diff --git a/SVSim.EmulatedEntrypoint/Controllers/CheckController.cs b/SVSim.EmulatedEntrypoint/Controllers/CheckController.cs
index c957023..af89b3a 100644
--- a/SVSim.EmulatedEntrypoint/Controllers/CheckController.cs
+++ b/SVSim.EmulatedEntrypoint/Controllers/CheckController.cs
@@ -5,6 +5,7 @@ using SVSim.Database.Repositories.Viewer;
 using SVSim.EmulatedEntrypoint.Extensions;
 using SVSim.EmulatedEntrypoint.Models.Dtos;
 using SVSim.EmulatedEntrypoint.Models.Dtos.Requests;
+using SVSim.EmulatedEntrypoint.Models.Dtos.Requests.Check;
 using SVSim.EmulatedEntrypoint.Models.Dtos.Responses;
 
 namespace SVSim.EmulatedEntrypoint.Controllers;
@@ -67,4 +68,19 @@ public class CheckController : SVSimController
             KorAuthorityId = 0
         };
     }
+
+    /// <summary>
+    /// Card-master rotation-period integrity probe. Wire path is
+    /// <c>check/check_time_slip_card_master_hash</c> but the client task is
+    /// <c>CheckTimeSlipRotationPeriodTask</c> — a pure <c>BaseTask</c> with no
+    /// <c>Parse()</c> override (Wizard/CheckTimeSlipRotationPeriodTask.cs). Fired from
+    /// <c>DeckDecisionUI.cs:140</c> (Arena "View Deck" path) and the TK2 prep screen.
+    /// Prod responds with <c>data: []</c> in every observed capture across
+    /// traffic_prod_taketwo_selections.ndjson + traffic_prod_tradeables_capture.ndjson.
+    /// </summary>
+    [HttpPost("check_time_slip_card_master_hash")]
+    public IActionResult CheckTimeSlipCardMasterHash([FromBody] CheckTimeSlipCardMasterHashRequest req)
+    {
+        return Ok(Array.Empty<object>());
+    }
 }
diff --git a/SVSim.EmulatedEntrypoint/Models/Dtos/Requests/Check/CheckTimeSlipCardMasterHashRequest.cs b/SVSim.EmulatedEntrypoint/Models/Dtos/Requests/Check/CheckTimeSlipCardMasterHashRequest.cs
new file mode 100644
index 0000000..71b88cc
--- /dev/null
+++ b/SVSim.EmulatedEntrypoint/Models/Dtos/Requests/Check/CheckTimeSlipCardMasterHashRequest.cs
@@ -0,0 +1,12 @@
+using MessagePack;
+using SVSim.EmulatedEntrypoint.Models.Dtos.Requests;
+
+namespace SVSim.EmulatedEntrypoint.Models.Dtos.Requests.Check;
+
+/// <summary>
+/// Empty request envelope. Prod ships only the standard BaseRequest fields
+/// (viewer_id / steam_id / steam_session_ticket) — verified in
+/// traffic_prod_taketwo_selections.ndjson + traffic_prod_tradeables_capture.ndjson.
+/// </summary>
+[MessagePackObject]
+public class CheckTimeSlipCardMasterHashRequest : BaseRequest { }
diff --git a/SVSim.UnitTests/RoutingSmokeTests.cs b/SVSim.UnitTests/RoutingSmokeTests.cs
index 8342fd3..88807e2 100644
--- a/SVSim.UnitTests/RoutingSmokeTests.cs
+++ b/SVSim.UnitTests/RoutingSmokeTests.cs
@@ -111,6 +111,7 @@ public class RoutingSmokeTests
     [TestCase("/arena_colosseum/get_fee_info")]
     [TestCase("/arena/get_challenge_info")]
     [TestCase("/arena/get_challenge_ranking_history")]
+    [TestCase("/check/check_time_slip_card_master_hash")]
     public async Task Authenticated_route_resolves(string path)
     {
         using var factory = new TestFactory();