SMS sending is coming soon. This guide describes the planned RCS → SMS fallback behaviour for campaign flows. The capability detection and flow configuration concepts are final — SMS delivery will activate when the SMS channel launches. See SMS overview.
When a campaign SEND node targets RCS but the contact’s device is not RCS-capable, the platform can automatically fall back to SMS. This is configured per SEND node, not globally.

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How capability detection works

Before executing a SEND node, the platform checks device capability internally (results are cached with a 4-hour TTL). If the device is not RCS-capable, the SEND node acts according to its fallback configuration — no RCS send attempt is made.
A 404 from POST /v1/messages on a direct API send means the device is not RCS-capable. In campaign flows, the fallback logic handles this automatically — the 404 is never surfaced to the campaign execution.

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Fallback options per SEND node

OptionBehavior
fallback: noneContact execution is skipped. The flow continues but no message is sent. A rcs_not_reachable event is logged and available for CONDITION branching.
fallback: smsAutomatic SMS using the same text content. Rich card content (images, suggestions) is converted to plain text.
fallback: sms_customSMS using a separate SMS template you configure on the node. Use this when your rich card content doesn’t translate well to plain text.

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Configuring fallback in the flow builder

In the campaign flow builder:
  1. Add a SEND node and select your RCS channel and template.
  2. In the node settings, open Fallback and choose your option.
  3. For sms_custom, select the SMS template to use when the RCS fallback fires.
  4. Connect the node’s output edges — the flow continues to the next node regardless of which channel was used.
Optionally, add a CONDITION node after the SEND to branch on whether the message used RCS or SMS: 
SEND (RCS, fallback: sms_custom)
  └─ CONDITION: channel_used == "sms"
       ├─ yes → different next step for SMS recipients
       └─ no  → standard next step for RCS recipients

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Billing

The fallback affects which pricing unit is applied — no RCS hold is created for a contact whose device fell back to SMS.
ScenarioBilling
RCS-capable deviceRCS pricing (Basic or Single depending on content)
Fell back to SMSSMS flat rate; no RCS reservation created
Skipped (fallback: none)No charge — execution skipped
The UsageEvent for a fallback send includes: 
{
  "original_channel": "RCS",
  "fallback_channel": "SMS",
  "fallback_reason": "DEVICE_NOT_CAPABLE"
}
This means your invoice and usage reports will show the send as SMS, not RCS — even though the campaign flow targeted RCS.

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Rich card → SMS text conversion (fallback: sms)

When fallback: sms is set, the platform converts rich card content automatically:
RCS contentSMS output
content.textSent as-is
rich_card.standalone.content.titleFirst line of SMS text
rich_card.standalone.content.descriptionSecond line
rich_card.standalone.content.mediaOmitted (SMS cannot carry images)
suggestions (reply chips)Omitted
rich_card.carouselEach card’s title — truncated to fit SMS length limit
For campaigns where visual content is essential, use fallback: sms_custom with a purpose-built SMS template instead of relying on automatic conversion.

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Direct API sends

When sending directly via POST /v1/messages, RCS capability is checked at the API layer. If the device is not capable, the API returns 404 — no automatic SMS fallback occurs. Fallback is a campaign flow feature only. For API-driven multi-channel logic, send separately to each channel and use the 404 response to decide your own fallback path: 
// Attempt RCS
POST /v1/messages
→ 404 device_not_capable

// Fall back to SMS in your own code
POST /v1/messages
{ "channel": "sms", "to": "+4917612345678", ... }

RCS messaging types

Content shapes and billing units for RCS.

Campaigns in depth

SEND node configuration and CONDITION branching.

RCS text API

Direct API sends and the 404 not-capable response.

Multi-channel campaign path

Combining RCS and email in one flow with condition-based routing.