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.
Mastra
TypeScript-first framework for building AI agents and workflows. Supports tool use, memory, RAG, and evals with first-class Vercel AI SDK integration.