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diff --git a/lib/pleroma/web/activity_pub/mrf/fo_direct_reply.ex b/lib/pleroma/web/activity_pub/mrf/fo_direct_reply.ex
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+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2024 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.Web.ActivityPub.MRF.FODirectReply do
+  @moduledoc """
+  FODirectReply alters the scope of replies to activities which are Followers Only to be Direct. The purpose of this policy is to prevent broken threads for followers of the reply author because their response was to a user that they are not also following.
+  """
+
+  alias Pleroma.User
+
+  @behaviour Pleroma.Web.ActivityPub.MRF.Policy
+
+  @impl true
+  def filter(
+        %{
+          "type" => "Create",
+          "to" => to,
+          "object" => %{
+            "actor" => actor,
+            "type" => "Note",
+            "inReplyTo" => in_reply_to
+          }
+        } = activity
+      ) do
+    with true <- is_binary(in_reply_to),
+         %User{follower_address: followers_collection, local: true} <- User.get_by_ap_id(actor),
+         true <- followers_only?(in_reply_to) do
+      direct_to = to -- [followers_collection]
+
+      updated_activity =
+        activity
+        |> Map.put("cc", [])
+        |> Map.put("to", direct_to)
+        |> Map.put("directMessage", true)
+        |> put_in(["object", "cc"], [])
+        |> put_in(["object", "to"], direct_to)
+
+      {:ok, updated_activity}
+    else
+      _ -> {:ok, activity}
+    end
+  end
+
+  @impl true
+  def filter(activity), do: {:ok, activity}
+
+  @impl true
+  def describe, do: {:ok, %{}}
+
+  defp followers_only?(parent_ap_id) do
+    with %Pleroma.Object{} = object <- Pleroma.Object.get_by_ap_id(parent_ap_id),
+         object_data <- Map.get(object, :data),
+         %Pleroma.User{} = user <- User.get_cached_by_ap_id(object_data["actor"]) do
+      if user.follower_address in object_data["to"] do
+        true
+      else
+        false
+      end
+    else
+      _ ->
+        false
+    end
+  end
+end