fix(battle-node): harden SIO parse + narrow Matched OppoId/Seed to int

#3: SocketIoFrame.Parse now range-checks the packet type char (was
unchecked cast — any char outside 0-6 produced an undefined enum
value) and uses int.TryParse for ack-id (was int.Parse — a >10-digit
ack-id threw OverflowException, tearing down the WS mid-game). Both
now throw ArgumentException consistently. The read loop in
RealParticipant wraps both EIO and SIO parse calls with try-catch so
a malformed frame is logged and skipped instead of killing the battle.

#4: MatchedSelfInfo/MatchedOppoInfo OppoId and Seed narrowed from
long to int. The client reads both with Convert.ToInt32 inside a
swallowing try/catch — any value > int.MaxValue silently dropped the
Matched event, preventing the battle from starting. Seed was already
int-range (BattleSeeds.Stable returns int); OppoId (viewer ID) is
~847M in captures, well under int.MaxValue. The narrowing cast now
happens explicitly in ServerBattleFrames.BuildMatched at the wire
boundary.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

SVSim.BattleNode/Lifecycle/ServerBattleFrames.cs

@@ -23,7 +23,7 @@ public static class ServerBattleFrames
     public static MsgEnvelope BuildMatched(
         MatchContext selfCtx, MatchContext oppoCtx,
         long selfViewerId, long oppoViewerId,
-        string battleId, long seed, IReadOnlyList<long> selfDeckOrder) =>
+        string battleId, int seed, IReadOnlyList<long> selfDeckOrder) =>
         EnvelopeForPush(NetworkBattleUri.Matched,
             new MatchedBody(
                 SelfInfo: new MatchedSelfInfo(
@@ -34,7 +34,7 @@ public static class ServerBattleFrames
                     DegreeId: selfCtx.DegreeId,
                     FieldId: selfCtx.FieldId,
                     IsOfficial: selfCtx.IsOfficial != 0,
-                    OppoId: oppoViewerId,
+                    OppoId: (int)oppoViewerId,
                     Seed: seed),
                 OppoInfo: new MatchedOppoInfo(
                     CountryCode: oppoCtx.CountryCode,
@@ -44,7 +44,7 @@ public static class ServerBattleFrames
                     DegreeId: oppoCtx.DegreeId,
                     FieldId: oppoCtx.FieldId,
                     IsOfficial: oppoCtx.IsOfficial != 0,
-                    OppoId: selfViewerId,
+                    OppoId: (int)selfViewerId,
                     Seed: seed,
                     OppoDeckCount: oppoCtx.SelfDeckCardIds.Count),
                 SelfDeck: BuildPlayerDeck(selfDeckOrder)),

SVSim.BattleNode/Protocol/Bodies/MatchedBody.cs

@@ -19,8 +19,8 @@ public sealed record MatchedSelfInfo(
     [property: JsonPropertyName("fieldId")] int FieldId,
     [property: JsonPropertyName("isOfficial")]
     [property: JsonConverter(typeof(NumericBoolJsonConverter))] bool IsOfficial,
-    [property: JsonPropertyName("oppoId")] long OppoId,
+    [property: JsonPropertyName("oppoId")] int OppoId,
-    [property: JsonPropertyName("seed")] long Seed);
+    [property: JsonPropertyName("seed")] int Seed);
 
 public sealed record MatchedOppoInfo(
     [property: JsonPropertyName("country_code")] string CountryCode,
@@ -31,8 +31,8 @@ public sealed record MatchedOppoInfo(
     [property: JsonPropertyName("fieldId")] int FieldId,
     [property: JsonPropertyName("isOfficial")]
     [property: JsonConverter(typeof(NumericBoolJsonConverter))] bool IsOfficial,
-    [property: JsonPropertyName("oppoId")] long OppoId,
+    [property: JsonPropertyName("oppoId")] int OppoId,
-    [property: JsonPropertyName("seed")] long Seed,
+    [property: JsonPropertyName("seed")] int Seed,
     [property: JsonPropertyName("oppoDeckCount")] int OppoDeckCount);
 
 public sealed record DeckCardRef(

SVSim.BattleNode/Sessions/Participants/RealParticipant.cs

@@ -134,7 +134,15 @@ public sealed class RealParticipant : IBattleParticipant, IHasHandshakePhase
                 {
                     var text = Encoding.UTF8.GetString(msg.Value.Bytes);
                     if (text.Length == 0) continue;
-                    var eio = EngineIoFrame.Parse(text);
+
+                    EngineIoFrame eio;
+                    try { eio = EngineIoFrame.Parse(text); }
+                    catch (ArgumentException ex)
+                    {
+                        _log.LogWarning(ex, "Dropping unparseable EIO frame from viewer {Vid}", ViewerId);
+                        continue;
+                    }
+
                     if (_diagnosticLogging)
                     {
                         _log.LogInformation(
@@ -149,7 +157,13 @@ public sealed class RealParticipant : IBattleParticipant, IHasHandshakePhase
                     }
                     if (eio.Type != EngineIoPacketType.Message) continue;
 
-                    var sio = SocketIoFrame.Parse(eio.Payload);
+                    SocketIoFrame sio;
+                    try { sio = SocketIoFrame.Parse(eio.Payload); }
+                    catch (ArgumentException ex)
+                    {
+                        _log.LogWarning(ex, "Dropping unparseable SIO frame from viewer {Vid}", ViewerId);
+                        continue;
+                    }
                     if (sio.AttachmentCount > 0)
                     {
                         pendingFrame = sio;

SVSim.BattleNode/Wire/SocketIoFrame.cs

@@ -52,7 +52,10 @@ public sealed class SocketIoFrame
         if (string.IsNullOrEmpty(raw))
             throw new ArgumentException("Empty SIO payload", nameof(raw));
 
-        var type = (SocketIoPacketType)(raw[0] - '0');
+        var typeChar = raw[0];
+        if (typeChar < '0' || typeChar > '6')
+            throw new ArgumentException($"Invalid SIO type char '{typeChar}'", nameof(raw));
+        var type = (SocketIoPacketType)(typeChar - '0');
         var cursor = 1;
 
         var attachmentCount = 0;
@@ -84,7 +87,9 @@ public sealed class SocketIoFrame
         {
             var start = cursor;
             while (cursor < raw.Length && char.IsDigit(raw[cursor])) cursor++;
-            ackId = int.Parse(raw.AsSpan(start, cursor - start));
+            if (!int.TryParse(raw.AsSpan(start, cursor - start), out var parsedAckId))
+                throw new ArgumentException("SIO ack-id overflows int32", nameof(raw));
+            ackId = parsedAckId;
         }
 
         var argsJson = cursor < raw.Length ? raw.Substring(cursor) : string.Empty;

SVSim.UnitTests/BattleNode/Lifecycle/ServerBattleFramesTests.cs

@@ -14,19 +14,19 @@ public class ServerBattleFramesTests
     {
         var env = ServerBattleFrames.BuildMatched(FixtureCtx(), FakeOpponentCtx(),
             selfViewerId: 906243102, oppoViewerId: 847666884,
-            battleId: "b", seed: 17_548_138L, selfDeckOrder: FixtureCtx().SelfDeckCardIds);
+            battleId: "b", seed: 17_548_138, selfDeckOrder: FixtureCtx().SelfDeckCardIds);
 
         Assert.That(env.Uri, Is.EqualTo(NetworkBattleUri.Matched));
         var body = (MatchedBody)env.Body;
-        Assert.That(body.SelfInfo.OppoId, Is.EqualTo(847666884L));
+        Assert.That(body.SelfInfo.OppoId, Is.EqualTo(847666884));
-        Assert.That(body.OppoInfo.OppoId, Is.EqualTo(906243102L));
+        Assert.That(body.OppoInfo.OppoId, Is.EqualTo(906243102));
         Assert.That(env.Bid, Is.EqualTo("b"));
     }
 
     [Test]
     public void BuildMatched_ContainsThirtyCardSelfDeck()
     {
-        var env = ServerBattleFrames.BuildMatched(FixtureCtx(), FakeOpponentCtx(), 1, 2, "b", 17_548_138L, FixtureCtx().SelfDeckCardIds);
+        var env = ServerBattleFrames.BuildMatched(FixtureCtx(), FakeOpponentCtx(), 1, 2, "b", 17_548_138, FixtureCtx().SelfDeckCardIds);
         var body = (MatchedBody)env.Body;
         Assert.That(body.SelfDeck.Count, Is.EqualTo(30));
     }
@@ -35,7 +35,7 @@ public class ServerBattleFramesTests
     public void BuildMatched_deck_idxs_pair_1to30_with_context_card_ids()
     {
         var draftedDeck = Enumerable.Range(1, 30).Select(i => 200_000_000L + i).ToList();
-        var env = ServerBattleFrames.BuildMatched(FixtureCtx(draftedDeck), FakeOpponentCtx(), 1, 2, "b", 17_548_138L, draftedDeck);
+        var env = ServerBattleFrames.BuildMatched(FixtureCtx(draftedDeck), FakeOpponentCtx(), 1, 2, "b", 17_548_138, draftedDeck);
         var body = (MatchedBody)env.Body;
 
         for (int i = 0; i < 30; i++)
@@ -56,7 +56,7 @@ public class ServerBattleFramesTests
             EmblemId = "888", DegreeId = "777", FieldId = 42, IsOfficial = 1,
         };
 
-        var env = ServerBattleFrames.BuildMatched(ctx, FakeOpponentCtx(), 1, 2, "b", 17_548_138L, ctx.SelfDeckCardIds);
+        var env = ServerBattleFrames.BuildMatched(ctx, FakeOpponentCtx(), 1, 2, "b", 17_548_138, ctx.SelfDeckCardIds);
         var body = (MatchedBody)env.Body;
 
         Assert.That(body.SelfInfo.CountryCode, Is.EqualTo("JPN"));

SVSim.UnitTests/BattleNode/Lifecycle/TypedBodyWireShapeTests.cs

@@ -28,7 +28,7 @@ public class TypedBodyWireShapeTests
         // with "Value cannot be null. Parameter name: source". The prod wire format
         // emits envelope keys (uri first) before body keys; we must too.
         var env = ServerBattleFrames.BuildMatched(FixtureCtx(), FakeOpponentCtx(),
-            selfViewerId: 1, oppoViewerId: 2, battleId: "b", seed: 17_548_138L,
+            selfViewerId: 1, oppoViewerId: 2, battleId: "b", seed: 17_548_138,
             selfDeckOrder: FixtureCtx().SelfDeckCardIds);
         var json = MsgEnvelope.ToJson(env);
 
@@ -48,7 +48,7 @@ public class TypedBodyWireShapeTests
     {
         var env = ServerBattleFrames.BuildMatched(FixtureCtx(), FakeOpponentCtx(),
             selfViewerId: 906243102, oppoViewerId: 847666884, battleId: "597830888107",
-            seed: 17_548_138L, selfDeckOrder: FixtureCtx().SelfDeckCardIds);
+            seed: 17_548_138, selfDeckOrder: FixtureCtx().SelfDeckCardIds);
 
         var json = MsgEnvelope.ToJson(env);
         var node = JsonNode.Parse(json)!.AsObject();

SVSim.UnitTests/BattleNode/Protocol/Bodies/MatchedBodyTests.cs

@@ -15,11 +15,11 @@ public class MatchedBodyTests
             SelfInfo: new MatchedSelfInfo(
                 CountryCode: "KOR", UserName: "Player", SleeveId: "3000011",
                 EmblemId: "701441011", DegreeId: "300003", FieldId: 43,
-                IsOfficial: false, OppoId: 847666884L, Seed: 17_548_138L),
+                IsOfficial: false, OppoId: 847666884, Seed: 17_548_138),
             OppoInfo: new MatchedOppoInfo(
                 CountryCode: "JPN", UserName: "Opponent", SleeveId: "704141010",
                 EmblemId: "400001100", DegreeId: "120027", FieldId: 5,
-                IsOfficial: false, OppoId: 906243102L, Seed: 17_548_138L, OppoDeckCount: 30),
+                IsOfficial: false, OppoId: 906243102, Seed: 17_548_138, OppoDeckCount: 30),
             SelfDeck: new[] { new DeckCardRef(Idx: 1, CardId: 100011010L) });
 
         var node = (JsonObject)JsonSerializer.SerializeToNode(body)!;
@@ -32,16 +32,16 @@ public class MatchedBodyTests
         Assert.That(selfInfo["degreeId"]!.GetValue<string>(), Is.EqualTo("300003"));
         Assert.That(selfInfo["fieldId"]!.GetValue<int>(), Is.EqualTo(43));
         Assert.That(selfInfo["isOfficial"]!.GetValue<int>(), Is.EqualTo(0));
-        Assert.That(selfInfo["oppoId"]!.GetValue<long>(), Is.EqualTo(847666884L));
+        Assert.That(selfInfo["oppoId"]!.GetValue<int>(), Is.EqualTo(847666884));
-        Assert.That(selfInfo["seed"]!.GetValue<long>(), Is.EqualTo(17_548_138L));
+        Assert.That(selfInfo["seed"]!.GetValue<int>(), Is.EqualTo(17_548_138));
     }
 
     [Test]
     public void OppoInfo_HasOppoDeckCount_OnTheWire()
     {
         var body = new MatchedBody(
-            SelfInfo: new MatchedSelfInfo("KOR","P","s","e","d",0,false,1L,1L),
+            SelfInfo: new MatchedSelfInfo("KOR","P","s","e","d",0,false,1,1),
-            OppoInfo: new MatchedOppoInfo("JPN","O","s","e","d",0,false,1L,1L, OppoDeckCount: 30),
+            OppoInfo: new MatchedOppoInfo("JPN","O","s","e","d",0,false,1,1, OppoDeckCount: 30),
             SelfDeck: System.Array.Empty<DeckCardRef>());
 
         var node = (JsonObject)JsonSerializer.SerializeToNode(body)!;
@@ -54,8 +54,8 @@ public class MatchedBodyTests
     public void SelfInfo_DoesNotHaveOppoDeckCount_OnTheWire()
     {
         var body = new MatchedBody(
-            SelfInfo: new MatchedSelfInfo("KOR","P","s","e","d",0,false,1L,1L),
+            SelfInfo: new MatchedSelfInfo("KOR","P","s","e","d",0,false,1,1),
-            OppoInfo: new MatchedOppoInfo("JPN","O","s","e","d",0,false,1L,1L,30),
+            OppoInfo: new MatchedOppoInfo("JPN","O","s","e","d",0,false,1,1,30),
             SelfDeck: System.Array.Empty<DeckCardRef>());
 
         var node = (JsonObject)JsonSerializer.SerializeToNode(body)!;
@@ -68,8 +68,8 @@ public class MatchedBodyTests
     public void ResultCode_DefaultsToOne_OnConstruction()
     {
         var body = new MatchedBody(
-            SelfInfo: new MatchedSelfInfo("KOR","P","s","e","d",0,false,1L,1L),
+            SelfInfo: new MatchedSelfInfo("KOR","P","s","e","d",0,false,1,1),
-            OppoInfo: new MatchedOppoInfo("JPN","O","s","e","d",0,false,1L,1L,30),
+            OppoInfo: new MatchedOppoInfo("JPN","O","s","e","d",0,false,1,1,30),
             SelfDeck: System.Array.Empty<DeckCardRef>());
 
         Assert.That(body.ResultCode, Is.EqualTo(1));
@@ -81,8 +81,8 @@ public class MatchedBodyTests
     public void SelfDeck_SerializesAsArray_WithIdxAndCardIdKeys()
     {
         var body = new MatchedBody(
-            SelfInfo: new MatchedSelfInfo("KOR","P","s","e","d",0,false,1L,1L),
+            SelfInfo: new MatchedSelfInfo("KOR","P","s","e","d",0,false,1,1),
-            OppoInfo: new MatchedOppoInfo("JPN","O","s","e","d",0,false,1L,1L,30),
+            OppoInfo: new MatchedOppoInfo("JPN","O","s","e","d",0,false,1,1,30),
             SelfDeck: new[]
             {
                 new DeckCardRef(Idx: 1, CardId: 100011010L),

SVSim.UnitTests/BattleNode/Sessions/BattleSessionDispatchTests.cs

@@ -99,8 +99,8 @@ public class BattleSessionDispatchTests
         var routes = s.ComputeFrames(a, NewEnvelope(NetworkBattleUri.InitBattle));
 
         var body = (MatchedBody)routes[0].Frame.Body;
-        Assert.That(body.SelfInfo.Seed, Is.EqualTo((long)BattleSeeds.Stable(s.MasterSeed)));
+        Assert.That(body.SelfInfo.Seed, Is.EqualTo(BattleSeeds.Stable(s.MasterSeed)));
-        Assert.That(body.OppoInfo.Seed, Is.EqualTo((long)BattleSeeds.Stable(s.MasterSeed)));
+        Assert.That(body.OppoInfo.Seed, Is.EqualTo(BattleSeeds.Stable(s.MasterSeed)));
     }
 
     [Test]

SVSim.UnitTests/BattleNode/Wire/SocketIoFrameTests.cs

@@ -125,4 +125,17 @@ public class SocketIoFrameTests
         // The event name must be JSON-escaped: each " becomes \", and the literal \ becomes \\.
         Assert.That(text, Does.Contain("\"weird \\\"name\\\" with \\\\ backslash\""));
     }
+
+    [Test]
+    public void Parse_InvalidTypeChar_Throws()
+    {
+        var ex = Assert.Throws<ArgumentException>(() => SocketIoFrame.Parse("9[\"msg\"]"));
+        Assert.That(ex!.Message, Does.Contain("Invalid SIO type char"));
+    }
+
+    [Test]
+    public void Parse_OverflowingAckId_Throws()
+    {
+        Assert.Throws<ArgumentException>(() => SocketIoFrame.Parse("2999999999999[\"msg\"]"));
+    }
 }