> ## Documentation Index
> Fetch the complete documentation index at: https://agenticadvertisingorg-snap-format-preview-links.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# si_terminate_session

> si_terminate_session is the AdCP task for ending an SI session. Supports five termination reasons including transaction handoff to ACP, with follow-up suggestions and checkout context for commerce.

<Note>
  **Experimental.** Sponsored Intelligence (`si_get_offering`, `si_initiate_session`, `si_send_message`, `si_terminate_session`) is part of AdCP 3.0 as an experimental surface — it may change between 3.x releases with at least 6 weeks' notice. Sellers implementing any of these tasks MUST declare `sponsored_intelligence.core` in `experimental_features`. See [experimental status](/docs/reference/experimental-status) for the full contract.
</Note>

End an SI session. Either the host or brand agent can initiate termination, with different reasons indicating how the session concluded.

## Request

| Field                 | Type   | Required | Description                            |
| --------------------- | ------ | -------- | -------------------------------------- |
| `session_id`          | string | Yes      | Session ID to terminate                |
| `reason`              | string | Yes      | Why the session is ending              |
| `termination_context` | object | No       | Additional context for the termination |

### Termination Reasons

| Reason                | Meaning                                | Typical Initiator                  |
| --------------------- | -------------------------------------- | ---------------------------------- |
| `handoff_transaction` | User wants to complete a purchase      | Brand agent (via pending\_handoff) |
| `handoff_complete`    | Conversation naturally concluded       | Brand agent                        |
| `user_exit`           | User explicitly ended the conversation | Host                               |
| `session_timeout`     | Inactivity timeout reached             | Host                               |
| `host_terminated`     | Host ended for policy/error reasons    | Host                               |

### Termination Context Object

Additional details vary by reason:

**For `handoff_transaction`:**

```json theme={null}
{
  "intent": { /* purchase intent from handoff */ },
  "context_for_checkout": { /* ACP context */ }
}
```

**For `user_exit`:**

```json theme={null}
{
  "user_signal": "changed_topic",
  "partial_context": { /* what was discussed */ }
}
```

**For `session_timeout`:**

```json theme={null}
{
  "last_activity": "2026-01-18T10:30:00Z",
  "timeout_seconds": 300
}
```

## Response

| Field         | Type    | Description                            |
| ------------- | ------- | -------------------------------------- |
| `session_id`  | string  | Confirms which session was terminated  |
| `terminated`  | boolean | Always `true` on success               |
| `acp_handoff` | object  | Present for transaction handoffs       |
| `follow_up`   | object  | Optional actions for future engagement |

### ACP Handoff Object

For transaction terminations, includes data needed for ACP checkout:

| Field            | Type     | Description                                                                                                            |
| ---------------- | -------- | ---------------------------------------------------------------------------------------------------------------------- |
| `checkout_url`   | uri      | Brand's ACP checkout endpoint. Hosts MUST validate this is HTTPS.                                                      |
| `checkout_token` | string   | Opaque token to pass to the checkout endpoint                                                                          |
| `payload`        | object   | Rich checkout context (product details, applied offers, pricing). Alternative to `checkout_token` for structured data. |
| `expires_at`     | datetime | When this handoff data expires                                                                                         |

### Follow-Up Object

Suggestions for future engagement:

| Field              | Type   | Description                  |
| ------------------ | ------ | ---------------------------- |
| `suggested_action` | string | What the host might do next  |
| `data`             | object | Relevant data for the action |
| `message`          | string | Optional message to display  |

## Examples

### Transaction Handoff

After receiving `pending_handoff` with `type: "transaction"`:

**Request:**

```json theme={null}
{
  "session_id": "sess_abc123",
  "reason": "handoff_transaction",
  "termination_context": {
    "intent": {
      "action": "purchase",
      "product": {
        "type": "flight",
        "flight_number": "DL628"
      }
    }
  }
}
```

**Response:**

```json theme={null}
{
  "session_id": "sess_abc123",
  "terminated": true,
  "acp_handoff": {
    "checkout_url": "https://delta.com/acp/checkout",
    "payload": {
      "session_id": "sess_abc123",
      "flight": "DL628",
      "passenger": {
        "email": "jane@example.com",
        "name": "Jane Smith"
      },
      "applied_offers": ["delta_chatgpt_3313"],
      "price": {
        "amount": 199,
        "currency": "USD"
      }
    },
    "expires_at": "2026-01-18T11:00:00Z"
  }
}
```

### Conversation Complete (No Purchase)

When the conversation naturally ends without a transaction:

**Request:**

```json theme={null}
{
  "session_id": "sess_abc123",
  "reason": "handoff_complete"
}
```

**Response:**

```json theme={null}
{
  "session_id": "sess_abc123",
  "terminated": true,
  "follow_up": {
    "suggested_action": "save_for_later",
    "data": {
      "flights_discussed": ["DL628", "DL632"],
      "destination": "BOS",
      "travel_date": "2026-01-27"
    },
    "message": "Let me know if you'd like to revisit Boston flights later!"
  }
}
```

### User Exit

When the user changes topic or explicitly leaves:

**Request:**

```json theme={null}
{
  "session_id": "sess_abc123",
  "reason": "user_exit",
  "termination_context": {
    "user_signal": "changed_topic",
    "partial_context": {
      "flights_viewed": ["DL628"],
      "last_topic": "seat selection"
    }
  }
}
```

**Response:**

```json theme={null}
{
  "session_id": "sess_abc123",
  "terminated": true,
  "follow_up": {
    "suggested_action": "remind_later",
    "data": {
      "incomplete_booking": {
        "flight": "DL628",
        "step": "seat_selection"
      }
    }
  }
}
```

### Session Timeout

When the session times out due to inactivity:

**Request:**

```json theme={null}
{
  "session_id": "sess_abc123",
  "reason": "session_timeout",
  "termination_context": {
    "last_activity": "2026-01-18T10:25:00Z",
    "timeout_seconds": 300
  }
}
```

**Response:**

```json theme={null}
{
  "session_id": "sess_abc123",
  "terminated": true
}
```

### Host Terminated

When the host ends the session for policy or error reasons:

**Request:**

```json theme={null}
{
  "session_id": "sess_abc123",
  "reason": "host_terminated",
  "termination_context": {
    "cause": "user_left_app"
  }
}
```

**Response:**

```json theme={null}
{
  "session_id": "sess_abc123",
  "terminated": true
}
```

## ACP Integration Flow

When the reason is `handoff_transaction`:

```mermaid theme={null}
sequenceDiagram
    participant H as Host
    participant B as Brand Agent
    participant A as ACP

    H->>B: si_terminate_session(handoff_transaction)
    B->>H: { acp_handoff: { checkout_url, checkout_token/payload } }
    H->>A: Initiate checkout with token/payload
    A->>H: Checkout flow
```

1. Host receives `acp_handoff` in the termination response
2. Host initiates ACP checkout using the provided `checkout_url` and `checkout_token` or `payload`
3. ACP handles the transaction while maintaining the user's trust with the host
4. Brand is not the merchant of record - ACP handles payment

## Key Points

1. **Always terminate sessions** - Even if the conversation seems done, call terminate to clean up resources and get follow-up suggestions.

2. **ACP handoff data has expiration** - The `expires_at` field indicates how long the checkout context is valid.

3. **Follow-up enables re-engagement** - Even non-transaction terminations can include suggestions for future engagement.

4. **Host maintains trust** - Transactions go through ACP, keeping the user's relationship with the host intact.