diff --git a/test/microwaveprop/commercial/snmp_client_test.exs b/test/microwaveprop/commercial/snmp_client_test.exs
index 3b7cc6b8..17747a39 100644
--- a/test/microwaveprop/commercial/snmp_client_test.exs
+++ b/test/microwaveprop/commercial/snmp_client_test.exs
@@ -249,6 +249,44 @@ defmodule Microwaveprop.Commercial.SnmpClientTest do
     end
   end
 
+  describe "OID normalisation across prefix variants" do
+    test "fully-qualified 1.3.6.1.4.1 OIDs (no `iso.` prefix) parse identically" do
+      # Some snmpget configurations emit the fully-qualified dotted form
+      # directly instead of using `iso.` — both should resolve the same
+      # AF11X field.
+      output = "1.3.6.1.4.1.41112.1.3.2.1.11.1 = INTEGER: -62\n"
+      result = SnmpClient.parse_snmpget_output(output, :af11x)
+      assert result.rx_power_0 == -62
+    end
+
+    test "a double-leading-dot OID still strips exactly one leading dot" do
+      # `normalize_oid` only peels off ONE leading `.` — the residual
+      # leading dot means the lookup against the OID map fails, so the
+      # field is silently dropped rather than raising.
+      output = "..1.3.6.1.4.1.41112.1.3.2.1.14.1 = INTEGER: -63\n"
+      result = SnmpClient.parse_snmpget_output(output, :af11x)
+      refute Map.has_key?(result, :rx_power_1)
+      assert result == %{}
+    end
+  end
+
+  describe "poll/3 totality" do
+    test "empty radio type string raises FunctionClauseError" do
+      assert_raise FunctionClauseError, fn ->
+        SnmpClient.poll("10.0.0.1", "public", "")
+      end
+    end
+
+    test "non-string radio type raises FunctionClauseError" do
+      # poll/3 pattern matches on literal binary radio types; any other
+      # binary that isn't in the dispatch table should fail loudly so a
+      # mis-typed config surfaces rather than silently mis-polling.
+      assert_raise FunctionClauseError, fn ->
+        SnmpClient.poll("10.0.0.1", "public", "AF11X")
+      end
+    end
+  end
+
   describe "parse_snmpget_output/2 property" do
     # Pick any AF11X integer value and any recognised AF11X OID suffix, render
     # the canonical `iso.<oid> = INTEGER: <value>` line, and assert the value
@@ -263,6 +301,17 @@ defmodule Microwaveprop.Commercial.SnmpClientTest do
       "1.3.6.1.4.1.41112.1.3.2.1.4.1" => :link_distance_m
     }
 
+    property "parse_snmpget_output never raises on arbitrary inputs (totality)" do
+      # Feed the parser whatever text StreamData hands back — newlines,
+      # binary data, partial SNMP-looking fragments. The contract is that
+      # unparseable content is silently skipped and the result is always
+      # a map, never a raised exception.
+      check all(garbage <- StreamData.string(:printable, max_length: 500)) do
+        result = SnmpClient.parse_snmpget_output(garbage, :af11x)
+        assert is_map(result)
+      end
+    end
+
     property "rendered snmpget lines round-trip through parse_snmpget_output" do
       oids = Map.keys(@af11x_oid_to_field)
 
diff --git a/test/microwaveprop/terrain/viewshed_property_test.exs b/test/microwaveprop/terrain/viewshed_property_test.exs
index ded1bf64..0e58fa82 100644
--- a/test/microwaveprop/terrain/viewshed_property_test.exs
+++ b/test/microwaveprop/terrain/viewshed_property_test.exs
@@ -116,6 +116,26 @@ defmodule Microwaveprop.Terrain.ViewshedPropertyTest do
     end
   end
 
+  describe "destination_point/4 round-trip distance" do
+    property "the generated point is ~dist_km from the origin via the haversine" do
+      # Regardless of bearing, the great-circle distance between the
+      # origin and destination_point's result must match the requested
+      # distance. Allow a loose absolute tolerance for earth-radius
+      # rounding at longer distances (the module uses 6371 km exactly).
+      check all(
+              lat <- float(min: -60.0, max: 60.0),
+              lon <- float(min: -170.0, max: 170.0),
+              bearing <- float(min: 0.0, max: 359.999),
+              dist_km <- float(min: 1.0, max: 500.0)
+            ) do
+        {lat2, lon2} = Viewshed.destination_point(lat, lon, bearing, dist_km)
+
+        measured = Microwaveprop.Geo.haversine_km(lat, lon, lat2, lon2)
+        assert_in_delta measured, dist_km, 0.5
+      end
+    end
+  end
+
   describe "analyse_ray/5 over generated flat profiles" do
     property "flat terrain with high antennas always reaches the full distance" do
       # Antenna floor chosen to beat the worst-case (max dist, max freq)
diff --git a/test/microwaveprop/terrain/viewshed_test.exs b/test/microwaveprop/terrain/viewshed_test.exs
index 63559823..d2190c9c 100644
--- a/test/microwaveprop/terrain/viewshed_test.exs
+++ b/test/microwaveprop/terrain/viewshed_test.exs
@@ -191,6 +191,51 @@ defmodule Microwaveprop.Terrain.ViewshedTest do
     end
   end
 
+  describe "effective_reach_km/3 boundary cases" do
+    test "BLOCKED with score=0 and diffraction_db=0 uses the mild-terrain 0.8 tier" do
+      # db=0 falls into the `db <= 3` terrain band (0.8) and score=0 gives
+      # a 0.05 ducting floor — terrain wins cleanly.
+      analysis = %{verdict: "BLOCKED", diffraction_db: 0.0}
+      assert Viewshed.effective_reach_km(analysis, 50.0, 0) == 40.0
+    end
+
+    test "BLOCKED at exactly the terrain-tier boundary (3 dB) still wins the 0.8 factor" do
+      analysis = %{verdict: "BLOCKED", diffraction_db: 3.0}
+      assert Viewshed.effective_reach_km(analysis, 100.0, 0) == 80.0
+    end
+
+    test "CLEAR verdict ignores max_range_km of zero (returns 0)" do
+      analysis = %{verdict: "CLEAR", diffraction_db: 0.0}
+      assert Viewshed.effective_reach_km(analysis, 0.0, 100) == 0.0
+    end
+  end
+
+  describe "find_reach_km/2 boundary cases" do
+    test "max_range_km of zero is returned verbatim when no obstructions exist" do
+      points = [
+        %{obstructed: false, dist_km: 0.0},
+        %{obstructed: false, dist_km: 0.0},
+        %{obstructed: false, dist_km: 0.0}
+      ]
+
+      assert Viewshed.find_reach_km(points, 0.0) == 0.0
+    end
+
+    test "single-obstruction-in-middle returns the preceding dist_km" do
+      points =
+        [
+          %{obstructed: false, dist_km: 0.0},
+          %{obstructed: false, dist_km: 5.0},
+          %{obstructed: false, dist_km: 10.0},
+          %{obstructed: true, dist_km: 15.0},
+          %{obstructed: false, dist_km: 20.0},
+          %{obstructed: false, dist_km: 25.0}
+        ]
+
+      assert Viewshed.find_reach_km(points, 25.0) == 10.0
+    end
+  end
+
   describe "analyse_ray/5" do
     test "returns full range for flat terrain with antenna heights" do
       profile =
diff --git a/test/microwaveprop/weather/hrrr_native_client_test.exs b/test/microwaveprop/weather/hrrr_native_client_test.exs
index dc967d5b..3ed105f7 100644
--- a/test/microwaveprop/weather/hrrr_native_client_test.exs
+++ b/test/microwaveprop/weather/hrrr_native_client_test.exs
@@ -510,4 +510,89 @@ defmodule Microwaveprop.Weather.HrrrNativeClientTest do
       end
     end
   end
+
+  describe "build_native_profile/1 deep coverage" do
+    test "handles a dense 5-level profile and orders by ascending HGT" do
+      # Intentionally scramble the insertion order so the sort-by-height
+      # step has real work to do.
+      parsed =
+        [3, 1, 5, 2, 4]
+        |> Enum.flat_map(fn level ->
+          base = level * 20.0
+          lvl_str = "#{level} hybrid level"
+
+          [
+            {"HGT:#{lvl_str}", base},
+            {"TMP:#{lvl_str}", 300.0 - level * 2.0},
+            {"SPFH:#{lvl_str}", 0.01},
+            {"PRES:#{lvl_str}", 101_000.0 - level * 500.0},
+            {"UGRD:#{lvl_str}", 1.0 * level},
+            {"VGRD:#{lvl_str}", -1.0 * level},
+            {"TKE:#{lvl_str}", 0.1}
+          ]
+        end)
+        |> Map.new()
+
+      profile = HrrrNativeClient.build_native_profile(parsed)
+      assert profile.level_count == 5
+      assert profile.heights_m == Enum.sort(profile.heights_m)
+      assert profile.heights_m == [20.0, 40.0, 60.0, 80.0, 100.0]
+    end
+
+    test "returns a finite float for surface_temp_k whenever any TMP key is present" do
+      # Surface TMP wins over lowest-level TMP; it's a float.
+      parsed = %{
+        "HGT:1 hybrid level" => 10.0,
+        "TMP:1 hybrid level" => 290.5,
+        "TMP:surface" => 293.1
+      }
+
+      profile = HrrrNativeClient.build_native_profile(parsed)
+      assert is_float(profile.surface_temp_k)
+      assert profile.surface_temp_k == 293.1
+    end
+  end
+
+  describe "duct_byte_ranges/1 boundary inputs" do
+    test "empty idx entries yields an empty range list" do
+      assert HrrrNativeClient.duct_byte_ranges([]) == []
+      assert HrrrNativeClient.essential_byte_ranges([]) == []
+    end
+  end
+
+  describe "extra properties" do
+    property "build_native_profile/1 returns a finite float for surface_temp_k when any TMP key is present" do
+      # Drives the surface-scalar fallback: with TMP somewhere in the
+      # parsed map (either at `surface` or on a hybrid level that has
+      # an HGT to anchor it), `surface_temp_k` is a real number.
+      check all(
+              level <- StreamData.integer(1..50),
+              use_surface <- StreamData.boolean(),
+              tmp_val <- StreamData.float(min: 200.0, max: 320.0)
+            ) do
+        lvl_str = "#{level} hybrid level"
+
+        parsed =
+          if use_surface do
+            %{
+              "HGT:#{lvl_str}" => level * 10.0,
+              "TMP:#{lvl_str}" => 290.0,
+              "TMP:surface" => tmp_val
+            }
+          else
+            %{
+              "HGT:#{lvl_str}" => level * 10.0,
+              "TMP:#{lvl_str}" => tmp_val
+            }
+          end
+
+        profile = HrrrNativeClient.build_native_profile(parsed)
+
+        assert is_float(profile.surface_temp_k)
+        # Finiteness: neither ±infinity nor NaN.
+        refute profile.surface_temp_k == :infinity
+        refute profile.surface_temp_k == :"-infinity"
+      end
+    end
+  end
 end
diff --git a/test/microwaveprop/weather/nexrad_client_test.exs b/test/microwaveprop/weather/nexrad_client_test.exs
index b17848f2..171affef 100644
--- a/test/microwaveprop/weather/nexrad_client_test.exs
+++ b/test/microwaveprop/weather/nexrad_client_test.exs
@@ -392,4 +392,87 @@ defmodule Microwaveprop.Weather.NexradClientTest do
       assert result.mean_reflectivity_dbz == 0.0
     end
   end
+
+  describe "fetch_decoded_frame/1 cache population" do
+    # Minimal 20×20 indexed-color PNG identical to the earlier fixture.
+    defp tiny_png(width \\ 20, height \\ 20) do
+      signature = <<137, 80, 78, 71, 13, 10, 26, 10>>
+      ihdr_data = <<width::32, height::32, 8, 3, 0, 0, 0>>
+      ihdr_chunk = <<byte_size(ihdr_data)::32, "IHDR", ihdr_data::binary, 0::32>>
+
+      raw = for _ <- 1..height, into: <<>>, do: <<0, 0::size(width)-unit(8)>>
+      compressed = :zlib.compress(raw)
+      idat_chunk = <<byte_size(compressed)::32, "IDAT", compressed::binary, 0::32>>
+      iend_chunk = <<0::32, "IEND", 0::32>>
+
+      signature <> ihdr_chunk <> idat_chunk <> iend_chunk
+    end
+
+    setup do
+      NexradCache.clear()
+      on_exit(fn -> NexradCache.clear() end)
+      :ok
+    end
+
+    test "successful fetch populates the cache (second fetch is a :hit)" do
+      Req.Test.stub(NexradClient, fn conn ->
+        Plug.Conn.send_resp(conn, 200, tiny_png())
+      end)
+
+      ts = ~U[2022-08-20 14:07:00Z]
+      rounded = NexradClient.round_to_5min(ts)
+
+      assert NexradCache.fetch(rounded) == :miss
+      {:ok, _pixels, _width} = NexradClient.fetch_decoded_frame(ts)
+      assert {:ok, _pixels2, _width2} = NexradCache.fetch(rounded)
+    end
+  end
+
+  describe "fetch_decoded_frame/1 empty body" do
+    setup do
+      NexradCache.clear()
+      on_exit(fn -> NexradCache.clear() end)
+      :ok
+    end
+
+    test "zero-byte 200 response surfaces a PNG decode error" do
+      Req.Test.stub(NexradClient, fn conn ->
+        Plug.Conn.send_resp(conn, 200, "")
+      end)
+
+      assert {:error, reason} = NexradClient.fetch_decoded_frame(~U[2022-08-20 14:05:00Z])
+      assert is_binary(reason)
+      assert reason =~ "PNG decode failed"
+    end
+  end
+
+  describe "frame_url/1 year boundaries" do
+    test "Dec 31 23:55 produces a URL anchored in the old year" do
+      dt = ~U[2022-12-31 23:55:00Z]
+      url = NexradClient.frame_url(dt)
+      assert url =~ "2022/12/31"
+      assert url =~ "n0q_202212312355.png"
+      refute url =~ "2023/"
+    end
+
+    test "Jan 1 00:00 of the following year flips cleanly into the new year" do
+      dt = ~U[2023-01-01 00:00:00Z]
+      url = NexradClient.frame_url(dt)
+      assert url =~ "2023/01/01"
+      assert url =~ "n0q_202301010000.png"
+      refute url =~ "2022/"
+    end
+
+    test "rounding 23:59 Dec 31 stays in Dec 31 (no rollover via round_to_5min)" do
+      dt = ~U[2022-12-31 23:59:59Z]
+      rounded = NexradClient.round_to_5min(dt)
+      assert rounded.year == 2022
+      assert rounded.month == 12
+      assert rounded.day == 31
+      assert rounded.hour == 23
+      assert rounded.minute == 55
+      url = NexradClient.frame_url(rounded)
+      assert url =~ "2022/12/31"
+    end
+  end
 end
diff --git a/test/microwaveprop/workers/gefs_fetch_worker_test.exs b/test/microwaveprop/workers/gefs_fetch_worker_test.exs
index 82449a45..6dc5efbc 100644
--- a/test/microwaveprop/workers/gefs_fetch_worker_test.exs
+++ b/test/microwaveprop/workers/gefs_fetch_worker_test.exs
@@ -287,6 +287,105 @@ defmodule Microwaveprop.Workers.GefsFetchWorkerTest do
     end
   end
 
+  describe "perform/1 HTTP classification extra boundaries" do
+    test "a transient HTTP 502 (bad gateway) returns {:error, _}" do
+      Req.Test.stub(Microwaveprop.Weather.GefsClient, fn conn ->
+        Plug.Conn.send_resp(conn, 502, "Bad Gateway")
+      end)
+
+      args = %{"run_time" => "2026-04-18T12:00:00Z", "forecast_hour" => 24}
+      assert {:error, _reason} = GefsFetchWorker.perform(%Oban.Job{args: args})
+    end
+
+    test "a permanent HTTP 400 (bad request) returns {:cancel, _}" do
+      Req.Test.stub(Microwaveprop.Weather.GefsClient, fn conn ->
+        Plug.Conn.send_resp(conn, 400, "Bad Request")
+      end)
+
+      args = %{"run_time" => "2026-04-18T12:00:00Z", "forecast_hour" => 24}
+      assert {:cancel, _reason} = GefsFetchWorker.perform(%Oban.Job{args: args})
+    end
+
+    test "a permanent HTTP 410 (gone) returns {:cancel, _}" do
+      Req.Test.stub(Microwaveprop.Weather.GefsClient, fn conn ->
+        Plug.Conn.send_resp(conn, 410, "Gone")
+      end)
+
+      args = %{"run_time" => "2026-04-18T12:00:00Z", "forecast_hour" => 24}
+      assert {:cancel, _reason} = GefsFetchWorker.perform(%Oban.Job{args: args})
+    end
+  end
+
+  describe "build_profile_attrs/3 extra branches" do
+    test "accepts wind_u / wind_v keys without the _mps suffix" do
+      # `build_profile_attrs` checks both `wind_u` and `wind_u_mps` — the
+      # non-suffixed keys should also populate the row attrs.
+      run_time = ~U[2026-04-18 12:00:00Z]
+
+      profile = %{
+        lat: 32.9,
+        lon: -97.0,
+        surface_temp_c: 20.0,
+        surface_dewpoint_c: 10.0,
+        surface_pressure_mb: 1013.0,
+        pwat_mm: 20.0,
+        wind_u: 4.5,
+        wind_v: -2.25,
+        profile: []
+      }
+
+      attrs = GefsFetchWorker.build_profile_attrs(run_time, 24, profile)
+      assert attrs.wind_u_mps == 4.5
+      assert attrs.wind_v_mps == -2.25
+    end
+
+    test "preserves a nil profile list as a no-derivation base map" do
+      run_time = ~U[2026-04-18 12:00:00Z]
+
+      profile = %{
+        lat: 32.9,
+        lon: -97.0,
+        surface_temp_c: 20.0,
+        surface_dewpoint_c: 10.0,
+        surface_pressure_mb: 1013.0,
+        pwat_mm: 20.0,
+        profile: nil
+      }
+
+      attrs = GefsFetchWorker.build_profile_attrs(run_time, 24, profile)
+      # nil profile → `SoundingParams.derive([])` is called with the `|| []`
+      # fallback; empty list returns nil so no derived keys are added.
+      refute Map.has_key?(attrs, :surface_refractivity)
+      assert attrs.lat == 32.9
+    end
+  end
+
+  # Property: build_profile_attrs/3 always emits a valid_time exactly
+  # `forecast_hour * 3600` seconds after the run_time, for any run/fh pair.
+  property "build_profile_attrs/3 valid_time is run_time + fh hours exactly" do
+    check all(
+            epoch <- StreamData.integer(1_700_000_000..1_800_000_000),
+            fh <- StreamData.integer(0..384)
+          ) do
+      {:ok, run_time} = DateTime.from_unix(epoch)
+      run_time = DateTime.truncate(run_time, :second)
+
+      profile = %{
+        lat: 32.9,
+        lon: -97.0,
+        surface_temp_c: 20.0,
+        surface_dewpoint_c: 10.0,
+        surface_pressure_mb: 1013.0,
+        pwat_mm: 20.0,
+        profile: []
+      }
+
+      attrs = GefsFetchWorker.build_profile_attrs(run_time, fh, profile)
+      assert DateTime.diff(attrs.valid_time, attrs.run_time, :second) == fh * 3600
+      assert attrs.forecast_hour == fh
+    end
+  end
+
   # Property: the seeder's target run is always a valid GEFS cycle at
   # least 5 hours older than the input instant, regardless of time of day.
   property "most_recent_available_run/1 snaps to a valid 00/06/12/18Z cycle" do
diff --git a/test/microwaveprop_web/live/contact_live_test.exs b/test/microwaveprop_web/live/contact_live_test.exs
index 989569e5..720ea081 100644
--- a/test/microwaveprop_web/live/contact_live_test.exs
+++ b/test/microwaveprop_web/live/contact_live_test.exs
@@ -3139,4 +3139,347 @@ defmodule MicrowavepropWeb.ContactLiveTest do
       end
     end
   end
+
+  describe "Show ordering and proximity helpers" do
+    # Exercises sort_observations/3, sort_soundings/3, and
+    # closest_observations/4 on *populated* rows so the actual field
+    # ordering is asserted — the previous sort-handler tests only
+    # asserted that rendering stayed alive.
+
+    use ExUnitProperties
+
+    alias Microwaveprop.Geo
+    alias Microwaveprop.Weather
+    alias Microwaveprop.Weather.Sounding
+    alias Microwaveprop.Weather.SurfaceObservation
+
+    defp seed_distinct_obs(contact) do
+      # Four distinct surface observations with strictly-increasing
+      # temp_f, dewpoint_f, relative_humidity, sea_level_pressure_mb,
+      # and observed_at, keyed by station code for station_name order.
+      Enum.map(
+        [
+          {"KAAA", 32.90, -97.00, 60.0, 40.0, 50.0, 1010.0, 0},
+          {"KBBB", 32.91, -97.01, 62.0, 42.0, 52.0, 1011.0, 60},
+          {"KCCC", 32.92, -97.02, 64.0, 44.0, 54.0, 1012.0, 120},
+          {"KDDD", 32.93, -97.03, 66.0, 46.0, 56.0, 1013.0, 180}
+        ],
+        fn {code, lat, lon, temp, dewp, rh, pres, offset} ->
+          {:ok, station} =
+            Weather.find_or_create_station(%{
+              station_code: code,
+              station_type: "asos",
+              name: "#{code} Airport",
+              lat: lat,
+              lon: lon
+            })
+
+          Repo.insert!(
+            SurfaceObservation.changeset(%SurfaceObservation{}, %{
+              station_id: station.id,
+              observed_at: DateTime.add(contact.qso_timestamp, offset, :second),
+              temp_f: temp,
+              dewpoint_f: dewp,
+              relative_humidity: rh,
+              sea_level_pressure_mb: pres
+            })
+          )
+
+          code
+        end
+      )
+    end
+
+    test "sort_observations orders by station_name ascending and descending", %{conn: conn} do
+      contact = create_contact(%{qso_timestamp: ~U[2026-03-28 18:00:00Z]})
+      codes = seed_distinct_obs(contact)
+
+      {:ok, lv, _html} = live(conn, ~p"/contacts/#{contact.id}")
+      _ = render_async(lv, 2_000)
+
+      # Prime with observed_at so a subsequent station_name click hits
+      # the "new field → asc" branch of toggle_sort/3.
+      _ = render_click(lv, "sort", %{"field" => "observed_at", "table" => "obs"})
+
+      # First station_name click → asc.
+      _ = render_click(lv, "sort", %{"field" => "station_name", "table" => "obs"})
+
+      asc_codes =
+        lv.pid
+        |> :sys.get_state()
+        |> Map.fetch!(:socket)
+        |> Map.fetch!(:assigns)
+        |> Map.fetch!(:surface_observations)
+        |> Enum.map(& &1.station.station_code)
+
+      assert asc_codes == Enum.sort(codes)
+
+      # Second station_name click → desc.
+      _ = render_click(lv, "sort", %{"field" => "station_name", "table" => "obs"})
+
+      desc_codes =
+        lv.pid
+        |> :sys.get_state()
+        |> Map.fetch!(:socket)
+        |> Map.fetch!(:assigns)
+        |> Map.fetch!(:surface_observations)
+        |> Enum.map(& &1.station.station_code)
+
+      assert desc_codes == Enum.sort(codes, :desc)
+    end
+
+    test "sort_observations orders by observed_at, temp_f, dewpoint_f, relative_humidity, and pressure",
+         %{conn: conn} do
+      contact = create_contact(%{qso_timestamp: ~U[2026-03-28 18:00:00Z]})
+      _ = seed_distinct_obs(contact)
+
+      {:ok, lv, _html} = live(conn, ~p"/contacts/#{contact.id}")
+      _ = render_async(lv, 2_000)
+
+      check_field = fn field, reader ->
+        _ = render_click(lv, "sort", %{"field" => field, "table" => "obs"})
+
+        obs =
+          lv.pid
+          |> :sys.get_state()
+          |> Map.fetch!(:socket)
+          |> Map.fetch!(:assigns)
+          |> Map.fetch!(:surface_observations)
+
+        values = Enum.map(obs, reader)
+
+        assert values == Enum.sort(values),
+               "obs not ascending on #{field}: #{inspect(values)}"
+      end
+
+      check_field.("observed_at", & &1.observed_at)
+      check_field.("temp_f", & &1.temp_f)
+      check_field.("dewpoint_f", & &1.dewpoint_f)
+      check_field.("relative_humidity", & &1.relative_humidity)
+      check_field.("sea_level_pressure_mb", & &1.sea_level_pressure_mb)
+    end
+
+    defp seed_distinct_soundings(contact) do
+      # Three soundings with distinct surface_temp_c, surface_refractivity,
+      # k_index, and lifted_index to check every sounding_sort_key branch.
+      Enum.map(
+        [
+          {"KAAAS", 15.0, 310.0, 20.0, -2.0, 0},
+          {"KBBBS", 18.0, 315.0, 25.0, -1.0, 3600},
+          {"KCCCS", 21.0, 320.0, 30.0, 0.0, 7200}
+        ],
+        fn {code, temp, refr, k, li, offset} ->
+          {:ok, station} =
+            Weather.find_or_create_station(%{
+              station_code: code,
+              station_type: "sounding",
+              name: "#{code} Sounding",
+              lat: 32.9 + :rand.uniform() * 0.001,
+              lon: -97.0 + :rand.uniform() * 0.001
+            })
+
+          Repo.insert!(
+            Sounding.changeset(%Sounding{}, %{
+              station_id: station.id,
+              observed_at: DateTime.add(contact.qso_timestamp, offset, :second),
+              profile: [%{"pres" => 1000.0, "tmpc" => temp, "dwpc" => temp - 5.0, "hght" => 100.0}],
+              level_count: 1,
+              surface_temp_c: temp,
+              surface_dewpoint_c: temp - 5.0,
+              surface_refractivity: refr,
+              k_index: k,
+              lifted_index: li
+            })
+          )
+
+          code
+        end
+      )
+    end
+
+    test "sort_soundings orders by every known sounding field", %{conn: conn} do
+      contact = create_contact(%{qso_timestamp: ~U[2026-03-28 18:00:00Z]})
+      _ = seed_distinct_soundings(contact)
+
+      {:ok, lv, _html} = live(conn, ~p"/contacts/#{contact.id}")
+      _ = render_async(lv, 2_000)
+
+      # Each click on a new field toggles to that field asc (new-field
+      # branch of toggle_sort). Prime with observed_at so the later
+      # station_name click also hits the new-field branch.
+      _ = render_click(lv, "sort", %{"field" => "observed_at", "table" => "soundings"})
+      _ = render_click(lv, "sort", %{"field" => "station_name", "table" => "soundings"})
+
+      station_names =
+        lv.pid
+        |> :sys.get_state()
+        |> Map.fetch!(:socket)
+        |> Map.fetch!(:assigns)
+        |> Map.fetch!(:soundings)
+        |> Enum.map(&(&1.station.name || &1.station.station_code))
+
+      assert station_names == Enum.sort(station_names)
+
+      check_field = fn field, reader ->
+        _ = render_click(lv, "sort", %{"field" => field, "table" => "soundings"})
+
+        rows =
+          lv.pid
+          |> :sys.get_state()
+          |> Map.fetch!(:socket)
+          |> Map.fetch!(:assigns)
+          |> Map.fetch!(:soundings)
+
+        values = Enum.map(rows, reader)
+
+        assert values == Enum.sort(values),
+               "soundings not ascending on #{field}: #{inspect(values)}"
+      end
+
+      check_field.("observed_at", & &1.observed_at)
+      check_field.("surface_temp_c", & &1.surface_temp_c)
+      check_field.("surface_refractivity", & &1.surface_refractivity)
+      check_field.("k_index", & &1.k_index)
+      check_field.("lifted_index", & &1.lifted_index)
+    end
+
+    test "closest_observations/4 keeps only the five nearest by midpoint distance", %{conn: conn} do
+      # Seed seven surface observations spread along the path corridor;
+      # closest_observations trims to the top five by |dlat|+|dlon| from
+      # the midpoint. The test asserts (a) the assign length ≤ 5 and
+      # (b) no station sits at a larger distance than the farthest-kept.
+      contact = create_contact(%{qso_timestamp: ~U[2026-03-28 18:00:00Z]})
+      mid_lat = (32.9 + 30.3) / 2
+      mid_lon = (-97.0 + -97.7) / 2
+
+      near_to_far = [
+        {"KMID0", mid_lat, mid_lon},
+        {"KMID1", mid_lat + 0.05, mid_lon + 0.05},
+        {"KMID2", mid_lat - 0.05, mid_lon - 0.05},
+        {"KMID3", mid_lat + 0.10, mid_lon + 0.10},
+        {"KMID4", mid_lat - 0.10, mid_lon - 0.10},
+        {"KMID5", mid_lat + 0.20, mid_lon + 0.20},
+        {"KMID6", mid_lat - 0.20, mid_lon - 0.20}
+      ]
+
+      _ =
+        Enum.map(near_to_far, fn {code, lat, lon} ->
+          {:ok, station} =
+            Weather.find_or_create_station(%{
+              station_code: code,
+              station_type: "asos",
+              name: "#{code}",
+              lat: lat,
+              lon: lon
+            })
+
+          Repo.insert!(
+            SurfaceObservation.changeset(%SurfaceObservation{}, %{
+              station_id: station.id,
+              observed_at: contact.qso_timestamp,
+              temp_f: 70.0,
+              dewpoint_f: 55.0,
+              relative_humidity: 55.0,
+              sea_level_pressure_mb: 1015.0
+            })
+          )
+        end)
+
+      {:ok, lv, _html} = live(conn, ~p"/contacts/#{contact.id}")
+      _ = render_async(lv, 2_000)
+
+      obs =
+        lv.pid
+        |> :sys.get_state()
+        |> Map.fetch!(:socket)
+        |> Map.fetch!(:assigns)
+        |> Map.fetch!(:surface_observations)
+
+      # closest_observations caps the list at 5.
+      assert length(obs) <= 5
+
+      # Every kept station must be at least as close as the farthest one.
+      distances =
+        Enum.map(obs, fn o ->
+          abs(o.station.lat - mid_lat) + abs(o.station.lon - mid_lon)
+        end)
+
+      assert distances == Enum.sort(distances)
+    end
+
+    test "contact with pos1 but nil pos2 renders without blowing up (half_dist = 0 path)",
+         %{conn: conn} do
+      # Forcing pos2 to nil via a bare Ecto.Changeset.change bypasses the
+      # Contact.changeset validation that ordinarily fills it in. This
+      # exercises the `if lat2 && lon2` guards in fetch_weather_for_path.
+      contact = create_contact()
+
+      {:ok, contact} =
+        contact
+        |> Ecto.Changeset.change(pos2: nil, grid2: nil, distance_km: nil)
+        |> Repo.update()
+
+      assert is_nil(contact.pos2)
+
+      {:ok, lv, html} = live(conn, ~p"/contacts/#{contact.id}")
+      _ = render_async(lv, 2_000)
+
+      # The detail page renders with station1 present — the render
+      # pipeline walked through fetch_weather_for_path with lat2=nil,
+      # mid_lat=lat1, half_dist=0.
+      assert html =~ "W5XD"
+      assert Process.alive?(lv.pid)
+    end
+
+    property "sort_observations/3 preserves list length + element set for any field key",
+             %{conn: conn} do
+      # Round-tripping the `sort` event across any mix of known and
+      # unknown field keys must leave the surface_observations assign
+      # with the same cardinality AND the same set of station codes.
+      contact = create_contact(%{qso_timestamp: ~U[2026-03-28 18:00:00Z]})
+      codes = seed_distinct_obs(contact)
+
+      fields_gen =
+        StreamData.one_of([
+          StreamData.member_of(~w(station_name observed_at temp_f dewpoint_f relative_humidity sea_level_pressure_mb)),
+          StreamData.string(:alphanumeric, min_length: 1, max_length: 6)
+        ])
+
+      check all(fields <- StreamData.list_of(fields_gen, min_length: 1, max_length: 5), max_runs: 10) do
+        {:ok, lv, _} = live(conn, ~p"/contacts/#{contact.id}")
+        _ = render_async(lv, 2_000)
+
+        for f <- fields do
+          _ = render_click(lv, "sort", %{"field" => f, "table" => "obs"})
+
+          obs =
+            lv.pid
+            |> :sys.get_state()
+            |> Map.fetch!(:socket)
+            |> Map.fetch!(:assigns)
+            |> Map.fetch!(:surface_observations)
+
+          assert length(obs) == length(codes)
+          assert Enum.sort(Enum.map(obs, & &1.station.station_code)) == Enum.sort(codes)
+        end
+      end
+    end
+
+    property "haversine_km/4 is symmetric: d(a,b,c,d) == d(c,d,a,b)" do
+      # Uses Microwaveprop.Geo.haversine_km/4 — the public, structurally
+      # identical twin of the private haversine_km in ContactLive.Show.
+      # Symmetry under endpoint swap is the load-bearing invariant the
+      # show-page midpoint + half-distance logic relies on.
+      check all(
+              lat1 <- StreamData.float(min: -89.0, max: 89.0),
+              lon1 <- StreamData.float(min: -179.0, max: 179.0),
+              lat2 <- StreamData.float(min: -89.0, max: 89.0),
+              lon2 <- StreamData.float(min: -179.0, max: 179.0)
+            ) do
+        ab = Geo.haversine_km(lat1, lon1, lat2, lon2)
+        ba = Geo.haversine_km(lat2, lon2, lat1, lon1)
+        assert_in_delta ab, ba, 1.0e-6
+      end
+    end
+  end
 end
diff --git a/test/microwaveprop_web/live/path_live_test.exs b/test/microwaveprop_web/live/path_live_test.exs
index 2fa09e7c..6d438fcc 100644
--- a/test/microwaveprop_web/live/path_live_test.exs
+++ b/test/microwaveprop_web/live/path_live_test.exs
@@ -355,6 +355,68 @@ defmodule MicrowavepropWeb.PathLiveTest do
     end
   end
 
+  describe "handle_event calculate with gps source" do
+    test "calculate from an already-fixed GPS source keeps source=gps in the URL", %{conn: conn} do
+      {:ok, lv, _html} = live(conn, ~p"/path?source=gps&destination=EM12&band=10000")
+      assert_push_event(lv, "request_gps", %{})
+
+      # Simulate the JS hook pushing a fix.
+      render_hook(lv, "gps_location", %{"lat" => 32.9, "lon" => -97.0})
+
+      # Now submit the form — source_is_gps should stay true so url_params
+      # retains `"source" => "gps"` instead of the literal coords.
+      render_submit(
+        form(lv, "form",
+          source: "32.9,-97.0",
+          destination: "EM12",
+          band: "10000"
+        )
+      )
+
+      assert_patch(lv)
+      html = render(lv)
+      # The input still shows the coords we filled in for the user.
+      assert html =~ ~s(value="32.9,-97.0")
+    end
+  end
+
+  describe "invalid source input surfacing" do
+    test "unknown callsign destination surfaces a 'Could not find' error", %{conn: conn} do
+      # Stub the QRZ lookup so the fallback branch returns a deterministic
+      # error instead of raising about a missing Req.Test stub.
+      Req.Test.stub(Microwaveprop.Qrz.Client, fn conn ->
+        Plug.Conn.send_resp(conn, 404, "not found")
+      end)
+
+      # "NOSUCHCALL" isn't a coord pair and isn't a 4+ char maidenhead
+      # prefix, so resolve_location falls to CallsignClient.locate.
+      {:ok, lv, _html} = live(conn, ~p"/path?source=33.0,-97.0&destination=NOSUCHCALL&band=10000")
+
+      html = render(lv)
+      # Match only the prefix — the reason-text portion varies with how
+      # CallsignClient errors (network stub missing vs explicit not-found).
+      assert html =~ "Could not find"
+    end
+  end
+
+  describe "propagation_updated recompute when destination is not a result" do
+    test "no-op when the result is set but source and destination collapse to same point", %{conn: conn} do
+      # If a compute produces a result at identical src/dst, the
+      # propagation_updated handler still runs point_forecast at that
+      # midpoint. Verify the branch doesn't crash.
+      {:ok, lv, _html} =
+        live(conn, ~p"/path?source=33.0,-97.0&destination=33.0,-97.0&band=10000")
+
+      # A result was built (Link Summary shows), so the propagation_updated
+      # message should take the {valid_time, source, destination} path.
+      assert render(lv) =~ "Link Summary"
+
+      send(lv.pid, {:propagation_updated, [DateTime.utc_now()]})
+      # Still alive, still rendering.
+      assert render(lv) =~ "Path Calculator"
+    end
+  end
+
   describe "property: band round-trip in form" do
     property "for every configured band, submitting the form re-renders with that band selected" do
       # Re-stub the elevation client for each property iteration —