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# Application Structure

## Overview

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

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

## Key Concepts

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

1. A [LangGraph configuration file](#configuration-file-concepts) (`langgraph.json`) that specifies the dependencies, graphs, and environment variables to use for the application.
2. The [graphs](#graphs) that implement the logic of the application.
3. A file that specifies [dependencies](#dependencies) required to run the application.
4. [Environment variables](#environment-variables) that are required for the application to run.

## File Structure

Below are examples of directory structures for applications:

:::python
=== "Python (requirements.txt)"

    ```plaintext
    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
    ├── requirements.txt # package dependencies
    └── langgraph.json # configuration file for LangGraph
    ```

=== "Python (pyproject.toml)"

    ```plaintext
    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
    ```

:::

:::js

```plaintext
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
```

:::

!!! note

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

## Configuration File {#configuration-file-concepts}

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

See the [LangGraph configuration file reference](../cloud/reference/cli.md#configuration-file) for details on all supported keys in the JSON file.

!!! tip

    The [LangGraph CLI](./langgraph_cli.md) defaults to using the configuration file `langgraph.json` in the current directory.

### Examples

:::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.

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

:::

:::js

- 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.

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

:::

## Dependencies

:::python
A LangGraph application may depend on other Python packages.
:::

:::js
A LangGraph application may depend on other TypeScript/JavaScript libraries.
:::

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

:::python

1. A file in the directory that specifies the dependencies (e.g. `requirements.txt`, `pyproject.toml`, or `package.json`).
   :::

:::js

1. A file in the directory that specifies the dependencies (e.g. `package.json`).
   :::

2. A `dependencies` key in the [LangGraph configuration file](#configuration-file-concepts) 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](#configuration-file-concepts).

## Graphs

Use the `graphs` key in the [LangGraph configuration file](#configuration-file-concepts) 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](#configuration-file-concepts).

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