Helicone vs Langfuse

Gateway capture or SDK instrumentation

Both are open-source-leaning observability options with self-hosting paths, and the real difference is how the data arrives. One is proxy-first: point your client at a different base URL and calls are captured without application changes. The other is SDK-first: instrument the code and emit structured traces that describe the shape of the work. Neither is strictly better, and the right answer is usually dictated by what you are trying to see.

If the immediate question is where the money is going, the proxy answers it fastest and with the least code. If the question is why a multi-step agent run took fourteen calls and produced the wrong answer, you need the nesting and the step-level detail that instrumentation gives. A number of teams run the gateway for enforcement and cost attribution and the SDK for the agent paths specifically, which is more sensible than it sounds — they are answering different questions.

A cheap way to settle it is to write down the three questions you most need answered next month. If they are all of the form 'what is this costing and how slow is it', the gateway gets you there in an afternoon. If any of them is 'why did this agent run go wrong', you will want the nesting that SDK instrumentation provides, and you will want it before the incident rather than after. Note also that whichever you pick, prompt payloads are the sensitive part — decide your redaction and retention policy before turning capture on, not once the store is full.

Where each one genuinely wins

• —Helicone genuinely wins on adoption cost and on being an enforcement point. A gateway you route through can also cache, rate-limit and apply policy, which an observability SDK by design cannot.
• —Langfuse genuinely wins on trace structure and evaluation. Nested spans for agent work, dataset and eval management next to the traces, and framework-agnostic instrumentation make it the better fit once the workload is more than single calls.