Slack error cant_delete_message: Not allowed to delete this message

The deletion was refused on ownership or policy grounds. chat.delete documents the description as "Authenticated user does not have permission to delete this message." As with edits, deletion rights follow authorship and workspace policy: a bot deletes its own messages; users delete theirs where settings allow; admin-level deletion of others' messages is a separate, admin-only capability. A bot asked to "clean up the channel" will hit this the moment it touches messages it did not author.

Workspace and org administrators can also restrict deletion outright (compliance-minded workspaces commonly do), in which case even your own messages may refuse to die by API. And the same neighboring conditions apply as for updates: the (channel, ts) must be exact (else message_not_found), and the channel must be active.

Design cleanup features around what the token owns. For moderation-style deletion of arbitrary messages, the app needs an appropriately privileged admin flow — an ordinary bot token will never do it, no matter which scopes you add.

{"ok": false, "error": "cant_delete_message"}

Track the author identity of every message your app might later delete and gate delete buttons and cleanup jobs on ownership, so the API refusal becomes unreachable in normal operation. Where compliance policies forbid deletion entirely, prefer redaction-by-edit of your own messages, and document for customer admins which retention or compliance settings the feature depends on so the limitation is discovered during onboarding rather than during an incident.