This guide walks you through migrating a WhatsApp integration from Kapso to Zernio. Both platforms are built on Meta's WhatsApp Cloud API, so the fundamentals you already know (approved templates, the 24-hour service window, webhooks, WABA-level assets) carry over unchanged. What changes is the API shape: Kapso exposes Meta's raw Cloud API envelope behind a proxy plus a separate platform API, while Zernio gives you a single flat, conversation-centric API.

Most integrations move in half a day to a day.

Quick Reference

The main differences at a glance:

What	Kapso	Zernio
Base URL	`api.kapso.ai/meta/whatsapp/v24.0` + `api.kapso.ai/platform/v1`	`zernio.com/api/v1`
Auth	`X-API-Key: KEY` (default)	`Authorization: Bearer KEY`
Request shape	Meta Cloud API envelope (`messaging_product`, `type`)	Flat JSON fields (`message`, `attachmentUrl`, `template`)
Send target	`{phone_number_id}/messages` + `to`	`accountId` + `conversationId`
Business-initiated send	`POST .../messages` with `type: "template"`	`POST /v1/inbox/conversations`
Templates	`POST /{waba_id}/message_templates`	`POST /v1/whatsapp/templates`
Webhook signature	`X-Webhook-Signature` (HMAC-SHA256 hex)	`X-Zernio-Signature` (same algorithm)
Multi-tenant unit	Customer + setup link	Profile + connect URL

Before You Start

What you'll need:

Your Kapso project API key (to export conversations and templates before cutover)
A Zernio account (sign up here)
A Zernio API key from your dashboard

How the concepts map

Kapso splits its surface across two layers (a Meta-compatible proxy and a platform API). Zernio has one API for everything. The objects map one-to-one:

Kapso	Zernio	Notes
Project + API key	Team + API key	Zernio keys can be scoped to specific profiles
Customer	Profile	The multi-tenant unit that groups accounts
WhatsApp phone number (`phone_number_id`)	WhatsApp account (`accountId`)	Returned by `/v1/accounts`
Setup link	Connect URL (`GET /v1/connect/whatsapp`)	Both are hosted Meta embedded signup
Conversation	Conversation	Zernio IDs are 24-hex strings
Contact	Contact (`/v1/contacts`)

Profile: "Acme Corp"                <- Kapso "Customer"
└── WhatsApp (+1 555 123 4567)      <- accountId (Kapso phone_number_id)
    ├── Conversations               <- threads with end users
    └── Templates, flows, business profile

WABA assets travel with the number, message history does not. Approved templates, your display name, quality rating, and messaging tier live on the WABA at Meta and carry over when you reconnect the same number through Zernio. Stored conversations and messages live in Kapso's database. Export anything you need (via Kapso's GET /platform/v1/whatsapp/messages) before you cancel.

Step 1: Set Up Zernio Profiles

For each Kapso Customer (or just once, if you run a single number), create a Zernio profile:

curl -X POST https://zernio.com/api/v1/profiles \
  -H "Authorization: Bearer YOUR_ZERNIO_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"name": "Acme Corporation"}'

Save the returned profile._id. You'll pass it as profileId when connecting numbers.

Step 2: Move Your WhatsApp Numbers

Pick the path that matches how the number was connected to Kapso:

For numbers connected through Kapso setup links or "Bring Your Own SIM" (the WABA belongs to your or your customer's Meta Business), request a connect URL:

curl -X GET "https://zernio.com/api/v1/connect/whatsapp?profileId=PROFILE_ID&redirect_url=https://yourapp.com/callback" \
  -H "Authorization: Bearer YOUR_ZERNIO_API_KEY"

The response includes an authUrl. Open it (or send it to your customer, exactly like a Kapso setup link) to run Meta's embedded signup with the Facebook login that owns the WABA. If the WABA has multiple numbers, the flow includes a phone number selection step.

Because the WABA stays the same, approved templates, display name, and quality rating come with it.

Coexistence numbers: pairing with the WhatsApp Business App is exclusive to one provider. Disconnect from Kapso first (in the app: Settings, then Account, then Business Platform, then Disconnect), then run the Zernio connect flow and scan the QR code again. See Connection & Setup.

If you connected to Kapso by posting Meta credentials directly, Zernio has the same headless flow:

Kapso:

curl -X POST https://api.kapso.ai/platform/v1/customers/CUSTOMER_ID/whatsapp/phone_numbers \
  -H "X-API-Key: KAPSO_API_KEY" \
  -d '{
    "whatsapp_phone_number": {
      "name": "Support Line",
      "kind": "production",
      "phone_number_id": "1234567890",
      "business_account_id": "98765432109",
      "access_token": "EAABsbCS...long-lived-token"
    }
  }'

Zernio:

curl -X POST https://zernio.com/api/v1/connect/whatsapp/credentials \
  -H "Authorization: Bearer YOUR_ZERNIO_API_KEY" \
  -d '{
    "profileId": "PROFILE_ID",
    "accessToken": "EAABsbCS...system-user-token",
    "wabaId": "98765432109",
    "phoneNumberId": "1234567890"
  }'

The token must be a permanent Meta System User token with whatsapp_business_management and whatsapp_business_messaging. Zernio subscribes its webhooks and returns the new account.

If you used a Kapso-managed number (Instant Setup), the number belongs to Kapso's pool, so purchase a dedicated number through Zernio instead:

curl -X POST https://zernio.com/api/v1/phone-numbers/purchase \
  -H "Authorization: Bearer YOUR_ZERNIO_API_KEY" \
  -d '{"profileId": "PROFILE_ID", "country": "US"}'

Your first purchase returns a Stripe checkoutUrl to complete payment; subsequent purchases provision inline. Numbers start at $2/month and are available in dozens of countries (list them via GET /v1/phone-numbers/countries). Regulated countries require KYC, which you can complete via API or hand off to your customer with a white-label hosted KYC link (POST /v1/phone-numbers/kyc/share, with your branding).

Track provisioning with the whatsapp.number.activated / whatsapp.number.action_required webhooks or by polling GET /v1/phone-numbers/{id}.

Just testing? Zernio has a sandbox too: POST /v1/whatsapp/sandbox/sessions with {"phone": "+15551234567"}, then reply to the verification message. See Sandbox.

Step 3: Get Your Account IDs

After connecting, fetch the WhatsApp accounts. The _id values replace Kapso's phone_number_id in every call:

curl -X GET "https://zernio.com/api/v1/accounts?platform=whatsapp" \
  -H "Authorization: Bearer YOUR_ZERNIO_API_KEY"

{
  "accounts": [
    {
      "_id": "abc123",
      "platform": "whatsapp",
      "username": "+1 555-123-4567",
      "displayName": "Acme Corp",
      "metadata": {
        "wabaId": "98765432109",
        "phoneNumberId": "1234567890",
        "qualityRating": "GREEN",
        "messagingLimitTier": "TIER_1K"
      }
    }
  ]
}

Store the phone_number_id to accountId mapping in your database. Quality rating and messaging tier are the same values you saw in Kapso's health endpoint; live WABA health is at GET /v1/whatsapp/number-info?accountId=....

Step 4: Update Message Sending

This is the biggest conceptual shift. Kapso is recipient-centric: every send goes to POST /{phone_number_id}/messages with a to phone number. Zernio is conversation-centric:

Business-initiated (template) messages create or reuse a conversation: POST /v1/inbox/conversations with participantId (the recipient's phone number).
Free-form messages inside the 24-hour window go into an existing conversation: POST /v1/inbox/conversations/{conversationId}/messages.

You get the conversationId from the create call's response, from every webhook, or from GET /v1/inbox/conversations. It's stable per participant and account, so store it alongside your contact records.

Business-initiated send (starts or re-engages a conversation):

Kapso:

curl -X POST https://api.kapso.ai/meta/whatsapp/v24.0/PHONE_NUMBER_ID/messages \
  -H "X-API-Key: KAPSO_API_KEY" \
  -d '{
    "messaging_product": "whatsapp",
    "to": "15551234567",
    "type": "template",
    "template": {
      "name": "order_update",
      "language": {"code": "en_US"},
      "components": [
        {"type": "body", "parameters": [{"type": "text", "text": "John"}]}
      ]
    }
  }'

Zernio:

curl -X POST https://zernio.com/api/v1/inbox/conversations \
  -H "Authorization: Bearer YOUR_ZERNIO_API_KEY" \
  -d '{
    "accountId": "abc123",
    "participantId": "15551234567",
    "templateName": "order_update",
    "templateLanguage": "en_US",
    "templateParams": ["John"]
  }'

templateParams fills body variables in order and works with both positional ({{1}}) and named ({{name}}) placeholders. Media-header templates are auto-filled from the approved template definition. The response returns the conversationId for follow-ups.

To send a template into an existing thread with full Meta-style components (for example a custom media header), use the messages endpoint instead:

{
  "accountId": "abc123",
  "template": {
    "elements": [
      {
        "name": "order_update",
        "language": "en_US",
        "components": [
          {"type": "body", "parameters": [{"type": "text", "text": "John"}]}
        ]
      }
    ]
  }
}

The components array is forwarded to Meta verbatim, so your existing Kapso component payloads drop in unchanged.

Free-form reply inside the 24-hour window:

Kapso:

curl -X POST https://api.kapso.ai/meta/whatsapp/v24.0/PHONE_NUMBER_ID/messages \
  -H "X-API-Key: KAPSO_API_KEY" \
  -d '{
    "messaging_product": "whatsapp",
    "to": "15551234567",
    "type": "text",
    "text": {"body": "Your order #12345 has shipped!"}
  }'

Zernio:

curl -X POST https://zernio.com/api/v1/inbox/conversations/CONVERSATION_ID/messages \
  -H "Authorization: Bearer YOUR_ZERNIO_API_KEY" \
  -d '{
    "accountId": "abc123",
    "message": "Your order #12345 has shipped!"
  }'

To quote-reply, pass replyTo with the WhatsApp message ID (wamid...), which arrives on webhooks as message.platformMessageId.

Kapso (link or a previously uploaded media id):

curl -X POST https://api.kapso.ai/meta/whatsapp/v24.0/PHONE_NUMBER_ID/messages \
  -H "X-API-Key: KAPSO_API_KEY" \
  -d '{
    "messaging_product": "whatsapp",
    "to": "15551234567",
    "type": "image",
    "image": {"link": "https://example.com/product.jpg"}
  }'

Zernio (public URL):

curl -X POST https://zernio.com/api/v1/inbox/conversations/CONVERSATION_ID/messages \
  -H "Authorization: Bearer YOUR_ZERNIO_API_KEY" \
  -d '{
    "accountId": "abc123",
    "attachmentUrl": "https://example.com/product.jpg",
    "attachmentType": "image"
  }'

attachmentType is image, video, audio, or file. For documents, add attachmentName so WhatsApp shows a filename. For voice notes, send an .ogg OPUS audio attachment with voiceNote: true (or upload any browser recording via multipart and Zernio transcodes it).

There is no Meta media-ID step. If your file isn't hosted anywhere, either send it as multipart/form-data (field attachment, up to 25MB) or upload it first:

curl -X POST https://zernio.com/api/v1/media/upload-direct \
  -H "Authorization: Bearer YOUR_ZERNIO_API_KEY" \
  -F "file=@invoice.pdf"

This returns a URL (valid 7 days) to pass as attachmentUrl.

Reply buttons use Zernio's shorthand instead of the interactive envelope:

Kapso:

{
  "messaging_product": "whatsapp",
  "to": "15551234567",
  "type": "interactive",
  "interactive": {
    "type": "button",
    "body": {"text": "Confirm your appointment?"},
    "action": {
      "buttons": [
        {"type": "reply", "reply": {"id": "btn_yes", "title": "Yes"}},
        {"type": "reply", "reply": {"id": "btn_no", "title": "No"}}
      ]
    }
  }
}

Zernio:

{
  "accountId": "abc123",
  "message": "Confirm your appointment?",
  "buttons": [
    {"type": "postback", "title": "Yes", "payload": "btn_yes"},
    {"type": "postback", "title": "No", "payload": "btn_no"}
  ]
}

Everything else (lists, CTA URLs, flows, location requests) keeps Meta's interactive object shape verbatim, so your Kapso payloads move as-is; just drop the outer envelope and add accountId:

{
  "accountId": "abc123",
  "interactive": {
    "type": "list",
    "body": {"text": "Pick an option"},
    "action": {
      "button": "View Options",
      "sections": [
        {"title": "Options", "rows": [{"id": "opt_1", "title": "Option 1"}]}
      ]
    }
  }
}

Supported interactive.type values: list, cta_url, flow, location_request_message, voice_call. Button and list taps arrive on the message.received webhook with metadata.interactiveType (button_reply / list_reply) and metadata.interactiveId.

Location pins keep the same fields (Zernio takes numbers, not strings):

{
  "accountId": "abc123",
  "location": {
    "latitude": 37.7749,
    "longitude": -122.4194,
    "name": "San Francisco Office",
    "address": "123 Market St, San Francisco, CA 94103"
  }
}

Contact cards mirror Meta's shape via the contacts field.

Reactions are their own endpoint instead of a message type. The path takes the WhatsApp message ID (the wamid, from webhook message.platformMessageId, the same ID replyTo uses):

curl -X POST https://zernio.com/api/v1/inbox/conversations/CONVERSATION_ID/messages/MESSAGE_ID/reactions \
  -H "Authorization: Bearer YOUR_ZERNIO_API_KEY" \
  -d '{"accountId": "abc123", "emoji": "👍"}'

Remove with DELETE on the same path, passing accountId as a query parameter.

Mark read and typing indicators

Kapso overloads the messages endpoint ("status": "read" + typing_indicator). Zernio has dedicated endpoints:

# Mark the conversation read (sends blue ticks)
curl -X POST https://zernio.com/api/v1/inbox/conversations/CONVERSATION_ID/read \
  -H "Authorization: Bearer YOUR_ZERNIO_API_KEY" \
  -d '{"accountId": "abc123"}'

# Show "typing..." for up to 25 seconds
curl -X POST https://zernio.com/api/v1/inbox/conversations/CONVERSATION_ID/typing \
  -H "Authorization: Bearer YOUR_ZERNIO_API_KEY" \
  -d '{"accountId": "abc123"}'

On coexistence numbers the phone app owns read state, so /read doesn't send blue ticks there.

Step 5: Update Webhooks

Kapso registers webhooks per phone number (plus project webhooks). Zernio webhooks are team-wide with event filtering. Message and template payloads carry an account object, so scope by account.id in your handler; whatsapp.number.* lifecycle events carry a number object with the profileId instead:

curl -X POST https://zernio.com/api/v1/webhooks/settings \
  -H "Authorization: Bearer YOUR_ZERNIO_API_KEY" \
  -d '{
    "name": "whatsapp-events",
    "url": "https://yourapp.com/webhooks/zernio",
    "events": [
      "message.received", "message.sent", "message.delivered",
      "message.read", "message.failed", "reaction.received",
      "conversation.started", "whatsapp.template.status_updated"
    ],
    "secret": "your-signing-secret"
  }'

Event mapping

Kapso event	Zernio event
`whatsapp.message.received`	`message.received`
`whatsapp.message.sent`	`message.sent`
`whatsapp.message.delivered`	`message.delivered`
`whatsapp.message.read`	`message.read`
`whatsapp.message.failed`	`message.failed`
Reaction messages	`reaction.received`
`whatsapp.conversation.created`	`conversation.started`
`whatsapp.conversation.ended` / `.inactive`	No equivalent (derive from conversation timestamps)
`whatsapp.phone_number.created`	`account.connected`, plus `whatsapp.number.*` lifecycle for purchased numbers
`whatsapp.phone_number.deleted`	`account.disconnected`
Template status changes	`whatsapp.template.status_updated`

Payloads are Zernio-shaped rather than Meta-shaped: the message text is at message.text, the wamid at message.platformMessageId, the sender at message.sender (with phoneNumber, and businessScopedUserId as the durable identity anchor), and WhatsApp extras (button taps, flow responses, CTWA referral with ctwa_clid) under metadata. Full shapes in the webhooks guide.

Signature verification

Same algorithm, different header. Your Kapso verification code needs a one-line change:

const expected = crypto
  .createHmac('sha256', process.env.WEBHOOK_SECRET)
  .update(rawBody)
  .digest('hex');

// Kapso:  req.headers['x-webhook-signature']
// Zernio: req.headers['x-zernio-signature']
const valid = crypto.timingSafeEqual(
  Buffer.from(expected),
  Buffer.from(req.headers['x-zernio-signature'])
);

Delivery behavior

	Kapso	Zernio
Retries	3 (10s / 40s / 90s)	Up to 7 attempts over ~51 hours, then dead-letter
Batching	`whatsapp.message.received` can batch	One event per request, always
Dedup key	`X-Idempotency-Key`	`payload.id` (also `X-Zernio-Event-Id` header)
Raw Meta forwarding	`kind: "meta"` webhooks	Not offered

Delivery is at-least-once, so dedupe on the event ID. Debug with GET /v1/webhooks/logs (30-day retention) and POST /v1/webhooks/test.

Step 6: Templates

Templates belong to the WABA at Meta. If you reconnected the same number in Step 2, your approved templates are already there; verify with:

curl -X GET "https://zernio.com/api/v1/whatsapp/templates?accountId=abc123" \
  -H "Authorization: Bearer YOUR_ZERNIO_API_KEY"

If you moved to a new number, recreate them. The components array is the same Meta shape with lowercase types:

Kapso:

curl -X POST https://api.kapso.ai/meta/whatsapp/v24.0/WABA_ID/message_templates \
  -H "X-API-Key: KAPSO_API_KEY" \
  -d '{
    "name": "order_confirmation",
    "language": "en_US",
    "category": "UTILITY",
    "components": [
      {"type": "BODY", "text": "Thank you! Your order {{1}} is confirmed."}
    ]
  }'

Zernio:

curl -X POST https://zernio.com/api/v1/whatsapp/templates \
  -H "Authorization: Bearer YOUR_ZERNIO_API_KEY" \
  -d '{
    "accountId": "abc123",
    "name": "order_confirmation",
    "language": "en_US",
    "category": "UTILITY",
    "components": [
      {
        "type": "body",
        "text": "Thank you! Your order {{1}} is confirmed.",
        "example": {"body_text": [["ORD-12345"]]}
      }
    ]
  }'

Categories (AUTHENTICATION, MARKETING, UTILITY), statuses, and Meta's review (up to 24h) are identical on both platforms. Approval outcomes arrive on the whatsapp.template.status_updated webhook.

Skip review entirely with library templates. Zernio can instantiate Meta's pre-approved template library (library_template_name on the create call). These come back APPROVED immediately. Introspect a library template's structure and required button inputs first via GET /v1/whatsapp/template-library?accountId=...&name=... (exact-name lookup). See Templates.

WhatsApp Flows

Zernio has a full Flows API: create (POST /v1/whatsapp/flows), upload Flow JSON (PUT /v1/whatsapp/flows/{flowId}/json, Meta-validated), browser preview, publish, and version history. Your existing Flow JSON moves unchanged.

Sending gets simpler. Instead of Kapso's interactive envelope, there's a dedicated endpoint that accepts a raw phone number and auto-generates the flow_token:

curl -X POST https://zernio.com/api/v1/whatsapp/flows/send \
  -H "Authorization: Bearer YOUR_ZERNIO_API_KEY" \
  -d '{
    "accountId": "abc123",
    "to": "+15551234567",
    "flow_id": "1197715005513101",
    "flow_cta": "Book now",
    "body": "Book your appointment",
    "flow_action_payload": {"screen": "BOOKING"}
  }'

(The interactive.type: "flow" shape from Kapso also works on the messages endpoint, and template buttons support type: flow.)

Responses arrive two ways: live on message.received webhooks (metadata.interactiveType: "nfm_reply" with metadata.flowResponseData), or in bulk via GET /v1/whatsapp/flow-responses. See Flows.

If your flows use data_exchange with Kapso-hosted data endpoint functions and managed encryption, you'll need to host that data endpoint yourself after migrating. Reach out and we'll help you wire it up.

Feature Map

Feature	Kapso	Zernio
Send / receive all message types	Meta proxy	Inbox API
Conversations & message history	Platform API	`GET /v1/inbox/conversations` (+ full-text search)
Contacts	Platform API	`/v1/contacts`
Broadcasts (bulk template sends)	Broadcasts API	`/v1/broadcasts` with recipients, schedule, progress
Conversation automation	Workflow builder, AI agent nodes	Workflows (`/v1/workflows`): visual builder with AI nodes (bring your own provider key), branching, webhooks, human handoff
Business calling	WebRTC (SDP offers via API)	Calling API: forward to any phone/SIP, recording, per-call cost breakdown
Flows	Proxy + hosted data endpoints	Full Flows API
Business profile / display name / username	Proxy + platform	`/v1/whatsapp/business-profile`
Block users	Proxy	`/v1/whatsapp/block-users`
CTWA attribution	Referral fields	`metadata.referral` on webhooks + conversion events API
Sandbox	6-character code	Verification reply
Number health	Health endpoint	`GET /v1/whatsapp/number-info`
MCP server	`api.kapso.ai/mcp`	`mcp.zernio.com/mcp`

You also gain: group chats API, sequences (drip campaigns), SMS and voice calling on the same purchased number, numbers in dozens of countries with API-driven KYC and white-label hosted KYC links, and a unified inbox that also covers Instagram, Facebook, Telegram, and SMS.

No Zernio equivalent (plan around these):

Hosted serverless functions. Custom code runs on your own infrastructure; workflow webhook nodes call out to your endpoints instead.
Embeddable inbox iframe. Zernio's inbox lives in the dashboard; there's no embed widget.
Raw Meta webhook forwarding (kind: "meta"). Zernio delivers its own payload shape only.
Interactive product and carousel messages (single product, product list, catalog message, interactive carousel). Template-based equivalents do work: carousel template components (2 to 10 cards) plus catalog and mpm template buttons.
Automatic audio transcription of voice notes.

Cutover Strategy

Migrate number by number, not gradually per number. A WhatsApp number's registration and webhook routing move with it, so plan a hard cutover for each number: export history from Kapso, reconnect through Zernio, verify webhooks, then cancel on Kapso. For multi-tenant platforms, migrate one customer (one Zernio profile) at a time.

Phase	Actions
Prep	Create profiles, build and test your integration against a Zernio sandbox number
Pilot	Move one low-traffic production number end-to-end; run it for a few days
Rollout	Migrate remaining numbers/customers in batches
Cutoff	Cancel the Kapso plan; keep your export of message history

Two things stay exactly the same and need no migration: Meta's per-template conversation charges (billed by Meta to your WABA payment method on both platforms) and template approvals (they live on the WABA).

Troubleshooting

Error	Cause	Fix
401 Unauthorized	Kapso-style `X-API-Key` header	Use `Authorization: Bearer YOUR_API_KEY`
`TEMPLATE_REQUIRED`	Free-form send to a new participant	Business-initiated messages need an approved template; free-form only works inside an existing conversation's 24h window
Fields ignored on send	Posting the Meta envelope (`messaging_product`, `type`)	Use flat fields: `message`, `attachmentUrl`, `interactive`, `template`
Media send fails	Passing a Meta media `id`	Zernio takes URLs; get one via `/v1/media/upload-direct`
Template send does nothing	Meta-style `template` object	Wrap it as `template.elements[0]` with `name`, `language`, `components`
Blue ticks not sent	Coexistence account	The phone app owns read state on coexistence numbers
Quote-reply not quoting	Using the Zernio message ID in `replyTo`	`replyTo` takes the wamid, from webhook `message.platformMessageId`

Code Example: Node.js

const ZERNIO = 'https://zernio.com/api/v1';
const headers = {
  'Authorization': `Bearer ${process.env.ZERNIO_API_KEY}`,
  'Content-Type': 'application/json',
};

// Business-initiated: send a template to any phone number.
// Creates (or reuses) the conversation and returns its id.
const sendTemplate = async ({ accountId, to, templateName, templateParams = [] }) => {
  const res = await fetch(`${ZERNIO}/inbox/conversations`, {
    method: 'POST',
    headers,
    body: JSON.stringify({
      accountId,
      participantId: to,
      templateName,
      templateLanguage: 'en_US',
      templateParams,
    }),
  });
  const { data } = await res.json();
  return data; // { messageId, conversationId, ... }
};

// Free-form reply inside the 24-hour window.
const reply = async ({ accountId, conversationId, message }) => {
  const res = await fetch(`${ZERNIO}/inbox/conversations/${conversationId}/messages`, {
    method: 'POST',
    headers,
    body: JSON.stringify({ accountId, message }),
  });
  const { data } = await res.json();
  return data.messageId;
};

// Usage: template first, then free-form once they reply
const { conversationId } = await sendTemplate({
  accountId: 'abc123',
  to: '15551234567',
  templateName: 'order_update',
  templateParams: ['John', 'ORD-123'],
});
await reply({ accountId: 'abc123', conversationId, message: 'Anything else I can help with?' });

Need Help?

WhatsApp platform guides: /platforms/whatsapp
Support: support@zernio.com
Rate Limits: 60-1,200 req/min, bucketed by your team's connected-account count (0-2: 60, 3-2,000: 600, 2,001+: 1,200), see /guides/rate-limits

Most integrations move in half a day to a day.

Quick Reference

The main differences at a glance:

What	Kapso	Zernio
Base URL	`api.kapso.ai/meta/whatsapp/v24.0` + `api.kapso.ai/platform/v1`	`zernio.com/api/v1`
Auth	`X-API-Key: KEY` (default)	`Authorization: Bearer KEY`
Request shape	Meta Cloud API envelope (`messaging_product`, `type`)	Flat JSON fields (`message`, `attachmentUrl`, `template`)
Send target	`{phone_number_id}/messages` + `to`	`accountId` + `conversationId`
Business-initiated send	`POST .../messages` with `type: "template"`	`POST /v1/inbox/conversations`
Templates	`POST /{waba_id}/message_templates`	`POST /v1/whatsapp/templates`
Webhook signature	`X-Webhook-Signature` (HMAC-SHA256 hex)	`X-Zernio-Signature` (same algorithm)
Multi-tenant unit	Customer + setup link	Profile + connect URL

Before You Start

What you'll need:

Your Kapso project API key (to export conversations and templates before cutover)
A Zernio account (sign up here)
A Zernio API key from your dashboard

How the concepts map

Kapso splits its surface across two layers (a Meta-compatible proxy and a platform API). Zernio has one API for everything. The objects map one-to-one:

Kapso	Zernio	Notes
Project + API key	Team + API key	Zernio keys can be scoped to specific profiles
Customer	Profile	The multi-tenant unit that groups accounts
WhatsApp phone number (`phone_number_id`)	WhatsApp account (`accountId`)	Returned by `/v1/accounts`
Setup link	Connect URL (`GET /v1/connect/whatsapp`)	Both are hosted Meta embedded signup
Conversation	Conversation	Zernio IDs are 24-hex strings
Contact	Contact (`/v1/contacts`)

Profile: "Acme Corp"                <- Kapso "Customer"
└── WhatsApp (+1 555 123 4567)      <- accountId (Kapso phone_number_id)
    ├── Conversations               <- threads with end users
    └── Templates, flows, business profile

Step 1: Set Up Zernio Profiles

For each Kapso Customer (or just once, if you run a single number), create a Zernio profile:

curl -X POST https://zernio.com/api/v1/profiles \
  -H "Authorization: Bearer YOUR_ZERNIO_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"name": "Acme Corporation"}'

Save the returned profile._id. You'll pass it as profileId when connecting numbers.

Step 2: Move Your WhatsApp Numbers

Pick the path that matches how the number was connected to Kapso:

For numbers connected through Kapso setup links or "Bring Your Own SIM" (the WABA belongs to your or your customer's Meta Business), request a connect URL:

curl -X GET "https://zernio.com/api/v1/connect/whatsapp?profileId=PROFILE_ID&redirect_url=https://yourapp.com/callback" \
  -H "Authorization: Bearer YOUR_ZERNIO_API_KEY"

Because the WABA stays the same, approved templates, display name, and quality rating come with it.

If you connected to Kapso by posting Meta credentials directly, Zernio has the same headless flow:

Kapso:

curl -X POST https://api.kapso.ai/platform/v1/customers/CUSTOMER_ID/whatsapp/phone_numbers \
  -H "X-API-Key: KAPSO_API_KEY" \
  -d '{
    "whatsapp_phone_number": {
      "name": "Support Line",
      "kind": "production",
      "phone_number_id": "1234567890",
      "business_account_id": "98765432109",
      "access_token": "EAABsbCS...long-lived-token"
    }
  }'

Zernio:

curl -X POST https://zernio.com/api/v1/connect/whatsapp/credentials \
  -H "Authorization: Bearer YOUR_ZERNIO_API_KEY" \
  -d '{
    "profileId": "PROFILE_ID",
    "accessToken": "EAABsbCS...system-user-token",
    "wabaId": "98765432109",
    "phoneNumberId": "1234567890"
  }'

The token must be a permanent Meta System User token with whatsapp_business_management and whatsapp_business_messaging. Zernio subscribes its webhooks and returns the new account.

If you used a Kapso-managed number (Instant Setup), the number belongs to Kapso's pool, so purchase a dedicated number through Zernio instead:

curl -X POST https://zernio.com/api/v1/phone-numbers/purchase \
  -H "Authorization: Bearer YOUR_ZERNIO_API_KEY" \
  -d '{"profileId": "PROFILE_ID", "country": "US"}'

Track provisioning with the whatsapp.number.activated / whatsapp.number.action_required webhooks or by polling GET /v1/phone-numbers/{id}.

Just testing? Zernio has a sandbox too: POST /v1/whatsapp/sandbox/sessions with {"phone": "+15551234567"}, then reply to the verification message. See Sandbox.

Step 3: Get Your Account IDs

After connecting, fetch the WhatsApp accounts. The _id values replace Kapso's phone_number_id in every call:

curl -X GET "https://zernio.com/api/v1/accounts?platform=whatsapp" \
  -H "Authorization: Bearer YOUR_ZERNIO_API_KEY"

{
  "accounts": [
    {
      "_id": "abc123",
      "platform": "whatsapp",
      "username": "+1 555-123-4567",
      "displayName": "Acme Corp",
      "metadata": {
        "wabaId": "98765432109",
        "phoneNumberId": "1234567890",
        "qualityRating": "GREEN",
        "messagingLimitTier": "TIER_1K"
      }
    }
  ]
}

Step 4: Update Message Sending

This is the biggest conceptual shift. Kapso is recipient-centric: every send goes to POST /{phone_number_id}/messages with a to phone number. Zernio is conversation-centric:

Business-initiated (template) messages create or reuse a conversation: POST /v1/inbox/conversations with participantId (the recipient's phone number).
Free-form messages inside the 24-hour window go into an existing conversation: POST /v1/inbox/conversations/{conversationId}/messages.

Business-initiated send (starts or re-engages a conversation):

Kapso:

curl -X POST https://api.kapso.ai/meta/whatsapp/v24.0/PHONE_NUMBER_ID/messages \
  -H "X-API-Key: KAPSO_API_KEY" \
  -d '{
    "messaging_product": "whatsapp",
    "to": "15551234567",
    "type": "template",
    "template": {
      "name": "order_update",
      "language": {"code": "en_US"},
      "components": [
        {"type": "body", "parameters": [{"type": "text", "text": "John"}]}
      ]
    }
  }'

Zernio:

curl -X POST https://zernio.com/api/v1/inbox/conversations \
  -H "Authorization: Bearer YOUR_ZERNIO_API_KEY" \
  -d '{
    "accountId": "abc123",
    "participantId": "15551234567",
    "templateName": "order_update",
    "templateLanguage": "en_US",
    "templateParams": ["John"]
  }'

To send a template into an existing thread with full Meta-style components (for example a custom media header), use the messages endpoint instead:

{
  "accountId": "abc123",
  "template": {
    "elements": [
      {
        "name": "order_update",
        "language": "en_US",
        "components": [
          {"type": "body", "parameters": [{"type": "text", "text": "John"}]}
        ]
      }
    ]
  }
}

The components array is forwarded to Meta verbatim, so your existing Kapso component payloads drop in unchanged.

Free-form reply inside the 24-hour window:

Kapso:

curl -X POST https://api.kapso.ai/meta/whatsapp/v24.0/PHONE_NUMBER_ID/messages \
  -H "X-API-Key: KAPSO_API_KEY" \
  -d '{
    "messaging_product": "whatsapp",
    "to": "15551234567",
    "type": "text",
    "text": {"body": "Your order #12345 has shipped!"}
  }'

Zernio:

curl -X POST https://zernio.com/api/v1/inbox/conversations/CONVERSATION_ID/messages \
  -H "Authorization: Bearer YOUR_ZERNIO_API_KEY" \
  -d '{
    "accountId": "abc123",
    "message": "Your order #12345 has shipped!"
  }'

To quote-reply, pass replyTo with the WhatsApp message ID (wamid...), which arrives on webhooks as message.platformMessageId.

Kapso (link or a previously uploaded media id):

curl -X POST https://api.kapso.ai/meta/whatsapp/v24.0/PHONE_NUMBER_ID/messages \
  -H "X-API-Key: KAPSO_API_KEY" \
  -d '{
    "messaging_product": "whatsapp",
    "to": "15551234567",
    "type": "image",
    "image": {"link": "https://example.com/product.jpg"}
  }'

Zernio (public URL):

curl -X POST https://zernio.com/api/v1/inbox/conversations/CONVERSATION_ID/messages \
  -H "Authorization: Bearer YOUR_ZERNIO_API_KEY" \
  -d '{
    "accountId": "abc123",
    "attachmentUrl": "https://example.com/product.jpg",
    "attachmentType": "image"
  }'

There is no Meta media-ID step. If your file isn't hosted anywhere, either send it as multipart/form-data (field attachment, up to 25MB) or upload it first:

curl -X POST https://zernio.com/api/v1/media/upload-direct \
  -H "Authorization: Bearer YOUR_ZERNIO_API_KEY" \
  -F "file=@invoice.pdf"

This returns a URL (valid 7 days) to pass as attachmentUrl.

Reply buttons use Zernio's shorthand instead of the interactive envelope:

Kapso:

{
  "messaging_product": "whatsapp",
  "to": "15551234567",
  "type": "interactive",
  "interactive": {
    "type": "button",
    "body": {"text": "Confirm your appointment?"},
    "action": {
      "buttons": [
        {"type": "reply", "reply": {"id": "btn_yes", "title": "Yes"}},
        {"type": "reply", "reply": {"id": "btn_no", "title": "No"}}
      ]
    }
  }
}

Zernio:

{
  "accountId": "abc123",
  "message": "Confirm your appointment?",
  "buttons": [
    {"type": "postback", "title": "Yes", "payload": "btn_yes"},
    {"type": "postback", "title": "No", "payload": "btn_no"}
  ]
}

Everything else (lists, CTA URLs, flows, location requests) keeps Meta's interactive object shape verbatim, so your Kapso payloads move as-is; just drop the outer envelope and add accountId:

{
  "accountId": "abc123",
  "interactive": {
    "type": "list",
    "body": {"text": "Pick an option"},
    "action": {
      "button": "View Options",
      "sections": [
        {"title": "Options", "rows": [{"id": "opt_1", "title": "Option 1"}]}
      ]
    }
  }
}

Location pins keep the same fields (Zernio takes numbers, not strings):

{
  "accountId": "abc123",
  "location": {
    "latitude": 37.7749,
    "longitude": -122.4194,
    "name": "San Francisco Office",
    "address": "123 Market St, San Francisco, CA 94103"
  }
}

Contact cards mirror Meta's shape via the contacts field.

Reactions are their own endpoint instead of a message type. The path takes the WhatsApp message ID (the wamid, from webhook message.platformMessageId, the same ID replyTo uses):

curl -X POST https://zernio.com/api/v1/inbox/conversations/CONVERSATION_ID/messages/MESSAGE_ID/reactions \
  -H "Authorization: Bearer YOUR_ZERNIO_API_KEY" \
  -d '{"accountId": "abc123", "emoji": "👍"}'

Remove with DELETE on the same path, passing accountId as a query parameter.

Mark read and typing indicators

Kapso overloads the messages endpoint ("status": "read" + typing_indicator). Zernio has dedicated endpoints:

# Mark the conversation read (sends blue ticks)
curl -X POST https://zernio.com/api/v1/inbox/conversations/CONVERSATION_ID/read \
  -H "Authorization: Bearer YOUR_ZERNIO_API_KEY" \
  -d '{"accountId": "abc123"}'

# Show "typing..." for up to 25 seconds
curl -X POST https://zernio.com/api/v1/inbox/conversations/CONVERSATION_ID/typing \
  -H "Authorization: Bearer YOUR_ZERNIO_API_KEY" \
  -d '{"accountId": "abc123"}'

On coexistence numbers the phone app owns read state, so /read doesn't send blue ticks there.

Step 5: Update Webhooks

curl -X POST https://zernio.com/api/v1/webhooks/settings \
  -H "Authorization: Bearer YOUR_ZERNIO_API_KEY" \
  -d '{
    "name": "whatsapp-events",
    "url": "https://yourapp.com/webhooks/zernio",
    "events": [
      "message.received", "message.sent", "message.delivered",
      "message.read", "message.failed", "reaction.received",
      "conversation.started", "whatsapp.template.status_updated"
    ],
    "secret": "your-signing-secret"
  }'

Event mapping

Kapso event	Zernio event
`whatsapp.message.received`	`message.received`
`whatsapp.message.sent`	`message.sent`
`whatsapp.message.delivered`	`message.delivered`
`whatsapp.message.read`	`message.read`
`whatsapp.message.failed`	`message.failed`
Reaction messages	`reaction.received`
`whatsapp.conversation.created`	`conversation.started`
`whatsapp.conversation.ended` / `.inactive`	No equivalent (derive from conversation timestamps)
`whatsapp.phone_number.created`	`account.connected`, plus `whatsapp.number.*` lifecycle for purchased numbers
`whatsapp.phone_number.deleted`	`account.disconnected`
Template status changes	`whatsapp.template.status_updated`

Signature verification

Same algorithm, different header. Your Kapso verification code needs a one-line change:

const expected = crypto
  .createHmac('sha256', process.env.WEBHOOK_SECRET)
  .update(rawBody)
  .digest('hex');

// Kapso:  req.headers['x-webhook-signature']
// Zernio: req.headers['x-zernio-signature']
const valid = crypto.timingSafeEqual(
  Buffer.from(expected),
  Buffer.from(req.headers['x-zernio-signature'])
);

Delivery behavior

	Kapso	Zernio
Retries	3 (10s / 40s / 90s)	Up to 7 attempts over ~51 hours, then dead-letter
Batching	`whatsapp.message.received` can batch	One event per request, always
Dedup key	`X-Idempotency-Key`	`payload.id` (also `X-Zernio-Event-Id` header)
Raw Meta forwarding	`kind: "meta"` webhooks	Not offered

Delivery is at-least-once, so dedupe on the event ID. Debug with GET /v1/webhooks/logs (30-day retention) and POST /v1/webhooks/test.

Step 6: Templates

Templates belong to the WABA at Meta. If you reconnected the same number in Step 2, your approved templates are already there; verify with:

curl -X GET "https://zernio.com/api/v1/whatsapp/templates?accountId=abc123" \
  -H "Authorization: Bearer YOUR_ZERNIO_API_KEY"

If you moved to a new number, recreate them. The components array is the same Meta shape with lowercase types:

Kapso:

curl -X POST https://api.kapso.ai/meta/whatsapp/v24.0/WABA_ID/message_templates \
  -H "X-API-Key: KAPSO_API_KEY" \
  -d '{
    "name": "order_confirmation",
    "language": "en_US",
    "category": "UTILITY",
    "components": [
      {"type": "BODY", "text": "Thank you! Your order {{1}} is confirmed."}
    ]
  }'

Zernio:

curl -X POST https://zernio.com/api/v1/whatsapp/templates \
  -H "Authorization: Bearer YOUR_ZERNIO_API_KEY" \
  -d '{
    "accountId": "abc123",
    "name": "order_confirmation",
    "language": "en_US",
    "category": "UTILITY",
    "components": [
      {
        "type": "body",
        "text": "Thank you! Your order {{1}} is confirmed.",
        "example": {"body_text": [["ORD-12345"]]}
      }
    ]
  }'

WhatsApp Flows

Sending gets simpler. Instead of Kapso's interactive envelope, there's a dedicated endpoint that accepts a raw phone number and auto-generates the flow_token:

curl -X POST https://zernio.com/api/v1/whatsapp/flows/send \
  -H "Authorization: Bearer YOUR_ZERNIO_API_KEY" \
  -d '{
    "accountId": "abc123",
    "to": "+15551234567",
    "flow_id": "1197715005513101",
    "flow_cta": "Book now",
    "body": "Book your appointment",
    "flow_action_payload": {"screen": "BOOKING"}
  }'

(The interactive.type: "flow" shape from Kapso also works on the messages endpoint, and template buttons support type: flow.)

Responses arrive two ways: live on message.received webhooks (metadata.interactiveType: "nfm_reply" with metadata.flowResponseData), or in bulk via GET /v1/whatsapp/flow-responses. See Flows.

Feature Map

Feature	Kapso	Zernio
Send / receive all message types	Meta proxy	Inbox API
Conversations & message history	Platform API	`GET /v1/inbox/conversations` (+ full-text search)
Contacts	Platform API	`/v1/contacts`
Broadcasts (bulk template sends)	Broadcasts API	`/v1/broadcasts` with recipients, schedule, progress
Conversation automation	Workflow builder, AI agent nodes	Workflows (`/v1/workflows`): visual builder with AI nodes (bring your own provider key), branching, webhooks, human handoff
Business calling	WebRTC (SDP offers via API)	Calling API: forward to any phone/SIP, recording, per-call cost breakdown
Flows	Proxy + hosted data endpoints	Full Flows API
Business profile / display name / username	Proxy + platform	`/v1/whatsapp/business-profile`
Block users	Proxy	`/v1/whatsapp/block-users`
CTWA attribution	Referral fields	`metadata.referral` on webhooks + conversion events API
Sandbox	6-character code	Verification reply
Number health	Health endpoint	`GET /v1/whatsapp/number-info`
MCP server	`api.kapso.ai/mcp`	`mcp.zernio.com/mcp`

No Zernio equivalent (plan around these):

Hosted serverless functions. Custom code runs on your own infrastructure; workflow webhook nodes call out to your endpoints instead.
Embeddable inbox iframe. Zernio's inbox lives in the dashboard; there's no embed widget.
Raw Meta webhook forwarding (kind: "meta"). Zernio delivers its own payload shape only.
Interactive product and carousel messages (single product, product list, catalog message, interactive carousel). Template-based equivalents do work: carousel template components (2 to 10 cards) plus catalog and mpm template buttons.
Automatic audio transcription of voice notes.

Cutover Strategy

Phase	Actions
Prep	Create profiles, build and test your integration against a Zernio sandbox number
Pilot	Move one low-traffic production number end-to-end; run it for a few days
Rollout	Migrate remaining numbers/customers in batches
Cutoff	Cancel the Kapso plan; keep your export of message history

Troubleshooting

Error	Cause	Fix
401 Unauthorized	Kapso-style `X-API-Key` header	Use `Authorization: Bearer YOUR_API_KEY`
`TEMPLATE_REQUIRED`	Free-form send to a new participant	Business-initiated messages need an approved template; free-form only works inside an existing conversation's 24h window
Fields ignored on send	Posting the Meta envelope (`messaging_product`, `type`)	Use flat fields: `message`, `attachmentUrl`, `interactive`, `template`
Media send fails	Passing a Meta media `id`	Zernio takes URLs; get one via `/v1/media/upload-direct`
Template send does nothing	Meta-style `template` object	Wrap it as `template.elements[0]` with `name`, `language`, `components`
Blue ticks not sent	Coexistence account	The phone app owns read state on coexistence numbers
Quote-reply not quoting	Using the Zernio message ID in `replyTo`	`replyTo` takes the wamid, from webhook `message.platformMessageId`

Code Example: Node.js

const ZERNIO = 'https://zernio.com/api/v1';
const headers = {
  'Authorization': `Bearer ${process.env.ZERNIO_API_KEY}`,
  'Content-Type': 'application/json',
};

// Business-initiated: send a template to any phone number.
// Creates (or reuses) the conversation and returns its id.
const sendTemplate = async ({ accountId, to, templateName, templateParams = [] }) => {
  const res = await fetch(`${ZERNIO}/inbox/conversations`, {
    method: 'POST',
    headers,
    body: JSON.stringify({
      accountId,
      participantId: to,
      templateName,
      templateLanguage: 'en_US',
      templateParams,
    }),
  });
  const { data } = await res.json();
  return data; // { messageId, conversationId, ... }
};

// Free-form reply inside the 24-hour window.
const reply = async ({ accountId, conversationId, message }) => {
  const res = await fetch(`${ZERNIO}/inbox/conversations/${conversationId}/messages`, {
    method: 'POST',
    headers,
    body: JSON.stringify({ accountId, message }),
  });
  const { data } = await res.json();
  return data.messageId;
};

// Usage: template first, then free-form once they reply
const { conversationId } = await sendTemplate({
  accountId: 'abc123',
  to: '15551234567',
  templateName: 'order_update',
  templateParams: ['John', 'ORD-123'],
});
await reply({ accountId: 'abc123', conversationId, message: 'Anything else I can help with?' });

Need Help?

WhatsApp platform guides: /platforms/whatsapp
Support: support@zernio.com
Rate Limits: 60-1,200 req/min, bucketed by your team's connected-account count (0-2: 60, 3-2,000: 600, 2,001+: 1,200), see /guides/rate-limits

Migrate from Kapso

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Migrate from Kapso

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