Legal-RAG

1 What is Legal-RAG?

Legal-RAG is an open-source, end-to-end legal Retrieval-Augmented Generation (RAG) system centered on statutory text. It integrates QueryType-aware routing, hybrid retrieval, bounded graph-augmented context expansion, and provider-agnostic generation. Running OpenAI models with an OPENAI_API_KEY as the generation model is optional; you can deploy with GPU to enable local models (default: Qwen), and other open-source models are configurable.

2 Online Demo

• Option 1 — Hosted Demo: Hugging Face Spaces (no GPU, slower, requires OpenAI key)
• Option 2 — Self‑Launch Demo: Colab notebook (launch the server on GPU, no OpenAI key required)

https://github.com/user-attachments/assets/1a380d62-d909-480a-8618-a03f3015e1bd

3 Features

Law-aware RAG

• Explicit article-level chunking
• Law-specific metadata (chapter / section / article number)
• Retrieval results are inspectable and auditable
• Language-aware corpus routing (zh/en)

Hybrid Retrieval

• Dense retrieval: FAISS
• Sparse retrieval: BM25
• ColBERT (late interaction)
• Weighted fusion

Query Routing & Graph Awareness

• Lightweight law_graph for structural reasoning
• Router decides between:
  • pure retrieval
  • graph-assisted RAG
• Clear extension point for richer legal knowledge graphs

Online PDF Ingestion (Incremental Indexing)

• Upload PDFs → parse → chunk → JSONL
• Incremental FAISS add
• BM25 rebuild in background

4 System Architecture

The system is organized into four clearly separated layers:

1. Offline Build Law text preprocessing, index construction, graph building

2. Index Artifacts FAISS, BM25, and law_graph as immutable read models

3. Online Ingestion PDF upload → background incremental indexing

4. Online Serving (RAG + Routing) FastAPI + RagPipeline + Router + LLM

See the architecture diagram for the full data flow.

5 Quickstart (Local)

1. Clone & install

git clone https://github.com/Fan-Luo/Legal-RAG.git
cd Legal-RAG
pip install -r requirements.txt

2. Prepare law data & build index

The default corpus includes:

• Chinese: PRC Civil Code
• English: Uniform Commercial Code (UCC)

Queries are routed to language-specific corpora and indexes.

# preprocess law text into structured JSONL
python -m scripts.preprocess_law

# build FAISS + BM25 indexes
python -m scripts.build_index

# build law_graph
python -m scripts.build_graph

Artifacts are generated per language:

• data/processed/law_zh.jsonl, data/processed/law_en.jsonl
• data/index/zh/..., data/index/en/...
• data/graph/law_graph_zh.jsonl, data/graph/law_graph_en.jsonl

3. Start API service

python -m uvicorn legalrag.api.server:app --host 127.0.0.1 --port 8000 

4. Launch Demo

visit http://127.0.0.1:8000/ or http://127.0.0.1:8000/ui/

6 Example

from legalrag.config import AppConfig
from legalrag.pipeline.rag_pipeline import RagPipeline

cfg = AppConfig.load()
pipeline = RagPipeline(cfg)

question = "What standards must goods satisfy to be merchantable？"
ans = pipeline.answer(question)

print(ans.answer)

7 LLM Backends & Cost Model

Supported backends:

• Local LLM (Qwen series, need GPU and enough memory)
• OpenAI-compatible API (need to provide OpenAI API key)
  • No API key is collected via UI
  • LLM keys are read only from environment variables Note: If no key is provided and no local model loaded, the system gracefully degrades

8 Project Structure

Legal-RAG/
│
├── legalrag/
│   ├── __init__.py
│   ├── config.py                   
│   ├── schemas.py                 # LawChunk / RetrievalHit / RoutingDecision / RagAnswer
│   ├── llm/
│   │   ├── __init__.py
│   │   ├── gateway.py
│   │   └── client.py              # Qwen / OpenAI LLMClient 
│   │
│   ├── routing/
│   │   ├── __init__.py
│   │   ├── legal_issue_extractor.py
│   │   └── router.py              # QueryType + Graph/RAG Suggestions
│   │
│   ├── retrieval/
│   │   ├── __init__.py
│   │   ├── builders
│   │   ├── dense_retriever.py     # Dense (BGE + FAISS)
│   │   ├── vector_store.py        
│   │   ├── bm25_retriever.py      # Sparse (BM25 + jieba)
│   │   ├── colbert_retriever.py
│   │   ├── hybrid_retriever.py    # Dense + Sparse + Colbert + Graph + Rerank
│   │   ├── by_lang_retriever.py   # zh/en routing
│   │   ├── corpus_loader.py       # read all chunks from processed_dir
│   │   ├── incremental_indexer.py
│   │   ├── graph_retriever.py
│   │   ├── graph_store.py         # law_graph / legal_kg  
│   │   └── rerankers.py
│   │
│   ├── pdf/
│   │   ├── __init__.py
│   │   └── parser.py              # pdfplumber + OCR fallback
│   │
│   ├── ingest/
│   │   ├── __init__.py
│   │   ├── orchestrator.py
│   │   ├── service.py
│   │   ├── task_queue.py
│   │   └── ingestor.py            # PDFIngestor 
│   │
│   ├── pipeline/
│   │   ├── __init__.py
│   │   └── rag_pipeline.py        # Graph-aware RAG Core Inference
│   │
│   ├── prompts/
│   │   ├── prompt_zh.json         # Chinese prompt
│   │   └── prompt_en.json         # English prompt
│   │
│   ├── utils/
│   │   ├── __init__.py
│   │   ├── lang.py
│   │   ├── logger.py             
│   │   └── text.py                
│   │
│   └── api/
│       ├── __init__.py
│       └── server.py              # FastAPI（/rag/retrieve, /rag/answer, /ingest/pdf）
│
├── ui/
│   ├── index.html
│   └── demo.qmd
│
├── scripts/
│   ├── preprocess_law.py          # parse law → LawChunk JSONL
│   ├── build_index.py             # FAISS + BM25 + Colbert indexes
│   ├── build_graph.py             # law_graph / legal_kg  
│   ├── bgenerate_synthetic_data.py
│   └── evaluate_retrieval.py      # Hit@K / MRR / nDCG
│
├── notebooks/
│   ├── 01_Launch_the_UI.ipynb
│   ├── 02_LegalRAG_Pipeline.ipynb
│   ├── 03_Retrieval_Performance_Evaluation.ipynb
│   └── 04_Law_Graph_Visualization.ipynb
│
├── data/
│   ├── raw/                         
│   │   ├── minfadian.txt            
│   │   └── ucc/                    
│   ├── processed/                 # law_zh.jsonl / law_en.jsonl
│   ├── index/                     # faiss/bm25/colbert per language
│   └── graph/                     # law_graph_zh.jsonl / law_graph_en.jsonl
│   └── eval/
│       
├── docs/
│   ├── architecture.mmd
│   └── architecture.png
│ 
├── tests/
│   ├── test_router.py
│   └── test_retrieval.py
│ 
├── README.md
├── README-zh.md
├── LICENSE
├── pyproject.toml
├── requirements.txt
├── _quarto.yml
├── index.qmd
├── app.py                           # Hugging Face Space entry
├── Dockerfile
└── .gitignore                       

9 Who is this project for?

This repository is intended for:

• Engineers exploring RAG system design
• Researchers working on legal NLP / AI + law
• Practitioners interested in traceable AI systems
• Candidates demonstrating architecture-level thinking

⚠️ This project provides legal information assistance for educational and research purposes only and does not constitute legal advice. Users should not rely on this project as a substitute for professional legal counsel. The authors and contributors disclaim any liability for any direct or indirect consequences arising from the use of this project.

10 Extensibility

Legal-RAG is intentionally structured to support:

• richer legal knowledge graphs
• multi-document reasoning
• multi-tenant isolation
• BYOK (Bring Your Own Key) SaaS models

These are architectural affordances, not product promises.

11 License

Apache License 2.0

This repository contains source code only. Users are responsible for complying with the licenses of any models or APIs they choose to integrate.