LangChain
FreeA framework for developing applications powered by language models.
FreeFree tier
Inputs: text, code, audio, videoOutputs: text, code, audio, video
About LangChain
LangChain is an agent engineering platform and open-source framework ecosystem for building, testing, deploying, and monitoring applications powered by large language models (LLMs). It provides a suite of tools including LangChain (rapid agent building), LangGraph (low-level control for production agents), Deep Agents (autonomous long-running agents), and LangSmith, a commercial platform offering observability, evaluation, deployment, and fleet management. LangSmith enables tracing, debugging, iterative improvement with human feedback, scalable deployment with checkpointing and human-in-the-loop, and autonomous issue detection via LangSmith Engine. Used by 35% of Fortune 500 companies, with over 1 billion open-source downloads and over 1 billion events processed daily on LangSmith.
Key Features
Open-source frameworks: LangChain, LangGraph, Deep Agents for building agents at varying levels of control
LangSmith Observability: native tracing, message threading, analytics, and AI-driven insights
LangSmith Evaluation: reusable LLM-as-judge evals, human feedback annotation, online/offline scoring
LangSmith Deployment: agent server with memory, conversational threads, durable checkpointing, human-in-the-loop, and scalable distributed runtime
LangSmith Fleet: no-code agent creation for routine tasks, with enterprise security and admin controls
LangSmith Engine: autonomous clustering of production failures, root cause analysis, and fix proposals
Framework-agnostic: supports Python, TypeScript, Go, Java SDKs and integration with any agent stack
Support for MCP and A2A protocol for interoperability
Pros & Cons
Pros
- Comprehensive platform covering the entire agent lifecycle: build, test, deploy, monitor
- Open-source core frameworks enable flexibility and community contributions
- Framework-agnostic LangSmith works with any agent stack, not just LangChain's own
- Used by major enterprises (35% of Fortune 500) with proven scalability
- LangSmith Engine autonomously identifies and diagnoses production issues, reducing debugging time
- Generous free tier (Developer plan with up to 5k traces/month) and pay-as-you-go pricing
Cons
- Advanced features (deployment, fleet, engine) require paid LangSmith plans, which can become expensive at scale
- Steep learning curve due to multiple frameworks and platform components
- Reliance on LangSmith for production-level observability and deployment may lock users into the ecosystem
Best For
Building and iterating on conversational AI agents and chatbotsDebugging complex agent behavior with detailed tracing and step-by-step timelinesEvaluating agent performance using real-world production traces and automated evalsDeploying long-running agents with managed scaling, fault tolerance, and human-in-the-loop interactionAutomating routine enterprise tasks like research, follow-ups, and status checks across toolsMonitoring and improving production AI systems with anomaly detection and issue resolution
FAQ
What is LangChain?
LangChain is an open-source framework and a commercial platform (LangSmith) for building, debugging, evaluating, deploying, and monitoring AI agents powered by large language models.
Is LangChain free to use?
Yes, LangChain's open-source frameworks (LangChain, LangGraph, Deep Agents) are free. LangSmith offers a free Developer plan with up to 5,000 base traces per month, then pay-as-you-go. Paid plans start at $39 per seat per month for Plus.
What is LangSmith?
LangSmith is LangChain's commercial agent engineering platform that provides observability (tracing), evaluation (evals, human feedback), deployment (agent server with checkpointing and human-in-the-loop), Fleet (no-code agent builder), and Engine (autonomous issue detection and root cause analysis).
Which programming languages does LangChain support?
LangChain and LangSmith provide SDKs for Python, TypeScript, Go, and Java. They also support OpenTelemetry for tracing.
How does LangSmith Engine work?
LangSmith Engine clusters production failures into prioritized issues, finds the root cause in traces and code, and proposes a fix for review. It uses AI to detect undetected issues autonomously.
Can I use LangSmith with non-LangChain agents?
Yes, LangSmith is framework-agnostic. You can trace any agent framework using its Python, TypeScript, Go, or Java SDKs, or integrate with any agent stack.