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.
Vercel AI SDK
Open-source SDK for building AI-powered streaming UIs in Next.js and Node.js. Unified provider API supports OpenAI, Anthropic, and 20+ others.