How-to Guides¶
Here you’ll find answers to “How do I...?” types of questions. These guides are goal-oriented and concrete; they're meant to help you complete a specific task. For conceptual explanations see the Conceptual guide. For end-to-end walk-throughs see Tutorials. For comprehensive descriptions of every class and function see the API Reference.
LangGraph¶
Controllability¶
LangGraph offers a high level of control over the execution of your graph.
These how-to guides show how to achieve that controllability.
- How to create branches for parallel execution
- How to create map-reduce branches for parallel execution
- How to control graph recursion limit
- How to combine control flow and state updates with Command
Persistence¶
LangGraph Persistence makes it easy to persist state across graph runs (thread-level persistence) and across threads (cross-thread persistence). These how-to guides show how to add persistence to your graph.
- How to add thread-level persistence to your graph
- How to add thread-level persistence to subgraphs
- How to add cross-thread persistence to your graph
- How to use Postgres checkpointer for persistence
- How to create a custom checkpointer using MongoDB
- How to create a custom checkpointer using Redis
Memory¶
LangGraph makes it easy to manage conversation memory in your graph. These how-to guides show how to implement different strategies for that.
- How to manage conversation history
- How to delete messages
- How to add summary conversation memory
- How to add long-term memory (cross-thread)
- How to use semantic search for long-term memory
Human-in-the-loop¶
Human-in-the-loop functionality allows you to involve humans in the decision-making process of your graph. These how-to guides show how to implement human-in-the-loop workflows in your graph.
- How to add breakpoints
- How to add dynamic breakpoints
- How to edit graph state
- How to wait for user input
- How to view and update past graph state
- How to review tool calls
Streaming¶
Streaming is crucial for enhancing the responsiveness of applications built on LLMs. By displaying output progressively, even before a complete response is ready, streaming significantly improves user experience (UX), particularly when dealing with the latency of LLMs.
- How to stream full state of your graph
- How to stream state updates of your graph
- How to stream LLM tokens
- How to stream LLM tokens without LangChain models
- How to stream custom data
- How to configure multiple streaming modes at the same time
- How to stream events from within a tool
- How to stream events from within a tool without LangChain models
- How to stream events from the final node
- How to stream from subgraphs
- How to disable streaming for models that don't support it
Tool calling¶
Tool calling is a type of chat model API that accepts tool schemas, along with messages, as input and returns invocations of those tools as part of the output message.
These how-to guides show common patterns for tool calling with LangGraph:
- How to call tools using ToolNode
- How to handle tool calling errors
- How to pass runtime values to tools
- How to pass config to tools
- How to handle large numbers of tools
Subgraphs¶
Subgraphs allow you to reuse an existing graph from another graph. These how-to guides show how to use subgraphs:
- How to add and use subgraphs
- How to view and update state in subgraphs
- How to transform inputs and outputs of a subgraph
State Management¶
- How to use Pydantic model as state
- How to define input/output schema for your graph
- How to pass private state between nodes inside the graph
Other¶
- How to run graph asynchronously
- How to visualize your graph
- How to add runtime configuration to your graph
- How to add node retries
- How to force function calling agent to structure output
- How to pass custom LangSmith run ID for graph runs
- How to return state before hitting recursion limit
- How to integrate LangGraph with AutoGen, CrewAI, and other frameworks
Prebuilt ReAct Agent¶
The LangGraph prebuilt ReAct agent is pre-built implementation of a tool calling agent.
One of the big benefits of LangGraph is that you can easily create your own agent architectures. So while it's fine to start here to build an agent quickly, we would strongly recommend learning how to build your own agent so that you can take full advantage of LangGraph.
These guides show how to use the prebuilt ReAct agent:
- How to create a ReAct agent
- How to add memory to a ReAct agent
- How to add a custom system prompt to a ReAct agent
- How to add human-in-the-loop processes to a ReAct agent
- How to create prebuilt ReAct agent from scratch
- How to add semantic search for long-term memory to a ReAct agent
LangGraph Platform¶
This section includes how-to guides for LangGraph Platform.
LangGraph Platform is a commercial solution for deploying agentic applications in production, built on the open-source LangGraph framework.
The LangGraph Platform offers a few different deployment options described in the deployment options guide.
Tip
- LangGraph is an MIT-licensed open-source library, which we are committed to maintaining and growing for the community.
- You can always deploy LangGraph applications on your own infrastructure using the open-source LangGraph project without using LangGraph Platform.
Application Structure¶
Learn how to set up your app for deployment to LangGraph Platform:
- How to set up app for deployment (requirements.txt)
- How to set up app for deployment (pyproject.toml)
- How to set up app for deployment (JavaScript)
- How to add semantic search
- How to customize Dockerfile
- How to test locally
- How to rebuild graph at runtime
- How to use LangGraph Platform to deploy CrewAI, AutoGen, and other frameworks
Deployment¶
LangGraph applications can be deployed using LangGraph Cloud, which provides a range of services to help you deploy, manage, and scale your applications.
- How to deploy to LangGraph cloud
- How to deploy to a self-hosted environment
- How to interact with the deployment using RemoteGraph
Assistants¶
Assistants is a configured instance of a template.
Threads¶
Runs¶
LangGraph Platform supports multiple types of runs besides streaming runs.
- How to run an agent in the background
- How to run multiple agents in the same thread
- How to create cron jobs
- How to create stateless runs
Streaming¶
Streaming the results of your LLM application is vital for ensuring a good user experience, especially when your graph may call multiple models and take a long time to fully complete a run. Read about how to stream values from your graph in these how to guides:
- How to stream values
- How to stream updates
- How to stream messages
- How to stream events
- How to stream in debug mode
- How to stream multiple modes
Human-in-the-loop¶
When designing complex graphs, relying entirely on the LLM for decision-making can be risky, particularly when it involves tools that interact with files, APIs, or databases. These interactions may lead to unintended data access or modifications, depending on the use case. To mitigate these risks, LangGraph allows you to integrate human-in-the-loop behavior, ensuring your LLM applications operate as intended without undesirable outcomes.
- How to add a breakpoint
- How to wait for user input
- How to edit graph state
- How to replay and branch from prior states
- How to review tool calls
Double-texting¶
Graph execution can take a while, and sometimes users may change their mind about the input they wanted to send before their original input has finished running. For example, a user might notice a typo in their original request and will edit the prompt and resend it. Deciding what to do in these cases is important for ensuring a smooth user experience and preventing your graphs from behaving in unexpected ways.
- How to use the interrupt option
- How to use the rollback option
- How to use the reject option
- How to use the enqueue option
Webhooks¶
Cron Jobs¶
LangGraph Studio¶
LangGraph Studio is a built-in UI for visualizing, testing, and debugging your agents.
- How to connect to a LangGraph Cloud deployment
- How to connect to a local dev server
- How to connect to a local deployment (Docker)
- How to test your graph in LangGraph Studio (MacOS only)
- How to interact with threads in LangGraph Studio
Troubleshooting¶
These are the guides for resolving common errors you may find while building with LangGraph. Errors referenced below will have an lc_error_code
property corresponding to one of the below codes when they are thrown in code.
- GRAPH_RECURSION_LIMIT
- INVALID_CONCURRENT_GRAPH_UPDATE
- INVALID_GRAPH_NODE_RETURN_VALUE
- MULTIPLE_SUBGRAPHS
- INVALID_CHAT_HISTORY