LangSmith vs Helicone

Two different entry points to the same problem

These tools approach observability from opposite directions, which is more useful than a feature table in deciding between them. One starts from the application layer: instrument your code, capture structured traces of chains and agents, and build evaluation on top. The other starts at the network layer: route your calls through a gateway and get logging, caching and cost attribution without changing application code. The integration cost and what you can see afterwards both follow from that choice.

Proxy-based capture is genuinely faster to adopt and gives you the cost and latency picture almost immediately, which is often what a team urgently needs. What it sees less naturally is the internal structure of a multi-step agent run — which call belonged to which task, what the parent step was trying to do. Application-level instrumentation sees that clearly and costs more to install. If your workload is mostly single calls, the proxy is efficient; if it is agentic, the structure is what you will want.

Whichever you choose, the field that makes the data useful is the same: a stable route identifier chosen in code, not derived from prompt text. Without it, cost and latency are aggregate numbers nobody can act on; with it, most attribution questions become a single grouping. Add it before you evaluate either tool, and the comparison becomes much easier to run on your own traffic rather than on a feature list.

Where each one genuinely wins

• —Helicone genuinely wins on time to value and on not touching application code. Changing a base URL and immediately having per-call cost and latency is hard to beat when you need attribution this week, and a proxy also gives you a natural enforcement point for caching and rate limits.
• —LangSmith genuinely wins on depth for complex applications. Nested traces of an agent run, tight coupling between traces and an evaluation suite, and prompt management as a first-class concern are worth the instrumentation effort once workflows stop being single calls.