When should you use Langfuse, and when should you skip it?

Use Langfuse when: self-hostable tracing, prompts and evals in one place. Skip it when: you want a fully managed product with a support contract.

When should you use LangSmith, and when should you skip it?

Use LangSmith when: teams already deep in LangChain needing tracing and datasets. Skip it when: traces cannot leave your infrastructure.

When should you use Braintrust, and when should you skip it?

Use Braintrust when: making evaluation, rather than tracing, the primary workflow. Skip it when: you need open formats and self-hosting.

When should you use Arize Phoenix, and when should you skip it?

Use Arize Phoenix when: OpenTelemetry-native evaluation you can run yourself. Skip it when: you want a vendor support contract behind it.

← Comparisons

Langfuse vs LangSmith vs Braintrust vs Phoenix

The interesting divide is not open versus closed, it is tracing versus evaluation. Most teams buy a tracing tool and then discover they still cannot answer whether a change helped.

Short answer

By Lattice editorial · Licence and cost facts verified 2026-09 · method

Evaluation & Observability

LangfuseSelf-hostable tracing, prompts and evals in one.
LangSmithDeep LangChain integration, strong dataset tooling.
BraintrustEval-first, with built-in scorers and a data flywheel.
Arize PhoenixOpen-source, OpenTelemetry-native evaluation.

Langfuse vs LangSmith vs Braintrust vs Phoenix compared across 6 dimensions
Dimension	Langfuse	LangSmith	Braintrust	Arize Phoenix
Best for	Self-hosting, or a privacy constraint	Teams already deep in LangChain	Making evaluation the primary workflow	OpenTelemetry-first, open-source everything
Self-hostable	Yes	Enterprise plan	Yes, paid	Yes, fully open
Open standards	OTel export	Partial	Proprietary	OTel-native throughout
Prompt management	First-class, with versioning and A/B	Basic	Yes	Limited
Evaluation	Datasets, scorers, CI-friendly	Strong offline and online eval	The strongest eval story of the four	Strong, trace-derived datasets
Where it loses	Depth of framework-specific debugging	Cost, and vendor lock-in at higher tiers	Traces are secondary to evals	Polish and support

Scroll the table sideways to see every tool.

What this table is not. These are editorial judgements, not benchmarks: Lattice has not run these tools head to head, and no cell uses GitHub stars or vendor benchmark claims as evidence. Licence and cost facts are re-checked on a schedule the build enforces — the receipt is public.

The recommendation

Which should you choose: Langfuse, LangSmith, Braintrust or Arize Phoenix?

If you cannot send traces outside your infrastructure, self-host Langfuse and stop deliberating. Otherwise pick on evaluation rather than tracing, because tracing is table stakes and evaluation is what you will actually rely on. Whatever you choose, make sure traces carry the full request and response — that is the input to every future decision.

Rules of thumb

Tracing answers 'what happened'. Only evaluation answers 'is this better'. Buying one and expecting the other is the common mistake.
Check that model names, versions and per-hop latency are captured, or your cost and regression analysis will be wrong.
Adopting OpenTelemetry as the export format keeps your future options open at close to no cost.

Quick answers

When should you use Langfuse, and when should you skip it?: Use Langfuse when: self-hostable tracing, prompts and evals in one place. Skip it when: you want a fully managed product with a support contract.
When should you use LangSmith, and when should you skip it?: Use LangSmith when: teams already deep in LangChain needing tracing and datasets. Skip it when: traces cannot leave your infrastructure.
When should you use Braintrust, and when should you skip it?: Use Braintrust when: making evaluation, rather than tracing, the primary workflow. Skip it when: you need open formats and self-hosting.
When should you use Arize Phoenix, and when should you skip it?: Use Arize Phoenix when: OpenTelemetry-native evaluation you can run yourself. Skip it when: you want a vendor support contract behind it.