diff --git a/SVSim.EmulatedEntrypoint/Services/MatchContextBuilder.cs b/SVSim.EmulatedEntrypoint/Services/MatchContextBuilder.cs
index 7d6fc8a..aee4b65 100644
--- a/SVSim.EmulatedEntrypoint/Services/MatchContextBuilder.cs
+++ b/SVSim.EmulatedEntrypoint/Services/MatchContextBuilder.cs
@@ -95,7 +95,12 @@ public class MatchContextBuilder : IMatchContextBuilder
         var sleeveId = deck.Sleeve.Id != 0
             ? deck.Sleeve.Id.ToString()
             : defaults.SleeveId.ToString();
-        var deckCardIds = deck.Cards.Select(c => c.Card.Id).ToList();
+        // DeckCard is count-based (one row per unique card + a Count). The node's deck
+        // is one entry PER PHYSICAL CARD (idx 1..N), so expand each row by its Count —
+        // otherwise a 3-copy card ships as a single in-battle card.
+        var deckCardIds = deck.Cards
+            .SelectMany(c => Enumerable.Repeat(c.Card.Id, c.Count))
+            .ToList();
 
         return new MatchContext(
             SelfDeckCardIds: deckCardIds,
diff --git a/SVSim.UnitTests/Services/MatchContextBuilderTests.cs b/SVSim.UnitTests/Services/MatchContextBuilderTests.cs
index 56b76d1..9667de0 100644
--- a/SVSim.UnitTests/Services/MatchContextBuilderTests.cs
+++ b/SVSim.UnitTests/Services/MatchContextBuilderTests.cs
@@ -137,6 +137,33 @@ public class MatchContextBuilderTests
         Assert.That(ctx.FieldId, Is.EqualTo(43));
     }
 
+    [Test]
+    public async Task BuildForRankBattle_expands_each_deck_card_by_its_count()
+    {
+        // Regression for the "matched deck only has 1 of each card" battle-node bug:
+        // DeckCard is count-based (one row per unique card + a Count), so
+        // deck.Cards.Select(c => c.Card.Id) collapsed 3 copies into a single entry.
+        // The MatchContext deck must carry one entry PER PHYSICAL CARD.
+        await using var factory = new SVSimTestFactory();
+        var viewerId = await factory.SeedViewerAsync(displayName: "Ranker");
+        await factory.SeedGlobalsAsync();
+        await factory.SeedDeckAsync(viewerId, Format.Unlimited, number: 1, name: "Triples");
+        await factory.AddCardToDeckAsync(viewerId, Format.Unlimited, 1, 10001001L, count: 3);
+        await factory.AddCardToDeckAsync(viewerId, Format.Unlimited, 1, 10001002L, count: 2);
+        await factory.AddCardToDeckAsync(viewerId, Format.Unlimited, 1, 10001003L, count: 1);
+
+        using var scope = factory.Services.CreateScope();
+        var builder = scope.ServiceProvider.GetRequiredService<IMatchContextBuilder>();
+
+        var ctx = await builder.BuildForRankBattleAsync(viewerId, Format.Unlimited, deckNo: 1);
+
+        Assert.That(ctx.SelfDeckCardIds.Count, Is.EqualTo(6),
+            "3 + 2 + 1 copies must produce 6 physical card entries, not 3 unique ids.");
+        Assert.That(ctx.SelfDeckCardIds.Count(id => id == 10001001L), Is.EqualTo(3));
+        Assert.That(ctx.SelfDeckCardIds.Count(id => id == 10001002L), Is.EqualTo(2));
+        Assert.That(ctx.SelfDeckCardIds.Count(id => id == 10001003L), Is.EqualTo(1));
+    }
+
     [Test]
     public async Task BuildForRankBattle_throws_when_no_deck_for_format()
     {