LangChain
Composable LLM application framework — chains, agents, RAG
Verdict
Battle-tested for RAG pipelines and agent orchestration. Large ecosystem but high abstraction cost. Use LCEL (LangChain Expression Language) — avoid legacy Chain classes.
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
- LlamaIndexProduction
Data framework for LLM applications — indexing and retrieval