Current Setup: - Twilio phone number configured to webhook to AWS Lambda endpoint (no assigned assistant - it uses the organization server url) - Lambda function configured to handle both VAPI and Twilio webhooks - Lambda contains logic to check user profiles and select appropriate VAPI assistants Integration Goal: Attempting to bridge Twilio's incoming call webhook with VAPI's voice service while maintaining the custom routing logic in the Lambda. Attempts and Errors: 1. Attempt: - Used Twilio

<Redirect>

to VAPI endpoint - TwiML Response:

xml
<Response>
    <Redirect method="POST"><https://api.vapi.ai/twilio/inbound_call></Redirect>
</Response>

- Error: "Document parse failure" (Error 12100) Key Issues: 1. The Lambda successfully processes webhooks and returns valid TwiML, but Twilio isn't able to establish the connection to VAPI 2. We've found VAPI documentation referencing a

/twilio/inbound_call

endpoint, but direct connection attempts are failing 3. The Lambda is correctly identifying Twilio vs VAPI requests, but we're missing the proper connection mechanism between Twilio and VAPI *Questions * 1. What is the correct TwiML response format to connect a Twilio call to VAPI? 2. Is there a specific authentication or configuration needed in the TwiML for VAPI to accept the connection? 3. Should we be handling the Twilio-to-VAPI connection differently, perhaps configuring it at the Twilio number level instead of through Lambda?

Marking this ticket as solved.

✅ Ticket status updated to solved by Vapi Ticket Bot#0124