LangSmith
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.
Verified against: langchain.comdocs.langchain.comlangchain.com as of 2026-10-03
Quick verdict: LangSmith is the pick when your agents are complex enough that you need tracing, evaluation and deployment in one place, and when the framework integration breadth matters more than a predictable bill. It is the only vendor here that tells you what a trace actually costs ($1.00 per LSU) and which actions upgrade retention, which makes the cost model learnable even where it is uncomfortable. Pick Langfuse instead if the seat-plus-unit meter is a problem and you want open source with a self-hosted path, Braintrust if scoring volume is your main cost driver and you want the per-1K rate published up front, or Arize AX if $50/mo and unlimited evals matter more than platform depth.
- Our rating: 4.4/5
- Strongest dimension: Functionality (5/5, research only)
- Weakest dimension: Localization (2/5, research only)
- Pricing: Free plan · $39/seat/mo (Plus)
- Verification: Research-only pass over official sources, last checked 2026-10-03. Sources: langchain.com, docs.langchain.com, langchain.com
LangSmith pricing details
- Free plan available
- paid plans from $39/seat/mo (Plus)
- developer $0/seat/mo (1 seat, 5K base traces included) · Plus $39/seat/mo (10K base traces included, unlimited seats) · Enterprise custom, then pay-as-you-go
- no annual pricing published on the LangSmith pricing page
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
In our index: Developer $0/seat/mo (1 seat, 5K base traces) · Plus $39/seat/mo (10K base traces, unlimited seats) · Enterprise custom · usage at $1.00/LSU · base traces retain 14 days, extended 180
How LangSmith scores across our 6 index dimensions
- Functionality: 5/5 (research only)
- Usability: 4/5 (research only)
- Stability: 4/5 (research only)
- Collaboration: 4/5 (research only)
- Localization: 2/5 (research only)
- Value: 3/5 (research only)
Score rationale: The deepest feature surface in the cluster - tracing, monitoring, evaluation, prompt hub, deployment, engine - and the only vendor whose pricing model is published down to the metering unit (LSU at $1.00). The catch is cost predictability: base traces retain 14 days, extended 180, and evaluators plus automation rules silently upgrade matching traces to the pricier tier, so a busy evaluation workload raises the bill in a way the seat price does not advertise.
What LangSmith does well
- 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
Where LangSmith falls short
- 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
- No published annual rate, and Enterprise (self-hosted or hybrid, custom SSO/ABAC/RBAC) is only reachable through sales
How LangSmith compares to other LLM Observability tools
Our index tracks 5 LLM Observability tools. LangSmith sits at 4.4/5, with no annual pricing published on the langsmith pricing page. Here are the 4 closest alternatives we hold pricing and scoring evidence for.
- Langfuse — 4.3/5 · Free plan · $29/mo (Core)
Langfuse is the open-source-first LLM observability platform: free Hobby with 50K units a month, Core at $29/mo for 100K units and 90-day retention, Pro at $199/mo with three-year retention, Enterprise at $2,499/mo. - Braintrust — 4.2/5 · Free plan · $249/mo (Pro)
Braintrust is the observability and eval platform with the most explicit score pricing in the cluster: Starter is $0 with 10K scores a month, Pro jumps to $249/mo with 50K scores plus cheaper per-1K rates. - Arize AX — 4.0/5 · Free plan · $50/mo (AX Pro)
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. - Helicone — 3.8/5 · Free plan · $79/mo (Pro)
Helicone is the request-level observability and gateway layer priced per request: Hobby free with 10,000 requests a month, Pro at $79/mo, Team at $799/mo, and usage-based pricing on top.
Frequently asked questions about LangSmith
How much does LangSmith cost?
Free plan available; paid plans from $39/seat/mo (Plus); developer $0/seat/mo (1 seat, 5K base traces included) · Plus $39/seat/mo (10K base traces included, unlimited seats) · Enterprise custom, then pay-as-you-go; no annual pricing published on the LangSmith pricing page. Billing detail: 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. Figures verified 2026-10-03.
Does LangSmith have a free plan?
Yes. LangSmith has a free tier; paid plans start at $39/seat/mo (Plus).
What is LangSmith rated in our index?
LangSmith sits at 4.4/5 in our index, strongest on functionality (5/5, research only) and weakest on localization (2/5, research only). LangSmith is the pick when your agents are complex enough that you need tracing, evaluation and deployment in one place, and when the framework integration breadth matters more than a predictable bill. It is the only vendor here that tells you what a trace actually costs ($1.00 per LSU) and which actions upgrade retention, which makes the cost model learnable even where it is uncomfortable. Pick Langfuse instead if the seat-plus-unit meter is a problem and you want open source with a self-hosted path, Braintrust if scoring volume is your main cost driver and you want the per-1K rate published up front, or Arize AX if $50/mo and unlimited evals matter more than platform depth.
What are the drawbacks of LangSmith?
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 No published annual rate, and Enterprise (self-hosted or hybrid, custom SSO/ABAC/RBAC) is only reachable through sales.
What does LangSmith do well?
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.
How was LangSmith verified?
Research-only pass over official sources, last checked 2026-10-03. Sources: langchain.com, docs.langchain.com, langchain.com.
What are the alternatives to LangSmith?
We track Langfuse, Braintrust, Arize AX, Helicone as the closest alternatives in our LLM Observability index, and 4 head-to-head comparisons against LangSmith are available.