dify

Build Agentic workflows, RAG pipelines, with rich AI model and tool support on one collaborative workspace. Deploy on cloud, VPC, or self-hosted, so teams move from prototype to production without rebuilding the stack. Maintained by langgenius on GitHub, where it has earned 154,537 stars from the community.

It's actively developed around ai, gpt, llm, and is a solid reference for anyone building with these tools.