diff --git a/DeepDrftPublic.Client/Common/SeoJsonLd.cs b/DeepDrftPublic.Client/Common/SeoJsonLd.cs
index 9c256fa..d9c5d61 100644
--- a/DeepDrftPublic.Client/Common/SeoJsonLd.cs
+++ b/DeepDrftPublic.Client/Common/SeoJsonLd.cs
@@ -63,7 +63,7 @@ public abstract record JsonLdNode
 /// <summary>The Deep DRFT collective entity — the home/about node.</summary>
 public sealed record MusicGroupNode : JsonLdNode
 {
-    public override string Type => "MusicGroup";
+    [JsonPropertyName("@type")] public override string Type => "MusicGroup";
 
     [JsonPropertyName("name")] public string Name { get; init; } = string.Empty;
     [JsonPropertyName("url")] public string? Url { get; init; }
@@ -76,7 +76,7 @@ public sealed record MusicGroupNode : JsonLdNode
 /// <summary>A studio cut or a live session release. <c>AlbumProductionType</c> distinguishes them.</summary>
 public sealed record MusicAlbumNode : JsonLdNode
 {
-    public override string Type => "MusicAlbum";
+    [JsonPropertyName("@type")] public override string Type => "MusicAlbum";
 
     [JsonPropertyName("name")] public string Name { get; init; } = string.Empty;
     [JsonPropertyName("byArtist")] public ArtistRef? ByArtist { get; init; }
@@ -96,7 +96,7 @@ public sealed record MusicAlbumNode : JsonLdNode
 /// <summary>A single recording — a mix release, or one track inside an album's <c>track</c> list.</summary>
 public sealed record MusicRecordingNode : JsonLdNode
 {
-    public override string Type => "MusicRecording";
+    [JsonPropertyName("@type")] public override string Type => "MusicRecording";
 
     [JsonPropertyName("name")] public string Name { get; init; } = string.Empty;
     [JsonPropertyName("byArtist")] public ArtistRef? ByArtist { get; init; }
@@ -112,7 +112,7 @@ public sealed record MusicRecordingNode : JsonLdNode
 /// <summary>A browse/index surface listing releases (cuts/sessions/mixes/archive).</summary>
 public sealed record CollectionPageNode : JsonLdNode
 {
-    public override string Type => "CollectionPage";
+    [JsonPropertyName("@type")] public override string Type => "CollectionPage";
 
     [JsonPropertyName("name")] public string Name { get; init; } = string.Empty;
     [JsonPropertyName("description")] public string? Description { get; init; }
diff --git a/DeepDrftTests/SeoModelTests.cs b/DeepDrftTests/SeoModelTests.cs
index b6dc92a..41fcace 100644
--- a/DeepDrftTests/SeoModelTests.cs
+++ b/DeepDrftTests/SeoModelTests.cs
@@ -268,6 +268,121 @@ public class SeoModelTests
             Is.EqualTo("Aphex Twin"));
     }
 
+    // --- AC5 regression: no stray CLR `Type` property emitted alongside `@type` ---
+    // System.Text.Json previously emitted both `@type` (from the base [JsonPropertyName]) and `Type`
+    // (the raw CLR override name) on concrete derived nodes, failing the schema.org validator.
+    // The fix: repeat [JsonPropertyName("@type")] directly on each concrete override.
+
+    [Test]
+    public void MusicAlbumNode_SerializesAtType_OnlyOnce_NoBareTypeProperty()
+    {
+        var tracks = new List<TrackDto> { new() { TrackName = "T", TrackNumber = 1, DurationSeconds = 30 } };
+        var node = Parse(SeoModel.ForRelease(Options, Release(ReleaseMedium.Cut), tracks).JsonLd);
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(node.GetProperty("@type").GetString(), Is.EqualTo("MusicAlbum"),
+                "MusicAlbumNode must emit @type");
+            Assert.That(node.TryGetProperty("Type", out _), Is.False,
+                "MusicAlbumNode must NOT emit a bare Type property");
+        });
+    }
+
+    [Test]
+    public void MusicRecordingNode_TopLevel_SerializesAtType_NoBareTypeProperty()
+    {
+        var tracks = new List<TrackDto> { new() { TrackName = "The Mix", DurationSeconds = 3600 } };
+        var node = Parse(SeoModel.ForRelease(Options, Release(ReleaseMedium.Mix), tracks).JsonLd);
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(node.GetProperty("@type").GetString(), Is.EqualTo("MusicRecording"),
+                "MusicRecordingNode must emit @type");
+            Assert.That(node.TryGetProperty("Type", out _), Is.False,
+                "MusicRecordingNode must NOT emit a bare Type property");
+        });
+    }
+
+    [Test]
+    public void MusicRecordingNode_NestedTrack_SerializesAtType_NoBareTypeProperty()
+    {
+        // The nested track[] MusicRecordingNode is a different code path from the top-level mix node.
+        var tracks = new List<TrackDto> { new() { TrackName = "T", TrackNumber = 1, DurationSeconds = 30 } };
+        var albumNode = Parse(SeoModel.ForRelease(Options, Release(ReleaseMedium.Cut), tracks).JsonLd);
+        var trackNode = albumNode.GetProperty("track")[0];
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(trackNode.GetProperty("@type").GetString(), Is.EqualTo("MusicRecording"),
+                "nested MusicRecordingNode must emit @type");
+            Assert.That(trackNode.TryGetProperty("Type", out _), Is.False,
+                "nested MusicRecordingNode must NOT emit a bare Type property");
+        });
+    }
+
+    [Test]
+    public void MusicGroupNode_SerializesAtType_NoBareTypeProperty()
+    {
+        var node = Parse(SeoModel.ForHome(Options).JsonLd);
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(node.GetProperty("@type").GetString(), Is.EqualTo("MusicGroup"),
+                "MusicGroupNode must emit @type");
+            Assert.That(node.TryGetProperty("Type", out _), Is.False,
+                "MusicGroupNode must NOT emit a bare Type property");
+        });
+    }
+
+    [Test]
+    public void CollectionPageNode_SerializesAtType_NoBareTypeProperty()
+    {
+        var node = Parse(SeoModel.ForBrowse(Options, ReleaseMedium.Cut, "/cuts").JsonLd);
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(node.GetProperty("@type").GetString(), Is.EqualTo("CollectionPage"),
+                "CollectionPageNode must emit @type");
+            Assert.That(node.TryGetProperty("Type", out _), Is.False,
+                "CollectionPageNode must NOT emit a bare Type property");
+        });
+    }
+
+    [Test]
+    public void ArtistRef_NestedByArtist_SerializesAtType_NoBareTypeProperty()
+    {
+        // ArtistRef (byArtist) was already clean — this asserts it stays clean after the fix.
+        var node = Parse(SeoModel.ForRelease(Options, Release(ReleaseMedium.Cut)).JsonLd);
+        var byArtist = node.GetProperty("byArtist");
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(byArtist.GetProperty("@type").GetString(), Is.EqualTo("MusicGroup"),
+                "ArtistRef must emit @type");
+            Assert.That(byArtist.TryGetProperty("Type", out _), Is.False,
+                "ArtistRef must NOT emit a bare Type property");
+        });
+    }
+
+    [Test]
+    public void AllNodes_ContextIsPresent_AndSchemaOrg()
+    {
+        // Belt-and-suspenders: @context must not regress alongside the @type fix.
+        var nodes = new[]
+        {
+            Parse(SeoModel.ForHome(Options).JsonLd),
+            Parse(SeoModel.ForAbout(Options).JsonLd),
+            Parse(SeoModel.ForBrowse(Options, ReleaseMedium.Cut, "/cuts").JsonLd),
+            Parse(SeoModel.ForRelease(Options, Release(ReleaseMedium.Cut)).JsonLd),
+            Parse(SeoModel.ForRelease(Options, Release(ReleaseMedium.Session)).JsonLd),
+            Parse(SeoModel.ForRelease(Options, Release(ReleaseMedium.Mix)).JsonLd),
+        };
+
+        foreach (var node in nodes)
+            Assert.That(node.GetProperty("@context").GetString(), Is.EqualTo("https://schema.org"),
+                "@context must remain present after the @type fix");
+    }
+
     // --- Critical: inline JSON-LD script-breakout escaping (XSS) -----------------
 
     [Test]