Best Open-Source LLM Frameworks and Gateways

DSPy is about programming language models with modules, signatures, and optimizers rather than prompt strings. Haystack is about building production-ready retrieval, search, and agent pipelines with strong component orchestration. LiteLLM is about making many model providers look and behave like one governed access layer.

That means the right choice depends less on hype and more on where the architecture is actually hurting.

All three tools have strong open-source stories, which makes adoption easier. But the real costs show up elsewhere. DSPy burns model spend during optimization. Haystack carries infrastructure, retrieval, and model-provider costs. LiteLLM is free at the software layer, but it still sits in front of real provider bills and may introduce an enterprise support layer once governance matters.

The most honest buying lens is total operating model, not license fee alone.

If the problem is prompt sprawl and weak optimization discipline, DSPy is the cleanest step up. If the problem is building reliable retrieval and production RAG pipelines, Haystack is often the better fit. If the problem is fragmented access across OpenAI, Anthropic, Bedrock, Vertex, and others, LiteLLM is usually the highest-leverage fix.

The best tool in this batch is the one that solves the bottleneck you already have, not the one that sounds most sophisticated.