# LangSmith vs promptfoo

The deciding difference is operational: promptfoo can run on infrastructure you control, LangSmith cannot. If that constraint is real for you, it settles the choice before anything else is considered.

| | LangSmith | promptfoo |
| --- | --- | --- |
| Licence | Proprietary | Open source |
| Pricing | freemium | open source |
| Self-hostable | No | Yes |
| Languages | Python, TypeScript | TypeScript, Python |
| Install | — | npm install -g promptfoo |
| Keys required | LANGSMITH_API_KEY | None |

## Full pages

- https://newagent.build/c/langsmith
- https://newagent.build/c/promptfoo

## Machine interfaces

- `GET https://newagent.build/api/registry` — every component as JSON
- `GET https://newagent.build/api/vendors` — vendors, with the repo and releases feed to watch
- `GET https://newagent.build/api/advise?q=<plain english>` — recommended stack for a description
- `GET https://newagent.build/api/stack?<layer>=<id>&format=sh|json|md|yml|agents|env` — a stack as files
- `GET https://newagent.build/llms.txt` — the whole registry in one fetch

Any page here also returns markdown if you send `Accept: text/markdown`.