## on_session_end()

Register a handler that fires when a call session ends. Use this to save call data, trigger post-call workflows, or log outcomes.

The `BotSessionEnded` event carries a `termination_reason` field that tells you why the session ended:

| Value               | Meaning                                     |
| ------------------- | ------------------------------------------- |
| `"user-hangup"`   | The caller hung up.                        |
| `"bot-hangup"`    | The agent ended the call (e.g. via `call.hangup()`). |
| `"bot-failure"`   | The session ended due to an internal error. |
| `"bot-transfer"`   | The call was transferred to another destination. |
| `"voicemail"`     | The outbound call reached voicemail.        |

### Signature

```python
@agent.on_session_end

def on_session_end(call: guava.Call, event: BotSessionEnded) -> None:
    ...
```

| Parameter | Type               | Default | Description                                                                                                         |
| --------- | ------------------ | ------- | ------------------------------------------------------------------------------------------------------------------- |
| call      | Call               | —       | The call object. Note: the call is already ended — do not issue commands on it.                                   |
| event     | BotSessionEnded     | —       | Contains `termination_reason` — one of `"user-hangup"`, `"bot-hangup"`, `"bot-failure"`, `"bot-transfer"`, `"voicemail"`. |

**Return value:** `None`

### Example

```python
import logging
from guava.events import BotSessionEnded

logger = logging.getLogger(__name__)

@agent.on_session_end
def on_session_end(call: guava.Call, event: BotSessionEnded):
    logger.info("session ended: reason=%s", event.termination_reason)
    if event.termination_reason == "user-hangup":
        # caller hung up — save any collected data
        ...
    elif event.termination_reason == "bot-transfer":
        # call was transferred to a human agent
        ...
```