LangSmith

What it is for

LangSmith is LangChain’s hosted observability and eval studio: traces, datasets, playground runs, and (on Plus) Deployment. Use it when the job is see what an agent did, then score it.

What makes it unique: the cover is LangSmith’s official Select generated examples UI from the datasets docs — Input / Output JSON pairs and Save examples.

Key features

• Generated examples table — Input / Output JSON pairs and Save examples (cover) from manage datasets.
• Traces — inspect nested spans, tokens, and tool calls in a tracing project (Tracing).
• Playground evals — run a prompt over a dataset from the UI.
• Annotation queues — send spans to a human review queue before you ship a change.
• Prompt hub — version a prompt and pin it on a later run.
• Deployment / Studio — host a graph and open it in Studio on Plus.

Who it's for

Best fit: engineers who already write agent code and will open traces when a run surprises them.

Pricing

Verified 2026-10-22 (Asia/Shanghai) from langchain.com/pricing. 1 LSU = $1.00. Seats bill monthly; traces bill in arrears.

• Developer — $0 / seat / month. 1 seat. 5,000 base traces/month, then pay-as-you-go. 7 LSU Fleet allowance/month. Community support.
• Plus — $39 / seat / month. Unlimited seats. 10,000 base traces/month, then pay-as-you-go. Deployment / Engine. 1 free small serverless deploy. 37 LSU Fleet allowance/month.
• Enterprise — custom (hybrid/self-host, SSO, SLA).

Base traces retain 14 days; extended traces 180 days (upgrade fee). LangSmith states it keeps traces private to the organization.

Limitations / costs

• Traces after 5k / 10k bill in arrears. A chatty agent leaves Developer quickly.
• Base traces expire in 14 days unless you upgrade retention.
• Engine / Fleet / sandboxes are LSU-metered. Plus includes a monthly allowance, then $1 / LSU.
• Developer is one seat. Team sharing starts on Plus.

Alternatives

• LangChain — the OSS libraries plus the same LangSmith seat table.
• Langfuse — OSS tracing you can self-host.
• Langflow — MIT visual builder on a similar agent idea.

Official tutorial

Official LangChain channel video: Getting Started with LangSmith (1/8): Tracing (oEmbed author: LangChain).

Written path: Create and manage datasets in the UI plus Pricing.

Website

https://www.langchain.com/langsmith

Source

Catalog row curated for AI Tools Nav. Cover is LangSmith’s official Select generated examples still from docs.langchain.com (Input/Output JSON + Save examples), a different still from the LangChain traces cover. Dollars checked on langchain.com/pricing (Developer $0; Plus $39; 1 LSU = $1). Tutorial: Getting Started with LangSmith on @LangChain (oEmbed).

Last verified

2026-10-22 (Asia/Shanghai) editorial check.