Chat

SMS chat

Enable text-based conversations with assistants via SMS messaging

Overview

Let customers chat with your Vapi assistants through SMS text messages. Perfect for businesses that want to provide AI support through familiar messaging channels.

What You’ll Enable:

  • Text-based conversations through SMS
  • Automatic session management for each customer
  • Context-aware responses across message exchanges

SMS chat requires a 10DLC-approved Twilio number. Only customers can initiate conversations - assistants cannot send the first message.

Prerequisites

Setup Steps

1

Import your 10DLC Twilio number

Bring your approved Twilio number into Vapi so we can manage SMS messaging.

SMS is enabled by default when importing Twilio numbers.

See: Import number from Twilio and Inbound SMS setup

2

Attach the number to an assistant

Assign the assistant that will handle SMS conversations for this number.

When customers text your number, they’ll automatically start a chat session with this assistant.

3

Test the integration

Send a text message to your phone number to verify the assistant responds correctly.

View all SMS conversations in the Session Logs page of your dashboard. Each SMS conversation creates a session where you can see the full message history and conversation flow.

How It Works

When a customer texts your number:

  1. Session Creation: Vapi automatically creates a chat session for the customer
  2. Context Management: All messages maintain conversation context within the session
  3. Response Delivery: Assistant responses are sent back as SMS messages
  4. Session Expiry: Sessions expire after 24 hours of inactivity, then create fresh sessions for new conversations

Session Management

SMS conversations use automatic session management:

  • New customers: Get a fresh session on first text
  • Returning customers: Continue existing session if under 24 hours
  • Session expiry: After 24 hours, new session created automatically
  • Context preservation: Full conversation history maintained within session

Limitations

Current SMS chat limitations:

  • 10DLC requirement: Only 10DLC-approved Twilio numbers support assistant responses
  • Customer-initiated: Assistants cannot send the first message to customers
  • Query tool: Knowledge-base searches are not supported (same as Chat API)
  • Twilio only: Other SMS providers are not currently supported

Next Steps

Enhance your SMS chat implementation:

For the best SMS experience, configure your assistant with concise responses and clear conversation flows. SMS users expect quick, direct answers.