Cloud only
Owners paste a Slack Incoming Webhook URL in workspace integrations. Only public HTTPS URLs on hooks.slack.com or hooks.slack-gov.com are accepted; private or local addresses are rejected. There is no Slack OAuth app, slash commands, or two-way sync. Connect and test are limited to 8 requests per minute per workspace. A test uses up to 2 HTTP attempts; reminder posts use up to 3.
Connect sends a test. Deadline reminders then post to that channel in addition to email. Disconnect stops Slack messages. The webhook URL is stored encrypted.