Messenger error 2018321: Thread controlled by Messenger automated flow

Code 2018321 is a thread-control error like 2018300, but the competing controller is Messenger itself. Meta's error-codes table quotes it in full: "The chat is currently controlled by Messenger while the user is in an automated question and answer flow. Please wait for the flow to finish before trying again." Pages can enable built-in automations, FAQ flows, away messages, the questions surface configured in the Business Suite inbox, and while a person is inside one of those guided flows, the platform holds the conversation and third-party sends are deferred.

Unlike the permanent errors in this catalogue, 2018321 resolves on its own: when the person completes or abandons the built-in flow, control returns and your sends succeed again. That makes it one of the few Messenger errors where a delayed retry is the designed behavior, retry the same message after a wait, rather than discarding it.

The strategic question is why the built-in flow and your bot are competing at all. A Page running a full chatbot usually wants the inbox automations off, since they intercept exactly the first-touch questions the bot exists to answer, and the interception is invisible in your logs except as this error. Audit the Page's automated responses in Meta Business Suite (Inbox -> Automations) whenever 2018321 appears at meaningful volume.

{
  "error": {
    "message": "(#2018321) The chat is currently controlled by Messenger while the user is in an automated question and answer flow. Please wait for the flow to finish before trying again.",
    "type": "OAuthException",
    "code": 2018321,
    "fbtrace_id": "BLBz/WZt8dN"
  }
}

Choose one automation owner per Page. If the bot is it, turn the inbox flows off and let the bot handle first touch; if the built-in flows stay, have the bot yield gracefully with delayed retries. Include an automation audit in Page onboarding, it takes minutes and prevents weeks of intermittent mystery. Thread-control conflicts of both kinds are walked through in the troubleshooting guide.