Changelog

Stay up to date with the latest changes to Synthflow.
April 14, 2026

In-call SMS and WhatsApp messaging

Voice agents can now send SMS or WhatsApp messages during a live call and feed the customer’s reply back into the conversation as a variable. This is useful for capturing details that are hard to relay by voice — one-time passcodes, email addresses, invoice IDs, links, and short menus of options.

  • Two new action types, INCALL_SMS and INCALL_WHATSAPP, attachable to a voice agent under the During phase.
  • Blocking or non-blocking reply handling with a configurable timeout and fallback message.
  • Replies are injected into the call transcript and exposed as {sms_reply} / {whatsapp_reply} variables.
  • Requires a connected Twilio account; in-call WhatsApp additionally requires a linked WhatsApp sender.

See the In-Call Messaging guide.

EndpointChange
POST /actionsAccepts INCALL_SMS and INCALL_WHATSAPP action types.
PUT /actions/{action_id}Accepts INCALL_SMS and INCALL_WHATSAPP action types.
GET /actions/{action_id}action_type may be INCALL_SMS or INCALL_WHATSAPP.
GET /actionsaction_type may be INCALL_SMS or INCALL_WHATSAPP.