Deferred Hangup for Long-Running Calls Initiated from Background Jobs (e.g., Hangfire)

[RezaBagheri8]

I'm establishing SIP calls from a Hangfire background job like this:

var userAgent = new SIPUserAgent(sipTransport, null);
var callResult = await userAgent.Call(callDescriptor, voipMediaSession);

if (callResult)
{
    await voipMediaSession.Start();
    await voipMediaSession.AudioExtrasSource.StartAudio();
}

The call needs to stay active for hours and be hung up later — either after a duration or at a specific datetime — triggered by a separate job, with no shared reference to the original SIPUserAgent.
My questions:

Is there a call/dialog identifier I can persist and later use to retrieve the active agent and call Hangup()?
Is a singleton registry (ConcurrentDictionary<string, SIPUserAgent> keyed by Call-ID) the right pattern here, or is there a better approach?
Is it safe to hold a SIPUserAgent and VoIPMediaSession in memory for several hours?
If not, then what is the best way to terminate the call in the same background job?

What's the recommended architecture for this use case?

[sipsorcery]

Yes, the Call-ID in the dictionary approach sounds sensible. Holdings those objects for a long time shouldn't cause any issues other than the memory they will take up. The only gotsha that comes to mind is that the underlying RTPSession can end up lcosing if no packets are received for 30s in some cases depending on whether your audio is two way and whether the call is on hold etc.

[RezaBagheri8]

Thanks