Helicone

Open-source LLM observability platform using a proxy-based architecture. Unlike LangSmith or Langfuse, Helicone requires NO Python SDK install for core tracing — it works by routing requests through its AI gateway (https://ai-gateway.helicone.ai) via a base_url override on the OpenAI/Anthropic client. All logging happens at the proxy layer. The 'helicone' PyPI package (helicone-helpers) is a thin optional helper with minimal functionality. Primary integration is via HTTP headers and base_url, not a Python library.