diff --git a/test/aprsme_web/live/map_live/historical_loader_test.exs b/test/aprsme_web/live/map_live/historical_loader_test.exs
new file mode 100644
index 0000000..27a9943
--- /dev/null
+++ b/test/aprsme_web/live/map_live/historical_loader_test.exs
@@ -0,0 +1,120 @@
+defmodule AprsmeWeb.MapLive.HistoricalLoaderTest do
+  use ExUnit.Case, async: true
+
+  alias AprsmeWeb.MapLive.HistoricalLoader
+  alias Phoenix.LiveView.Socket
+
+  defp build_socket(assigns) do
+    defaults = %{
+      map_bounds: nil,
+      map_zoom: 10,
+      visible_packets: %{},
+      historical_packets: %{},
+      loading_generation: 0,
+      pending_batch_tasks: [],
+      pending_bounds: nil,
+      tracked_callsign: "",
+      historical_hours: "1",
+      historical_loading: false,
+      loading_batch: 0,
+      total_batches: 1,
+      historical_cursor: nil,
+      __changed__: %{}
+    }
+
+    %Socket{assigns: Map.merge(defaults, assigns)}
+  end
+
+  describe "cancel_pending_loads/1" do
+    test "cancels pending timers and clears the list" do
+      timer1 = Process.send_after(self(), :noop, 60_000)
+      timer2 = Process.send_after(self(), :noop, 60_000)
+
+      socket = build_socket(%{pending_batch_tasks: [timer1, timer2]})
+
+      result = HistoricalLoader.cancel_pending_loads(socket)
+
+      assert result.assigns.pending_batch_tasks == []
+      # Timers should no longer be active (returns false after cancel).
+      assert Process.cancel_timer(timer1) == false
+      assert Process.cancel_timer(timer2) == false
+    end
+
+    test "is a no-op when no timers are pending" do
+      socket = build_socket(%{pending_batch_tasks: []})
+      result = HistoricalLoader.cancel_pending_loads(socket)
+      assert result.assigns.pending_batch_tasks == []
+    end
+  end
+
+  describe "load_historical_batch/3" do
+    test "returns the socket unchanged when map_bounds is nil" do
+      socket = build_socket(%{map_bounds: nil})
+      result = HistoricalLoader.load_historical_batch(socket, 0, nil)
+      assert result == socket
+    end
+
+    test "skips when the generation argument doesn't match loading_generation" do
+      socket = build_socket(%{loading_generation: 5})
+      # Stale generation — should return socket unchanged without any DB query.
+      result = HistoricalLoader.load_historical_batch(socket, 0, 1)
+      assert result == socket
+    end
+  end
+
+  describe "start_progressive_historical_loading/1" do
+    test "bumps loading_generation and schedules a failsafe" do
+      socket =
+        build_socket(%{
+          map_bounds: nil,
+          map_zoom: 5,
+          loading_generation: 0
+        })
+
+      # With nil bounds, load_historical_batch returns the socket as-is, but
+      # start_progressive_historical_loading should still have mutated
+      # loading_batch / historical_loading / generation before calling into
+      # do_load_historical_batch.
+      result = HistoricalLoader.start_progressive_historical_loading(socket)
+      assert result.assigns.loading_generation == 1
+      assert result.assigns.historical_loading
+      assert result.assigns.historical_cursor == nil
+      # With map_zoom 5, progressive (non-single-batch) path is used —
+      # total_batches should be a positive integer determined by the zoom.
+      assert is_integer(result.assigns.total_batches)
+      assert result.assigns.total_batches >= 2
+    end
+
+    test "uses a single batch at high zoom" do
+      socket =
+        build_socket(%{
+          map_bounds: nil,
+          map_zoom: 15,
+          loading_generation: 0
+        })
+
+      result = HistoricalLoader.start_progressive_historical_loading(socket)
+      assert result.assigns.total_batches == 1
+      assert result.assigns.historical_loading
+    end
+
+    test "cancels pending timers on restart" do
+      timer = Process.send_after(self(), :noop, 60_000)
+
+      socket =
+        build_socket(%{
+          map_bounds: nil,
+          map_zoom: 10,
+          pending_batch_tasks: [timer],
+          loading_generation: 3,
+          historical_loading: true
+        })
+
+      result = HistoricalLoader.start_progressive_historical_loading(socket)
+      assert result.assigns.loading_generation == 4
+      assert result.assigns.pending_batch_tasks == []
+      # Original timer should have been cancelled.
+      assert Process.cancel_timer(timer) == false
+    end
+  end
+end