> ## Documentation Index
> Fetch the complete documentation index at: https://docs.celesto.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Run a GitHub app on a Celesto computer

> Clone a GitHub web app onto a Celesto computer, install dependencies, run it on port 8000, and share a public HTTPS preview URL.

This guide walks you through taking any GitHub repository that runs as a web app, starting it on a Celesto computer, and getting a public URL that anyone (including you, your team, or an agent) can open in a browser.

Use this when you want a quick way to:

* Preview a Vite, React, or Node app without deploying it to a hosting provider.
* Share a work-in-progress build with someone for review.
* Let an AI agent spin up a repo and verify it actually runs.

By the end, you will have a public HTTPS URL pointing at port `8000` on a Celesto computer running your app.

## Before you start

You need:

* The [Celesto CLI installed](/celesto-sdk/quickstart) and authenticated.
* The GitHub URL of a repo that runs as a web app (for example, a Vite or Node project).
* The repo's install and start commands. If you don't know them, the project's `README.md` usually tells you.

Confirm you are logged in:

```bash theme={null}
celesto auth status
```

## Step 1: Create a computer

Create a `coding-agent` computer. This template comes with Node, npm, and git already installed, which is what most web apps need.

```bash theme={null}
celesto computer create --template coding-agent --json
```

Save the `name` from the output. The rest of this guide uses `einstein` as an example name — replace it with your computer's name.

## Step 2: Clone and install the app

Clone the repo into a fresh directory on the computer and install its dependencies.

```bash theme={null}
celesto computer run einstein "rm -rf /my-app && git clone https://github.com/<owner>/<repo> /my-app && cd /my-app && npm install" --timeout 300
```

<Tip>
  Pick a directory name that matches your project. The `rm -rf` at the start makes the command safe to re-run if something fails partway through.
</Tip>

## Step 3: Start the app on port 8000

Bind the app to `0.0.0.0:8000` so Celesto can forward traffic to it. The exact command depends on the framework — these are the common ones:

<CodeGroup>
  ```bash Vite / React theme={null}
  celesto computer run einstein "cd /my-app && setsid -f sh -c 'npm run dev -- --host 0.0.0.0 --port 8000 > /tmp/app.log 2>&1 < /dev/null'" --timeout 60
  ```

  ```bash Node / Express theme={null}
  celesto computer run einstein "cd /my-app && setsid -f sh -c 'PORT=8000 npm start > /tmp/app.log 2>&1 < /dev/null'" --timeout 60
  ```
</CodeGroup>

`setsid -f` detaches the server from the shell session so it keeps running after the command returns.

<Note>
  If your app needs environment variables (API keys, database URLs, and so on), set them in the same command, for example: `setsid -f sh -c 'OPENAI_API_KEY=sk-... npm run dev -- --host 0.0.0.0 --port 8000 > /tmp/app.log 2>&1 < /dev/null'`.
</Note>

## Step 4: Verify the app is running

Before exposing the app publicly, confirm it is actually serving traffic inside the computer.

```bash theme={null}
celesto computer run einstein "curl -I --max-time 5 http://127.0.0.1:8000"
```

You should see an `HTTP/1.1 200 OK` response. If you don't, check the log:

```bash theme={null}
celesto computer run einstein "tail -50 /tmp/app.log"
```

## Step 5: Publish port 8000

Expose port `8000` to the public internet.

```bash theme={null}
celesto computer port publish einstein --port 8000 --json
```

The response includes a `url` field — that's your public HTTPS link. Open it in a browser to confirm the app loads.

You can also list everything currently published for the computer:

```bash theme={null}
celesto computer port list einstein --json
```

## Step 6: Clean up when you're done

Public URLs are meant for short-lived previews. Unpublish the port and delete the computer when you no longer need them.

```bash theme={null}
celesto computer port unpublish einstein --port 8000
celesto computer delete einstein
```

## Troubleshooting

<AccordionGroup>
  <Accordion title="The public URL returns 502 or won't load">
    The app probably isn't listening on `0.0.0.0:8000`. Re-run the verification curl from Step 4 and check `/tmp/app.log` for errors. Many frameworks default to `localhost` only — pass `--host 0.0.0.0` or the equivalent flag.
  </Accordion>

  <Accordion title="`celesto auth status` says I'm not logged in">
    Run `celesto auth login` and try again. If you're running inside a sandboxed environment, your OS keychain may not be visible — re-run the CLI command from your normal shell.
  </Accordion>

  <Accordion title="`npm install` fails or times out">
    Increase `--timeout` on the `celesto computer run` call. Large dependency trees can take several minutes on first install.
  </Accordion>
</AccordionGroup>

## Related

* [Publish ports](/celesto-sdk/features/publish-ports) — the underlying primitive for exposing services from a computer.
* [Computers](/celesto-sdk/computers) — full reference for creating and managing computers.
* [CLI reference](/celesto-sdk/cli) — every `celesto` command and flag.