diff --git a/test/fixtures/config.json b/test/fixtures/config.json
index 76192bf24..513d14d63 100644
--- a/test/fixtures/config.json
+++ b/test/fixtures/config.json
@@ -174,6 +174,69 @@
       "refresh_if_loaded_before": null,
       "tags": [],
       "vendor": "lg_mri"
+    },
+    "EIG-604": {
+      "disabled": false,
+      "name": null,
+      "app_id": "gl_eink_v2",
+      "app_params": {
+        "header": {
+          "direction_id": 0,
+          "route_id": "Green-E"
+        },
+        "departures": {
+          "sections": [
+            {
+              "header": {
+                "title": null,
+                "arrow": null,
+                "read_as": null
+              },
+              "filters": {
+                "max_minutes": null,
+                "route_directions": null
+              },
+              "query": {
+                "opts": {
+                  "include_schedules": false
+                },
+                "params": {
+                  "direction_id": 0,
+                  "stop_ids": ["place-nuniv"],
+                  "route_ids": ["Green-E"],
+                  "route_type": null
+                }
+              },
+              "layout": {
+                "max": null,
+                "min": 1,
+                "base": null,
+                "include_later": false
+              },
+              "bidirectional": false
+            }
+          ]
+        },
+        "footer": {
+          "stop_id": "place-nuniv"
+        },
+        "alerts": {
+          "stop_id": "70243"
+        },
+        "evergreen_content": [],
+        "line_map": {
+          "stop_id": "70243",
+          "direction_id": 0,
+          "route_id": "Green-E",
+          "station_id": "place-nuniv"
+        },
+        "platform_location": "front"
+      },
+      "device_id": null,
+      "hidden_from_screenplay": false,
+      "refresh_if_loaded_before": null,
+      "tags": [],
+      "vendor": "mercury"
     }
   }
 }
diff --git a/test/screens/v2/screen_data_test.exs b/test/screens/v2/screen_data_test.exs
index c4bef8863..ac135abfc 100644
--- a/test/screens/v2/screen_data_test.exs
+++ b/test/screens/v2/screen_data_test.exs
@@ -1,30 +1,3 @@
-defmodule Screens.V2.ScreenDataTest.Stub do
-  defmacro candidate_generator(name, instances_fn) do
-    quote do
-      defmodule unquote(name) do
-        alias Screens.V2.CandidateGenerator
-        alias Screens.V2.Template.Builder
-        alias Screens.V2.WidgetInstance.Placeholder
-
-        @behaviour CandidateGenerator
-
-        @impl CandidateGenerator
-        def screen_template(), do: Builder.build_template({:screen, %{normal: [:main]}})
-
-        @impl CandidateGenerator
-        def candidate_instances(config) do
-          unquote(instances_fn).(config)
-        end
-
-        @impl CandidateGenerator
-        def audio_only_instances(_widgets, _config), do: []
-
-        defp placeholder(color), do: %Placeholder{color: color, slot_names: [:main]}
-      end
-    end
-  end
-end
-
 defmodule Screens.V2.ScreenDataTest do
   use ExUnit.Case, async: true
 
@@ -32,7 +5,7 @@ defmodule Screens.V2.ScreenDataTest do
   alias Screens.V2.ScreenData
   alias Screens.V2.WidgetInstance.MockWidget
   alias Screens.V2.WidgetInstance.Placeholder
-  alias Screens.V2.ScreenDataTest.Stub
+  alias Screens.TestSupport.CandidateGeneratorStub, as: Stub
 
   import ExUnit.CaptureLog
   import Screens.Inject
diff --git a/test/screens_web/controllers/v2/screen_api_controller_test.exs b/test/screens_web/controllers/v2/screen_api_controller_test.exs
new file mode 100644
index 000000000..f9fcbc062
--- /dev/null
+++ b/test/screens_web/controllers/v2/screen_api_controller_test.exs
@@ -0,0 +1,79 @@
+defmodule ScreensWeb.V2.ScreenApiControllerTest do
+  use ScreensWeb.ConnCase
+
+  alias ScreensConfig.Screen
+  alias Screens.TestSupport.CandidateGeneratorStub, as: Stub
+
+  import Screens.Inject
+  import Mox
+  setup :verify_on_exit!
+
+  @cache injected(Screens.Config.Cache)
+  @parameters injected(Screens.V2.ScreenData.Parameters)
+
+  require Stub
+
+  Stub.candidate_generator(MercuryGenerator, fn _ -> [placeholder(:green)] end)
+  Stub.candidate_generator(LgMriGenerator, fn _ -> [placeholder(:red)] end)
+
+  describe "show/2" do
+    test "only returns flex_zone for Mercury screens", %{conn: conn} do
+      expect(@cache, :screen, fn
+        "EIG-604" ->
+          struct(Screen, app_id: :gl_eink_v2, vendor: :mercury)
+      end)
+
+      expect(@parameters, :variants, fn _ -> [nil] end)
+
+      stub(
+        @parameters,
+        :candidate_generator,
+        fn %Screen{vendor: :mercury}, nil -> MercuryGenerator end
+      )
+
+      stub(@parameters, :refresh_rate, fn _app_id -> 0 end)
+
+      conn = get(conn, "/v2/api/screen/EIG-604?last_refresh=2024-12-02T00:00:00Z")
+
+      assert %{
+               "audio_data" => "",
+               "data" => %{
+                 "main" => %{"color" => "green", "type" => "placeholder"},
+                 "type" => "normal"
+               },
+               "disabled" => false,
+               "flex_zone" => [],
+               "force_reload" => false,
+               "last_deploy_timestamp" => nil
+             } == json_response(conn, 200)
+    end
+
+    test "omits flex_zone from non-Mercury screens", %{conn: conn} do
+      expect(@cache, :screen, fn
+        "1401" ->
+          struct(Screen, app_id: :bus_shelter_v2, vendor: :lg_mri)
+      end)
+
+      expect(@parameters, :variants, fn _ -> [nil] end)
+
+      stub(
+        @parameters,
+        :candidate_generator,
+        fn %Screen{vendor: :lg_mri}, nil -> LgMriGenerator end
+      )
+
+      stub(@parameters, :refresh_rate, fn _app_id -> 0 end)
+
+      conn = get(conn, "/v2/api/screen/1401?last_refresh=2024-12-02T00:00:00Z")
+
+      assert %{
+               "data" => %{
+                 "main" => %{"color" => "red", "type" => "placeholder"},
+                 "type" => "normal"
+               },
+               "disabled" => false,
+               "force_reload" => false
+             } == json_response(conn, 200)
+    end
+  end
+end