diff --git a/examples/blog/app/channels/post_activity_channel.rb b/examples/blog/app/channels/post_activity_channel.rb
new file mode 100644
index 0000000..f5fa44c
--- /dev/null
+++ b/examples/blog/app/channels/post_activity_channel.rb
@@ -0,0 +1,56 @@
+require 'uri'
+require 'json'
+
+# ActionCable-lite channel for posts#show: anyone with a post open can
+# subscribe (GET /cable?post_id=N, upgraded to a WebSocket) to hear about
+# moderation events on that post's comments - approved, rejected, or
+# removed - the instant they happen, instead of polling or reloading.
+# CommentsController broadcasts through the same Hub every time one of
+# those three actions changes the post's *visible* (approved) comment
+# count; this channel itself never accepts anything back from the client,
+# it only ever pushes.
+class PostActivityChannel
+  # A hard cap on live viewers per post - without one, one post going viral
+  # would mean one Hub#broadcast call fanning out to an unbounded number of
+  # live sockets on every single moderation action. Real, but generous
+  # enough that the demo's handful of viewers never trips it by accident.
+  MAX_VIEWERS_PER_POST = 500
+
+  def self.hub
+    @hub ||= Prism::WebSocket::Hub.new(max_subscribers_per_stream: MAX_VIEWERS_PER_POST)
+  end
+
+  def self.stream_for(post_id)
+    "post_#{post_id}_comments"
+  end
+
+  def on_open(connection)
+    post_id = post_id_from(connection)
+    return connection.close(1008, 'post_id query parameter is required') unless post_id
+    unless self.class.hub.subscribe(self.class.stream_for(post_id), connection)
+      return connection.close(1008, 'this post already has the maximum number of live viewers')
+    end
+    connection.write_text(JSON.generate(event: 'subscribed', post_id: post_id))
+  end
+
+  def on_message(connection, _message)
+    # Read-only stream - nothing a client sends is ever acted on.
+  end
+
+  def on_close(connection)
+    self.class.hub.unsubscribe_all(connection)
+  end
+
+  private
+
+  # The handshake request never reaches a Prism::Request/Params, just the
+  # raw Rack env the server captured before the Upgrade (see
+  # Prism::Server#handle_websocket) - so the query string is decoded by
+  # hand here instead of through Prism::Params#nested_from, which only
+  # ever runs as part of an ordinary Request#params call.
+  def post_id_from(connection)
+    query = URI.decode_www_form(connection.env['QUERY_STRING'].to_s).to_h
+    id = query['post_id'].to_s
+    id.empty? ? nil : id
+  end
+end