# browser.open

Open a URL in the system's default browser using Atmos's native cross-platform browser opener.

## Usage

```python
browser.open("http://localhost:3000")
browser.open(url="https://atmos.tools")
```

The URL must be absolute, use HTTP or HTTPS, and contain no embedded username or password.
The function returns `None` after requesting the launch. It does not wait for the page to load,
check service readiness, or control whether the browser reuses a tab or opens a window.

The browser opens on the machine running Atmos. A desktop session and an available default
browser are required. Launch errors fail the script. Dry runs do not launch a browser.

## Custom Commands

Expose a local dashboard through a custom command in `atmos.yaml`:

```yaml
commands:
  - name: portal
    commands:
      - name: open
        description: Open the local dashboard
        steps:
          - type: script
            interpreter: starlark
            script: |
              browser.open("http://localhost:3000")
```

Run `atmos portal open` after the service is running. The function is also available to
standalone scripts and functions loaded with `module.load(...)`; no shell command or
operating-system detection is needed.