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SMS Setup (Twilio)

Hermes connects to SMS through the Twilio API. People text your Twilio phone number and get AI responses back — same conversational experience as Telegram or Discord, but over standard text messages.

::info Shared Credentials The SMS gateway shares credentials with the optional telephony skill. If you’ve already set up Twilio for voice calls or one-off SMS, the gateway works with the same TWILIO_ACCOUNT_SID, TWILIO_AUTH_TOKEN, and TWILIO_PHONE_NUMBER.

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Prerequisites

  • Twilio account — Sign up at twilio.com (free trial available)
  • A Twilio phone number with SMS capability
  • A publicly accessible server — Twilio sends webhooks to your server when SMS arrives
  • aiohttp — pip install 'hermes-agent[sms]'

Step 1: Get Your Twilio Credentials

  1. Go to the Twilio Console
  2. Copy your Account SID and Auth Token from the dashboard
  3. Go to Phone Numbers → Manage → Active Numbers — note your phone number in E.164 format (e.g., +15551234567)

Step 2: Configure Hermes

hermes gateway setup

Select SMS (Twilio) from the platform list. The wizard will prompt for your credentials.

Manual setup

Add to ~/.hermes/.env:

TWILIO_ACCOUNT_SID=ACxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
TWILIO_AUTH_TOKEN=your_auth_token_here
TWILIO_PHONE_NUMBER=+15551234567

# Security: restrict to specific phone numbers (recommended)
SMS_ALLOWED_USERS=+15559876543,+15551112222

# Optional: set a home channel for cron job delivery
SMS_HOME_CHANNEL=+15559876543

Step 3: Configure Twilio Webhook

Twilio needs to know where to send incoming messages. In the Twilio Console:

  1. Go to Phone Numbers → Manage → Active Numbers
  2. Click your phone number
  3. Under Messaging → A MESSAGE COMES IN, set:
    • Webhook: https://your-server:8080/webhooks/twilio
    • HTTP Method: POST

:::tip Exposing Your Webhook If you’re running Hermes locally, use a tunnel to expose the webhook:

# Using cloudflared
cloudflared tunnel --url http://localhost:8080

# Using ngrok
ngrok http 8080
Set the resulting public URL as your Twilio webhook.
::

Set SMS_WEBHOOK_URL to the same URL you configured in Twilio. This is required for Twilio signature validation — the adapter will refuse to start without it:

# Must match the webhook URL in your Twilio Console
SMS_WEBHOOK_URL=https://your-server:8080/webhooks/twilio

The webhook port defaults to 8080. Override with:

SMS_WEBHOOK_PORT=3000

Step 4: Start the Gateway

hermes gateway

You should see:

[sms] Twilio webhook server listening on 0.0.0.0:8080, from: +1555***4567

If you see Refusing to start: SMS_WEBHOOK_URL is required, set SMS_WEBHOOK_URL to the public URL configured in your Twilio Console (see Step 3).

Text your Twilio number — Hermes will respond via SMS.

Environment Variables

VariableRequiredDescription
TWILIO_ACCOUNT_SIDYesTwilio Account SID (starts with AC)
TWILIO_AUTH_TOKENYesTwilio Auth Token (also used for webhook signature validation)
TWILIO_PHONE_NUMBERYesYour Twilio phone number (E.164 format)
SMS_WEBHOOK_URLYesPublic URL for Twilio signature validation — must match the webhook URL in your Twilio Console
SMS_WEBHOOK_PORTNoWebhook listener port (default: 8080)
SMS_WEBHOOK_HOSTNoWebhook bind address (default: 0.0.0.0)
SMS_INSECURE_NO_SIGNATURENoSet to true to disable signature validation (local dev only — not for production)
SMS_ALLOWED_USERSNoComma-separated E.164 phone numbers allowed to chat
SMS_ALLOW_ALL_USERSNoSet to true to allow anyone (not recommended)
SMS_HOME_CHANNELNoPhone number for cron job / notification delivery
SMS_HOME_CHANNEL_NAMENoDisplay name for the home channel (default: Home)

SMS-Specific Behavior

  • Plain text only — Markdown is automatically stripped since SMS renders it as literal characters
  • 1600 character limit — Longer responses are split across multiple messages at natural boundaries (newlines, then spaces)
  • Echo prevention — Messages from your own Twilio number are ignored to prevent loops
  • Phone number redaction — Phone numbers are redacted in logs for privacy

Security

Webhook signature validation

Hermes validates that inbound webhooks genuinely originate from Twilio by verifying the X-Twilio-Signature header (HMAC-SHA1). This prevents attackers from injecting forged messages.

SMS_WEBHOOK_URL is required. Set it to the public URL configured in your Twilio Console. The adapter will refuse to start without it.

For local development without a public URL, you can disable validation:

# Local dev only — NOT for production
SMS_INSECURE_NO_SIGNATURE=true

User allowlists

The gateway denies all users by default. Configure an allowlist:

# Recommended: restrict to specific phone numbers
SMS_ALLOWED_USERS=+15559876543,+15551112222

# Or allow all (NOT recommended for bots with terminal access)
SMS_ALLOW_ALL_USERS=true
:::warning SMS has no built-in encryption. Don’t use SMS for sensitive operations unless you understand the security implications. For sensitive use cases, prefer Signal or Telegram.
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Troubleshooting

Messages not arriving

  1. Check your Twilio webhook URL is correct and publicly accessible
  2. Verify TWILIO_ACCOUNT_SID and TWILIO_AUTH_TOKEN are correct
  3. Check the Twilio Console → Monitor → Logs → Messaging for delivery errors
  4. Ensure your phone number is in SMS_ALLOWED_USERS (or SMS_ALLOW_ALL_USERS=true)

Replies not sending

  1. Check TWILIO_PHONE_NUMBER is set correctly (E.164 format with +)
  2. Verify your Twilio account has SMS-capable numbers
  3. Check Hermes gateway logs for Twilio API errors

Webhook port conflicts

If port 8080 is already in use, change it:

SMS_WEBHOOK_PORT=3001

Update the webhook URL in Twilio Console to match.