LangSmith vs Arize AX 2026: Enterprise Platform Against $50 Unlimited Seats
Quick verdict: LangSmith is our overall pick for langsmith vs arize-ax.
Arize AX gives unlimited users and unlimited evals on every tier and enters at $50/mo; LangSmith starts at $0 for one seat but pays $39 per seat beyond that and meters every trace in LSUs.
| Tool | Rating | Pricing | Best for |
|---|---|---|---|
| LangSmith Best overall Best for teams | 4.4/5 | Free $39/seat/mo (Plus) | LangSmith is the observability and evaluation platform from the LangChain team: $0/seat wi… |
| Arize AX Best free | 4.0/5 | Free $50/mo (AX Pro) | Arize AX is the cheapest paid step in the cluster at $50/mo, with a $0 Free tier (25K span… |
Bottom line: if a wide group needs read-only visibility - support, product, leadership - seat pricing works against you and Arize AX never charges for seats. LangSmith is the pick when the platform around the traces (deployment, engine, prompt hub) justifies the seat model. Arize also has the stronger local story: Phoenix is free and open source, while AX self-hosting is Enterprise-only. Pick Langfuse for a mid-point price with self-hosting at every tier.
Pricing and details
LangSmith · 4.4/5
Free plan available · $39/seat/mo (Plus)
Trace volume is metered in LangChain Standard Units (LSU) at $1.00/LSU on top of the seat fee; base traces carry 14-day retention, extended traces 180 days, and retention auto-upgrades can raise your bill
No annual pricing published on the LangSmith pricing page
LangSmith is the observability and evaluation platform from the LangChain team: $0/seat with 5K base traces a month, Plus at $39/seat with 10K, then pay-as-you-go at $1.00 per LangChain Standard Unit.
Score breakdown
Pros
- Widest platform in the cluster - tracing, monitoring, evaluation, prompt hub, deployment, sandboxes and an autonomous debugging engine under one login
- The only vendor that publishes its metering unit (LSU at $1.00) and per-resource rates, so a bill can be estimated before you commit
- 14-day base and 180-day extended retention are documented explicitly, including which actions upgrade a trace and which do not
- Native integrations for the major agent frameworks plus OpenTelemetry SDKs for Python, TypeScript, Go and Java
Cons
- Retention auto-upgrades are the bill trap: online evaluators and automation rules push matching traces to the pricier extended tier unless you opt out per evaluator
- Extended retention for SaaS tops out at 180 days as of 2026-09-14, so long-horizon analysis has to go to Enterprise customization
- Plus is $39/seat with unlimited seats, which punishes a wide read-only audience paying for observability they do not act on
Pricing verified 2026-10-03
Arize AX · 4.0/5
Free plan available · $50/mo (AX Pro)
Billed on signals, spans, ingestion volume and retention rather than seats - users and evals are unlimited on every tier; self-hosted deployment is Enterprise-only, while the open-source Phoenix platform is free and local
No published annual rate; a separate startup pricing track exists on the pricing page
Arize AX is the cheapest paid step in the cluster at $50/mo, with a $0 Free tier (25K spans, 1 GB, 15-day retention) and a free open-source sibling in Arize Phoenix for fully local tracing.
Score breakdown
Pros
- Unlimited users and unlimited evaluations on every tier, including the free one - the only cluster member that never charges for seats
- $50/mo is the cheapest paid step in the set, undercutting Braintrust Pro by 5x
- Arize Phoenix is a genuinely free, open-source, local-first platform for tracing and evaluation with no account required
- Session-level and multi-modal tracing (image, voice, PDF), agent trajectory visualizations and online/offline evals are unlimited on all tiers
Cons
- The free tier is narrow - 10 signals a month and 25K spans, so production volume will not fit
- Self-hosted deployment is Enterprise-only; the free local option is the separate Phoenix project, not AX itself
- SOC 2 Type II, SSO, audit logs, HIPAA and data-region choice start at Enterprise
Pricing verified 2026-10-03
Frequently asked questions
Which is better overall, LangSmith or Arize AX?
LangSmith is our overall pick (4.4/5 vs 4.0/5). Arize AX gives unlimited users and unlimited evals on every tier and enters at $50/mo; LangSmith starts at $0 for one seat but pays $39 per seat beyond that and meters every trace in LSUs.
Do LangSmith and Arize AX offer free plans?
LangSmith and Arize AX have a free tier. LangSmith paid plans start at $39/seat/mo (Plus); Arize AX paid plans start at $50/mo (AX Pro).
What does LangSmith cost?
$39/seat/mo (Plus) — Trace volume is metered in LangChain Standard Units (LSU) at $1.00/LSU on top of the seat fee; base traces carry 14-day retention, extended traces 180 days, and retention auto-upgrades can raise your bill. Prices were last verified on 2026-10-03.