Slack

The Slack bridge connects Ghast to a Slack app you've installed in your workspace. Messages from mapped channels go into Ghast conversations; agent replies post back via the Slack app.

Setup

1. Create a Slack app

1. Go to Slack API – Your Apps and click Create New App → From scratch.
2. Name it and pick the workspace where you want to install it.

2. Configure scopes

In your app's settings, OAuth & Permissions → Scopes → Bot Token Scopes:

• chat:write — post messages
• chat:write.public — post in channels the bot hasn't been invited to (optional)
• channels:history — read channel messages
• channels:read — list channels
• groups:history, groups:read — same for private channels
• im:history, im:read, im:write — DMs
• mpim:history, mpim:read, mpim:write — multi-party DMs
• reactions:read, reactions:write — reactions both directions
• files:read — read attachments
• users:read — resolve user names

3. Enable Socket Mode

1. Socket Mode → Enable Socket Mode.
2. Generate an App-Level Token with connections:write scope. Save it (starts with xapp-).
3. Event Subscriptions → Enable Events and subscribe to:
   • message.channels, message.groups, message.im, message.mpim
   • reaction_added, reaction_removed

4. Install to workspace

1. Install App → Install to Workspace.
2. Approve the requested scopes.
3. Slack returns a Bot User OAuth Token (starts with xoxb-). Save it.

5. Add tokens to Ghast

1. Settings → Channels → Slack.
2. Paste both the App-Level Token (xapp-…) and the Bot User OAuth Token (xoxb-…).
3. Click Connect. Ghast lists your channels and DMs.

6. Map channels

For each channel, pick a workspace and (optionally) prompt and skill overrides. The bot needs to be invited to non-public channels — /invite @YourBot.

Supported content

Direction	Supported
Inbound text	Yes
Inbound images / files	Yes
Inbound voice (Slack huddles / clips)	Limited — text transcripts when available
Threads	Yes — agent replies thread-aware
Outbound text	Yes
Outbound Block Kit	Yes (buttons, sections, dividers)
Reactions	Both directions

Block Kit

For multi-step decisions the agent can build interactive cards using Block Kit — buttons, select menus, dividers — and respond to clicks. Useful for approval flows in shared channels.

Enterprise considerations

• For Enterprise Grid workspaces, install the app at the workspace level. Org-level installs are not currently supported.
• Slack rate limits apply (most APIs are tier-2: ~50/min). Ghast respects rate limits and queues messages internally.

Privacy and revocation

• Tokens encrypted in Profile Vault.
• Revoke via OAuth & Permissions → Revoke Tokens in the Slack API dashboard.
• Workspace admins can also revoke the install at any time.

Failure modes

Symptom	Cause	Action
Connect fails with not_authed	Wrong token, wrong order, or token revoked	Regenerate from Slack API dashboard, paste both tokens
Bot doesn't post in a channel	Bot not in channel	/invite @YourBot in that channel
Inbound events arrive empty	Event Subscriptions not enabled	Enable Events and the message scopes
Slow replies	Rate limit hit	Wait; Ghast retries with backoff

Related pages

• Remote Channels Overview
• Approval Flow