Haystack

Haystack is an open-source Python framework, created by deepset, for building production-ready applications with large language models. It offers composable pipelines and components for retrieval, generation, and evaluation, making it a popular foundation for RAG systems, semantic search, question answering, and agentic workflows. Its pipeline model lets developers wire together retrievers, rerankers, prompt builders, and generators cleanly.

Haystack is designed for developers who want flexibility and control over their LLM stack without vendor lock-in. It integrates with many model providers, vector databases, and document stores, and its component-based architecture makes complex pipelines readable and testable. Teams often prototype with Haystack and deploy it directly, or move to deepset Cloud for a managed experience.