One-Way Audio — agent audio not reaching caller when SIP participant joins room before agent

Fancy
Wed, 08 Apr 2026 02:49:34 +0000
Agents

We hit a one-way audio issue on an inbound SIP call where the agent’s greeting was generated and published to the room but never reached the caller’s phone.

Same caller made 4 calls to the same trunk within 15 minutes. 3 worked fine, 1 had this issue.
The only difference found in these 4 calls is that on the broken call, the SIP participant was already in the room when the agent worker joined. On all 3 working calls, the agent joined first and the SIP participant connected after.

So our hypothesis is that when the SIP participant is already in the room and the agent joins and publishes a new audio track, the room-level subscription completes (unblocking capture_frame), but the SIP bridge’s RTP forwarding to the phone isn’t ready yet — so the initial audio is lost.

Has anyone encountered similar issues and what could be a good fix to it?

3 posts - 3 participants