Spanlens Open-Sources LLM Observability Platform with One-Line Integration

Spanlens is an MIT-licensed LLM observability platform that monitors calls to OpenAI, Anthropic, Gemini, and other models via a proxy or CLI wizard. It tracks cost, latency, and tokens per request, and offers agent tracing, anomaly detection, and alerts. The platform also includes PII scanning, prompt injection blocking, and A/B testing with statistical significance.