Table of Contents
Quick Answer
LangChain wins for general-purpose LLM apps and agents; LlamaIndex wins for advanced RAG and data-heavy workflows; Haystack wins for production-grade NLP pipelines at enterprise scale.
- Best for LLM apps & agents: LangChain + LangGraph
- Best for RAG & data ingestion: LlamaIndex
- Best for enterprise NLP pipelines: Haystack
LangChain Overview
LangChain (open source, $100M+ raised by LangChain Inc.) is the most-used LLM framework in 2027. LangChain provides chains, tools, and integrations; LangGraph adds durable agent state; LangSmith provides observability and evals. Deployed in 200K+ production apps.
LlamaIndex Overview
LlamaIndex focuses on the data side of LLM apps — ingestion, indexing, retrieval, and agents over structured and unstructured data. LlamaParse handles complex PDFs and tables; LlamaCloud offers managed services. Preferred for document-heavy RAG.
Haystack Overview
Haystack by deepset is the mature enterprise pipeline framework — production-ready from day one, with strong NLP heritage. Haystack 2.0 uses a clean component pipeline model and integrates with vector DBs, LLMs, and evaluation tools. Trusted by regulated enterprises.
Head-to-Head Comparison
Feature
LangChain
LlamaIndex
Haystack
Agent framework
LangGraph (industry leading)
Yes
Limited
RAG depth
Good
Excellent
Excellent
Document parsing
Good
LlamaParse (excellent)
Good
Observability
LangSmith
Limited
Yes
Production maturity
Maturing
Maturing
Yes (industry leading)
Community size
Largest
Large
Medium
Language support
Python, JS
Python, TS
Python
Enterprise adoption
Large
Growing
Large
Pricing Comparison
Offering
LangChain
LlamaIndex
Haystack
Open source
Free
Free
Free
Hosted / Cloud
LangSmith (paid)
LlamaCloud (paid)
deepset Cloud (paid)
Starter
$39/mo
$50/mo
Custom
Enterprise
Custom
Custom
Custom
Best For
- Building AI agents: LangChain + LangGraph
- Advanced RAG over PDFs: LlamaIndex + LlamaParse
- Enterprise NLP pipelines: Haystack
- Prototyping: LangChain — biggest ecosystem
- Data-heavy apps: LlamaIndex — deeper data abstractions
- Regulated industries: Haystack — production hardening
Our Verdict
For greenfield LLM apps in 2027, LangChain + LangGraph + LangSmith is the most complete stack. For document-heavy RAG, LlamaIndex is better optimized. For enterprise deployments requiring observability and hardening, Haystack remains a safer bet.
FAQs
Which has the largest community? LangChain — most GitHub stars, most Stack Overflow answers.
Which has the best RAG? LlamaIndex — particularly with LlamaParse for PDFs.
Which is most production-ready out of the box? Haystack — pipelines designed for scale.
Can I mix them? Yes — LangChain can call LlamaIndex retrievers.
Which supports TypeScript? LangChain (LangChain.js) and LlamaIndex (LlamaIndex.TS).
Conclusion
Agents → LangChain + LangGraph. Document RAG → LlamaIndex. Enterprise pipelines → Haystack. Most teams start with LangChain and add the others as they specialize.