@resend/chat-sdk-adapter

Vercel Chat SDK adapter for Resend email. Bidirectional: receive emails via Resend webhooks, send emails via Resend API.

Install

pnpm add @resend/chat-sdk-adapter chat @chat-adapter/shared

Quick Start

import { createResendAdapter } from "@resend/chat-sdk-adapter";
import { MemoryStateAdapter } from "@chat-adapter/state-memory";
import { Chat } from "chat";

const resend = createResendAdapter({
  fromAddress: "bot@yourdomain.com",
  fromName: "My Bot",         // optional
  // apiKey: "re_...",        // or set RESEND_API_KEY env var
  // webhookSecret: "whsec_..." // or set RESEND_WEBHOOK_SECRET env var
});

const chat = new Chat({
  userName: "email-bot",
  adapters: { resend },
  state: new MemoryStateAdapter(),
});

// New inbound email (new thread)
chat.onNewMention(async (thread, message) => {
  await thread.subscribe();
  await thread.post(`Got your email: ${message.text}`);
});

// Follow-up email in a subscribed thread
chat.onSubscribedMessage(async (thread, message) => {
  await thread.post(`Reply: ${message.text}`);
});

Forward Resend webhooks to your server's /webhook endpoint. See examples/basic for a full working server.

Configuration

Environment Variables

Variable	Description
RESEND_API_KEY	Resend API key (overridden by config.apiKey)
RESEND_WEBHOOK_SECRET	Webhook signing secret (overridden by config.webhookSecret)
FROM_ADDRESS	Used by example apps only

ResendAdapterConfig

interface ResendAdapterConfig {
  /** Sender email address (required). */
  fromAddress: string;
  /** Display name for the From header. */
  fromName?: string;
  /** Resend API key. Falls back to RESEND_API_KEY env var. */
  apiKey?: string;
  /** Webhook signing secret. Falls back to RESEND_WEBHOOK_SECRET env var. */
  webhookSecret?: string;
}

Features

Email Threading

Threads are resolved using standard Message-ID, In-Reply-To, and References email headers. Reply chains are automatically grouped into Chat SDK threads.

Send Emails Proactively

Use openDM to start a new email thread to any address:

const threadId = await chat.adapters.resend.openDM("user@example.com");
const thread = await chat.thread("resend", threadId);
await thread.post("Hello from the bot!");

Card Emails

Send rich HTML emails using Chat SDK Card elements, rendered via @react-email/components:

await thread.post({
  card: {
    type: "card",
    title: "Order Confirmed",
    children: [
      { type: "text", content: "Your order #1234 has been shipped." },
      { type: "divider" },
      { type: "link-button", label: "Track Order", url: "https://example.com/track/1234" },
    ],
  },
  fallbackText: "Order #1234 confirmed",
});

Attachments

Inbound email attachments are available in message.raw.attachments with filename, content_type, and url fields.

Unsupported Operations

Email is inherently one-shot. The following operations throw NotImplementedError:

• editMessage / deleteMessage
• addReaction / removeReaction
• startTyping

Examples

Example	Description
basic	Echo bot - replies to every email
welcome-cards	Sends a styled card email on first contact
notifications	Proactive emails via openDM() + HTTP POST
support-bot	Multi-turn support with subscribe/unsubscribe
attachments	Detects attachments and replies with a summary

Documentation

Official docs available at resend.com/docs/chat-sdk.

License

MIT