Spanlens – Open-Source LLM Observability & Monitoring Spanlens is an open-source LLM observability platform that helps teams monitor AI applications with detailed agent traces, model costs, token usage, latency, caching, and evaluations. Its drop-in integration works across multiple AI providers while supporting streaming, tools, and structured outputs. Teams can identify performance issues, compare prompt versions, run evaluations in CI, and track AI workloads through a centralized dashboard. Visit: https://www.spanlens.io