> ## Documentation Index
> Fetch the complete documentation index at: https://flatfileinc-remove-rss-json.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Developing

> npx flatfile develop

<Snippet file="shared/dxpbanner.mdx" />

The Flatfile CLI provides a suite of tools to help you develop and deploy
[Listeners](/learning-center/concepts/listeners) to Flatfile.

Listeners are at the core of the Flatfile ecosystem, they are responsible for
picking up on [Events](/learning-center/concepts/events) and responding to them
accordingly.

<Note>
  Agents are listeners deployed server-side on Flatfile's secure cloud.
</Note>

When developing with Flatfile, listeners can [deployed](/documentation/core-libraries/cli/deploy) to
Flatfile on every change, or they can run directly on your machine.

### Commands

The Flatfile CLI provides the following commands:

| Command  | Description                             |
| -------- | --------------------------------------- |
| develop  | Run your project as a local listener    |
| deploy   | Deploy your project as a Flatfile Agent |
| list     | List deployed Agents in an environment  |
| download | Download an agent from your environment |
| delete   | Delete an Agent                         |

### Before You Begin

You can add a `.env` file to bypass having to enter your API Key when running
the develop command.

```json theme={"system"}
FLATFILE_API_KEY=sk_123456
```

### Develop

Run `npx flatfile develop` from terminal to launch a local listener. As your
code changes, file changes are detected and will be reflected immediately.

<Warning>
  Add the file name to the command: `npx flatfile develop path-to-file` if
  you're not running an index file.
</Warning>

1. In your terminal, you'll see a detailed log of each HTTP request made within
   a listener. It includes the request timing and status, enabling tracking and
   debugging of HTTP operations.
2. A pub/sub stream system will deliver Events with a latency of approximately
   10-50ms. This provides a local development experience closely resembling the
   production environment speed.
3. Events that are being processed will be shown, along with their respective
   handlers. You can then respond to those Events accordingly.

```bash theme={"system"}
> npx flatfile develop
✔ 1 environment(s) found for these credentials
✔ Environment "development" selected
ncc: Version 0.36.1
ncc: Compiling file index.js into CJS
  ✓ 427ms      GET    200 https://platform.flatfile.com/api/v1/subscription 12345

 File change detected. 🚀
  ✓ Connected to event stream for scope us_env_1234
 ▶ commit:created  10:13:05.159 AM us_evt_1234
 ↳ on(**, {})
 ↳ on(commit:created, {"sheetSlug":"contacts"})

```

## Shared Environments

It is highly recommended to utilize an isolated environment when developing with
the local listener. That's why the CLI is warning you when working in an
environment that already has a deployed agent.

Having deployed code running at the same time within the same development
environment can lead to interference, potentially resulting in a recursive loop
and undesirable consequences for your local listener.

To avoid such complications, it's advisable to keep your local environment
separate from any deployed code. This ensures optimal performance and helps
maintain a stable development environment.