---
license: apache-2.0
language:
  - en
  - zh
datasets:
  - m-a-p/Code-Feedback
metrics:
  - pass@k 
base_model: Qwen/Qwen3-4B-Instruct
tags:
  - code
  - agent
  - react
  - code-review
  - lora
  - unsloth
  - qwen3
library_name: transformers
pipeline_tag: text-generation
model-index:
  - name: Qwen3-4B-CodeAgent
    results:
      - task:
          type: text-generation
          name: Code Generation
        dataset:
          name: HumanEval (10-problem subset)
          type: openai/openai_humaneval
        metrics:
          - name: Pass@1
            type: pass@1
            value: 62.6
          - name: Pass@3
            type: pass@3
            value: 75.61
---

# Qwen3-4B-CodeAgent

A fine-tuned code execution and Code Review agent based on Qwen3-4B-Instruct, trained to follow a structured ReAct (Plan → Execute → Reflect → Finish) workflow with XML-formatted responses.

## Model Description

This model is a LoRA fine-tuned version of [Qwen3-4B-Instruct](https://huggingface.co/Qwen/Qwen3-4B) designed to function as an autonomous coding agent. It generates structured XML responses that can be parsed by an orchestration framework to execute code, review results, and iteratively debug.

| Attribute | Value |
|-----------|-------|
| Base Model | Qwen3-4B-Instruct (3.6B params) |
| Architecture | Qwen3ForCausalLM, 36 layers, 2560 hidden size, GQA (32 heads / 8 KV heads) |
| Fine-tuning Method | LoRA (4-bit quantization + LoRA r=32, alpha=32) |
| Framework | Unsloth + TRL SFTTrainer |
| Training Data | m-a-p/Code-Feedback (~47K train samples) |
| Context Length | 4096 tokens |
| Precision | bfloat16 (merged weights) |

## Intended Use

This model is designed for building code agent systems that need structured, parseable output. It is suitable for:

- Automated code generation with execution feedback loops
- Code review and iterative debugging pipelines
- Tool-augmented LLM applications with sandbox execution
- Educational coding assistants

## Output Format

The model outputs XML-structured responses following a ReAct workflow:

```xml
<agent_response>
  <node>Plan</node>
  <next_node>Execute</next_node>
  <content>
    ## Analysis
    The task requires implementing a binary search algorithm.
    
    ## Plan
    1. Define the function signature
    2. Implement iterative binary search
    3. Handle edge cases (empty array, target not found)
  </content>
</agent_response>
```

### Node Types

| Node | Trigger | Content | Next Node |
|------|---------|---------|-----------|
| **Plan** | User sends a task | Markdown-formatted solution plan | Execute |
| **Execute** | After Plan or Reflect | `{"tool_name": "python_sandbox", "arguments": {"code": "..."}}` | Execute |
| **Reflect** | Execute fails (exit_code=1) | Root cause analysis and fix direction | Execute |
| **Finish** | Execute succeeds (exit_code=0) | Task summary | Finish |

### Standard Workflow

```
Plan → Execute → (failure → Reflect → Execute → ...) → Finish
```

## Usage

### With Transformers

```python
from transformers import AutoModelForCausalLM, AutoTokenizer

model_name = "Nanami14138/qwen3-4b-instruct-code-agent"
model = AutoModelForCausalLM.from_pretrained(model_name, torch_dtype="auto", device_map="auto")
tokenizer = AutoTokenizer.from_pretrained(model_name)

## 🛠️ Prompting Strategy (系统提示词策略)

本模型被设计为一个基于 ReAct 框架的智能 Code Agent。为了让模型严格按照状态机（Plan -> Execute -> Reflect -> Finish）运行，并输出结构化的 XML 格式，**强烈建议在推理时使用以下 System Prompt**：

system_prompt = """你是一个专业的代码执行与Code Review智能Agent，遵循ReAct工作流。

## 输出格式
你的每一次回复都必须严格使用以下XML格式：
<agent_response>
  <node>当前节点</node>
  <next_node>下一个节点</next_node>
  <content>输出内容</content>
</agent_response>

## 节点定义
### Plan（规划）
- 触发：收到用户任务后立即进入
- <content>：分析任务需求，以 Markdown 格式输出解决方案规划
- <next_node>：Execute

### Execute（执行）
- 触发：Plan 或 Reflect 之后进入
- <content>：输出 {"tool_name": "python_sandbox", "arguments": {"code": "你的代码"}}
- <next_node>：Execute（等待执行结果）

### Reflect（反思）
- 触发：Execute 执行失败（exit_code=1）后进入
- <content>：分析失败原因，定位根因，给出修正方向
- <next_node>：Execute（修正后重新执行）

### Finish（完成）
- 触发：Execute 执行成功（exit_code=0）后进入
- <content>：输出任务总结
- <next_node>：Finish

## 标准工作流
Plan → Execute → (失败 → Reflect → Execute → ...) → Finish"""

messages = [
    {"role": "system", "content": system_prompt},
    {"role": "user", "content": "任务：Write a Python function to check if a number is prime.\n\n当前状态：Start"}
]

text = tokenizer.apply_chat_template(messages, tokenize=False, add_generation_prompt=True, enable_thinking=False)
inputs = tokenizer(text, return_tensors="pt").to(model.device)

with torch.no_grad():
    output = model.generate(**inputs, max_new_tokens=1024, temperature=0.1, top_p=0.95)

response = tokenizer.decode(output[0][inputs["input_ids"].shape[1]:], skip_special_tokens=True)
print(response)
```

### With Unsloth (Faster Inference)

```python
from unsloth import FastLanguageModel

model, tokenizer = FastLanguageModel.from_pretrained(
    model_name="your-username/qwen3-4b-code-agent",
    max_seq_length=4096,
    load_in_4bit=True,
)
FastLanguageModel.for_inference(model)
# Then use the same message format as above
```

## Training Details

### Data

Trained on [m-a-p/Code-Feedback](https://huggingface.co/datasets/m-a-p/Code-Feedback), a multi-turn code conversation dataset with ~66K examples. The data was processed into three pools:

| Pool | Description | Train Samples | Ratio |
|------|-------------|---------------|-------|
| Pool A (Base SFT) | Single-turn code Q&A, plain text | 117 | 0.2% |
| Pool B (Code Review) | Multi-turn debug/review → ReAct XML format | 29,562 | 62.3% |
| Pool C (Discussion) | Multi-turn code discussion → ReAct XML format | 17,737 | 37.4% |

The system prompt is injected at training time (not stored in the data) to ensure consistent behavior.

### Hyperparameters

| Parameter | Value |
|-----------|-------|
| LoRA rank (r) | 32 |
| LoRA alpha | 32 |
| LoRA target modules | q_proj, k_proj, v_proj, o_proj, gate_proj, up_proj, down_proj |
| Learning rate | 2e-4 (cosine schedule) |
| Warmup ratio | 0.1 |
| Batch size | 4 × 4 (gradient accumulation) = 16 effective |
| Max sequence length | 4096 |
| Precision | LoRA 4-bit (training), bfloat16 (merged) |
| Optimizer | AdamW 8-bit |
| Epochs | 3 (stopped early at ~5.8% progress, step 620/8892) |

### Training Curve

| Step | Train Loss | Eval Loss |
|------|-----------|-----------|
| 20 | 1.927 | 1.905 |
| 100 | 0.649 | 0.573 |
| 200 | 0.463 | 0.454 |
| 300 | 0.412 | 0.422 |
| 400 | 0.413 | 0.409 |
| 500 | 0.374 | 0.401 |
| 600 | 0.383 | 0.397 |

Loss decreased from 1.90 to 0.40 with no signs of overfitting. The checkpoint at step 620 was merged for this release.

### Hardware

- 8× NVIDIA L20 (48GB each), single-GPU training via LoRA

## Evaluation

### HumanEval (10-problem subset)

| Metric | Score |
|--------|-------|
| Pass@1 | 62.6% |
| Pass@2 | 71.14% |
| Pass@3 | 75.61% |
| Avg tokens/problem | 215.2 |

Evaluation was conducted on a 10-problem subset of HumanEval. Full 164-problem evaluation is planned.

## Limitations

- **Early checkpoint**: This model was merged at step 620 out of 8892 total steps (~3.4% of training). Performance will likely improve with continued training.
- **English-centric data**: The training data (Code-Feedback) is predominantly in English. Chinese language coding tasks may have lower quality.
- **XML format dependency**: The model is trained to output structured XML. Without the system prompt, it may not follow the expected format.
- **No real execution**: The training data simulates tool responses; the model has not been trained with actual code execution feedback.
- **Limited code languages**: While the training data covers multiple languages, Python is heavily overrepresented.
- **Hallucination risk**: Like all LLMs, the model may generate plausible but incorrect code, especially for complex algorithms or domain-specific tasks.

## Ethical Considerations

- The model should not be used to generate malicious code or exploit vulnerabilities.
- Generated code should always be reviewed by a human before deployment in production systems.
- The model may reproduce biases present in the training data (e.g., coding style preferences, library choices).

## Citation

If you use this model, please cite the base model and training dataset:

```bibtex
@article{qwen3,
  title={Qwen3 Technical Report},
  author={Qwen Team},
  year={2025}
}

@misc{code-feedback,
  title={Code-Feedback: Multi-turn Code Conversation Dataset},
  author={m-a-p},
  url={https://huggingface.co/datasets/m-a-p/Code-Feedback}
}
```
