Overview
LangSmith is LangChain’s commercial platform for tracing, evaluating, and monitoring LLM applications. If you are building with LangChain, LangGraph, or almost any LLM framework, LangSmith provides the debugging, testing, and production-monitoring infrastructure that turns a fragile prototype into a service you can operate. Every execution of your app — an agent run, an evaluator run, or a playground session — becomes a trace containing each LLM call, tool use, and retrieval step, with inputs, outputs, latency, token usage, and errors all visible.
Beyond tracing, LangSmith adds a prompt playground for side-by-side iteration, datasets and evaluators for offline and online testing, annotation queues for human review, and online evaluations that run on live traffic. In our evaluation its core strength is closing the loop between building and operating: you can capture real production traces, turn them into an evaluation dataset, and block a prompt regression before it ships. The 2026 pricing also bundles LangGraph Cloud deployment, Fleet agents, and an Engine for autonomous failure diagnosis, so the platform is expanding from observability into a fuller agent-operations stack.
Key Features
- End-to-end tracing — every LLM call, tool, and retrieval step in a run is inspectable with latency, tokens, and errors.
- Prompt playground — test and compare prompt variants side by side without rerunning your app.
- Datasets and evaluators — build regression-proofing suites from production traces and run them offline or online.
- Annotation queues — structured human review of model outputs inside the same UI.
- LangGraph deployment — one-click deploy and horizontally scale long-running agents with auth and cron scheduling.
- Engine and Fleet — autonomous trace clustering that diagnoses failures and suggests prompt or code fixes.
Pricing
| Plan | Price | For |
|---|---|---|
| Developer | $0 /seat | 1 seat, 5,000 base traces/mo, 14-day retention, community support |
| Plus | $39/seat/mo | Unlimited seats, 10k traces + $2.50/1k overage, 400-day retention, email support |
| Enterprise | Custom | SSO/RBAC, self-host or hybrid, SLA, custom retention and volume |
Comparison
vs. LangChain: LangChain the framework is open-source and free; LangSmith is the paid platform that makes LangChain apps observable and testable. You can use one without the other, but together they cover build and operate.
vs. Dify: Dify is a full visual agent-building platform with its own built-in observability, whereas LangSmith assumes you build elsewhere and focuses purely on tracing and evaluation. Pick Dify to build and ship, LangSmith to deeply monitor a code-first stack.
vs. n8n: n8n is a general workflow automator you can wire to LLMs, with basic execution logs; LangSmith is purpose-built LLM observability with evaluations and datasets. Choose n8n for broad automation, LangSmith when trace-level debugging of AI calls is the priority.