Unifying every channel with OneSignal: email, push, in-app, SMS… and now WhatsApp

How we helped a medical SaaS unify their patient communications by bringing WhatsApp into OneSignal Journeys.

TL;DR

With this setup, you can run all your channels from one place in OneSignal: push, email, SMS, in-app, and now WhatsApp. Customers reply in natural language on WhatsApp, an AI agent understands them, and the result (confirmed, declined, not_sure) gets synced back into OneSignal tags. That way your Journeys stay unified and consistent across every touchpoint.

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Why we built this

At Bildung (OneSignal’s top partner in LatAm), we worked with a client, a SaaS for medical practices, that faced two big challenges:

1. WhatsApp was siloed.
   They managed push, in-app, and email in OneSignal… but WhatsApp ran in parallel, totally disconnected. That meant duplicated logic, inconsistent user states, and no way to run an omnichannel journey.

2. A static WhatsApp bot that failed real patients.
   Their bot only offered rigid options (“Reply A to confirm, B to reschedule, C to cancel”). But patients wrote in natural language: “Hey, I might not make it tomorrow, could I come later?”. Those replies broke the flow and got lost, leaving the clinic blind.

The goal: bring WhatsApp into OneSignal Journeys, powered by AI, so patients could reply naturally, the system would understand, and OneSignal would remain the single source of truth.

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Architecture at a glance

1. OneSignal Journey orchestrates all your channels (push, email, SMS, in-app… and now WhatsApp)

2. Webhook step → POST to Kapso

3. Kapso Flow starts with the payload (phone, name, date, hour, external_id)

4. WhatsApp Template (created & approved inside Kapso) is sent via Meta API

5. User replies on WhatsApp (free text) → Kapso AI classifies reply

6. Kapso → OneSignal User API (PATCH) updates appointment_status

7. OneSignal Journey branches on that tag and continues

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Step 1 — Start with a OneSignal Journey

Everything begins inside OneSignal Journeys, where you orchestrate all your channels from a single place: push notifications, email, SMS, in-app messages… and now WhatsApp too.

From there, you simply add a Webhook step that POSTs to Kapso, sending along the user data (phone, name, date, hour, external_id) to kick off the WhatsApp flow.

POST https://app.kapso.ai/api/v1/flows/{{FLOW_ID}}/executions
Authorization: Bearer {{KAPSO_API_KEY}}
Content-Type: application/json

{
  “phone_number”: “{{ user.tags.phone_number }}”,
  “name”: “{{ user.tags.name | default: “” }}”,
  “date”: “{{ user.tags.appointment_date }}”,
  “hour”: “{{ user.tags.appointment_hour }}”,
  “external_id”: “{{ user.external_id }}”
}

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Step 2 — WhatsApp Template inside Kapso

Kapso makes this step simple: you can create and manage WhatsApp templates directly in Kapso, send them for Meta approval, and then use them in your flows without coding JSON.

For example, a template could be:

“Hi {{name}}, please confirm your doctor’s appointment for {{date}} at {{hour}}.”

When the webhook fires, the template is sent with the right variables.

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Step 3 — AI classification of replies

Kapso’s AI agent reads the free-text response and classifies it into branches:

• “Yes, confirmed” → confirmed

• “I can’t tomorrow” → declined

• “Mmm I should check my agenda?” → not_sure

This is the big shift: no more static options. Patients type naturally, the AI interprets, and the flow continues.

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Step 4 — PATCH back to OneSignal

Once Kapso knows the outcome, it calls OneSignal’s Users API to update the user tag:

PATCH https://api.onesignal.com/apps/{{ONESIGNAL_APP_ID}}/users/by/external_id/{{ external_id }}
Authorization: Bearer {{ONESIGNAL_REST_API_KEY}}
Content-Type: application/json

{
  “tags”: {
    “appointment_status”: “{{ branch_label }}”
  }
}

Because we sent external_id in the first webhook, we can deterministically update the right profile in OneSignal.

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Step 5 — Continue the Journey in OneSignal

Now the tag appointment_status is available:

• If confirmed → stop reminders, send prep info.

• If declined → trigger a reschedule journey.

• If not_sure → escalate or offer a reschedule link.

And because everything lives in OneSignal, you can experiment with channels—WhatsApp, push, email, SMS, in-app—without duplicating logic.

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Outcome for the client

For the medical SaaS:

• Unified orchestration: WhatsApp is now just another channel in their OneSignal Journeys.

• Smarter conversations: Free-text patient replies are understood and acted on.

• Single source of truth: Appointment status lives in OneSignal, not scattered.

The result: higher confirmation rates, fewer missed appointments, smoother rescheduling, and less manual work for clinic staff.

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Why this matters

This project shows what’s possible when you stop treating WhatsApp as an isolated bot and start treating it as part of a unified journey.

At Bildung, our mission as OneSignal’s reseller in LatAm is to help companies design data-driven, omnichannel engagement strategies. Integrations like this are how you unlock the full power of your stack: all your channels, all your touchpoints, one journey.