fix: host client SyncVar hooks ignoring AOI visibility

Assets/Mirror/Core/NetworkBehaviour.cs

@@ -565,7 +565,9 @@ public void GeneratedSyncVarSetter<T>(T value, ref T field, ulong dirtyBit, Acti
                     // in client-only mode, OnDeserialize would call it.
                     // we use hook guard to protect against deadlock where hook
                     // changes syncvar, calling hook again.
-                    if (NetworkServer.activeHost && !GetSyncVarHookGuard(dirtyBit))
+                    // IMPORTANT: only call hook if object is visible to host client (in NetworkClient.spawned).
+                    // This prevents hooks from firing at spawn for objects out of AOI range.
+                    if (NetworkServer.activeHost && !GetSyncVarHookGuard(dirtyBit) && NetworkClient.spawned.ContainsKey(netIdentity.netId))
                     {
                         SetSyncVarHookGuard(dirtyBit, true);
                         OnChanged(oldValue, value);
@@ -592,7 +594,9 @@ public void GeneratedSyncVarSetter_GameObject(GameObject value, ref GameObject f
                     // in client-only mode, OnDeserialize would call it.
                     // we use hook guard to protect against deadlock where hook
                     // changes syncvar, calling hook again.
-                    if (NetworkServer.activeHost && !GetSyncVarHookGuard(dirtyBit))
+                    // IMPORTANT: only call hook if object is visible to host client (in NetworkClient.spawned).
+                    // This prevents hooks from firing at spawn for objects out of AOI range.
+                    if (NetworkServer.activeHost && !GetSyncVarHookGuard(dirtyBit) && NetworkClient.spawned.ContainsKey(netIdentity.netId))
                     {
                         SetSyncVarHookGuard(dirtyBit, true);
                         OnChanged(oldValue, value);
@@ -619,7 +623,9 @@ public void GeneratedSyncVarSetter_NetworkIdentity(NetworkIdentity value, ref Ne
                     // in client-only mode, OnDeserialize would call it.
                     // we use hook guard to protect against deadlock where hook
                     // changes syncvar, calling hook again.
-                    if (NetworkServer.activeHost && !GetSyncVarHookGuard(dirtyBit))
+                    // IMPORTANT: only call hook if object is visible to host client (in NetworkClient.spawned).
+                    // This prevents hooks from firing at spawn for objects out of AOI range.
+                    if (NetworkServer.activeHost && !GetSyncVarHookGuard(dirtyBit) && NetworkClient.spawned.ContainsKey(netIdentity.netId))
                     {
                         SetSyncVarHookGuard(dirtyBit, true);
                         OnChanged(oldValue, value);
@@ -647,7 +653,9 @@ public void GeneratedSyncVarSetter_NetworkBehaviour<T>(T value, ref T field, ulo
                     // in client-only mode, OnDeserialize would call it.
                     // we use hook guard to protect against deadlock where hook
                     // changes syncvar, calling hook again.
-                    if (NetworkServer.activeHost && !GetSyncVarHookGuard(dirtyBit))
+                    // IMPORTANT: only call hook if object is visible to host client (in NetworkClient.spawned).
+                    // This prevents hooks from firing at spawn for objects out of AOI range.
+                    if (NetworkServer.activeHost && !GetSyncVarHookGuard(dirtyBit) && NetworkClient.spawned.ContainsKey(netIdentity.netId))
                     {
                         SetSyncVarHookGuard(dirtyBit, true);
                         OnChanged(oldValue, value);
@@ -795,7 +803,10 @@ public void GeneratedSyncVarDeserialize<T>(ref T field, Action<T, T> OnChanged,
             field = value;
 
             // any hook? then call if changed.
-            if (OnChanged != null && !SyncVarEqual(previous, ref field))
+            // in host mode initial spawn, also call hook even if value hasn't changed,
+            // because the field was already set on server but hook wasn't called yet.
+            bool changed = !SyncVarEqual(previous, ref field);
+            if (OnChanged != null && (changed || netIdentity.hostInitialSpawn))
             {
                 OnChanged(previous, field);
             }
@@ -856,7 +867,10 @@ public void GeneratedSyncVarDeserialize_GameObject(ref GameObject field, Action<
             field = GetSyncVarGameObject(netIdField, ref field);
 
             // any hook? then call if changed.
-            if (OnChanged != null && !SyncVarEqual(previousNetId, ref netIdField))
+            // in host mode initial spawn, also call hook even if value hasn't changed,
+            // because the field was already set on server but hook wasn't called yet.
+            bool changed = !SyncVarEqual(previousNetId, ref netIdField);
+            if (OnChanged != null && (changed || netIdentity.hostInitialSpawn))
             {
                 OnChanged(previousGameObject, field);
             }
@@ -918,7 +932,10 @@ public void GeneratedSyncVarDeserialize_NetworkIdentity(ref NetworkIdentity fiel
             field = GetSyncVarNetworkIdentity(netIdField, ref field);
 
             // any hook? then call if changed.
-            if (OnChanged != null && !SyncVarEqual(previousNetId, ref netIdField))
+            // in host mode initial spawn, also call hook even if value hasn't changed,
+            // because the field was already set on server but hook wasn't called yet.
+            bool changed = !SyncVarEqual(previousNetId, ref netIdField);
+            if (OnChanged != null && (changed || netIdentity.hostInitialSpawn))
             {
                 OnChanged(previousIdentity, field);
             }
@@ -982,7 +999,10 @@ public void GeneratedSyncVarDeserialize_NetworkBehaviour<T>(ref T field, Action<
             field = GetSyncVarNetworkBehaviour(netIdField, ref field);
 
             // any hook? then call if changed.
-            if (OnChanged != null && !SyncVarEqual(previousNetId, ref netIdField))
+            // in host mode initial spawn, also call hook even if value hasn't changed,
+            // because the field was already set on server but hook wasn't called yet.
+            bool changed = !SyncVarEqual(previousNetId, ref netIdField);
+            if (OnChanged != null && (changed || netIdentity.hostInitialSpawn))
             {
                 OnChanged(previousBehaviour, field);
             }

Assets/Mirror/Core/NetworkClient.cs

@@ -1384,7 +1384,30 @@ internal static void OnHostClientSpawn(SpawnMessage message)
                     aoi.SetHostVisibility(identity, true);
 
                 identity.isOwned = message.isOwner;
-                BootstrapIdentity(identity);
+
+                // Set flag to indicate initial spawn deserialization in host mode.
+                // This forces SyncVar hooks to fire even if values haven't changed,
+                // because the field was already set on server but hook wasn't called yet.
+                identity.hostInitialSpawn = true;
+
+                // Configure flags before deserializing
+                InitializeIdentityFlags(identity);
+
+                // Deserialize components if any payload.
+                // This will trigger SyncVar hooks via GeneratedSyncVarDeserialize.
+                if (message.payload.Count > 0)
+                {
+                    using (NetworkReaderPooled payloadReader = NetworkReaderPool.Get(message.payload))
+                    {
+                        identity.DeserializeClient(payloadReader, true);
+                    }
+                }
+
+                // Clear flag after deserialization
+                identity.hostInitialSpawn = false;
+
+                // Invoke callbacks after deserializing
+                InvokeIdentityCallbacks(identity);
             }
         }
 

Assets/Mirror/Core/NetworkIdentity.cs

@@ -118,6 +118,11 @@ public sealed class NetworkIdentity : MonoBehaviour
         // internal so NetworkManager can reset it from StopClient.
         internal bool clientStarted;
 
+        // flag to indicate we're deserializing initial spawn in host mode.
+        // used to force SyncVar hooks to fire even if value hasn't changed.
+        // only set temporarily during OnHostClientSpawn deserialization.
+        internal bool hostInitialSpawn;
+
         /// <summary>The set of network connections (players) that can see this object.</summary>
         public readonly Dictionary<int, NetworkConnectionToClient> observers =
             new Dictionary<int, NetworkConnectionToClient>();