Last updated 06-27-2026
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LangChain
LangChain is the company behind the most widely used open source stack for building LLM agents, plus LangSmith, a commercial platform for observing, evaluating, and deploying them in production. Teams use it to move from a prototype chatbot to a reliable agent with tracing, evals, and managed deployment without rebuilding their stack each time.
The product line spans three open source frameworks (LangChain, LangGraph, and Deep Agents) and a LangSmith suite that covers observability, evaluation, deployment, Fleet no-code agents, Sandboxes for agent-generated code, and Engine for autonomous failure diagnosis. LangSmith is framework agnostic, with native tracing for popular agent frameworks, OpenTelemetry, and SDKs for Python, TypeScript, Go, and Java.
It is built for software engineers, ML teams, and platform groups shipping agent features inside real products. Customer stories on the site cite Klarna, ServiceNow, and C.H. Robinson using LangSmith in production, and LangChain reports 6,000+ active LangSmith customers with five Fortune 10 companies on the platform.
Open source LangChain, LangGraph, and Deep Agents frameworks with 1,000+ model and tool integrations
LangSmith traces every agent step with SDKs for Python, TypeScript, Go, and Java
Turn production traces into datasets and score agents with human review or LLM-as-judge evals
Deploy LangGraph agents with durable memory, human-in-the-loop flows, and MCP or A2A support
Fleet lets non-technical teams describe recurring tasks in plain language and run them as agents
LangSmith Engine clusters production failures and proposes fixes from your traces and code
Open source LangChain framework is MIT-licensed with 1 billion+ downloads reported on the site.
LangSmith covers the full agent lifecycle from tracing and evals to production deployment.
Framework-agnostic observability works beyond LangChain-only stacks.
Enterprise deployment options include SaaS, hybrid, and self-hosted hosting.
LangSmith Deployment and Sandboxes require a Plus or Enterprise plan, not the free Developer tier.
Usage-based trace, deployment, and Engine metering can add cost quickly at scale.
Fleet and several advanced LangSmith services are not available on the free Developer plan.
Is LangChain free to use?
Yes. The LangChain open source framework is MIT-licensed and free to use. LangSmith also offers a free Developer plan at $0 per seat with 5,000 base traces per month included, then pay-as-you-go usage.
How much does LangSmith cost?
LangSmith's Developer plan is $0 per seat per month with pay-as-you-go usage after 5,000 base traces. The Plus plan is $39 per seat per month with 10,000 base traces included. Enterprise pricing is custom and requires contacting sales.
What is the difference between LangChain and LangSmith?
LangChain is the open source framework for building agents with pre-built architectures and integrations. LangSmith is LangChain's commercial agent engineering platform for observability, evaluation, deployment, and no-code agents. LangChain integrates with LangSmith through environment configuration.
Does LangSmith work with frameworks other than LangChain?
Yes. LangSmith is framework agnostic. It offers native tracing for popular agent frameworks and OpenTelemetry, so teams can observe and evaluate agents built with other stacks, not only LangChain.
What hosting options does LangSmith offer?
LangSmith offers SaaS cloud hosting with US or EU data residency on Developer and Plus plans. Enterprise customers can choose cloud, hybrid, or fully self-hosted deployments with custom SSO, RBAC, and support SLAs.
Does LangChain train on my LangSmith data?
No. LangChain states that LangSmith does not use customer traces, prompts, or outputs to train models. Organization data stays private under LangSmith's terms of service.