Call transfer

A bot can transfer a call at any time during the conversation. For example, it can transfer the call to a human agent when it cannot resolve the issue, or to another bot that handles the next stage of the interaction.

The bot initiates the transfer and can include SIP headers in the transfer request that Live Hub generates.

To transfer a call using a phone number purchased from AudioCodes, contact AudioCodes.

How the transfer is made

Live Hub makes the transfer in one of two ways, depending on what the SIP server that started the call supports.

A new call, with SIP INVITE. Live Hub takes this route when the originating SIP server does not support SIP REFER, which is typical of a SIP trunk or an AudioCodes phone number. Live Hub then anchors two SIP calls, and this route needs a routing rule.

Call transfer using SIP INVITE

A SIP REFER, typical of contact centers. After a successful transfer, the remote SIP server drops its call with Live Hub. To take this route, set REFER as the transfer method on the SIP connection's Advanced tab. No routing rule is needed.

Call transfer using SIP REFER

Live Hub converts a tel URI to a SIP URI by default: "transferTarget": "tel:+14077511320" becomes Refer-To: <sip:+14077511320@{SBC IP address}:5060>. To keep the tel URI, the administrator sets VAICPreserveTelURI to 1.

Trigger the transfer

How the bot triggers the transfer differs by framework, but what goes inside activityParams does not. Select your framework:

AudioCodes Bot API: HTTP mode

The bot sends a transfer event with the destination in transferTarget. The name handover means the same thing. See HTTP mode.

{
  "activities": [
    {
      "id": "59f09f09-feb6-40d4-8852-b960502d9841",
      "timestamp": "2025-10-18T15:22:35.211Z",
      "type": "event",
      "name": "transfer",
      "activityParams": {
        "transferTarget": "tel:+123456789"
      }
    }
  ]
}
AudioCodes Bot API: WebSocket mode

The bot sends a transfer event with the destination in transferTarget. The name handover means the same thing. See WebSocket mode.

{
  "type": "activities",
  "activities": [
    {
      "type": "event",
      "name": "transfer",
      "activityParams": {
        "transferTarget": "tel:+123456789"
      }
    }
  ]
}
Microsoft Bot Framework

The bot sends a transfer event with the parameters inside channelData. The name handover means the same thing.

{
  "type": "event",
  "name": "transfer",
  "channelData": {
    "activityParams": {
      "transferTarget": "tel:+123456789"
    }
  }
}
Microsoft Copilot Studio

Live Hub supports Copilot Studio's native Transfer to agent. Store the transfer parameters as a record first, and then pass that record to the transfer.

To set up a transfer:

  1. Store the transfer details as a record.

    Storing the transfer details as a record

  2. Insert the transfer parameters as a formula.

    The transfer parameters as a formula

  3. Give the destination in transferTarget.

    Setting transferTarget

  4. Under topic management, create a transfer conversation.

    Creating a transfer conversation

  5. Add the variable in the dialog.

    Adding the variable

The formula takes this form:

{
  activityParams: {
    transferTarget: "tel:+123456789",
    transferNotifications: true
  }
}

To take the target from a Copilot variable, remove the quotation marks and name the variable:

{
  activityParams: {
    transferTarget: Topic.variable,
    transferNotifications: true
  }
}
Microsoft Copilot Studio legacy bot

Legacy bots also support native Transfer to agent. Select it in the topic that should transfer the call.

Transfer to agent in a legacy Copilot Studio bot

In the 'Private message to agent' text, enter the transfer parameters.

The Private message to agent field 

{
  "activityParams": {
    "transferTarget": "tel:+123456789"
  }
}
Google Dialogflow CX

The bot triggers the transfer with a Live agent handoff fulfillment, configured in the Dialogflow CX console.

The Live agent handoff fulfillment in the Dialogflow CX console

The fulfillment content carries the parameters:

{
  "activityParams": {
    "transferTarget": "tel:+123456789"
  }
}

Alternatively, add a Custom Payload fulfillment with a transfer event:

{
  "activities": [
    {
      "type": "event",
      "name": "transfer",
      "activityParams": {
        "transferTarget": "tel:+123456789"
      }
    }
  ]
}
Google Dialogflow ES

The bot sends a transfer event as a Custom Payload response. The name handover means the same thing.

{
  "activities": [
    {
      "type": "event",
      "name": "transfer",
      "activityParams": {
        "transferTarget": "tel:+123456789"
      }
    }
  ]
}
Google CX Agent Studio

The bot triggers the transfer by adding LIVE_AGENT_HANDOFF to the params of the end_session tool.

{
  "reason": "User asked to escalate.",
  "session_escalated": true,
  "params": {
    "LIVE_AGENT_HANDOFF": {}
  }
}

For anything beyond a bare handoff, add an activityParams field inside it:

{
  "reason": "User asked to escalate.",
  "session_escalated": true,
  "params": {
    "LIVE_AGENT_HANDOFF": {
      "activityParams": {
        "transferTarget": "sip:+123456789"
      }
    }
  }
}
Amazon Lex

The bot sends a custom payload alongside the text going to the caller.

{
  "type": "event",
  "name": "transfer",
  "activityParams": {
    "transferTarget": "tel:+123456789"
  }
}

Event parameters

These parameters go inside activityParams:

Parameter Type Description
transferTarget string Where to transfer the call. A SIP URI per RFC 3261, such as sip:+14155550100@example.com;user=phone or sip:alice@example.com, or a tel URI per RFC 3966, tel:+14155550100.
handoverReason string Why the call was transferred, in words. Appears on the call's CDR.
transferSipHeaders array SIP headers to send to the transferee. See SIP headers.
transferReferredByURL string The party that initiated the referral. Live Hub adds a SIP Referred-By header to the outgoing INVITE or the forwarded REFER.
transferNotifications boolean Tells the bot how each transfer attempt turned out. Default false. See Handle a failed transfer.
transferNotificationsHangupMS number Grace period in milliseconds before the call is disconnected after a successful transfer, 0 to 10000. Default 5000. Only applies with transferNotifications on.

SIP headers

transferSipHeaders carries data into the SIP message Live Hub generates. It is an array of objects, each with a name and a value. The array takes up to 100 headers and 12,000 characters in total.

Where the headers land depends on how the transfer is made. In a SIP INVITE, Live Hub adds each one as a header:

X-My-Header: my_value

In a SIP REFER, Live Hub puts each one inside the URI of the Refer-To header:

Refer-To: <sip:john@host.com?X-My-Header=my_value>

These examples add X-My-Header: my_value from the bot:

AudioCodes Bot API: HTTP mode
{
  "activities": [
    {
      "id": "59f09f09-feb6-40d4-8852-b960502d9841",
      "timestamp": "2025-10-18T15:22:35.211Z",
      "type": "event",
      "name": "transfer",
      "activityParams": {
        "transferTarget": "sip:john@host.com",
        "transferSipHeaders": [
          { "name": "X-My-Header", "value": "my_value" }
        ]
      }
    }
  ]
}
AudioCodes Bot API: WebSocket mode
{
  "type": "activities",
  "activities": [
    {
      "type": "event",
      "name": "transfer",
      "activityParams": {
        "transferTarget": "sip:john@host.com",
        "transferSipHeaders": [
          { "name": "X-My-Header", "value": "my_value" }
        ]
      }
    }
  ]
}
Microsoft Bot Framework
{
  "type": "event",
  "name": "transfer",
  "channelData": {
    "activityParams": {
      "transferTarget": "sip:john@host.com",
      "transferSipHeaders": [
        { "name": "X-My-Header", "value": "my_value" }
      ]
    }
  }
}
Microsoft Copilot Studio
{
  "activityParams": {
    "transferTarget": "sip:john@host.com",
    "transferSipHeaders": [
      { "name": "X-My-Header", "value": "my_value" }
    ]
  }
}
Microsoft Copilot Studio legacy bot
{
  "activityParams": {
    "transferTarget": "sip:john@host.com",
    "transferSipHeaders": [
      { "name": "X-My-Header", "value": "my_value" }
    ]
  }
}
Google Dialogflow CX

The fulfillment content carries the headers:

{
  "activityParams": {
    "transferTarget": "sip:john@host.com",
    "transferSipHeaders": [
      { "name": "X-My-Header", "value": "my_value" }
    ]
  }
}
Google Dialogflow ES
{
  "activities": [
    {
      "type": "event",
      "name": "transfer",
      "activityParams": {
        "transferTarget": "sip:john@host.com",
        "transferSipHeaders": [
          { "name": "X-My-Header", "value": "my_value" }
        ]
      }
    }
  ]
}
Google CX Agent Studio
{
  "reason": "User asked to escalate.",
  "session_escalated": true,
  "params": {
    "LIVE_AGENT_HANDOFF": {
      "activityParams": {
        "transferTarget": "sip:john@host.com",
        "transferSipHeaders": [
          { "name": "X-My-Header", "value": "my_value" }
        ]
      }
    }
  }
}
Amazon Lex
{
  "type": "event",
  "name": "transfer",
  "activityParams": {
    "transferTarget": "sip:john@host.com",
    "transferSipHeaders": [
      { "name": "X-My-Header", "value": "my_value" }
    ]
  }
}

Handle a failed transfer

By default, Live Hub disconnects the bot as soon as it performs the transfer, whether or not the transfer worked.

Set transferNotifications to true, and Live Hub tells the bot how each attempt turned out by sending a transferStatus event after the transfer:

These examples keep the bot on the call when a transfer fails:

AudioCodes Bot API: HTTP mode
{
  "activities": [
    {
      "id": "59f09f09-feb6-40d4-8852-b960502d9841",
      "timestamp": "2025-10-18T15:22:35.211Z",
      "type": "event",
      "name": "transfer",
      "activityParams": {
        "transferTarget": "sip:john@host.com",
        "transferNotifications": true
      }
    }
  ]
}
AudioCodes Bot API: WebSocket mode
{
  "type": "activities",
  "activities": [
    {
      "type": "event",
      "name": "transfer",
      "activityParams": {
        "transferTarget": "sip:john@host.com",
        "transferNotifications": true
      }
    }
  ]
}
Microsoft Bot Framework
{
  "type": "event",
  "name": "transfer",
  "channelData": {
    "activityParams": {
      "transferTarget": "sip:john@host.com",
      "transferNotifications": true
    }
  }
}
Microsoft Copilot Studio
{
  "activityParams": {
    "transferTarget": "sip:john@host.com",
    "transferNotifications": true
  }
}
Microsoft Copilot Studio legacy bot
{
  "activityParams": {
    "transferTarget": "sip:john@host.com",
    "transferNotifications": true
  }
}
Google Dialogflow CX
{
  "activityParams": {
    "transferTarget": "sip:john@host.com",
    "transferNotifications": true
  }
}
Google Dialogflow ES
{
  "activities": [
    {
      "type": "event",
      "name": "transfer",
      "activityParams": {
        "transferTarget": "sip:john@host.com",
        "transferNotifications": true
      }
    }
  ]
}
Google CX Agent Studio
{
  "reason": "User asked to escalate.",
  "session_escalated": true,
  "params": {
    "LIVE_AGENT_HANDOFF": {
      "activityParams": {
        "transferTarget": "sip:john@host.com",
        "transferNotifications": true
      }
    }
  }
}
Amazon Lex
{
  "type": "event",
  "name": "transfer",
  "activityParams": {
    "transferTarget": "sip:john@host.com",
    "transferNotifications": true
  }
}

Set the transfer target number

The target can come from the bot, in transferTarget, or from the bot connection. If both are set, the value from the bot takes precedence.

To set the target number on the bot connection:

  1. In the Navigation pane, select Bot connections.
  2. On the bot connection, click Edit, and then select the Features tab.
  3. Under Call Transfer, in the 'Transfer number' field, enter the number.

The Call Transfer feature on the Features tab

Create a routing rule

A routing rule is needed only when the transfer goes out as a new call over SIP INVITE. A SIP connection that supports SIP REFER needs no rule: Live Hub forwards the request as a REFER.

To create the routing rule:

  1. In the Navigation pane, select Routing, and then select the Routing Rules tab.
  2. Click Add new routing rule.
  3. Under General, from the 'Type' drop-down list, select Transfer.
  4. Under Call criteria, from the 'Transferred by' drop-down list, select the bot that initiates the transfer.
  5. Under Route to, from the 'Call destination' drop-down list, select the phone number to transfer from, or the SIP connection to route through.

A routing rule for call transfer

Target numbers must be in E.164 format, for example +9725211111.

For everything else a rule can do, see Routing rules.

View transferred calls

A transferred call appears in call history as two records, one incoming and one outgoing.

To see both halves of a transferred call:

  1. In the Navigation pane, select Call history.

    The Call history screen

  2. Select the call, and then click Search for related call records.

Where the call was part of a transfer, Live Hub shows the incoming and outgoing records together.