***

title: context.once
description: Subscribe to the next matching browser-context event exactly once.
-------------------------------------------------------------------------------

`context.once` is a browser runtime capability in the `context` namespace.

## Availability

* Runtime: `browser`
* Kind: `event`
* Category: `events`
* Supported drivers: Playwright

## SDK Surface

* SDK path: `runtime.browserContext.once`
* Async: No

## HTTP Surface

* Transport: resource route
* Route: `POST /workspaces/{id}/runtimes/{alias}/events/wait`
* Long-running: No

## Reference Semantics

* Requires refs: `context`

## Arguments

| Argument    | Type       | Required | Description                              |
| ----------- | ---------- | -------- | ---------------------------------------- |
| `eventName` | `string`   | Yes      | Context event name to subscribe to once. |
| `listener`  | `function` | Yes      | Local SDK listener invoked once.         |

## Result

* Type: `runtime listener`
* Description: Registers a one-shot local SDK listener for context events.

## SDK Example

```ts
runtime.browserContext.once('console', (event) => {
  console.log(event);
});
```

## HTTP Example

```http
POST /workspaces/{id}/runtimes/{alias}/events/wait
```

## Related Capabilities

* [`context.on`](../events/context-on)
* [`context.off`](../events/context-off)
* [`context.waitForEvent`](../events/context-wait-for-event)