SIP Integration with Amazon Connect

SIP trunking is only available on the Synthflow Enterprise Plan.

This guide covers connecting Amazon Connect to Synthflow via SIP using an Amazon Chime SDK Voice Connector as the SIP trunk layer. Amazon Connect Contact Flows route calls to Synthflow for AI handling; Synthflow can escalate back to live Amazon Connect agents.

Prerequisites

Requirement	Detail
Amazon Connect	Active instance with Admin access; telephony and outbound calling enabled
AWS	IAM permissions to create and configure Chime SDK Voice Connectors and Lambda functions
Synthflow	Enterprise Plan with a configured AI assistant (v2.0+)
Phone Number	At least one DID claimed in Amazon Connect (E.164 format)
Network	Firewall allows SIP (UDP/TCP 32681 or TLS 32682) and RTP media between AWS and Synthflow

Amazon Connect Configuration

Step 1: Create an Amazon Chime Voice Connector (SIP Trunk)

Amazon Connect uses Amazon Chime SDK Voice Connectors to establish SIP trunks with external systems.

In the AWS Console, navigate to Amazon Chime SDK → Voice Connectors.
Click Create Voice Connector.
Configure the connector:

Field	Value
Name	`Synthflow AI Trunk`
AWS Region	Match your Amazon Connect instance region
Encryption	Required (TLS/SRTP)

Click Create Voice Connector.

Step 2: Configure Origination (Inbound to Synthflow)

Origination settings define where the Voice Connector routes inbound calls.

Select your new Voice Connector and go to the Origination tab.
Enable Origination.
Click Add Route and configure:

Field	Value
Host	`sip.synthflow.ai`
Port	`32681` (UDP/TCP) or `32682` (TLS)
Protocol	UDP/TCP or TLS
Priority	`1`
Weight	`1`

Save the origination settings.

Step 3: Configure Termination (Outbound from Synthflow)

Termination settings define credentials Synthflow uses to authenticate with the Voice Connector.

Go to the Termination tab of your Voice Connector.
Enable Termination.
Under Allowed hosts, add Synthflow’s SIP signaling IP addresses. Contact Synthflow support for the current IP list.
Under Credentials, add a SIP username and password. Note these — you will need them in Synthflow configuration.
Copy the Outbound host name (e.g. abcdefgh.voiceconnector.chime.aws). This is your Termination URI for Synthflow.
Save termination settings.

The Outbound host name of the Chime Voice Connector is what Synthflow uses as its Termination URI — not sip.synthflow.ai.

Step 4: Claim a Phone Number and Assign to Voice Connector

In Amazon Chime SDK → Phone number management, claim a phone number.
Assign it to your Synthflow AI Trunk Voice Connector.
In Amazon Connect, claim the same number (or port it) under Phone numbers in the Connect console.

Step 5: Create a Contact Flow to Route Calls to Synthflow

In Amazon Connect → Contact Flows, create a new flow or edit an existing one.
Add a Transfer to phone number block.
Set the destination to the DID associated with your Synthflow SIP number.
Set Timeout to 30 seconds and Resume contact flow after disconnect to Yes (for post-AI routing).
Publish the Contact Flow and assign it to your inbound phone number.

For passing metadata (caller ID, customer context) to Synthflow, use Lambda function blocks before the transfer step to set contact attributes.

Synthflow Configuration

Add the SIP Number

Go to the Synthflow Phone Numbers page.
Click Add Number → Custom / SIP.
Enter the phone number in E.164 format (the DID assigned to your Chime Voice Connector).
Fill in the SIP connection details:

Field	Value
Termination URI	Your Chime Voice Connector outbound hostname (e.g. `abcdefgh.voiceconnector.chime.aws`)
SIP Username	Username configured in Chime Voice Connector termination credentials
SIP Password	Password configured in Chime Voice Connector termination credentials
Outbound Proxy (if required)	Leave blank

The Termination URI is your Chime Voice Connector’s outbound host — this routes Synthflow calls back into AWS for PSTN termination.

Be precise when copying SIP credentials. Incorrect values will cause registration failure.

Attach to the Assistant

Go to Assistants and create or select an assistant (v2.0+).
In the assistant settings, attach the SIP number you just created.
Wait 1–2 minutes for SIP registration to complete.

The SIP trunk is created at the moment of attaching the SIP number to the assistant.

Call Flow Summary

Scenario	Flow
Inbound to AI	Caller → PSTN → Amazon Connect → Contact Flow → Transfer → Chime Voice Connector → Synthflow AI Agent
AI transfers to live agent	Synthflow AI → SIP transfer → Chime Voice Connector → Amazon Connect → Queue → Live Agent

Verification

Test	What to check
Inbound call	Call the Amazon Connect DID. Verify the Contact Flow routes to Synthflow AI. Check two-way audio.
Transfer to live agent	Trigger a transfer during a Synthflow call. Confirm the call lands in the correct Connect queue with caller ID intact.
Chime Voice Connector health	In AWS Console, verify Voice Connector status shows no errors.

Quick Troubleshooting

Issue	Fix
Registration fails	Verify Termination URI is the Chime Voice Connector hostname. Check credentials and firewall (UDP/TCP 32681 or TLS 32682).
Calls not reaching Synthflow	Confirm origination route points to `sip.synthflow.ai` with correct port. Check Chime origination is enabled.
One-way or no audio	Ensure SRTP/TLS is configured on both sides. Verify RTP media ports are open (16384–32767 for AWS).
Caller ID missing	Set the From header in E.164 format. Check Chime Voice Connector caller ID passthrough settings.
Transfer fails	Verify the Contact Flow has a valid post-transfer path. Check Lambda function logs if using Lambda for routing.
SIP registration rejected	Ensure Synthflow’s SIP signaling IPs are in the Chime Voice Connector’s Allowed hosts list.

Reference

Amazon Chime SDK Voice Connectors: docs.aws.amazon.com/chime-sdk/latest/ag/voice-connectors.html
Amazon Connect Contact Flows: docs.aws.amazon.com/connect/latest/adminguide/concepts-contact-flows.html
Amazon Connect Phone Numbers: docs.aws.amazon.com/connect/latest/adminguide/ag-phone.html
Synthflow SIP Overview: docs.synthflow.ai/about-sip
Synthflow X-EI SIP Header: docs.synthflow.ai/x-ei-sip-header