LangSmith
LangChain's platform for tracing, evaluating and deploying AI agents, built to work with any framework.
LangSmith is LangChain's framework-agnostic platform for observing, evaluating and deploying AI agents, with tracing SDKs for Python, TypeScript, Go and Java. Developer is free for one seat and 5k base traces a month; Plus is $39 per seat a month, billed monthly, and usage past the included traces is pay-as-you-go.
About LangSmith
Tracing records every step of an agent run, natively for popular agent frameworks and through OpenTelemetry, and the FAQ says it also works with apps built on the OpenAI SDK, Anthropic SDK, Vercel AI SDK, LlamaIndex or custom code, not just LangChain. Dashboards track token usage, latency, error rates, cost and feedback scores with alerts by webhook or PagerDuty, Insights clusters traces into usage patterns and failure modes, and Polly, a built-in AI assistant, helps read large traces.
Evaluation runs LLM-as-judge, code-based or multi-turn evaluators on real production traces, compares agent versions side by side and lets subject-matter experts annotate traces; Observability and Evaluation can be used separately. LangSmith Engine, scheduled every 6 hours, clusters production failures into issues, finds root causes in traces and code and proposes fixes for review.
LangSmith Deployment runs agents on a durable runtime with human-in-the-loop approvals and background agents, managed through a central registry with versioning, rollbacks and MCP and A2A support. Fleet lets non-technical teams describe the agent they need and asks permission before sensitive actions; Sandboxes run agent-generated code in isolation; and the LLM Gateway adds cost controls, rate limits, model fallbacks and PII redaction.
Usage across LangSmith products is metered in LangChain Standard Units, at $1 per LSU. Plus includes 1 free small serverless deployment, and Enterprise adds self-hosted and hybrid deployment, custom SSO, ABAC and RBAC, a support SLA and custom seats and workspaces, invoiced annually upfront. VC-backed startups can apply for discounted rates and up to $10,000 in credits.
Sources: langchain.com/langsmith/observability, /pricing, docs.langchain.com/oss/python/langchain/overview and /langsmith-platform, read 2026-10-26
LangSmith pros and cons
Pros
- The Developer plan costs nothing for one seat and, per the FAQ, covers development and small-scale production.
- The FAQ says tracing adds no latency: the SDK sends traces asynchronously, and your agent keeps running if LangSmith has an incident.
- LangSmith says it does not train on your data, and you own all rights to it.
- Hosting ranges from LangChain's cloud in the US or EU to bring-your-own-cloud and self-hosted setups.
Cons
- Developer is limited to 1 seat; teammates need Plus at $39 per seat a month, billed monthly.
- Self-hosted and hybrid deployment, custom SSO and a support SLA are listed only under Enterprise, which has custom pricing.
- Base traces are kept for 14 days; 180-day extended retention costs an extra fee.
- Usage beyond the included allowances is metered, and a single Engine run can use about 7 to 45 LSUs ($1 each).
Tagged
- Supports Claude
- Supports GPT
- Supports Gemini
- Supports Local Models
- Web-based
- Enterprise Plan
- Free
- Freemium
LangSmith alternatives
More from AI Web Apps.
- 01→Cohere Parse 5
Turn complex docs, tables & images into AI-ready data
- 02→Hy4 preview
Tencent's open-sourced 770B model with 49B active parameters and a 1M-token context, for long-horizon work.
- 03→1752vc Pitch Deck Analyzer
Know what investors will say before you ever hit send.
- 04Paid →Microduck
25 cm biped robot from Pollen Robotics, playable out of the box and retrainable with reinforcement learning.
- 05→Gemini 3.5 Transcribe
Our most precise speech-to-text model yet
- 06Freemium →Lenz
Fact-checking API that checks AI-written text against independent public sources and returns sourced verdicts.
Related reading
Concepts you should know
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</a>Frequently asked questions
- What is LangSmith?
- LangSmith — LangChain's platform for tracing, evaluating and deploying AI agents, built to work with any framework.
- Is LangSmith free?
- LangSmith offers a free tier and paid plans with higher limits or premium features.
- What are the alternatives to LangSmith?
- Similar tools in AI Web Apps on vibedonalds: Cohere Parse 5, Hy4 preview, 1752vc Pitch Deck Analyzer, Microduck.
- What are the downsides of LangSmith?
- Developer is limited to 1 seat; teammates need Plus at $39 per seat a month, billed monthly. Self-hosted and hybrid deployment, custom SSO and a support SLA are listed only under Enterprise, which has custom pricing. Base traces are kept for 14 days; 180-day extended retention costs an extra fee. Usage beyond the included allowances is metered, and a single Engine run can use about 7 to 45 LSUs ($1 each).
- How much does LangSmith cost?
- Developer is $0 for one seat with up to 5k base traces a month. Plus is $39 per seat a month, billed monthly, with up to 10k base traces; after that, traces are pay-as-you-go and billed monthly in arrears. Enterprise has custom pricing and is invoiced annually upfront.
- Does LangSmith only work with LangChain?
- No: LangSmith says it works with any LLM framework, including apps built with the OpenAI SDK, Anthropic SDK, Vercel AI SDK, LlamaIndex or custom code. It offers SDKs for Python, TypeScript, Go and Java and can send trace data to OpenTelemetry tools or ingest OpenTelemetry data.
- Can I self-host LangSmith?
- Yes: LangSmith offers managed cloud, bring-your-own-cloud and self-hosted options, and the pricing page lists self-hosted and hybrid deployment under Enterprise. Its SmithDB trace database can be self-hosted inside your VPC so sensitive traces stay in your infrastructure.
- What is LangSmith Fleet?
- Fleet is LangSmith's no-code agent builder for non-technical teams: you describe what you need, and it builds the agent, learns from your feedback and asks permission before sensitive actions. It is metered in LSUs with model costs included; each organization gets 7 LSUs a month on Developer and 37 on Plus.
- How do I turn on LangSmith tracing?
- The LangChain docs say to set LANGSMITH_TRACING=true and your API key to get started; for other stacks, LangSmith offers SDKs for Python, TypeScript, Go and Java and OpenTelemetry support.