diff --git a/SVSim.UnitTests/BattleNode/Integration/CaptureConformanceTests.cs b/SVSim.UnitTests/BattleNode/Integration/CaptureConformanceTests.cs
index bdc97aa..44f3c13 100644
--- a/SVSim.UnitTests/BattleNode/Integration/CaptureConformanceTests.cs
+++ b/SVSim.UnitTests/BattleNode/Integration/CaptureConformanceTests.cs
@@ -221,6 +221,48 @@ public class CaptureConformanceTests
         var seq = 0;
         return NodeCrypto.GenerateKey(() => (seq++ * 13) % 16);
     }
+
+    [Test]
+    public void SynthesizedKnownList_matches_prod_recv_PlayActions_entry_shape()
+    {
+        // Prod recv PlayActions knownList entry (battle-traffic_tk2_regular.ndjson:27).
+        const string prodEntry = """
+        { "idx": 17, "cardId": 128821011, "to": 20, "cost": 2, "clan": 8, "tribe": "7,16", "spellboost": 0, "attachTarget": "" }
+        """;
+
+        // Build the same entry through our synthesizer.
+        var deckMap = new Dictionary<int, long> { [17] = 128821011L };
+        var orderList = new List<object?>
+        {
+            new Dictionary<string, object?>
+            {
+                ["move"] = new Dictionary<string, object?>
+                {
+                    ["idx"] = new List<object?> { 17L }, ["isSelf"] = 1L, ["from"] = 10L, ["to"] = 20L,
+                }
+            }
+        };
+        var entry = SVSim.BattleNode.Sessions.Dispatch.KnownListBuilder.BuildPlayedCard(deckMap, 17, orderList);
+        Assert.That(entry, Is.Not.Null);
+
+        var body = new SVSim.BattleNode.Protocol.Bodies.PlayActionsBroadcastBody(
+            PlayIdx: 17, Type: 30, KnownList: new[] { entry! }, OppoTargetList: null);
+        var env = new MsgEnvelope(NetworkBattleUri.PlayActions, ViewerId: 1, Uuid: "u", Bid: null, Try: 0,
+            Cat: EmitCategory.Battle, PubSeq: null, PlaySeq: null, Body: body);
+
+        using var ourDoc = JsonDocument.Parse(MsgEnvelope.ToJson(env));
+        var ourEntry = ourDoc.RootElement.GetProperty("knownList")[0];
+        using var prodDoc = JsonDocument.Parse(prodEntry);
+
+        // We are responsible for idx/cardId/to (+ spellboost/attachTarget). cost/clan/tribe are deferred.
+        foreach (var key in new[] { "idx", "cardId", "to" })
+        {
+            Assert.That(ourEntry.TryGetProperty(key, out var ours), Is.True, $"knownList entry missing '{key}'");
+            var prodVal = prodDoc.RootElement.GetProperty(key);
+            Assert.That(ours.ValueKind, Is.EqualTo(prodVal.ValueKind), $"'{key}' type category mismatch");
+        }
+        Assert.That(ourEntry.GetProperty("cardId").GetInt64(), Is.EqualTo(128821011L));
+    }
 }
 
 /// <summary>