Channels: The Intelligent Abstraction Layer

Channels in Sent represent an intelligent abstraction layer that fundamentally changes how applications approach messaging. Rather than forcing developers to manage multiple messaging platforms, channels provide a unified interface that automatically handles routing, adaptation, and optimization across diverse communication pathways. This architecture treats channels as implementation details rather than primary interfaces, enabling intent-based messaging that optimizes delivery and engagement.

The Channel Architecture

The Sent channel architecture is designed to be flexible and extensible.

Intent-Based Messaging Over Channel Selection

Most messaging platforms expose channels as separate APIs with distinct interfaces and content formats, placing the burden of channel management on developers. Sent inverts this model through intent-based messaging: instead of choosing a channel, you express intent—send a notification, deliver an authentication code, or engage a customer. The system interprets this intent and determines the optimal delivery path.

// Single API call, intelligent routing
await sendMessage({
  phoneNumber: "+1234567890",
  templateId: "welcome_message",
  templateVariables: {
    name: "John Doe"
  }
});

This approach provides a unified developer experience where a single API call can result in SMS delivery in one region, WhatsApp in another, with automatic content adaptation and fallback handling managed transparently.

The Three-Layer Channel Model

Sent's channel architecture operates on three complementary layers:

Progressive Enhancement

Channels, by relying on templates, are designed using progressive enhancement principles (content adapted to the capabilities of the channel):

• Universal Compatibility: Every message starts with content that works on SMS—the most constrained channel—ensuring universal deliverability.

• Automatic Enrichment: When delivered through WhatsApp, the same template automatically gains interactive buttons, media headers, branded business profiles, and rich formatting.

• Graceful Degradation: Complex WhatsApp templates automatically simplify for SMS delivery, preserving essential information and functionality.

Channel Intelligence

Sent channels are not just static endpoints—they are dynamic, intelligent, and fully discoverable. Every supported channel (such as SMS, WhatsApp, or RCS) is deeply integrated to expose its current status, features, and capabilities in real time.

This intelligence allows Sent to always select the best possible channel for each recipient and message, adapting immediately as circumstances change—if a user registers for WhatsApp after previously only having SMS, future messages can automatically upgrade in experience. The discoverable nature of channels also enables transparent monitoring, reporting, and adaptation to new carrier or provider policies, ensuring optimal deliverability and compliance without developer intervention.

Real-Time Availability Detection

When a contact is first encountered, Sent performs comprehensive channel discovery:

Contextual Routing Logic

Channel selection employs sophisticated decision-making that goes beyond availability:

Technical Implementation

Character Limit Management: Rich templates compress automatically to fit SMS constraints while preserving essential information and call-to-action elements.

Media Handling: Images and videos convert to descriptive text with links for SMS, while delivering full media experiences through RCS and WhatsApp.

Interactive Element Conversion: Buttons and quick replies become text alternatives with URL links for SMS, while maintaining full interactivity on RCS and WhatsApp.

Channel Infrastructure

RCS

Carrier-Native Delivery: RCS messages are delivered over carrier networks directly within the default Android messaging app (Google Messages), requiring no separate app installation by the recipient.

Branded Sender: Unlike SMS, which shows a phone number, RCS messages display your company logo, name, and a verified checkmark — making your brand instantly recognizable in the recipient's inbox.

No Number Provisioning: RCS does not use phone numbers. Each business operates an "RCS Agent" — a branded sender identity — so you don't need short codes or carrier number registration like SMS requires.

Rich Interactive Features: RCS supports suggestion chips (quick reply, open URL, dial a number buttons below the message), rich cards (title, description, image or video, and action buttons), and carousel cards (up to 10 scrollable rich cards). These interactive features are not available on SMS.

Read Receipts: Like WhatsApp, RCS delivers read receipts when the recipient opens the message. SMS has no equivalent.

STOP Chip Auto-Injection: Every RCS message automatically includes a built-in STOP button for compliance. You do not need to add opt-out footer text manually.

Inbound STOP handling: Taps on the built-in STOP chip in Google Messages are delivered as a regular message.received webhook with the keyword in payload.text. Sent automatically flips the contact's opt_out flag and the pre-send consent gate then blocks subsequent sends to that contact.

Automatic Fallback: If RCS is unavailable for a recipient (unsupported device or carrier), Sent automatically falls back to SMS. Use "channel": ["rcs", "sms"] in your send request to enable this pattern explicitly.

Sender Profile Verification: RCS requires an approved RCS sender profile (logo, verified name, brand color) before messages can be sent, managed through the Sent dashboard.

WhatsApp

Template System Integration: Sent automatically manages Meta's template approval process, submitting new templates and tracking approval status without requiring developer intervention in Meta's platform.

Business Verification: WhatsApp Business accounts display verification badges and professional profiles that build user trust and engagement rates compared to SMS from unknown numbers.

SMS

Carrier Network Integration: Leverages aggregator and carrier agnostic SMS integration for real-time phone number validation, SMS capability assessment, and optimized routing through carrier networks.

Regulatory Compliance: Automatically handles regional SMS requirements, carrier filtering, spam prevention, and opt-out management across different countries and regulations.

Economic Predictability: Straightforward per-message pricing model makes cost calculation and customer billing transparent, with international delivery optimized through carrier relationships.

Channels for Developers

Channels for Businesses