The paylod of webhook event "chat_message.sent" has empty contact_id

According to the change log, the contact_id would be empty only when the user is external.

However, we found that the webhook event chat_message.sent has empty contact_id even when the user is internal. In our test scenario, internal user A sends a direct message to another internal user B, but the webhook event we received has empty string in contact_id field. This issue is breaking our application.

Is this a breaking change or a bug?

Here is the X-Zm-Signature and X-Zm-Trackingid for test DM webhook event (an internal user sends message to another internal user).
v0=c6b45d9e9ba02743e8ca00d9c234491926c4f51e722de9fa88af156eb5f67709
v=2.0;rid=Webhook_f20e90c947544e1daf92f62005987cca

Hi @k-root
I am happy to take a closer look into this issue e
I will send you a DM, could you follow up there with the payload you are getting from this event please?

Hi @elisa.zoom Have there been any updates since I sent you the payload?