Fix IsProjected nested object selection rewriting

src/HotChocolate/Data/src/Data/Projections/Optimizers/IsProjectedProjectionOptimizer.cs

@@ -1,5 +1,6 @@
 using HotChocolate.Execution.Processing;
 using HotChocolate.Language;
+using HotChocolate.Types;
 
 namespace HotChocolate.Data.Projections.Optimizers;
 
@@ -38,6 +39,14 @@ public Selection RewriteSelection(
             }
 
             var field = context.TypeContext.Fields[fieldName];
+
+            // Only inject leaf fields. Forcing internal object projections can create
+            // invalid EF Core tracking shapes (e.g. owned entities without owner materialization).
+            if (field.Type.NamedType().IsCompositeType())
+            {
+                continue;
+            }
+
             var fieldNode = new FieldNode(
                 null,
                 new NameNode(fieldName),

src/HotChocolate/Data/test/Data.Projections.SqlServer.Tests/Issue6329ReproTests.cs

@@ -0,0 +1,71 @@
+using HotChocolate.Execution;
+using Microsoft.EntityFrameworkCore;
+
+namespace HotChocolate.Data.Projections;
+
+public class Issue6329ReproTests
+{
+    private readonly SchemaCache _cache = new();
+
+    private readonly BookWithProjectedAuthor[] _books =
+    [
+        new()
+        {
+            Id = 1,
+            Title = "Book",
+            Author = new AuthorWithProjectedId
+            {
+                Id = 10,
+                Name = "Author"
+            }
+        }
+    ];
+
+    [Fact]
+    public async Task IsProjected_SubObject_Can_Be_Omitted_From_Selection()
+    {
+        var tester = _cache.CreateSchema(
+            _books,
+            onModelCreating: modelBuilder =>
+                modelBuilder.Entity<BookWithProjectedAuthor>().OwnsOne(x => x.Author),
+            usePaging: true);
+
+        var result = await tester.ExecuteAsync(
+            OperationRequestBuilder.New()
+                .SetDocument(
+                    """
+                    {
+                      root {
+                        edges {
+                          node {
+                            id
+                          }
+                        }
+                      }
+                    }
+                    """)
+                .Build());
+
+        var operationResult = result.ExpectOperationResult();
+        Assert.Empty(operationResult.Errors ?? []);
+    }
+
+    public class BookWithProjectedAuthor
+    {
+        public int Id { get; set; }
+
+        public string Title { get; set; } = string.Empty;
+
+        [IsProjected(true)]
+        public AuthorWithProjectedId Author { get; set; } = new();
+    }
+
+    [Owned]
+    public class AuthorWithProjectedId
+    {
+        [IsProjected(true)]
+        public int Id { get; set; }
+
+        public string Name { get; set; } = string.Empty;
+    }
+}