I am implementing SMS with a Twilio phone number that is connected to my Vapi assistant. Inbound SMS reaches Vapi successfully and I can see the SMS message in Vapi chat logs (including the SMS message log entries), but Vapi does not send any webhook events to my backend for inbound SMS. To troubleshoot, I enabled all events in the Assistant “Server Messages” section (Select All) and tested multiple channels: - Voice call to the same Vapi connected number: webhook events are delivered to my backend normally. - Vapi Web Console Chat: webhook events are delivered to my backend normally. - SMS sent from my mobile phone to the same number: no webhook event is delivered, and there is no entry in Observe → Webhook Logs at the time of the SMS. I am attaching the session ID for reference: 256c99c4-bd6d-44d4-a808-e29b323af48c Could you please confirm whether I may have misconfigured something, or if this is a system issue or limitation with inbound SMS webhooks? If there are any additional settings required specifically for inbound SMS webhook delivery, please let me know. https://cdn.discordapp.com/attachments/1470534666107748505/1470534666443296860/Screenshot_2026-02-05_162113.png?ex=698ba5a1&is=698a5421&hm=39528a8ba7db208dd46f5862bfcdcd5d19a4ba47c3c70075dd552760228bf3c2&

Based on the documentation, ensure that your Twilio number is US-based, SMS is enabled in both Twilio and Vapi, and that

smsEnabled: true

is set for your number. You can verify or update this via the API as shown below:

python
client.phone_numbers.update(
    id="your_number_id",
    request=UpdateByoPhoneNumberDto(smsEnabled=True),
)

If these settings are correct and the issue persists, the documentation does not specify further SMS-specific webhook settings—this may indicate a system limitation or require Vapi support intervention. Reference: [Vapi Inbound SMS documentation](https://docs.vapi.ai/phone-numbers/inbound-sms) Source: - [Vapi Inbound SMS documentation](https://docs.vapi.ai/phone-numbers/inbound-sms)

From what you’ve described, your setup looks correct since voice and web chat are triggering webhooks properly. The main issue is that inbound SMS is often handled differently in the Vapi–Twilio flow and doesn’t always fire the standard assistant server events. So this is likely a system limitation rather than something you misconfigured. In most cases, the best workaround is to rely on Twilio’s SMS webhook and forward the data to your backend yourself. Are you currently using Twilio’s messaging webhook, or only Vapi’s server URL for this flow? @yookywooky

@yookywooky add a webhook into Twilio also to listen the response going from Vapi. This will solve the issue.

I’m only using Vapi’s server URL. Does that mean I need to set up a Twilio webhook endpoint, receive inbound SMS messages from Twilio first, and then forward them to Vapi? I want to support both voice calls and SMS chat with a single assistant.

query from your number to twilio phone number(connected to vapi agent)-> vapi api -> response from vapi agent -> response get back to your number via wenhook in twilio that u got from vapi this always works

I think there may be a misunderstanding. My goal is to have my backend receive the SMS conversation (inbound and outbound) between the user (my phone) and the Vapi assistant via webhook.

yes, so the agent/LLM is the backend here u send via http protocol vapi api I mentioned that is backend here

Yes, that’s basically the core issue you’re running into. With SMS, Twilio sits in front of everything, and Vapi doesn’t always fire assistant webhooks the same way it does for voice and web chat. Since Twilio only lets you set one inbound SMS webhook, the best setup is usually to point it to your own endpoint first, handle the message there, and then forward it to Vapi through their API. That way, you keep full control and don’t lose any events. This also makes it much easier to support voice and SMS with the same assistant. If you’d like, you can send me a private message and I’ll walk you through it step by step. @yookywooky

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