
Langfuse
Helicone AI
LangSmith
Opik
Comet.com
RapidClaw.dev
Corrath
Open source LLM observability and monitoring for OpenAI, Anthropic, and Gemini. Request logging, cost tracking, agent tracing. Self-hostable, MIT licensed.

Opik
WordLlama
xseek
Acrux Core
Langfuse
Future AGI
Kiln AI
Lighteval is your all-in-one toolkit for evaluating LLMs across multiple backends - huggingface/lighteval

Which is more popular?
Website, pricing, platforms and company facts side by side.
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|---|---|---|
| Website | spanlens.io | github.com |
| Pricing | — | |
| Company | 2026 | — |
| Listed in |
In their own words, as submitted to SaaSHub.


Spanlens is an open source observability tool for LLM apps. You point your OpenAI, Anthropic, or Gemini client at the Spanlens proxy by changing the baseURL, and it records every request with the full body, token counts, cost, and latency. The dashboard shows per-model costs, latency percentiles,...
No description of LightEval yet.
What each product offers, as listed by its team.


Possible disadvantages
An editorial look at what each product does well and who it suits.


Overall verdict
Why this product is good
Recommended for
No analysis of LightEval yet.
How often each product is chosen within a category, 0–100% relative to the other.


As answered by people managing Spanlens and LightEval.
Spanlens's answer
I was building LLM apps on the side and kept pasting token counts into a spreadsheet to figure out what each feature cost me. The tools I tried were either acquired mid-migration, closed source, or heavier to self-host than the app I was trying to monitor. So in April 2026 I started building the tool I actually wanted: change one line, see every request. It launched in June 2026, and the whole codebase went up on GitHub under MIT from day one.
Spanlens's answer
The entire product is MIT licensed, including the dashboard, evals, and prompt A/B testing. There is no separate enterprise edition. Everything ships in one repo you can run with a single Docker Compose file. Integration is one line: you change the baseURL on your OpenAI, Anthropic, or Gemini client, and every call gets logged with its full body, token counts, cost, and latency. A few things that are usually paid add-ons come built in, like agent traces with a critical path view, A/B tests that use Welch's t-test to tell you whether a difference is real, and a recommender that flags cheaper models based on the traffic you actually send.
Spanlens's answer
Mostly because of where the market went. Helicone was acquired, LangSmith is closed source, and self-hosting Langfuse takes real setup work. Spanlens fills the gap those tools left: setup in about five minutes, one Docker Compose file if you want the data on your own servers, and no feature gating between free and paid tiers. To be fair, if you need SOC 2 reports and enterprise support today, the bigger platforms are ahead. If you want request logs, costs, and traces without adopting a heavy platform, that is what Spanlens was built for.
Spanlens's answer
Developers who ship LLM features in production apps. The typical user is a solo developer or a small team that added OpenAI or Anthropic calls to their product and now has no clear picture of what those calls cost or why some are slow. Agent builders are the second group, since multi-step workflows are hard to debug without traces. It is a developer tool through and through: if you don't touch code, you won't get much out of it.
Spanlens's answer
We don't publish customer names yet. Spanlens launched in June 2026, and most users so far are indie developers and small AI teams.
Spanlens's answer
TypeScript across the stack. The dashboard is Next.js, the API and proxy run on Hono, and data is split between Supabase Postgres for accounts and relational data and ClickHouse for request logs, which grow fast. The repo is a pnpm monorepo that also holds the JavaScript and Python SDKs, a CLI, and an MCP server. Self-hosting runs on Docker Compose, and OpenTelemetry traces can be ingested over OTLP.
Share your experience with using Spanlens and LightEval. For example, how are they different and which one is better?
When comparing Spanlens and LightEval, you can also consider the following products.

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Open-source LLM Observability for Developers
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Things you can do with the token embeddings of an LLM - dleemiller/WordLlama
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Build and deploy LLM applications with confidence
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xSeek helps marketing teams understand what to create and optimize to get cited by ChatGPT, Claude, Perplexity, and Gemini. Clarity that leads to action.
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