LiteLLM
OSS proxy that normalizes 100+ LLMs to the OpenAI format. Add routing, fallbacks, caching, and cost tracking in one layer.
Langfuse
Open-source platform for tracing, evaluations, and prompt management. Self-hostable alternative to LangSmith with broad framework support. Acquired by ClickHouse in January 2026; OSS core continues with deeper ClickHouse-backed analytics.