Phone Number Fallback Destination & Inbound Settings

Overview

A phone number's fallbackDestination lets you specify where an inbound call should route if no assistant, squad, or workflow can handle it, instead of the call simply dropping. The destination can be a phone number or a SIP URI.

Configuring a Fallback Destination

The fallbackDestination field accepts a destination object at the phone number level. If no assistantId, squadId, or workflowId is configured for the number, or if a dynamic assistant-request webhook to your server fails to return a valid assistant in time, the call is forwarded to this destination instead of dropping.

Number and SIP Fallback Examples

Fallback to a standard phone number:

{
  "assistantId": "your-assistant-id",
  "fallbackDestination": {
    "type": "number",
    "number": "+11234567890",
    "message": "Please hold while we connect you."
  }
}

Fallback to a SIP URI:

{
  "assistantId": "your-assistant-id",
  "fallbackDestination": {
    "type": "sip",
    "sipUri": "sip:[email protected]"
  }
}

Inbound Settings Overview

A phone number's inbound configuration has a few related fields that work together:

Field	Purpose
assistantId	The saved assistant that handles inbound calls to this number.
workflowId	An alternative to a direct assistant — routes inbound calls through a workflow instead.
fallbackDestination	The backup destination used if no handler is configured or available.

If none of assistantId, workflowId, or squadId is set, the platform will request an assistant dynamically from your server for each inbound call.

Supported Transfer Scenarios

Fallback routing is subject to the same underlying transfer-scenario support as any other call transfer. For the full matrix and the technical detail behind it, see Call Forwarding & Transfer Modes. In summary:

From	To	Supported
Phone call	Phone number	Yes
Web call	Phone number	No
Phone call	SIP number	No
SIP call	SIP number	Yes
SIP call	Phone number	Yes

Best Practices

Always configure a fallback destination on production numbers — a call that can't reach an assistant should still reach a human, not drop silently.
Use a different number or provider for your fallback destination than the one hosting the primary number, so a provider-wide outage doesn't take down both the primary path and the fallback at once.
Test that the fallback actually activates under failure conditions rather than assuming it works once configured.
Include a clear spoken message in the fallback destination so callers understand they're being transferred rather than hearing dead air.

Fallback destination handles routing when no assistant is available at all. If you instead need a backup voice provider for an assistant that is otherwise working normally, see the related but distinct Voice Fallback Plans page.

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Phone Number Fallback Destination & Inbound Settings