Tracking a call through transfers using compliance bot

I'm trying to come up with a way to track calls that are occurring in Teams, both peer to peer and calls from PSTN. Sadly there is no easy way to do this. One thing that sort of works is setting the bot & all Teams users up for recording compliance, so it gets dragged into every call and is aware of the participants.

I have the bot set up and it is being notified of calls being created/updated/terminated, but I'm struggling to find the documentation needed to decipher the messages it receives. I'm currently using the API rather than the SDK.

The questions I currently have are:

• In a PSTN-Teams call, the bot gets two calls- when the callee picks up, one of the calls is deleted, and one persists. In a Teams-Teams call, the bot receives 4 calls- one seems to end when the bot answers the call, another ends when the callee picks up, and the remaining two calls persist until someone leaves or transfers the call. What is the meaning of these extra calls that disappear?

• When a call gets transferred, the bot essentially sees the current call end and a completely new one begin. Is there a reliable way to relate a call that is the result of a transfer to the call it was transferred from? It seems that for PSTN-Teams calls there is a CallChainId in the message the bot receives, which seems to remain the same through each call that results from a transfer. This is not the case for Teams-Teams calls however, where each transfer seems to result in a new call CallChainId so you can't use it to determine if a new Teams-Teams call is the result of a transfer.

Start with the Microsoft Graph Communications API notifications the bot receives for call creation, updates, and termination, focusing on PSTN-Teams and Teams-Teams transfers. Review the call messages described in the issue and document the meaning of disappearing calls and whether transferred calls can be reliably related; done means both behaviors are clearly explained.