Slack

Connect an agent to Slack as its own app. Formation supports direct messages, group conversations and channel threads; each agent keeps its own perspective and credentials even when several agents share a workspace.

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Set up Slack

Follow Automatic Slack setup to create and install an app through Formation. You can also generate a manifest and connect an existing app with its App ID, bot token and signing secret. Use the agent’s app and account, not another agent’s credentials. Set a stable, publicly reachable HTTPS PUBLIC_URL before setup. Formation uses the HTTP Events API, not Socket Mode. After installation, send a DM and invite the app to its intended channels. A connected app does not automatically discover and join every public channel. Managed apps use /api/slack/events/{appID}. Manual apps use /slack/events. Use the exact URL shown by the setup flow. Changing Formation’s hostname requires updating the app’s stored event URL; managed apps provide Update Slack configuration for this.

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Permissions and connection health

The generated manifest includes the event subscriptions and bot scopes Formation needs. Existing apps may need updated scopes and a reinstall when capabilities change. Check permissions on a managed app checks the token’s live identity and granted scopes. Update Slack permissions updates the existing app and opens Slack approval for the same installation. Missing files:read prevents attachment fetches. Channel and DM names require metadata scopes (channels:read, groups:read, im:read, mpim:read) as well as user access. Valid scopes do not prove membership in a particular channel. The dashboard resolves channel and participant names through the owning installation, with cached names and stored IDs as fallbacks. A failed metadata lookup does not hide conversation history.

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Messages, threads and identity

Slack events route by (api_app_id, team_id) to one agent connector. The lookup selects that installation’s signing secret; then Formation verifies the timestamped HMAC. An unknown route and an invalid signature both receive 401. Timestamps must fall within five minutes of Formation’s clock. Being present in a channel does not mean every message addresses the agent. Addressing decides whether it observes or engages. Self-authored echoes are dropped; another participant’s bot flag is a message signal, not a global classification of that participant as an agent or human. Formation does not tell an agent that a peer is hosted by the same deployment. Inbound Slack formatting is normalized for model context. Outbound canonical Markdown is rendered to Slack’s format at delivery, with chunking as needed. Formation conversation keys are internal identities and are never passed as Slack channel IDs.

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Attachments

Image attachments can be fetched for a turn when the selected model supports image input and authorization succeeds. If the image cannot be fetched or shown, the prompt reports that limitation instead of implying the agent saw it. For documents, list_documents and read_document read authorized PDF, DOCX and UTF-8 TXT attachments, including eligible earlier uploads. See Document reading for format coverage, pagination and limits. Scanned PDFs and omitted document structures are not silently treated as read. Attachment access uses the owning connector’s credentials, current audience checks, URL/redirect restrictions and byte limits. A file URL in an event is not permission to send a Slack token to an arbitrary host.

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Delivery and troubleshooting

Ingress acknowledges accepted events promptly and runs work outside the HTTP request lifetime. PostgreSQL-backed event claims distinguish completed duplicates from in-flight work; transient claim failures return a retryable response. An in-memory dedupe set also exists as a fallback, not the production durability guarantee. Durable claims alone do not make all runtime configuration multi-replica ready. Slack sends have bounded recovery for explicitly rejected HTTP 429 responses. Ambiguous network outcomes are not blindly retried, and a partially delivered multi-part reply is not reported as fully delivered. See Slack delivery recovery. Formation uses best-effort reactions for working, done and failed states. Reactions can fail independently of a reply and are not delivery receipts. If an agent is silent, check the event URL, app permissions, channel membership, engagement verdict and run/delivery outcome in Observability. Implementation: internal/connector/slack and internal/app/slack_ingress.go.