AdCP — si_terminate

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:

{
  "intent": { /* purchase intent from handoff */ },
  "context_for_checkout": { /* ACP context */ }
}

For user_exit:

{
  "user_signal": "changed_topic",
  "partial_context": { /* what was discussed */ }
}

For session_timeout:

{
  "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`	string	Brand’s ACP checkout endpoint
`payload`	object	Data to pass to ACP
`expires_at`	string	ISO 8601 expiration for the checkout context

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:

{
  "session_id": "sess_abc123",
  "reason": "handoff_transaction",
  "termination_context": {
    "intent": {
      "action": "purchase",
      "product": {
        "type": "flight",
        "flight_number": "DL628"
      }
    }
  }
}

Response:

{
  "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:

{
  "session_id": "sess_abc123",
  "reason": "handoff_complete"
}

Response:

{
  "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:

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

Response:

{
  "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:

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

Response:

{
  "session_id": "sess_abc123",
  "terminated": true
}

Host Terminated

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

{
  "session_id": "sess_abc123",
  "reason": "host_terminated",
  "termination_context": {
    "cause": "user_left_app"
  }
}

Response:

{
  "session_id": "sess_abc123",
  "terminated": true
}

ACP Integration Flow

When the reason is handoff_transaction:

Host receives acp_handoff in the termination response
Host initiates ACP checkout using the provided checkout_url and payload
ACP handles the transaction while maintaining the user’s trust with the host
Brand is not the merchant of record - ACP handles payment

Key Points

Always terminate sessions - Even if the conversation seems done, call terminate to clean up resources and get follow-up suggestions.
ACP handoff data has expiration - The expires_at field indicates how long the checkout context is valid.
Follow-up enables re-engagement - Even non-transaction terminations can include suggestions for future engagement.
Host maintains trust - Transactions go through ACP, keeping the user’s relationship with the host intact.

Getting Started

Building with AdCP

Protocol

FAQ

Trust & Security

Reference

Certification

si_terminate_session

Request

Termination Reasons

Termination Context Object

Response

ACP Handoff Object

Follow-Up Object

Examples

Transaction Handoff

Conversation Complete (No Purchase)

User Exit

Session Timeout

Host Terminated

ACP Integration Flow

Key Points

​Request

​Termination Reasons

​Termination Context Object

​Response

​ACP Handoff Object

​Follow-Up Object

​Examples

​Transaction Handoff

​Conversation Complete (No Purchase)

​User Exit

​Session Timeout

​Host Terminated

​ACP Integration Flow

​Key Points

Request

Termination Reasons

Termination Context Object

Response

ACP Handoff Object

Follow-Up Object

Examples

Transaction Handoff

Conversation Complete (No Purchase)

User Exit

Session Timeout

Host Terminated

ACP Integration Flow

Key Points