[mike-engel]

Summary

The backend serves POST /v1/send/whatsapp, but the SDK did not expose it. This adds a sendWhatsApp transactional method mirroring the existing sendSMS/sendPush surface.

Changes

• SendWhatsAppRequest builder in lib/api/requests.ts — mirrors SendSMSRequest, plus the from and tracked fields the handler reads. to/from are E.164 phone numbers, optional only when the referenced transactional_message_id already defines them.
• APIClient.sendWhatsApp(req) → POST /v1/send/whatsapp, with the same instance guard as the other send methods.
• Exports: SendWhatsAppRequest re-exported from lib/api.ts; SendWhatsAppRequestOptions + WhatsAppMessage from index.ts.
• Unit tests (invalid-object throw, template success, all optional params, error path).
• Live integration test gated on CIO_TEST_WHATSAPP_TRANSACTIONAL_ID (+ CIO_TEST_WHATSAPP_RECIPIENT), plus env-example and header docs.
• docs/app.md WhatsApp subsection.

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Note

Low Risk
Additive API surface following the existing sendSMS pattern; no changes to auth or shared request plumbing beyond a new POST route.

Overview
Exposes transactional WhatsApp on the App API client for POST /v1/send/whatsapp, which existed on the backend but was missing from the SDK.

Adds SendWhatsAppRequest (same builder pattern as SMS, with optional E.164 to / from, plus tracked and the usual transactional flags), APIClient.sendWhatsApp, and public exports for SendWhatsAppRequestOptions / WhatsAppMessage. Unit tests cover instance validation, payload shape, and errors; a gated live test uses CIO_TEST_WHATSAPP_* env vars. docs/app.md documents usage with an example.

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