diff --git a/SVSim.EmulatedEntrypoint/Models/Dtos/Requests/DeckBuilder/GenerateDeckCodeRequest.cs b/SVSim.EmulatedEntrypoint/Models/Dtos/Requests/DeckBuilder/GenerateDeckCodeRequest.cs
index 4a28ada..64d5b28 100644
--- a/SVSim.EmulatedEntrypoint/Models/Dtos/Requests/DeckBuilder/GenerateDeckCodeRequest.cs
+++ b/SVSim.EmulatedEntrypoint/Models/Dtos/Requests/DeckBuilder/GenerateDeckCodeRequest.cs
@@ -28,12 +28,17 @@ public class GenerateDeckCodeRequest
     [Key("deck_format")]
     public int DeckFormat { get; set; }
 
-    [JsonPropertyName("card_id")]
-    [Key("card_id")]
+    // Wire key is camelCase mid-word capital — verified in data_dumps/traffic.ndjson live
+    // capture (`"cardID":[...]`). The client's LitJson serializer emits the C# property name
+    // verbatim, and the param classes in Wizard/GenerateDeckCodeTask.cs use `cardID` /
+    // `phantomCardID`. Snake-case would silently bind to empty and the controller would emit
+    // INVALID_DECK; that was the 2026-05-28 "blank code in the deck builder UI" symptom.
+    [JsonPropertyName("cardID")]
+    [Key("cardID")]
     public List<long> CardID { get; set; } = new();
 
-    [JsonPropertyName("phantom_card_id")]
-    [Key("phantom_card_id")]
+    [JsonPropertyName("phantomCardID")]
+    [Key("phantomCardID")]
     public List<long>? PhantomCardID { get; set; }
 
     [JsonPropertyName("rotation_id")]
diff --git a/SVSim.EmulatedEntrypoint/Models/Dtos/Responses/DeckBuilder/GetDeckFromCodeResponse.cs b/SVSim.EmulatedEntrypoint/Models/Dtos/Responses/DeckBuilder/GetDeckFromCodeResponse.cs
index a52a043..e6383aa 100644
--- a/SVSim.EmulatedEntrypoint/Models/Dtos/Responses/DeckBuilder/GetDeckFromCodeResponse.cs
+++ b/SVSim.EmulatedEntrypoint/Models/Dtos/Responses/DeckBuilder/GetDeckFromCodeResponse.cs
@@ -46,7 +46,9 @@ public class DeckPayload
     [Key("rotation_id")]
     public object RotationId { get; set; } = 0;
 
-    [JsonPropertyName("card_id")]
-    [Key("card_id")]
+    // Wire key is camelCase mid-word capital to mirror the client's `cardID` parser
+    // (Wizard/GetDeckDataFromCodeTask.cs:44 reads `jsonData["cardID"]`).
+    [JsonPropertyName("cardID")]
+    [Key("cardID")]
     public List<long> CardID { get; set; } = new();
 }