Caller ID Pass-Through for AI Warm Transfers — Workforce Wave

When AI hands off to a human, the caller's number should survive the transfer.

This technical white paper covers how to preserve the original caller's phone number through an AI-to-human warm transfer. It addresses Twilio transfer configuration, the SIP-level tradeoff between caller ID continuity and warm handoff whisper prompts, and the operational impact on callback workflows when the caller's number is lost.

What’s Inside

• Twilio transfer configuration: How to configure Twilio conference and dial XML so the original caller's number is presented to the human receiving the transfer.
• SIP tradeoff analysis: Why you often can't have both caller ID continuity and a warm handoff whisper prompt — and how to decide which matters more for your use case.
• Callback workflow impact: What happens to callbacks and voicemail when the caller's number is lost in transfer — and why this is a silent revenue leak.
• Implementation patterns: Concrete transfer flow patterns for different scenarios: direct transfer, conference transfer, and supervised warm handoff.

Who This Is For

• →Operations and engineering teams building AI-to-human transfer flows with Twilio and ElevenLabs
• →Call center managers evaluating whether caller ID preservation or warm handoff whisper matters more for their business
• →Developers integrating AI voice agents with existing PBX or human receptionist workflows
• →Anyone who has lost a callback because the caller's number didn't survive the transfer