Send channel messages

Outbound delivery in @anvia/channel has two layers: sendChannelMessage() for complete portable messages that may need splitting, and channel.send() for one already-bounded message. See Channel core for addresses and the full utility map.

Send a portable message

Use sendChannelMessage() for any complete portable message — proactive output or a reply to an inbound event. It takes one options object, validates the payload, asks the adapter to split it, and sends the parts sequentially:

import { sendChannelMessage } from '@anvia/channel'

const messages = await sendChannelMessage({
  channel,
  address,
  message: {
    text: report,
    replyToMessageId: sourceMessageId,
    actions: [
      { id: 'report:acknowledge', label: 'Acknowledge', style: 'primary' },
      { id: 'report:dismiss', label: 'Dismiss', style: 'danger' },
    ],
    attachments: [
      {
        type: 'file',
        mediaType: 'text/csv',
        filename: 'report.csv',
        source: { type: 'data', data: csvBuffer.toString('base64') },
      },
    ],
  },
})

channel.send() is the lower-level operation: it delivers one already-bounded message with no splitting. Application code normally goes through sendChannelMessage(); only call send() directly when you know the message fits the platform.

Reply metadata lands on every part; actions and attachments ride on the final part. A media-only message uses text: '' and at least one attachment.

If a later part fails to send, sendChannelMessage() throws PartialDeliveryError carrying the sent prefix, the failedPart, and its zero-based failedIndex, so callers can resume without resending delivered parts. It extends Error (name: 'PartialDeliveryError', message Channel message delivery failed after N delivered part(s)) and chains the original failure as cause — use instanceof to distinguish a partial send from other failures.

URL-backed attachments

URL-backed attachments carry a reference instead of bytes:

const message = {
  text: 'Dashboard snapshot',
  attachments: [
    {
      type: 'image' as const,
      mediaType: 'image/png',
      filename: 'dashboard.png',
      source: { type: 'url' as const, url: 'https://cdn.example.com/dashboard.png' },
    },
  ],
}

Slack and Discord download URL-backed files in the application process. Pass a restricted fetch implementation to those adapters when a URL can be selected by a user or model: enforce an origin allowlist and block private-network destinations.

Continue with

• Channel core — addresses and the utility map.
• Channel events — handle normalized inbound events.
• Splitting and validation — text limits and portable payload rules.