Application Structure

:::info[Prerequisites]

• LangGraph Server
• LangGraph Glossary

Overview

A LangGraph application consists of one or more graphs, a LangGraph API Configuration file (langgraph.json), a file that specifies dependencies, and an optional .env file that specifies environment variables.

This guide shows a typical structure for a LangGraph application and shows how the required information to deploy a LangGraph application using the LangGraph Platform is specified.

Key Concepts

To deploy using the LangGraph Platform, the following information should be provided:

1. A LangGraph API Configuration file (langgraph.json) that specifies the dependencies, graphs, environment variables to use for the application.
2. The graphs that implement the logic of the application.
3. A file that specifies dependencies required to run the application.
4. Environment variable that are required for the application to run.

File Structure

Below are examples of directory structures for Python and JavaScript applications:

=== JS (package.json)

my-app/
├── src # all project code lies within here
│   ├── utils # optional utilities for your graph
│   │   ├── tools.ts # tools for your graph
│   │   ├── nodes.ts # node functions for your graph
│   │   └── state.ts # state definition of your graph
│   └── agent.ts # code for constructing your graph
├── package.json # package dependencies
├── .env # environment variables
└── langgraph.json # configuration file for LangGraph

=== Python (requirements.txt)

my-app/
├── my_agent # all project code lies within here
│   ├── utils # utilities for your graph
│   │   ├── __init__.py
│   │   ├── tools.py # tools for your graph
│   │   ├── nodes.py # node functions for your graph
│   │   └── state.py # state definition of your graph
│   ├── requirements.txt # package dependencies
│   ├── __init__.py
│   └── agent.py # code for constructing your graph
├── .env # environment variables
└── langgraph.json # configuration file for LangGraph

=== Python (pyproject.toml)

my-app/
├── my_agent # all project code lies within here
│   ├── utils # utilities for your graph
│   │   ├── __init__.py
│   │   ├── tools.py # tools for your graph
│   │   ├── nodes.py # node functions for your graph
│   │   └── state.py # state definition of your graph
│   ├── __init__.py
│   └── agent.py # code for constructing your graph
├── .env # environment variables
├── langgraph.json  # configuration file for LangGraph
└── pyproject.toml # dependencies for your project

:::note

The directory structure of a LangGraph application can vary depending on the programming language and the package manager used.

Configuration File

The langgraph.json file is a JSON file that specifies the dependencies, graphs, environment variables, and other settings required to deploy a LangGraph application.

The file supports specification of the following information:

Key	Description
dependencies	Required. Array of dependencies for LangGraph API server. Dependencies can be one of the following: (1) ".", which will look for local Python packages, (2) pyproject.toml, setup.py or requirements.txt in the app directory "./local_package", or (3) a package name.
graphs	Required. Mapping from graph ID to path where the compiled graph or a function that makes a graph is defined. Example: ./your_package/your_file.py:variable, where variable is an instance of langgraph.graph.state.CompiledStateGraph ./your_package/your_file.py:make_graph, where make_graph is a function that takes a config dictionary (langchain_core.runnables.RunnableConfig) and creates an instance of langgraph.graph.state.StateGraph / langgraph.graph.state.CompiledStateGraph.
env	Path to .env file or a mapping from environment variable to its value.
node_version	Defaults to 20.
dockerfile_lines	Array of additional lines to add to Dockerfile following the import from parent image.

:::tip

The LangGraph CLI defaults to using the configuration file langgraph.json in the current directory.

Examples

=== JavaScript

• The dependencies will be loaded from a dependency file in the local directory (e.g., package.json).
• A single graph will be loaded from the file ./your_package/your_file.js with the function agent.
• The environment variable OPENAI_API_KEY is set inline.

{
    "dependencies": [
      "."
    ],
    "graphs": {
      "my_agent": "./your_package/your_file.js:agent"
    },
    "env": {
      "OPENAI_API_KEY": "secret-key"
    }
}

=== Python

• The dependencies involve a custom local package and the langchain_openai package.
• A single graph will be loaded from the file ./your_package/your_file.py with the variable variable.
• The environment variables are loaded from the .env file.

{
    "dependencies": [
        "langchain_openai",
        "./your_package"
    ],
    "graphs": {
        "my_agent": "./your_package/your_file.py:agent"
    },
    "env": "./.env"
}

Dependencies

A LangGraph application may depend on other Python packages or JavaScript libraries (depending on the programming language in which the application is written).

You will generally need to specify the following information for dependencies to be set up correctly:

1. A file in the directory that specifies the dependencies (e.g., requirements.txt, pyproject.toml, or package.json).
2. A dependencies key in the LangGraph configuration file that specifies the dependencies required to run the LangGraph application.
3. Any additional binaries or system libraries can be specified using dockerfile_lines key in the LangGraph configuration file.

Graphs

Use the graphs key in the LangGraph configuration file to specify which graphs will be available in the deployed LangGraph application.

You can specify one or more graphs in the configuration file. Each graph is identified by a name (which should be unique) and a path for either: (1) the compiled graph or (2) a function that makes a graph is defined.

Environment Variables

If you're working with a deployed LangGraph application locally, you can configure environment variables in the env key of the LangGraph configuration file.

For a production deployment, you will typically want to configure the environment variables in the deployment environment.

Related

Please see the following resources for more information:

• How-to guides for Application Structure.