@Shah-Fazal thanks for the thorough answer.
The Conversation-Flow transfer step doesn’t work for us, and your reply says why: the REFER releases only the leg directly beneath the referring agent, so the first agent stays bridged to the caller and the trunk leg never releases. We tested that and reported it in post 9. With BYO numbers it’s worse — the first agent’s INVITE loops back out through our trunk and in again.
If you mean something other than chaining to a second agent — swapping the response engine in place on the same leg, with no new leg — say so and we’ll test it today. Otherwise no configuration inside Retell takes you out of the media path.
That makes the WebSocket field the fix. Everything downstream of it already works: a Conversation Flow agent on the same trunk and the same number completes the REFER in 463 ms and drops Retell out of the path (call_57983cc866e0d1e76579990671c, post 7). From out here it reads as passing an existing enum through to a handler that currently assumes INVITE, rather than building anything new.
Can you get us a yes/no and a date from the team? This is blocking production for several of our clients.
Feature request, already submitted and live: Expose cold_transfer_mode (SIP REFER) on the custom LLM WebSocket frame — prod impact
Description: expose cold_transfer_mode on the Custom LLM WebSocket transfer response and agent_interrupt, so a Custom LLM agent can select sip_refer the way the Transfer Call tool does on Retell LLM and Conversation Flow.
Use case: our own LLM drives the conversation over the custom-LLM WebSocket, so Conversation Flow isn’t open to us. We need cold transfers that take Retell out of the media path.
Priority/impact: blocking production for several of our clients.