Langfuse or Helicone?

Langfuse if you want traces and evals (the published LangSmith stack). Helicone if you want that Apache-2.0 proxy — /compare/langfuse-vs-helicone.

Useful, and not OSI. Elastic License 2.0 forbids offering it as a hosted service to third parties — /compare/langfuse-vs-phoenix.

Is this Weights and Biases?

No. Training runs are /replace/wandb (MLflow). This page is LLM traces.

Stacks / AI chat

Medium

Langfuse / Helicone

LLM traces you host. Langfuse core is MIT; Helicone is Apache-2.0 — LangSmith without the hosted observability seat.

The problem

LangSmith is LangChain's hosted trace and eval product. You wanted traces on Postgres you control. Langfuse is MIT outside ee/ (langfuse/langfuse) — skip ee/. Helicone is Apache-2.0 (Helicone/helicone). Phoenix (Arize-ai/phoenix) is Elastic License 2.0 — not OSI; you may not provide it as a hosted service to third parties. This is not LangSmith's every eval SKU. Training runs stay on /replace/wandb. You still pay tokens to the model vendor.

Replaces

LangSmith

Replace LangSmith See all best open-source LLM observability tools

Estimated SaaS saved

$1,200

per year, small team, before lock-in

Start on Railway

MLflow if this is training runs, not LLM traces

Sponsor this stack Tip jar

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.

The stack

Langfuse
MIT core LLM traces and evals (skip ee/)
Catalog entry →
Helicone
Apache-2.0 LLM observability proxy you can self-host
Catalog entry →

Cost table

You stop paying	Typical / year	Self-host instead
LangSmith (small team)	$1,200	Langfuse (MIT core) or Helicone

Agent setup prompt

Replace LangSmith with Langfuse (MIT core; skip ee/) or Helicone.

- Official compose. Persist Postgres. Point one app at the ingest URL. Do not enable ee/ and call that OSS.
- Phoenix is Elastic License 2.0 — not the OSI path. Training runs stay on /stacks/mlflow-tracking.
- Write AGENT_PROMPT.md.

Also as markdown: /stacks/langfuse-observe.md

FAQ

Langfuse or Helicone?: Langfuse if you want traces and evals (the published LangSmith stack). Helicone if you want that Apache-2.0 proxy — /compare/langfuse-vs-helicone.
What about Phoenix?: Useful, and not OSI. Elastic License 2.0 forbids offering it as a hosted service to third parties — /compare/langfuse-vs-phoenix.
Is this Weights and Biases?: No. Training runs are /replace/wandb (MLflow). This page is LLM traces.