LlamaIndex
Data framework for LLM applications — indexing and retrieval
Verdict
Best-in-class for document ingestion, chunking strategies, and advanced retrieval (HyDE, hybrid search). Prefer it over LangChain when the core workflow is RAG-heavy.
Other Frameworks & SDKs
- DSPyStable
Stanford framework for programming (not prompting) LMs
- GuidanceExperimental
Microsoft's constrained generation library for structured LLM output
- HaystackStable
Deepset open-source NLP framework for production LLM pipelines
- InstructorProduction
Structured outputs from LLMs using Pydantic schemas
- LMQLExperimental
Query language for LLMs — SQL-like syntax for constrained generation
- LangChainProduction
Composable LLM application framework — chains, agents, RAG