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Channel capability coverage matrix

Every channel page under Channels documents one channel’s full surface. That granularity answers “how do I use channel X,” but the question a routing decision actually asks is across channels: can RCS carry this payload, is the recipient reachable on it in this market, and if not, which channel next? This page owns the unifying model — the capability taxonomy, the coverage dimensions that gate a channel per recipient, which rounds of channels are eligible for the org-level fallback chain, and a one-row-per-channel index into the individual channel pages. It deliberately does not re-teach each channel’s send shapes; it indexes them.

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1. Capability taxonomy

A capability in Orbit is a named, machine-checkable message feature — not a vague “this channel is rich.” Every channel is assessed against the same taxonomy, so comparing them is apples-to-apples:
  • Send — outbound (MT) delivery: text, or text plus structured payloads.
  • Receive — inbound (MO) delivery into the inbox and webhooks.
  • Templates — a pre-registered, provider-approved structured shape (WhatsApp templates, RCS rich cards/carousels, Messenger generic templates, email block-builder templates).
  • Media — attachments beyond plain text: images, video, audio, documents.
  • Delivery receipts (DLRs) — a terminal delivery verdict from the carrier or provider, distinguishing delivered from the three failure classes described in Message status lifecycle.
  • Read receipts — a recipient-opened signal beyond delivery: RCS and Viber seen, WhatsApp/Meta read, email open-tracking.
These are the columns in the matrix below. A channel’s mapping to them is fixed by its upstream provider, not by Orbit — the matrix is a description of provider contracts, not a product toggle.

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2. Coverage dimensions

Having a capability is necessary but not sufficient. Whether a channel can carry a specific recipient is gated by three coverage dimensions, each checked before the send commits:
  • Geography. Channel reach varies by recipient market. SMS reaches effectively every MSISDN worldwide; RCS depends on per-carrier RBM rollout in the recipient’s country; Viber availability is market-bounded by Rakuten’s allow-list; WhatsApp and Messenger are near-global but live behind Meta’s per-market business policies. The regional messaging apps are Asia-market bounded by design: KakaoTalk covers Korea, Zalo covers Vietnam, WeChat covers mainland China, and LINE covers Japan, Taiwan, and Thailand. Treat each region-bounded channel as an Orbit-side boundary for the fallback chain — a chain hop into Kakao, Zalo, WeChat, or LINE only reaches a recipient inside that app’s home market. The recipient’s number and country are evaluated the same way the Number Lookup and reachability model evaluates them.
  • Feature set. The exact capability needed: media stops the chain at SMS unless MMS carries it; interactive buttons belong to WhatsApp, RCS, and Messenger templates; voicemail-style one-way blasts belong on voice.
  • Cost class. Channels cluster into per-message-charged carriers (SMS, RCS, Viber), Meta conversation-priced channels (WhatsApp, Messenger), and flat/unmetered lanes (email, push). A routing policy like Least-cost routing treats the class, not the sticker price, as the comparable axis.
Note — pricing lives elsewhere. Per-channel rate resolution, the pricing ladder, and route preview are owned by Least-cost routing and the Route preview model. This matrix ranks channels by cost class only — it never quotes rates.

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3. Fallback eligibility

The org-level chain (Cross-channel fallback) advances a failed send to the next channel — but only across deployments where the next hop can plausibly reach the same recipient. The candidates, in the order a chain normally descends:
  1. Rich messaging carriers — RCS, WhatsApp, Viber. Each is eligible as a primary and as a fallback hop (the canonical RCS → SMS chain; Viber → WhatsApp → SMS).
  2. SMS (MMS where media applies) — the floor of every messaging chain: the one channel reachable on virtually every handset.
  3. Email — eligible as a terminal hop for notification-class traffic where content survivability matters more than real-time delivery; not eligible mid-chain for interactive payloads, since email does not carry them.
  4. Voice / fax — never in the message fallback chain. Their delivery surface (a call, a document) is not interchangeable with a message, so the router never advances a message send onto them; they are configured and reported separately.
Messenger, Instagram, and other Meta DM channels are send-capable but not chain candidates beyond their own Meta family: a Messenger hop only works when the recipient has an open Meta conversation, which the generic capability check cannot guarantee. The same read applies to the regional messaging apps: Kakao, Zalo, WeChat, and LINE are send-capable channels that are chain candidates only within their own carrier family. A hop is plausible only when the recipient has an open conversation with your sender profile there — a followed WeChat Official Account, a LINE friend-added account, a KakaoTalk channel the user added as a friend, or a Zalo template landing on a reachable Zalo-linked number. A Korean, Vietnamese, Chinese, or Japanese recipient counted reachable on SMS and nothing else gives the router no basis to hop into one of these apps. When you encode a chain entry, the router re-validates eligibility per hop — an ineligible entry is rejected at configuration time rather than silently skipped at send time.

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4. Per-channel capability matrix

One row per channel, every capability from the taxonomy as a column. Yes = the channel carries it; No = it does not, or carries it only in a degenerate form (marked where relevant). Follow the channel link for the send shapes, rate limits, and provider contract.

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Regional messaging apps (Asia)

Four Asia-market channels run beside the global carriers. Each maps onto the same taxonomy, but the geography dimension bounds them harder than any global channel: none of them substitutes for SMS reach, and each is reachable only when the recipient is inside the app’s home market and satisfies that app’s own conversation gate (a followed Official Account, a friend-added channel, or a bot-followed recipient — see Fallback eligibility). Two routing notes: template-only channels (Zalo, WeChat, and Kakao’s Alimtalk type) carry transactional notifications, not free-form conversation — a hop into them re-enters the template gate for that market, so a chain that descends to them needs an approved template per market. LINE is the only one of the four with full media and free-form conversational payloads, which makes it the natural rich primary inside its markets (Japan, Taiwan, Thailand) the way RCS or WhatsApp is elsewhere. The matrix answers two questions at once: capability (which channels can carry this payload class at all) and fallback eligibility (which of those channels the org-level chain may legitimately descend to). Everything else — the exact request envelope, provider tiers, rate limits, and per-market quirks — belongs to the channel page it links.

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Where the other models plug in