Chat SDK Attachments - Resend

When someone sends an email with file attachments, the adapter makes them available on message.raw.attachments. The adapter does not download the attachment content.

An attachment of an email.received email has filename and contentType.
An attachment of an inbox email has id, filename, size and contentType. The inbox API does not return the MIME type, so contentType is always application/octet-stream.

Attachment shape

interface ResendAttachment {
  content?: string;
  contentType: string;
  filename: string;
  id?: string;
  size?: number;
  url?: string;
}

Field	Type	Description
`content`	`string`	Base64-encoded content. The adapter does not set it
`contentType`	`string`	MIME type (e.g., `application/pdf`). Always `application/octet-stream` for an inbox email
`filename`	`string`	Original filename (e.g., `invoice.pdf`)
`id`	`string`	Attachment ID. Set on inbox emails only
`size`	`number`	Size in bytes. Set on inbox emails only
`url`	`string`	Download URL. The adapter does not set it

Detecting and processing attachments

import type { ResendRawMessage } from '@resend/chat-sdk-adapter';

chat.onNewMention(async (thread, message) => {
  const raw = message.raw as ResendRawMessage;
  const attachments = raw.attachments ?? [];

  if (attachments.length === 0) {
    await thread.subscribe();
    await thread.post('Got your email. No attachments found.');
    return;
  }

  const summary = attachments
    .map((a) => `${a.filename} (${a.contentType})`)
    .join(', ');

  await thread.subscribe();
  await thread.post(`Received ${attachments.length} attachment(s): ${summary}`);
});

For more on receiving email attachments outside the Chat SDK, see Receiving Attachments.

Try it yourself

Attachments Example

Detects attachments and replies with a summary