Slack error messages_tab_disabled: The app's Messages tab is disabled

Your bot tried to send a direct message, and Slack refused because the app's Messages tab is switched off. The chat.postMessage reference documents the string as "Messages tab for the app is disabled." Every Slack app has an App Home with up to three tabs — Home, Messages, and About — and the Messages tab is the surface where DMs between users and the app live. When that tab is disabled in the app's configuration, there is nowhere for a DM to land, so the API rejects the send.

This error is a pure configuration toggle, which is what makes it maddening when unrecognized: the token is valid, every scope is present, conversations.open may even succeed in returning a DM conversation ID, and then the actual chat.postMessage into that conversation fails. Teams routinely burn hours auditing scopes because the error's wording does not obviously say "flip a switch in the app config". No scope change, reinstall, or code change fixes it — only the toggle does.

The fix lives in your app's settings on the Slack app management page: under App Home, enable the Messages Tab. If you also want users to be able to type back to your bot, tick the companion setting ("Allow users to send Slash commands and messages from the messages tab") — otherwise the DM is a one-way surface and user replies stay disabled, which many teams then misread as broken event delivery. Changes to these toggles take effect without a reinstall, though users may need to reopen the DM.

Because it fails at send time, this is one of the errors worth checking during onboarding: if DMing users is part of your app's behavior, send a test DM as part of installation validation rather than discovering the disabled tab when your first real notification fails. In logs it looks like every other platform error (ErrorCode.PlatformError / SlackApiError with this string), and it is completely deterministic — retries are pointless until the configuration changes.

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

Include the Messages tab settings in your app manifest so environment rebuilds cannot lose them, and add a DM smoke test to installation validation. Document the toggle in your team's runbook — it is the rare Slack failure whose fix is a checkbox, and knowing that turns an hour of scope archaeology into a minute of configuration. Related DM plumbing lives under user_not_found and the app-surface overview in Slack chatbot.