> ## Documentation Index
> Fetch the complete documentation index at: https://plivo.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.
# Transfer to Human Agent
> When to hand an AI-handled call to a human agent, and how to choose between DID forward, SIP auth forward, and a Multiparty Call.
> [!NOTE]
>
> * **What:** Hand an AI-handled call to a human agent by phone, SIP, or Multiparty Call. Only a Multiparty Call does warm transfer.
> * **Watch out:** A SIP transfer needs [two Plivo IP ranges whitelisted](https://plivo.com/docs/voice/use-cases/transfer-to-human-agent/sip-auth-forward.md#what-your-contact-center-must-do), not one.
When your AI agent hits an escalation, a query it can't handle, or a fallback, it hands the caller to a human agent. This page helps you pick how. Each option has its own page with the XML, API calls, and setup, and [Troubleshooting](https://plivo.com/docs/voice/use-cases/transfer-to-human-agent/troubleshooting.md) covers failed transfers.
The video walks through all three options in about a minute. Select a chapter to jump to it.
Video chapters
***
## When to Transfer to a Human Agent
Transfer the caller to a human agent when your AI agent detects an escalation trigger, for example:
* The caller asks for a human.
* The caller's intent is unclear.
* The query is one your AI agent can't handle.
* Your AI agent hits a fallback.
A transfer is either cold or warm:
* **Cold transfer:** the caller is connected to the human agent, and your AI agent leaves the call without briefing them.
* **Warm transfer:** your AI agent briefs the human agent first, while the caller is on hold. Then the caller is connected.
***
## Transfer Approaches
| Option | What It Does | Best For | Warm Transfer |
| - | - | - | - |
| **[Option 1: DID Forward](https://plivo.com/docs/voice/use-cases/transfer-to-human-agent/did-forward.md)** | Transfer to a regular phone number | Simple call centers, agents on PSTN phones, no SIP infrastructure | No |
| **[Option 2: SIP Auth Forward](https://plivo.com/docs/voice/use-cases/transfer-to-human-agent/sip-auth-forward.md)** (recommended) | Transfer to a SIP endpoint (softphone, contact center, PBX) with credentials | Modern contact centers, softphone-based agents, lower latency | No |
| **[Option 3: Multiparty Call](https://plivo.com/docs/voice/use-cases/transfer-to-human-agent/multiparty-call.md)** | Put the caller, your AI agent, and the human agent in one Multiparty Call (MPC) | Warm transfer, and transfers that don't wait for your AI agent's WebSocket to close | Yes |
***
## Choosing a Transfer Approach
Pick the option recommended for your situation:
* **Your AI agent should brief the human agent before the caller joins (warm transfer):** [Option 3, Multiparty Call](https://plivo.com/docs/voice/use-cases/transfer-to-human-agent/multiparty-call.md#warm-transfer-with-a-multiparty-call). Options 1 and 2 can't do a warm transfer. Option 2 can still [pass the call's context in SIP headers](https://plivo.com/docs/voice/use-cases/transfer-to-human-agent/sip-auth-forward.md#pass-call-context-to-the-human-agent).
* **Your human agents answer on regular phone numbers:** [Option 1, DID forward](https://plivo.com/docs/voice/use-cases/transfer-to-human-agent/did-forward.md).
* **Your human agents use a SIP contact center, softphone, or PBX:** [Option 2, SIP auth forward](https://plivo.com/docs/voice/use-cases/transfer-to-human-agent/sip-auth-forward.md).
Option 3 only works if your own server controls the call. It puts the caller in a Multiparty Call, then uses the Plivo API to add the human agent and remove the AI agent. If another platform answers calls on your Plivo number for you, use Option 1 or 2.
***
## Full API Reference
* [Dial XML](https://plivo.com/docs/voice/xml/routing.md) — Complete reference for ``, ``, and `` elements
* [SIP Authentication](https://plivo.com/docs/voice/concepts/sip-authentication.md) — How outbound SIP auth works
* [Voice Call API](https://plivo.com/docs/voice/api/calls.md) — Transfer a Call, to redirect a live call leg from your server
* [Multiparty Call XML](https://plivo.com/docs/voice/xml/multiparty-call.md) — `` and its participant roles, including `ai-agent`
* [Multiparty Call API](https://plivo.com/docs/voice/api/multiparty-calls.md) — Add, update, and kick participants
* [Firewall and Network Configuration](https://plivo.com/docs/voice/concepts/firewall-network-configuration.md) — Plivo IPs to whitelist
* [Hangup Causes](https://plivo.com/docs/voice/troubleshooting/hangup-causes.md) — Every hangup code and its meaning
## Related
* [Option 1: DID Forward](https://plivo.com/docs/voice/use-cases/transfer-to-human-agent/did-forward.md) — Transfer to a phone number
* [Option 2: SIP Auth Forward](https://plivo.com/docs/voice/use-cases/transfer-to-human-agent/sip-auth-forward.md) — Transfer to a SIP endpoint with credentials
* [Option 3: Multiparty Call](https://plivo.com/docs/voice/use-cases/transfer-to-human-agent/multiparty-call.md) — Cold or warm transfer in a Multiparty Call
* [Troubleshoot Transfer to Human Agent](https://plivo.com/docs/voice/use-cases/transfer-to-human-agent/troubleshooting.md) — Test a transfer and fix failed ones
* [Connect External Phone Numbers](https://plivo.com/docs/voice/use-cases/connect-external-numbers.md) — Route external numbers into Plivo applications
* [Build with Audio Streaming](https://plivo.com/docs/voice-agents/audio-streaming/overview.md) — AI voice agent setup
* [SIP REFER](https://plivo.com/docs/sip-trunking/concepts/sip-refer.md) — Transfers started by a platform connected over Plivo SIP Trunking, which work differently from the ones on this page