Helicone is an open-source LLM observability platform that provides logging, monitoring, caching, and cost analytics for AI applications with a single line of code change. It captures every LLM request with full prompt and response details, latency, token counts, and costs — providing the visibility needed to debug AI applications, optimize prompt performance, and control API spending. AI engineers building production LLM applications use Helicone to maintain operational awareness of their AI systems, identify performance bottlenecks, and make data-driven decisions about model selection and prompt optimization.