Comparisons

Pick LangSmith for LangGraph agents you want traced and hosted by one vendor. Pick Arize when the same team also watches classic ML models, or when traces must stay on your own servers through free Phoenix.

Pick Langfuse when your license policy needs MIT or you want cloud usage billed in units, where Arize AX bills by spans and GB. Pick Arize when the same team also monitors classic ML models. Phoenix, under the Elastic License 2.0, is Arize's free self-hosted tracer.

On Parlance Labs' 100 production traces, Braintrust Loop caught the most failures and 91% of Arize Alyx's flags were valid. Pick Arize to self-host free on Phoenix; pick Braintrust for Pro overage rates you can price, US$474 a month at 200,000 traces in GILD's calculation.

Handshake built both into one internal LLM service. Pick Datadog Agent Observability when your operators already live in Datadog and want agent traces beside APM, billed per LLM span. Pick Arize when AI engineers need their own evaluation workspace or Phoenix to self-host.