Messenger error 4: Minimum delay between marketing notifications

Code 4 with subcode 2018354 belongs to Messenger's marketing-messages feature, the opt-in system that lets a Page send recurring promotional notifications after the standard window closes. Each opt-in carries a frequency the person agreed to, stored in the notification_messages_frequency field, and this error fires when a send would breach that agreed cadence: two notifications too close together for the topic the person subscribed to.

Meta's error-codes page is unusually reassuring about it: "This error code will not cause your app to be flagged or blocked for abuse. It is okay to ignore this error." The platform is enforcing the cadence for you, dropping the premature message rather than punishing the attempt. The same page adds the operational advice that matters: keep track of which users you have already messaged within the agreed cadence, so you can exclude them from the next batch of broadcast messages.

In practice this error is a symptom of broadcast bookkeeping drift. Campaign tools that select "all opted-in users" for every blast, without recording who received the previous notification and when, will hit 2018354 on the overlap set every time two campaigns run close together. The failure is harmless per Meta, but the noise buries real errors, and the users involved received nothing, so the campaign report overstates reach unless the errors are counted. Contrast with 10/1893015, where the person actively clicked "Stop these messages," a permanent stop rather than a timing rule.

{
  "error": {
    "message": "(#4) There has to be a minimum delay between 2 notifications for the given notification",
    "type": "OAuthException",
    "code": 4,
    "error_subcode": 2018354,
    "fbtrace_id": "BLBz/WZt8dN"
  }
}

Build the cadence into the scheduler rather than discovering it at send time: one row per (user, topic) with last-sent timestamp, and audiences computed as opted-in minus recently-notified. Honor the person's chosen frequency as a product decision, not just an API constraint, cadence violations that do get through are what drive the blocks and negative feedback that end in 368. The marketing-messages caps sit with the other volume rules in the limits reference.