Traces of what it did, and a score for whether that was any good.
| Option | What it does | Licence | Self-host |
|---|---|---|---|
| Langfuse | Open-source tracing, prompt management and evals. Self-hostable in one compose file. | Open source | Yes |
| LangSmith | Tracing, datasets and evals from the LangChain team. | Proprietary | No |
| Braintrust | Eval-first platform — scorers, datasets and a playground for prompt iteration. | Proprietary | Yes |
| Arize Phoenix | OpenTelemetry-native tracing and evals you can run locally. | Open source | Yes |
| Pydantic Logfire | OpenTelemetry observability with first-class Python and Pydantic AI support. | Open source | No |
| promptfoo | Local eval and red-team harness that runs in CI. No account needed. | Open source | Yes |
Traces of what it did, and a score for whether that was any good. Every stack needs one — it is not optional.
This registry tracks 6. 4 are open source and 4 can run on your own infrastructure.
It depends on constraints rather than preference: whether you must self-host, whether the budget allows a hosted service, and which language your team writes. Describe what you are building and the advisor fills this layer along with the other 9.
Every page here answers to Accept: text/markdown and returns the same content at roughly a tenth the tokens. No separate site, no toggle — same URL.
curl -s -H "Accept: text/markdown" https://newagent.build/layers/observability