langchain

Free

The agent engineering platform

Model APIsFreeFree tier

Inputs: textOutputs: text

Type

Open Source

Visit Website GitHub (135.7k stars)

About langchain

LangChain is an open-source agent engineering platform that provides a minimal, highly configurable agent harness called create_agent. The harness allows developers to compose exactly the agent their use case requires from model, tools, prompt, and middleware. It supports a wide range of large language model providers including OpenAI, Anthropic, Google, and others. LangChain is part of a broader ecosystem that includes LangGraph for low-level orchestration, Deep Agents for a batteries-included agent experience, and LangSmith for tracing, debugging, and evaluating agents. The platform is designed for developers who need to build custom agentic workflows with fine-grained control over behavior.

Key Features

Minimal, configurable agent harness (create_agent)

Support for multiple LLM providers (OpenAI, Anthropic, Google, etc.)

Composable primitives: model, tools, prompt, and middleware

Integration with LangGraph for advanced orchestration

Integration with LangSmith for tracing, debugging, and evaluation

Deep Agents offering batteries-included features like context compression and virtual filesystem

Open-source codebase available on GitHub

Pros & Cons

Pros

Highly configurable and minimal design allows for tailored agent creation
Supports a wide range of popular LLM providers out of the box
Part of a comprehensive ecosystem (LangGraph, LangSmith, Deep Agents) for scaling and monitoring
Open-source with an active community and extensive documentation
Free to use with no apparent licensing fees (open-source license)

Cons

Requires programming knowledge (Python) to use effectively
May have a learning curve for developers new to agent frameworks
Free tier usage limits or costs for hosted services (e.g., LangSmith) should be verified
Documentation and ecosystem can be complex due to multiple related projects
Performance and reliability depend on underlying LLM providers and their APIs

Best For

Building custom conversational agents with specific tools and promptsDeveloping agentic workflows that combine deterministic and LLM-driven stepsPrototyping and iterating on agent behavior with tracing and debuggingCreating agents that interact with external APIs or databases via custom toolsEducational projects to learn about agent architectures and LLM integration

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FAQ

Is LangChain free to use?

LangChain is open-source and appears to be free to use under its license. However, usage of integrated LLM providers or hosted services like LangSmith may incur costs; these should be verified on the respective provider's pricing page.

What programming language does LangChain use?

LangChain is primarily used with Python, as shown in the documentation examples. There may be other language bindings, but Python is the primary supported language based on available information.

What LLM providers does LangChain support?

LangChain supports multiple providers including OpenAI, Anthropic (Claude), Google (Gemini), and others such as OpenRouter, Fireworks, Baseten, Ollama, Azure, AWS Bedrock, and HuggingFace, based on the documentation.

Can I use LangChain without LangSmith?

Yes, LangChain can be used independently. LangSmith is an optional tool for tracing, debugging, and evaluating agents, but it is not required to use LangChain.