Warm transfer
A warm transfer is a call handoff in which the current agent privately contacts and briefs the intended recipient before connecting the caller, giving the recipient context and an opportunity to accept.
The caller is usually placed on hold while the agent creates a separate call leg to the recipient. The agent explains why the caller is being transferred and can share relevant details from the conversation. If the recipient accepts, the call legs are joined. If the recipient declines or does not answer, the original agent can return to the caller and choose another path.
Warm transfer differs from cold transfer. In a cold transfer, the caller is sent directly to a number or endpoint without a private conversation first. Cold transfer is faster and uses a simpler call flow, but the recipient may answer without context and the caller may reach voicemail. Warm transfer adds time and telephony complexity in exchange for a more controlled handoff.
For an AI phone agent, a useful transfer policy defines when a human is needed, which recipient or team should receive the call, what information may be included in the private brief, and what happens when nobody accepts. The brief should be concise and based on information collected during the call. It should not expose details that the recipient does not need.
The fallback path is part of the feature, not an edge case. A system may return to the caller, try another destination, offer voicemail, schedule a follow-up, or end the call with clear next steps. Teams should test each outcome, including unanswered calls and mailbox pickup, rather than verifying only the successful connection.
Warm transfers also require suitable telephony. The system must keep the caller's leg active, place another call, and connect the legs after acceptance. Caller ID, hold behavior, timeouts, and transfer billing can depend on the number and carrier setup.
In practice on ThunderPhone
ThunderPhone supports cold and attended warm transfers. In warm mode, the caller waits on hold while the agent privately briefs the recipient. The agent connects the call after acceptance and returns to the caller with the outcome if the recipient declines, does not answer, or reaches voicemail. Warm transfer requires an eligible production number that can place an outbound SIP leg; demo numbers and browser-based calls are limited to cold transfer.