https://github.com/QwenLM/Qwen - Agent) to make the best use of the agentic ability of Qwen3. Qwen - Agent encapsulates tool - calling templates and tool - calling parsers internally, greatly reducing coding complexity.
To define the available tools, you can use the MCP configuration file, use the integrated tool of Qwen - Agent, or integrate other tools by yourself.
from qwen_agent.agents import Assistant
# Define LLM
llm_cfg = {
'model': 'Qwen3-4B',
# Use the endpoint provided by Alibaba Model Studio:
# 'model_type': 'qwen_dashscope',
# 'api_key': os.getenv('DASHSCOPE_API_KEY'),
# Use a custom endpoint compatible with OpenAI API:
'model_server': 'http://localhost:8000/v1', # api_base
'api_key': 'EMPTY',
# Other parameters:
# 'generate_cfg': {
# # Add: When the response content is `<think>this is the thought</think>this is the answer;
# # Do not add: When the response has been separated by reasoning_content and content.
# 'thought_in_content': True,
# },
}
# Define Tools
tools = [
{'mcpServers': { # You can specify the MCP configuration file
'time': {
'command': 'uvx',
'args': ['mcp-server-time', '--local-timezone=Asia/Shanghai']
},
"fetch": {
"command": "uvx",
"args": ["mcp-server-fetch"]
}
}
},
'code_interpreter', # Built-in tools
]
# Define Agent
bot = Assistant(llm=llm_cfg, function_list=tools)
# Streaming generation
messages = [{'role': 'user', 'content': 'https://qwenlm.github.io/blog/ Introduce the latest developments of Qwen'}]
for responses in bot.run(messages=messages):
pass
print(responses)
Processing Long Texts
Qwen3 natively supports context lengths of up to 32,768 tokens. For conversations where the total length (including both input and output) significantly exceeds this limit, we recommend using RoPE scaling techniques to handle long texts effectively. We have validated the model's performance on context lengths of up to 131,072 tokens using the YaRN method.
YaRN is currently supported by several inference frameworks, e.g., transformers
and llama.cpp
for local use, vllm
and sglang
for deployment. In general, there are two approaches to enabling YaRN for supported frameworks:
- Modifying the model files:
In the
config.json
file, add therope_scaling
fields:
For{ ..., "rope_scaling": { "rope_type": "yarn", "factor": 4.0, "original_max_position_embeddings": 32768 } }
llama.cpp
, you need to regenerate the GGUF file after the modification. - Passing command line arguments:
For
vllm
, you can usevllm serve ... --rope-scaling '{"rope_type":"yarn","factor":4.0,"original_max_position_embeddings":32768}' --max-model-len 131072
📄 License
This project is licensed under the Apache - 2.0 license.

