Stack 2.9
A fine-tuned code assistant built on Qwen2.5-Coder-1.5B, trained on Stack Overflow data
Stack 2.9 is a specialized code generation model fine-tuned from Qwen/Qwen2.5-Coder-1.5B on Stack Overflow Q&A data for improved programming assistance.
Key Features
- Specialized for Code: Trained on Stack Overflow patterns for better code generation
- 128K Context: Handle larger codebases and complex documentation
- Efficient: Runs on consumer GPUs (RTX 3060+)
- Open Source: Apache 2.0 licensed
Model Details
| Attribute | Value |
|---|---|
| Base Model | Qwen/Qwen2.5-Coder-1.5B |
| Parameters | 1.5B |
| Context Length | 131,072 tokens (128K) |
| Fine-tuning Method | LoRA (Rank 8) |
| Precision | FP16 |
| License | Apache 2.0 |
| Release Date | April 2026 |
Architecture
| Specification | Value |
|---|---|
| Architecture | Qwen2ForCausalLM |
| Hidden Size | 1,536 |
| Num Layers | 28 |
| Attention Heads | 12 (Q) / 2 (KV) |
| GQA | Yes (2 KV heads) |
| Intermediate Size | 8,960 |
| Vocab Size | 151,936 |
| Activation | SiLU (SwiGLU) |
| Normalization | RMSNorm |
Quickstart
Installation
pip install transformers>=4.40.0 torch>=2.0.0 accelerate
Code Example
from transformers import AutoModelForCausalLM, AutoTokenizer
model_name = "my-ai-stack/Stack-2-9-finetuned"
# Load model and tokenizer
model = AutoModelForCausalLM.from_pretrained(
model_name,
torch_dtype="auto",
device_map="auto"
)
tokenizer = AutoTokenizer.from_pretrained(model_name)
# Chat interface
messages = [
{"role": "system", "content": "You are Stack 2.9, a helpful coding assistant."},
{"role": "user", "content": "Write a Python function to calculate fibonacci numbers"}
]
# Apply chat template
text = tokenizer.apply_chat_template(
messages,
tokenize=False,
add_generation_prompt=True
)
# Generate
model_inputs = tokenizer([text], return_tensors="pt").to(model.device)
generated_ids = model.generate(
**model_inputs,
max_new_tokens=512,
temperature=0.7,
do_sample=True
)
# Decode response
response = tokenizer.decode(
generated_ids[0][len(model_inputs.input_ids[0]):],
skip_special_tokens=True
)
print(response)
Interactive Chat
python chat.py
Training Details
| Specification | Value |
|---|---|
| Method | LoRA (Low-Rank Adaptation) |
| LoRA Rank | 8 |
| LoRA Alpha | 16 |
| Target Modules | q_proj, k_proj, v_proj, o_proj, gate_proj, up_proj, down_proj |
| Epochs | ~0.8 |
| Final Loss | 0.0205 |
| Data Source | Stack Overflow Q&A |
Training Data
Fine-tuned on Stack Overflow code Q&A pairs including:
- Python code solutions and snippets
- Code explanations and documentation
- Programming patterns and best practices
- Bug fixes and debugging examples
- Algorithm implementations
Evaluation
| Benchmark | Score | Notes |
|---|---|---|
| HumanEval | ~35-40% | Based on base model benchmarks |
| MBPP | ~40-45% | Python-focused evaluation |
Note: Full benchmark evaluation is in progress. The model inherits strong coding capabilities from Qwen2.5-Coder and is specialized for Stack Overflow patterns.
Hardware Requirements
| Configuration | GPU | VRAM |
|---|---|---|
| FP16 | RTX 3060+ | ~4GB |
| 8-bit | RTX 3060+ | ~2GB |
| 4-bit | Any modern GPU | ~1GB |
| CPU | None | ~8GB RAM |
Capabilities
- Code Generation: Python, JavaScript, TypeScript, SQL, Go, Rust, and more
- Code Completion: Functions, classes, and entire snippets
- Debugging: Identify and fix bugs with explanations
- Code Explanation: Document and explain code behavior
- Programming Q&A: Answer technical questions
Limitations
- Model Size: At 1.5B parameters, smaller than state-of-the-art models (7B+)
- Training Data: Python-heavy; other languages may have lower quality
- Hallucinations: May occasionally generate incorrect code; verification recommended
- Tool Use: Base model without native tool-calling (see enhanced version)
Comparison
| Feature | Qwen2.5-Coder-1.5B | Stack 2.9 |
|---|---|---|
| Code Generation | General | Stack Overflow patterns |
| Python Proficiency | Baseline | Enhanced |
| Context Length | 128K | 128K |
| Specialization | General code | Stack Overflow Q&A |
Citation
@misc{my-ai-stack/stack-2-9-finetuned,
author = {Walid Sobhi},
title = {Stack 2.9: Fine-tuned Qwen2.5-Coder-1.5B on Stack Overflow Data},
year = {2026},
publisher = {HuggingFace},
url = {https://huggingface.co/my-ai-stack/Stack-2-9-finetuned}
}
Related Links
License
Licensed under the Apache 2.0 license. See LICENSE for details.
Model Card Version: 2.0 Last Updated: April 2026