diff --git a/lib/localiser/localisation/tag/filter.ex b/lib/localiser/localisation/tag/filter.ex
index 6a22be5..296a1b8 100644
--- a/lib/localiser/localisation/tag/filter.ex
+++ b/lib/localiser/localisation/tag/filter.ex
@@ -57,6 +57,8 @@ defmodule Localiser.Localisation.Tag.Filter do
   def handle_cast({:ingest, measurements}, state) do
     {:ok, {x, y}, new_filter_state} = state.filter_module.update(state.filter_state, measurements)
 
+    publish_particles(state.tag_id, new_filter_state, {x, y})
+
     new_room = find_room(state.rooms, x, y)
     new_room_id = if new_room, do: new_room.id, else: nil
 
@@ -79,7 +81,7 @@ defmodule Localiser.Localisation.Tag.Filter do
     end
   end
 
-  # Room geometry changed — reload the rooms cache so containment checks stay accurate.
+  # Room geometry changed: reload the rooms cache so containment checks stay accurate.
   @impl true
   def handle_info({event, _}, state) when event in [:room_created, :room_updated] do
     {:noreply, %{state | rooms: load_rooms()}}
@@ -91,6 +93,27 @@ defmodule Localiser.Localisation.Tag.Filter do
 
   def handle_info(_msg, state), do: {:noreply, state}
 
+  # Only publish if the filter exposes particle state (i.e. is the particle filter).
+  defp publish_particles(tag_id, filter_state, {x, y}) do
+    # Other filter implementations may not have a :particles key - silently skip.
+    with %{particles: particles, weights: weights} <- filter_state do
+      payload = %{
+        tag_id:    tag_id,
+        estimate:  %{x: x, y: y},
+        particles: Enum.zip(particles, weights)
+                   |> Enum.map(fn {p, w} ->
+                     {px, py} = particle_xy(p)
+                     %{x: px, y: py, w: w}
+                   end)
+      }
+
+      Phoenix.PubSub.broadcast(Localiser.PubSub, "particles:#{tag_id}", {:particles_updated, payload})
+    end
+  end
+
+  defp particle_xy({x, y}), do: {x, y}
+  defp particle_xy({x, y, _vx, _vy}), do: {x, y}
+
   defp load_rooms do
     Floors.list_floors_with_rooms()
     |> Enum.flat_map(& &1.rooms)