Lunary vs Sentry
Both are observability & tracing tools. Here is how they actually differ on price, billing model and deployment.
Lunary
A lightweight Apache-2.0 observability platform aimed at RAG pipelines and chatbots. The fastest path from nothing to basic tracing, with a free tier metered daily rather than monthly - which catches people out.
Sentry
Excellent error tracking that keeps appearing in LLM observability roundups where it does not belong. Its AI product, Seer, is a code-debugging agent billed per contributor - not an LLM tracing or evaluation platform.
| Lunary | Sentry | |
|---|---|---|
| Category | Observability & Tracing | Observability & Tracing |
| Our rating | 3/5 | 2/5 |
| Starting price | Around $20-30/mo | $26/mo |
| Billing meter | event | event |
| Free plan | Yes | Yes |
| Free self-hosting | Yes, free | No or paid tier only |
| Best for | Small teams shipping RAG pipelines or chatbots who want basic tracing working this afternoon, and who will either stay small or self-host before volume becomes expensive. | Error tracking and front-end debugging, which it does superbly. It is not the right tool for observing or evaluating LLM applications, and should be paired with one rather than substituted for one. |
Our verdict on Lunary
Lunary is a good starter tool that knows what it is. It is optimised for RAG pipelines and chatbots rather than trying to be a complete AI engineering platform, it is Apache 2.0 and self-hostable, and it is among the fastest things in the category to get running. Radar - which buckets responses against criteria you define - is a genuinely useful idea for spotting patterns that individual traces hide. Two caveats matter. The free tier is 1,000 events per day rather than per month, which is a meaningfully tighter constraint than the headline suggests and will not survive a real chatbot for long. And published pricing is inconsistent across sources in a way we could not resolve, with figures ranging from around $20 to $200 a month depending on where you look. Against Langfuse it is lighter on nearly every axis, and Langfuse is the better default for most teams. Lunary earns its place when speed to first trace matters more than depth.
Full Lunary review →Our verdict on Sentry
We are including Sentry because it keeps appearing in LLM observability comparisons, and the most useful thing we can tell you is that it does not belong in them. Sentry is an outstanding error tracking and performance monitoring product. What it is not is an LLM observability platform. It does not do prompt and completion capture, token accounting, per-model cost attribution or output-quality evaluation in the way this category means those terms. The confusion comes from Seer, Sentry's AI product, which roundups see and file as AI observability. Seer is a code debugging agent - it looks at your errors and proposes fixes - billed at $40 per active contributor per month, where an active contributor is anyone opening two or more pull requests to a Seer-enabled repository in a billing cycle. That is a developer productivity tool, not agent observability. Run Sentry for your application errors, absolutely. Run something else for your LLM calls.
Full Sentry review →Frequently Asked Questions
What is the main difference between Lunary and Sentry?
Lunary: Small teams shipping RAG pipelines or chatbots who want basic tracing working this afternoon, and who will either stay small or self-host before volume becomes expensive. Sentry: Error tracking and front-end debugging, which it does superbly. It is not the right tool for observing or evaluating LLM applications, and should be paired with one rather than substituted for one. Both sit in Observability & Tracing, so the decision usually comes down to billing model and deployment rather than raw capability.
Which is cheaper, Lunary or Sentry?
It depends entirely on your workload shape, because they meter differently - Lunary bills on event and Sentry bills on event. Published starting prices are Around $20-30/mo and $26/mo respectively, but those numbers are not comparable until you apply them to the same traffic. Use our cost calculator to model both against your own request volume and span count.
Can I self-host Lunary or Sentry?
Lunary: Yes, free. Sentry: No or paid tier only. Free self-hosting means no licence fee, not no cost - you still own the infrastructure, upgrades and on-call.