Pick LangSmith if
engineers who already write agent code and will open traces when a run surprises them.
Read the LangSmith pageLangSmith vs Phoenix
Our take
Pick LangSmith if engineers who already write agent code and will open traces when a run surprises them. Pick Phoenix if agent teams who will self-host Phoenix for $0 (uvx arize-phoenix serve) and only open Arize AX when they want a managed cloud.
LangSmith
LangChain’s hosted observability and eval
Best for
LangSmith See what an agent did, then score it
Phoenix See why an agent failed and prove a fix
Free plan
LangSmith $0 · / seat / month. 1 seat. 5,000 base traces/month, then pay-as-you-go. 7 LSU Fleet allowance/month. Community support
Phoenix $0 · local / Docker / Kubernetes. You bring compute. Homepage: uvx arize-phoenix serve
Lowest paid
LangSmith Plus $39/mo
Phoenix AX Pro $50/mo
Runs where
LangSmith Hosted
Phoenix Hosted
Watch out
LangSmith Traces after 5k / 10k bill in arrears
Phoenix ELv2, not Apache
Last checked
LangSmith 2026-10-22 · langchain.com/pricing
Phoenix 2026-10-22 · arize.com/pricing
Which one, then?
Pick Phoenix if
agent teams who will self-host Phoenix for $0 (uvx arize-phoenix serve) and only open Arize AX when they want a managed cloud.
Read the Phoenix page