How to obtain the telephonySessionId for an inbound call answered by the softphone in case of multi-softphones in a single-queue case?

You can subscribe to the presence event notification instead of the telephony session event.

var eventFilters = [
    '/restapi/v1.0/account/~/extension/AgentExt1ID/presence?detailedTelephonyState=true',
    '/restapi/v1.0/account/~/extension/AgentExt2ID/presence?detailedTelephonyState=true',
    '/restapi/v1.0/account/~/extension/AgentExt3ID/presence?detailedTelephonyState=true',
    '/restapi/v1.0/account/~/extension/AgentExt4ID/presence?detailedTelephonyState=true'
  ]

When a call is answered by an agent, you will get the event with the "telephonyStatus": "CallConnected" and an active call object which contains the call Id.

{
    "extensionId": Agent4ExtId,
    "telephonyStatus": "CallConnected",
    "activeCalls": [
      {
        "id": "e9d2b7f8-0d9f-4dde-b0f3-a93596b7425c",
        "direction": "Inbound",
        "fromName": "...",
        "from": "+1...",
        "toName": "Agent 4",
        "to": "+1...",
        "telephonyStatus": "CallConnected",
        "sessionId": "211010xxxx",
        "startTime": "2026-06-....",
        "partyId": "p-a0d7bc9041c98z19ed138595dz69b29d0000-2",
        "telephonySessionId": "s-a0d7bc9041c98z19ed138595dz69b29d0000"
      }
    ],
...

The active call Id “e9d2b7f8-0d9f-4dde-b0f3-a93596b7425c” can be used to match with the call-Id header value from your SIP phone. And thus you can use the partyId and the telephonySessionId values for your call log.

​@PhongVu Thank you for your reply.

We store internal logs associating the call-Id header value from SIP phone.
And we have to track and save all Telephony lifecycle: the full call history —call answered → transfer → answered/rejected → transferred again → ended — which we obtain only from an account-level `telephony/sessions` webhook subscription.
The extension level webhook subscription does not seem to provide event after the call is transferred to another extension.

1. How can we obtain full Telephony lifecycle and correlate with the internal logs (stored with call-Id header value from SIP phone) using your approach?
2. And is there anyway we can achieve this without maintaining four subscription for each softphone users?

If we create subscriptions for all softphone users:

1. Can we control the subscription expiration time ourselves? What is the maximum expiration period allowed?
2. Are there any scenarios where a subscription could become invalid or stop delivering events? If so, what is the recommended approach to automatically renew or recreate subscriptions to ensure call logging continues without interruption?
3. If we create a new subscription without revoking the existing one, will both subscriptions continue receiving the same events, or will only the most recently created subscription receive them?

In your case, you will need to use that workaround solution by subscribe to both telephony session event and user presence?detailedTelephonyState=true event. You can use the telephony event payload to create your call log. The presence event payload is only for getting the call-Id to match with the agent’s SIP phone as you were asking in your previous question. Since the call queue is small (4 members) and if the queue is not very busy, you can call the user active calls API to read active call data instead of subscribing to the presence? event. Remember that the call-Id is only available in the active call object after the call is answered/connected.

Since you have only 4 agents, the best approach is to use a super admin user to subscribe to event notifications for all 4 agents.

var eventFilters = [
    '/restapi/v1.0/account/~/extension/AgentExt1ID/telephony/sessions',
    '/restapi/v1.0/account/~/extension/AgentExt1ID/telephony/sessions',
    '/restapi/v1.0/account/~/extension/AgentExt1ID/telephony/sessions',
    '/restapi/v1.0/account/~/extension/AgentExt1ID/telephony/sessions',
    '/restapi/v1.0/account/~/extension/AgentExt1ID/presence?detailedTelephonyState=true',
    '/restapi/v1.0/account/~/extension/AgentExt2ID/presence?detailedTelephonyState=true',
    '/restapi/v1.0/account/~/extension/AgentExt3ID/presence?detailedTelephonyState=true',
    '/restapi/v1.0/account/~/extension/AgentExt4ID/presence?detailedTelephonyState=true'
  ]

Q/ Can we control the subscription expiration time ourselves? What is the maximum expiration period allowed?

A/ Set the expiresIn parameter when you create the subscription

Q/ Are there any scenarios where a subscription could become invalid or stop delivering events? If so, what is the recommended approach to automatically renew or recreate subscriptions to ensure call logging continues without interruption?

A/ If your server becomes unreachable, the subscription will be blacklisted. Read this dev guide article for details.

Q/ If we create a new subscription without revoking the existing one, will both subscriptions continue receiving the same events, or will only the most recently created subscription receive them?

A/ Multiple subscriptions will work. Each user can have max 20 active subscriptions. Avoid multiple subscriptions if you don’t really need them. Use update instead of revoke and create new one.

​@PhongVu 

Thank you for your reply.

How can we detect when a subscription has been blacklisted or when event delivery has stopped, so that we can automatically renew the subscription or create a new one?

Additionally, if a subscription becomes blacklisted, what is the recommended approach: should we attempt to renew the existing blacklisted subscription, or should we delete it and create a new subscription instead?

No notification if the subscription is blacklisted!

You need to make sure that the deliver address is always publicly accessible.

You should return 200 Ok for every notification event.

You can create a subscription with the expiresIn = 87000 (over a day) and renew it daily.

Once the subscription is blacklisted, delete and create a new one.