Anvia

Slack messaging ​

Send text, thread replies, files, buttons, and message lifecycle operations through the Slack Web API. Outbound Web API calls do not require Socket Mode to be started. See @anvia/slack for setup.

Send messages ​

ts
import { sendChannelMessage } from '@anvia/channel'

await sendChannelMessage({
  channel,
  address: { platform: 'slack', conversationId: process.env.SLACK_CHANNEL_ID! },
  message: {
    text: 'The import needs review.',
    attachments: [
      {
        type: 'file',
        mediaType: 'text/csv',
        filename: 'invalid-rows.csv',
        source: { type: 'data', data: csvBuffer.toString('base64') },
      },
    ],
  },
})

Text is posted first with chat.postMessage (link previews disabled), then files are uploaded sequentially with files.uploadV2. A multi-file delivery may be partially visible if a later upload fails; use idempotent application retries. sendChannelMessage splits text longer than 4000 characters into multiple messages and returns the sent parts. Direct channel.send() does not split: text over 4000 characters throws a RangeError, as does an empty message with no attachments.

Actions become Slack actions blocks with one button per action; the action id is returned as the actionId of an action event, and style: 'primary' | 'danger' maps to the matching Slack button color.

Model-generated text is protected against unintended notifications: token mentions such as <@U123>, <!channel>, and <#channel> are HTML-escaped in outbound text, and link_names is disabled on every post.

Threads and replies ​

Slack thread timestamps map directly to ChannelAddress.threadId. replyToMessageId takes precedence when explicitly provided; otherwise sends target the address thread:

ts
if (event.type !== 'message') return

await channel.send(
  {
    platform: 'slack',
    conversationId: event.conversation.id,
    threadId: event.conversation.threadId,
  },
  { text: 'Following up in this thread.' },
)

Message IDs and thread IDs are Slack timestamps such as 1712345678.123456, not arbitrary UUIDs, and are validated before any API call. A thread reply arriving without its own mention sets replyTo on the message event.

Attachments ​

Incoming file URLs are token-bearing and private, so they are retained only inside the validated raw event. channel.loadAttachment() performs an authenticated, size-capped download with the bot token and returns base64 data; the token-bearing URL never reaches the agent prompt. Download URLs are restricted to Slack-controlled HTTPS domains.

Outbound attachments accept HTTPS URLs or base64 data. Each file is downloaded or decoded, size-checked against maximumAttachmentBytes, and uploaded with files.uploadV2 (into the thread when the target is threaded). A files-only message uses a zero-width-space text fallback because Slack requires one.

Edits, deletes, and reactions ​

ts
const [sent] = await sendChannelMessage({ channel, address, message })

await channel.edit(sent, { text: 'The import is under review.' })
await channel.react(sent, 'eyes')
await channel.delete(sent)

edit() accepts text-only changes; attachments and reply targets cannot be edited and throw a TypeError. react() strips surrounding colons from the emoji name before calling reactions.add. unreact() removes the bot's own reaction through reactions.remove, stripping colons the same way.

The adapter reports actions, replies, reactions, reactionRemovals, delete, and messageEdits, with outbound attachments of every kind. capabilities.typing is absent: Slack has no general bot typing-indicator API, so there is no showTyping. Use the channel agent placeholder message when users need progress feedback.

Continue with ​

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