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Inbound SMS conversations route through the Flex Conversations service as messaging tasks. When the AI hands off, your rep replies from the Flex UI and the reply lands on the contact’s phone as an SMS.

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Pre-requisites

Set up AI SMS first. Flex SMS handoff depends on AI SMS being wired up end-to-end — start with AI SMS Support and come back here.
  • AI SMS configured and receiving messages — see AI SMS Support.
  • Twilio Flex credentials saved — see Connect Twilio Flex.
  • Both webhooks registered (TaskRouter + Conversations service).

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How messages land in Flex

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What the rep sees

  • A messaging task in the Flex UI with the contact’s phone number as the subject.
  • The full AI-to-contact SMS transcript in the conversation thread.
  • The handoff note above the transcript with summary, sentiment, and reason.
  • The six handoff* attributes on the task panel.
  • Any flex_* custom data the workflow set during routing.
  • Replies typed in the Flex UI send as SMS to the contact’s number.

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Channel-specific details

Twilio’s default opt-out keywords (STOP, UNSUBSCRIBE, etc.) are handled upstream by your carrier — the OpenCX AI never sees a message from an opted-out number, and no Flex task is created.
Flex SMS inherits the same or toll-free verification rules as any other Twilio SMS integration. OpenCX does not add or waive those — fix any registration issues with Twilio.
OpenCX matches an inbound SMS to an existing session by the contact’s phone number. A new number is a new session; an existing number continues the last session until it closes.
MMS attachments flow through to the Flex conversation as media attachments. Reps can view them inline and reply with their own attachments; MMS quotas and size limits follow your Twilio plan.

AI SMS Support

The channel itself — numbers, routing, compliance.

Connect Twilio Flex

Credentials, webhook, workflow filters.

Twilio Flex overview

What else Flex lights up across every channel.

Troubleshooting

Missing task, wrong queue, events routed to the wrong org.