diff --git a/app/channels/unread_rooms_channel.rb b/app/channels/unread_rooms_channel.rb
index f7fcc08..a3f6cc0 100644
--- a/app/channels/unread_rooms_channel.rb
+++ b/app/channels/unread_rooms_channel.rb
@@ -1,5 +1,12 @@
 class UnreadRoomsChannel < ApplicationCable::Channel
+  # Scoped per user, like ReadRoomsChannel. A single global stream would tell every
+  # authenticated connection when any room on the account is active, including closed
+  # rooms and direct conversations they're not part of.
+  def self.stream_name_for(user_id)
+    "user_#{user_id}_unreads"
+  end
+
   def subscribed
-    stream_from "unread_rooms"
+    stream_from self.class.stream_name_for(current_user.id)
   end
 end
diff --git a/app/models/message/broadcasts.rb b/app/models/message/broadcasts.rb
index 1f909dc..4623f2a 100644
--- a/app/models/message/broadcasts.rb
+++ b/app/models/message/broadcasts.rb
@@ -1,10 +1,19 @@
 module Message::Broadcasts
   def broadcast_create
     broadcast_append_to room, :messages, target: [ room, :messages ]
-    ActionCable.server.broadcast("unread_rooms", { roomId: room.id })
+    broadcast_unread_room
   end
 
   def broadcast_remove
     broadcast_remove_to room, :messages
   end
+
+  private
+    # Fanned out to the room's members rather than published on one global stream, so
+    # that the timing of activity in a room only reaches people who are in it.
+    def broadcast_unread_room
+      room.memberships.pluck(:user_id).each do |user_id|
+        ActionCable.server.broadcast UnreadRoomsChannel.stream_name_for(user_id), { roomId: room.id }
+      end
+    end
 end
diff --git a/test/channels/unread_rooms_channel_test.rb b/test/channels/unread_rooms_channel_test.rb
new file mode 100644
index 0000000..4444eb1
--- /dev/null
+++ b/test/channels/unread_rooms_channel_test.rb
@@ -0,0 +1,47 @@
+require "test_helper"
+
+class UnreadRoomsChannelTest < ActionCable::Channel::TestCase
+  test "streams only the subscriber's own unread stream" do
+    stub_connection(current_user: users(:jz))
+
+    subscribe
+
+    assert subscription.confirmed?
+    assert_has_stream "user_#{users(:jz).id}_unreads"
+    assert_not_includes subscription.streams, "unread_rooms"
+  end
+
+  test "an outsider is not told about activity in a room they can't see" do
+    direct = rooms(:bender_and_kevin)
+    assert_not direct.users.include?(users(:jz)), "jz must be an outsider for this test to mean anything"
+
+    broadcasts = capture_unread_broadcasts_for(users(:jz)) do
+      direct.messages.create!(body: "Private", creator: users(:kevin), client_message_id: "outsider").broadcast_create
+    end
+
+    assert_empty broadcasts
+  end
+
+  test "a member is told about activity in their own room" do
+    direct = rooms(:bender_and_kevin)
+
+    broadcasts = capture_unread_broadcasts_for(users(:kevin)) do
+      direct.messages.create!(body: "Private", creator: users(:bender), client_message_id: "member").broadcast_create
+    end
+
+    assert_equal [ direct.id ], broadcasts.collect { |broadcast| broadcast["roomId"] }
+  end
+
+  private
+    def capture_unread_broadcasts_for(user)
+      stub_connection(current_user: user)
+      subscribe
+
+      stream = subscription.streams.sole
+      before = ActionCable.server.pubsub.broadcasts(stream).size
+
+      yield
+
+      ActionCable.server.pubsub.broadcasts(stream).drop(before).collect { |broadcast| JSON.parse(broadcast) }
+    end
+end
diff --git a/test/controllers/messages_controller_test.rb b/test/controllers/messages_controller_test.rb
index 1f556bf..8088694 100644
--- a/test/controllers/messages_controller_test.rb
+++ b/test/controllers/messages_controller_test.rb
@@ -57,9 +57,22 @@ class MessagesControllerTest < ActionDispatch::IntegrationTest
     end
   end
 
-  test "creating a message broadcasts unread room" do
-    assert_broadcasts "unread_rooms", 1 do
-      post room_messages_url(@room, format: :turbo_stream), params: { message: { body: "New one", client_message_id: 999 } }
+  test "creating a message broadcasts unread room to each member" do
+    @room.users.each do |member|
+      assert_broadcasts UnreadRoomsChannel.stream_name_for(member.id), 1 do
+        post room_messages_url(@room, format: :turbo_stream), params: { message: { body: "New one #{member.id}", client_message_id: member.id } }
+      end
+    end
+  end
+
+  test "creating a message doesn't broadcast unread room to non-members" do
+    outsiders = User.where.not(id: @room.users.map(&:id))
+    assert outsiders.any?, "need someone outside the room for this test to mean anything"
+
+    outsiders.each do |outsider|
+      assert_no_broadcasts UnreadRoomsChannel.stream_name_for(outsider.id) do
+        post room_messages_url(@room, format: :turbo_stream), params: { message: { body: "New one", client_message_id: 999 } }
+      end
     end
   end