Build Retrieval-Augmented Generation systems for LLM

RAG Implementation

Master Retrieval-Augmented Generation (RAG) to build LLM applications that provide accurate, grounded responses using external knowledge sources.

When to Use This Skill

• Building Q&A systems over proprietary documents
• Creating chatbots with current, factual information
• Implementing semantic search with natural language queries
• Reducing hallucinations with grounded responses
• Enabling LLMs to access domain-specific knowledge
• Building documentation assistants
• Creating research tools with source citation

Core Components

1. Vector Databases

Purpose: Store and retrieve document embeddings efficiently

Options:

• Pinecone: Managed, scalable, serverless
• Weaviate: Open-source, hybrid search, GraphQL
• Milvus: High performance, on-premise
• Chroma: Lightweight, easy to use, local development
• Qdrant: Fast, filtered search, Rust-based
• pgvector: PostgreSQL extension, SQL integration

2. Embeddings

Purpose: Convert text to numerical vectors for similarity search

Models (2026):

Model	Dimensions	Best For
voyage-3-large	1024	Claude apps (Anthropic recommended)
voyage-code-3	1024	Code search
text-embedding-3-large	3072	OpenAI apps, high accuracy
text-embedding-3-small	1536	OpenAI apps, cost-effective
bge-large-en-v1.5	1024	Open source, local deployment
multilingual-e5-large	1024	Multi-language support

3. Retrieval Strategies

Approaches:

• Dense Retrieval: Semantic similarity via embeddings
• Sparse Retrieval: Keyword matching (BM25, TF-IDF)
• Hybrid Search: Combine dense + sparse with weighted fusion
• Multi-Query: Generate multiple query variations
• HyDE: Generate hypothetical documents for better retrieval

4. Reranking

Purpose: Improve retrieval quality by reordering results

Methods:

• Cross-Encoders: BERT-based reranking (ms-marco-MiniLM)
• Cohere Rerank: API-based reranking
• Maximal Marginal Relevance (MMR): Diversity + relevance
• LLM-based: Use LLM to score relevance

Quick Start with LangGraph

from langgraph.graph import StateGraph, START, END
from langchain_anthropic import ChatAnthropic
from langchain_voyageai import VoyageAIEmbeddings
from langchain_pinecone import PineconeVectorStore
from langchain_core.documents import Document
from langchain_core.prompts import ChatPromptTemplate
from langchain_text_splitters import RecursiveCharacterTextSplitter
from typing import TypedDict, Annotated

class RAGState(TypedDict):
    question: str
    context: list[Document]
    answer: str

# Initialize components
llm = ChatAnthropic(model="claude-sonnet-5")
embeddings = VoyageAIEmbeddings(model="voyage-3-large")
vectorstore = PineconeVectorStore(index_name="docs", embedding=embeddings)
retriever = vectorstore.as_retriever(search_kwargs={"k": 4})

# RAG prompt
rag_prompt = ChatPromptTemplate.from_template(
    """Answer based on the context below. If you cannot answer, say so.

    Context:
    {context}

    Question: {question}

    Answer:"""
)

async def retrieve(state: RAGState) -> RAGState:
    """Retrieve relevant documents."""
    docs = await retriever.ainvoke(state["question"])
    return {"context": docs}

async def generate(state: RAGState) -> RAGState:
    """Generate answer from context."""
    context_text = "\n\n".join(doc.page_content for doc in state["context"])
    messages = rag_prompt.format_messages(
        context=context_text,
        question=state["question"]
    )
    response = await llm.ainvoke(messages)
    return {"answer": response.content}

# Build RAG graph
builder = StateGraph(RAGState)
builder.add_node("retrieve", retrieve)
builder.add_node("generate", generate)
builder.add_edge(START, "retrieve")
builder.add_edge("retrieve", "generate")
builder.add_edge("generate", END)

rag_chain = builder.compile()

# Use
result = await rag_chain.ainvoke({"question": "What are the main features?"})
print(result["answer"])

Detailed patterns and worked examples

Detailed pattern documentation lives in references/details.md. Read that file when the navigation tier above is insufficient.