Introduction

Ha Tang is a developer platform for businesses in Vietnam, built from modules: transactional email, customer support chat, bank-transfer payments, a product catalogue and a CRM. Each business turns on the modules it needs. They all share one account, one team, one set of API keys and one stream of webhooks, so a single integration covers everything you use.

The modules

Module	What it does	Start here
Email	Resend-compatible email API and SMTP relay, several sending domains, templates, audiences, broadcasts, automations and inbound mail	Email overview
Support (Customer Support)	Website chat widget, native SDKs for iOS, Android, Flutter and React Native, one inbox for Zalo (OA and personal), Messenger, Instagram, TikTok, TikTok Shop, WhatsApp, Telegram, LINE, X and email, plus tickets and an AI assistant	Support overview
Payments	VietQR transfers straight into your own bank account, automatic matching and e-invoices	Payments overview
Products	Product catalogue and orders, product cards and payment links sent inside a conversation	Support REST API
CRM	One customer profile across every channel, custom fields, filters by stage, label and channel, and Zalo ZNS messages	Support REST API

There is no "website" or "sales channel" layer above the modules. Each module owns its own resources and can have many of them: Email has several sending domains, and Support has several widget sites and mobile apps.

An owner or admin turns modules on and off in Business settings → Modules. See Businesses and modules.

One API key, one webhook stream

Every module is served by the same REST API at https://api.hatang.dev, with the same conventions:

• One kind of API key. A key starts with ht_ and carries scopes such as email:send or chat:read. Send it as Authorization: Bearer ht_123....
• One error format. Every error is a JSON object { statusCode, name, message }. See Errors.
• One webhook stream. A webhook endpoint subscribes to events from any module (email.delivered, chat.message.created, payment.succeeded, …) and every delivery is signed the same way. See Webhooks.
• Shared rules for rate limits, pagination and idempotency.

Two more hosts serve specific clients:

Host	Used by
https://api.hatang.dev	Your server: REST API for every module
https://chat.hatang.dev	The chat widget and the mobile chat SDKs (realtime gateway)
smtp.hatang.dev:5870 (STARTTLS)	Apps that send email over SMTP
https://app.hatang.dev	The dashboard, for you and your team

How to use this hub

The hub has two parts:

• Guides (this part) explain how to do something end to end: send your first email, put the chat widget on a site, take a payment, verify a webhook. Start with Getting started, then open the guides of the modules you use.
• References list every detail: the REST API reference, the chat gateway reference, the webhook events, the error codes, the limits and the realtime protocol.

Code samples in the guides come in cURL, Node.js (with @hatang/sdk), Python and PHP. Pick a language once and every page follows it.

Integration checklist

1. Create an account at app.hatang.dev and pick the modules you need.
2. Create an API key with the scopes of those modules (Authentication).
3. Call the API at https://api.hatang.dev, or use the Node SDK @hatang/sdk.
4. Add a webhook endpoint to hear about events.
5. Invite your team and give each person the access they need (Team and roles).

Next steps

• Quickstart: send your first email
• Quickstart: add live chat to your site
• Payments quickstart
• Authentication