diff --git a/SourceGenerators/Mapper/MintPlayer.Mapper/AnalyzerReleases.Unshipped.md b/SourceGenerators/Mapper/MintPlayer.Mapper/AnalyzerReleases.Unshipped.md
index ca11c578..4b80cba1 100644
--- a/SourceGenerators/Mapper/MintPlayer.Mapper/AnalyzerReleases.Unshipped.md
+++ b/SourceGenerators/Mapper/MintPlayer.Mapper/AnalyzerReleases.Unshipped.md
@@ -7,5 +7,5 @@ Rule ID | Category | Severity | Notes
 --------|----------|----------|-------
 MAPC001 | MapperGenerator | Error | DiagnosticRules
 MAPC002 | MapperGenerator | Error | DiagnosticRules
-MAPC003 | MapperGenerator | Error | DiagnosticRules
+MAPC003 | Mapping | Warning | DiagnosticRules
 MAPC004 | MapperGenerator | Error | DiagnosticRules
\ No newline at end of file
diff --git a/SourceGenerators/Mapper/MintPlayer.Mapper/Generators/MapperGenerator.Producer.cs b/SourceGenerators/Mapper/MintPlayer.Mapper/Generators/MapperGenerator.Producer.cs
index 6a9fb3ca..83bbe938 100644
--- a/SourceGenerators/Mapper/MintPlayer.Mapper/Generators/MapperGenerator.Producer.cs
+++ b/SourceGenerators/Mapper/MintPlayer.Mapper/Generators/MapperGenerator.Producer.cs
@@ -26,7 +26,9 @@ public IEnumerable<Diagnostic> GetDiagnostics()
                 EAppliedOn.Assembly => DiagnosticRules.GenerateMapperTwoParameters.Create(type.TypeToMap.Location),
                 _ => null,
             })
-            .NotNull();
+            .NotNull()
+            .Concat()
+            ;
     }
 
     protected override void ProduceSource(IndentedTextWriter writer, CancellationToken cancellationToken)
@@ -294,6 +296,9 @@ private static string GetElementType(string collectionType)
 
     private static void HandleProperty(IndentedTextWriter writer, PropertyDeclaration source, PropertyDeclaration destination, EWriteType writeType)
     {
+        // Skip init-only properties for assignment
+        if (destination.IsInitOnly) return;
+
         var prefix = writeType switch
         {
             EWriteType.Initializer => $"{source.PropertyName} = ",
diff --git a/SourceGenerators/Mapper/MintPlayer.Mapper/Generators/MapperGenerator.Rules.cs b/SourceGenerators/Mapper/MintPlayer.Mapper/Generators/MapperGenerator.Rules.cs
index f68acad1..ca7c2be9 100644
--- a/SourceGenerators/Mapper/MintPlayer.Mapper/Generators/MapperGenerator.Rules.cs
+++ b/SourceGenerators/Mapper/MintPlayer.Mapper/Generators/MapperGenerator.Rules.cs
@@ -19,4 +19,12 @@ public static partial class DiagnosticRules
         category: "MapperGenerator",
         defaultSeverity: DiagnosticSeverity.Error,
         isEnabledByDefault: true);
+
+    public static readonly DiagnosticDescriptor InitOnlyPropertyNotMapped = new(
+        id: "MAPC003",
+        title: "Init-only property not mapped",
+        messageFormat: "The property '{0}' on type '{1}' is init-only and will not be mapped from '{2}'",
+        category: "Mapping",
+        defaultSeverity: DiagnosticSeverity.Warning,
+        isEnabledByDefault: true);
 }
\ No newline at end of file
diff --git a/SourceGenerators/Mapper/MintPlayer.Mapper/Generators/MapperGenerator.cs b/SourceGenerators/Mapper/MintPlayer.Mapper/Generators/MapperGenerator.cs
index d459ac53..29380d0d 100644
--- a/SourceGenerators/Mapper/MintPlayer.Mapper/Generators/MapperGenerator.cs
+++ b/SourceGenerators/Mapper/MintPlayer.Mapper/Generators/MapperGenerator.cs
@@ -273,6 +273,7 @@ private static string CreateMethodName(TypedConstant preferred, INamedTypeSymbol
                 //IsNullable = p.NullableAnnotation == NullableAnnotation.Annotated,
                 //IsReadOnly = p.IsReadOnly,
                 IsStatic = p.IsStatic,
+                IsInitOnly = p.SetMethod is { IsInitOnly: true },
                 //IsVirtual = p.IsVirtual,
                 //IsAbstract = p.IsAbstract,
                 //IsOverride = p.IsOverride,
diff --git a/SourceGenerators/Mapper/MintPlayer.Mapper/Models/PropertyDeclaration.cs b/SourceGenerators/Mapper/MintPlayer.Mapper/Models/PropertyDeclaration.cs
index bc37b746..07213eab 100644
--- a/SourceGenerators/Mapper/MintPlayer.Mapper/Models/PropertyDeclaration.cs
+++ b/SourceGenerators/Mapper/MintPlayer.Mapper/Models/PropertyDeclaration.cs
@@ -12,6 +12,7 @@ public partial class PropertyDeclaration
     public int? StateName { get; set; }
     public bool IsStatic { get; set; }
     public bool IsPrimitive { get; set; }
+    public bool IsInitOnly { get; set; }
 
     public override string ToString() => $"{PropertyName} ({PropertyType})";
 }