Replace / LangSmith
Best free LangSmith alternatives (open source, self-hosted) 2026
The best open-source alternative to LangSmith is Langfuse or Helicone, self-hosted on Railway. LLM traces you host. Langfuse core is MIT; Helicone is Apache-2.0 — LangSmith without the hosted observability seat.
Estimated save $1,200 a year.
Open the stackStart on Railway
How LangSmith compares
| LangSmith | Langfuse / Helicone | |
|---|---|---|
| Pricing model | Hosted subscription | Open-source or fair-code license; you pay the host |
| Hosting | Vendor cloud | Self-hosted on Railway or any VPS |
| Rough monthly cost | Public list price not verified this run | Hosting only — no SaaS seat meter in this repo |
- Langfuse
MIT core LLM traces and evals (skip ee/)
- Helicone
Apache-2.0 LLM observability proxy you can self-host
FAQ
- What is the best free open-source LangSmith alternative?
- The best open-source alternative to LangSmith is Langfuse or Helicone, self-hosted on Railway. LLM traces you host. Langfuse core is MIT; Helicone is Apache-2.0 — LangSmith without the hosted observability seat.
- Is it free?
- The Langfuse / Helicone licenses are open source or fair-code. You still pay hosting (Railway or any VPS) and any APIs the stack calls. There is no LangSmith seat or task bill on this path.
- Can I migrate from LangSmith?
- Yes. Start with the workflows or data you actually use, then cut over. The Langfuse / Helicone stack page has the agent prompt and the cost table; most teams rebuild the slice that matters and leave old LangSmith links until they expire.
- How do I deploy it?
- Open the Langfuse / Helicone stack, copy the agent prompt, and deploy on Railway (one service, PORT, and a volume when the app needs disk). Placeholder: Langfuse (MIT core; skip ee/) plus Postgres. Helicone if that proxy is the shape. Phoenix is ELv2 — not the OSI path. No one-click template in this repo yet — Start on Railway. Serving stays on /stacks/vllm-inference.
- What does this replace?
- LangSmith. The published small-team estimate on this stack is $1,200 a year.
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