Haystack

Haystack is an open-source Python framework for building applications on top of language models, with a special focus on search and retrieval. You assemble pipelines out of components such as retrievers, rankers and generators, and see exactly how data flows between them. Because the pieces are modular, you can swap a vector database or model without rewriting the app. It is designed with production in mind, including serialization, evaluation and monitoring hooks. Haystack is free and open source, and deepset offers an enterprise platform on top of it. It is well liked by teams who want clear, testable pipelines.