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

# Preload lifecycle

> When MoveNet loads, cold-start modes, and the lobby warmer pattern.

Mounting `PoseTrackerProvider` alone does **not** load the model (unless `autoPreload`).

## What starts what

| Action                                  | Loads AI / model?       | Opens camera?    |
| --------------------------------------- | ----------------------- | ---------------- |
| Mount `<PoseTrackerProvider>`           | No                      | No               |
| `<PoseTrackerProvider autoPreload>`     | Yes — `preload()` basic | No               |
| `preload()` / `warmup()`                | Yes (default **basic**) | No               |
| `preload({ coldStart: 'full' })`        | Yes                     | Yes (may prompt) |
| `<WebViewPoseView coldStart="basic" />` | When page boots         | No               |
| `<WebViewPoseView />` (default `full`)  | When page boots         | Yes              |

## Cold-start modes

| Mode                             | Behaviour                                              | Use when                     |
| -------------------------------- | ------------------------------------------------------ | ---------------------------- |
| `basic` (preload default)        | TF.js + MoveNet + zeros warm-up; **no** `getUserMedia` | Lobby / home / hidden warmer |
| `full` (WebViewPoseView default) | Same, then open camera                                 | Visible camera screen        |

## Recommended pattern

```tsx theme={null}
// Root — client only
<PoseTrackerProvider>
  <Navigation />
</PoseTrackerProvider>

// Lobby — model warm-up, no permission prompt
function HomeScreen() {
  const { preload, status } = usePoseTracker();

  useEffect(() => {
    void preload(); // basic, idempotent
  }, [preload]);

  return (
    <>
      <View style={{ width: 1, height: 1, opacity: 0 }} pointerEvents="none">
        <WebViewPoseView coldStart="basic" />
      </View>
      <Button title="Start" disabled={status !== 'ready'} onPress={goToCamera} />
    </>
  );
}

// Camera — user expects the permission prompt
function CameraScreen() {
  return <WebViewPoseView style={{ flex: 1 }} />; // coldStart="full"
}
```

Optional: `<PoseTrackerProvider autoPreload>` still uses **basic** (no camera).

## Important WebView detail

For the default WebView backend, `preload()` / `warmup()` **waits** until a mounted `WebViewPoseView` posts `ready`. Calling `preload()` with **no** WebView in the tree waits until timeout.

Usage metering (`camera_start`) runs when the camera session actually starts — not during basic preload.

## Status path

Typical: `configuring` → `downloading` → `warming` → `ready` (fatal `error` only if the local/online model path fails hard). Handshake/engine failures degrade to **keypoints-only** without blocking `ready`.

## Background / battery

Handled inside the WebView page (no host wiring):

* App backgrounded → camera tracks stopped, inference loop halted; model stays in RAM for fast resume
* Foreground → camera reacquired (including any quality downgrade)
* Unmount `WebViewPoseView` → page destroyed; camera / WebGL / model freed
* \~45 consecutive inference failures → stop loop, release camera, `error` event
* iOS `inactive` (Control Center) is **not** treated as background

`client.dispose()` tears down everything.

## Related

* [Permissions](/permissions)
* [Provider & client](/reference/provider-client)
* [Adaptive quality](/advanced/adaptive-quality)