Helicone

Helicone is an LLM observability and proxy platform that provides instant visibility into every LLM call your application makes, logging requests, tracking costs, measuring latency, and enabling prompt management, with a one-line integration that requires no SDK changes to your existing codebase. The proxy model is Helicone's core technical differentiator: rather than wrapping LLM calls with SDK decorators throughout your code, you change one base URL to route traffic through Helicone's proxy, and full observability activates for every call automatically. This approach works for any programming language and any LLM provider that uses the OpenAI API format without modifying application code beyond the URL change. The dashboard aggregates request data into views of cost by model, latency percentiles, error rates, and token usage over time, the operational metrics that production AI applications require but that LLM providers don't surface in their own dashboards.

Prompt management stores prompt versions with the ability to deploy changes from the dashboard without code deployments, enabling prompt iteration without engineering involvement. Caching reduces costs for repeated queries by returning stored responses for identical inputs. Rate limiting per user or API key prevents cost overruns from heavy or unexpected usage. A/B testing different prompt versions or model configurations with statistical comparison enables data-driven optimization decisions.

Free tier covers 10,000 requests per month. Paid plans scale from $79/month (Pro) to $799/month (Team), plus metered usage overages. Commonly used alongside Langfuse for teams that want proxy-based observability and prompt management without SDK integration overhead.