This issue has also been reported on the plugin's GitHub repository: https://github.com/atlassian-labs/atlassian-slack-integration-server/issues/511

Issue Summary

When using the Slack for Confluence Data Center app with Confluence 9.1+, calendar event notifications posted to Slack contain broken links that return 404 errors. The links now point to an invalid path structure introduced by readable URL format changes.

Steps to Reproduce

1. Set up a Confluence Data Center 9.1+ instance with the Slack for Confluence Data Center app (connection instructions)
2. Create an event in the Team Calendar
3. Verify the Slack notification is posted to the channel
4. Click the calendar link in the Slack notification message

Expected Results

The link should redirect to the correct space calendars page (for example, /spaces/{SPACE_KEY}/calendars)

Actual Results

The link points to /spaces/{SPACE_KEY}/overview/calendars?atlLinkOrigin=... which returns a 404 error.

Environment

• Confluence Data Center version: 9.1+
• Slack integration app version: all versions
• Condition: Occurs when confluence.readable.url dark feature is enabled (default in Confluence 9.1+)

Root Cause

Before Confluence 9.1, space URLs followed the "Pretty" format /display/{SPACE_KEY}.

Starting with Confluence 9.1, when readable URLs are enabled by default, space URLs now follow the new format: /spaces/{SPACE_KEY}/overview.

The Slack integration plugin appends /calendars to the space URL path. With the new URL format, this results in /spaces/{SPACE_KEY}/overview/calendars, which is not a valid endpoint in Confluence. The correct endpoint should be /spaces/{SPACE_KEY}/calendars.

Workaround

Disable readable URLs in Confluence by setting the dark feature confluence.readable.url.disable, followed by a full reindex of the instance.

Note: This workaround will affect all URLs and link generation across the instance, reverting to the old URL format for the entire system. It should be tested in a non-production environment first before applying to production instances, as the impact is system-wide and may require validation of application integrations and bookmarks.