diff --git a/src/AnthropicClient/Json/SourceConverter.cs b/src/AnthropicClient/Json/SourceConverter.cs
index 642295d..f8dd163 100644
--- a/src/AnthropicClient/Json/SourceConverter.cs
+++ b/src/AnthropicClient/Json/SourceConverter.cs
@@ -23,8 +23,12 @@ class SourceConverter : JsonConverter<Source>
 
   private static Source DeserializeBase64Source(JsonElement root, JsonSerializerOptions options)
   {
-    var mediaType = root.GetProperty("media_type").GetString() ?? throw new JsonException("Missing 'media_type' property");
+    var mediaType = root.TryGetProperty("media_type", out var mediaTypeElement)
+      ? mediaTypeElement.GetString() ?? throw new JsonException("Missing 'media_type' property")
+      : throw new JsonException("Missing 'media_type' property");
+
     var isImage = ImageType.IsValidImageType(mediaType);
+
     return isImage
       ? JsonSerializer.Deserialize<ImageSource>(root.GetRawText(), options)!
       : JsonSerializer.Deserialize<DocumentSource>(root.GetRawText(), options)!;
diff --git a/src/AnthropicClient/Models/Citation.cs b/src/AnthropicClient/Models/Citation.cs
index db42878..e502e5b 100644
--- a/src/AnthropicClient/Models/Citation.cs
+++ b/src/AnthropicClient/Models/Citation.cs
@@ -30,11 +30,6 @@ public abstract class Citation
   [JsonPropertyName("document_title")]
   public string DocumentTitle { get; init; } = string.Empty;
 
-  [JsonConstructor]
-  internal Citation()
-  {
-  }
-
   /// <summary>
   /// Initializes a new instance of the <see cref="Citation"/> class with a specified type.
   /// </summary>
diff --git a/tests/AnthropicClient.Tests/Data/EventTestData.cs b/tests/AnthropicClient.Tests/Data/EventTestData.cs
index 6fe6a87..ea08c7f 100644
--- a/tests/AnthropicClient.Tests/Data/EventTestData.cs
+++ b/tests/AnthropicClient.Tests/Data/EventTestData.cs
@@ -24,7 +24,13 @@ public class EventTestData : IEnumerable<object[]>
         Usage = new Usage { InputTokens = 472, OutputTokens = 91 },
         StopReason = "tool_use",
         Content = [
-          new TextContent("Okay, let's check the weather for San Francisco, CA:"),
+          new TextContent("Okay, let's check the weather for San Francisco, CA:")
+          {
+            Citations = [
+              new CharacterLocationCitation(),
+              new CharacterLocationCitation(),
+            ]
+          },
           new ToolUseContent()
           {
             Id = "toolu_01T1x1fJ34qAmk2tNTrN7Up6",
@@ -380,6 +386,46 @@ public class EventTestData : IEnumerable<object[]>
       },
     };
 
+    yield return new object[]
+    {
+      """
+      event: content_block_delta
+      data: {"type":"content_block_delta","index":0,"delta":{"type":"citations_delta","citation": {"type":"char_location","start_char_index":0,"end_char_index":0, "cited_text":"","document_index":0,"document_title":""}}}
+      """,
+      new AnthropicEvent()
+      {
+        Type = EventType.ContentBlockDelta,
+        Data = new ContentDeltaEventData()
+        {
+          Index = 0,
+          Delta = new CitationDelta()
+          {
+            Citation = new CharacterLocationCitation()
+          }
+        },
+      },
+    };
+
+    yield return new object[]
+    {
+      """
+      event: content_block_delta
+      data: {"type":"content_block_delta","index":0,"delta":{"type":"citations_delta","citation":{"type":"char_location","start_char_index":0,"end_char_index":0,"cited_text":"","document_index":0,"document_title":""}}}
+      """,
+      new AnthropicEvent()
+      {
+        Type = EventType.ContentBlockDelta,
+        Data = new ContentDeltaEventData()
+        {
+          Index = 0,
+          Delta = new CitationDelta()
+          {
+            Citation = new CharacterLocationCitation()
+          },
+        },
+      },
+    };
+
     yield return new object[]
     {
       """
diff --git a/tests/AnthropicClient.Tests/Unit/Json/SourceConverterTests.cs b/tests/AnthropicClient.Tests/Unit/Json/SourceConverterTests.cs
new file mode 100644
index 0000000..f62395c
--- /dev/null
+++ b/tests/AnthropicClient.Tests/Unit/Json/SourceConverterTests.cs
@@ -0,0 +1,31 @@
+namespace AnthropicClient.Tests.Unit.Json;
+
+public class SourceConverterTests : SerializationTest
+{
+  [Fact]
+  public void JsonDeserialization_WhenTypeIsUnknown_ItThrowsException()
+  {
+    var json = @"{ ""type"": ""unknown"" }";
+
+    var action = () => Deserialize<Source>(json);
+
+    action.Should().Throw<JsonException>();
+  }
+
+  [Fact]
+  public void JsonSerialization_WhenSourceIsNotKnown_ItShouldHaveExpectedShape()
+  {
+    var source = new TestSource();
+
+    var result = Serialize<Source>(source);
+
+    JsonAssert.Equal(@"{ ""type"": ""test"" }", result);
+  }
+
+  private class TestSource : Source
+  {
+    public TestSource() : base("test")
+    {
+    }
+  }
+}
\ No newline at end of file
diff --git a/tests/AnthropicClient.Tests/Unit/Models/Base64SourceTests.cs b/tests/AnthropicClient.Tests/Unit/Models/Base64SourceTests.cs
index 1a6972b..33761d7 100644
--- a/tests/AnthropicClient.Tests/Unit/Models/Base64SourceTests.cs
+++ b/tests/AnthropicClient.Tests/Unit/Models/Base64SourceTests.cs
@@ -1,7 +1,13 @@
 namespace AnthropicClient.Tests.Unit.Models;
 
-public class Base64SourceTests
+public class Base64SourceTests : SerializationTest
 {
+  private readonly string _testJson = @"{
+    ""type"": ""base64"",
+    ""media_type"": ""application/pdf"",
+    ""data"": ""base64data""
+  }";
+
   [Fact]
   public void Constructor_WhenCalledWithValidArguments_ItShouldSetProperties()
   {
@@ -36,4 +42,47 @@ public class Base64SourceTests
 
     action.Should().Throw<ArgumentNullException>();
   }
+
+  [Fact]
+  public void JsonSerialization_WhenSerialized_ItShouldHaveExpectedShape()
+  {
+    var mediaType = "application/pdf";
+    var data = "base64data";
+    var source = new Base64Source(mediaType, data);
+
+    var result = Serialize<Source>(source);
+
+    JsonAssert.Equal(_testJson, result);
+  }
+
+  [Fact]
+  public void JsonDeserialization_WhenDeserialized_ItShouldHaveExpectedShape()
+  {
+    var source = Deserialize<Source>(_testJson);
+
+    var base64Source = source.As<Base64Source>();
+    base64Source!.Type.Should().Be("base64");
+    base64Source.MediaType.Should().Be("application/pdf");
+    base64Source.Data.Should().Be("base64data");
+  }
+
+  [Fact]
+  public void JsonDeserialization_WhenMediaTypeIsMissing_ItShouldThrowException()
+  {
+    var json = @"{ ""type"": ""base64"", ""data"": ""base64data"" }";
+
+    var action = () => Deserialize<Source>(json);
+
+    action.Should().Throw<JsonException>();
+  }
+
+  [Fact]
+  public void JsonDeserialization_WhenMediaTypeIsNull_ItShouldThrowException()
+  {
+    var json = @"{ ""type"": ""base64"", ""media_type"": null, ""data"": ""base64data"" }";
+
+    var action = () => Deserialize<Source>(json);
+
+    action.Should().Throw<JsonException>();
+  }
 }
\ No newline at end of file
diff --git a/tests/AnthropicClient.Tests/Unit/Models/CustomSourceTests.cs b/tests/AnthropicClient.Tests/Unit/Models/CustomSourceTests.cs
index 53d8379..fd7dc0b 100644
--- a/tests/AnthropicClient.Tests/Unit/Models/CustomSourceTests.cs
+++ b/tests/AnthropicClient.Tests/Unit/Models/CustomSourceTests.cs
@@ -1,7 +1,17 @@
 namespace AnthropicClient.Tests.Unit.Models;
 
-public class CustomSourceTests
+public class CustomSourceTests : SerializationTest
 {
+  private readonly string _testJson = @"{
+    ""type"": ""content"",
+    ""content"": [
+      {
+        ""type"": ""text"",
+        ""text"": ""Sample text""
+      }
+    ]
+  }";
+
   [Fact]
   public void Constructor_WhenCalled_ItShouldSetProperties()
   {
@@ -32,4 +42,30 @@ public class CustomSourceTests
 
     act.Should().Throw<ArgumentNullException>();
   }
+
+  [Fact]
+  public void JsonSerialization_WhenSerialized_ItShouldHaveExpectedShape()
+  {
+    var content = new List<TextContent>
+    {
+      new("Sample text")
+    };
+    var source = new CustomSource(content);
+
+    var result = Serialize<Source>(source);
+
+    JsonAssert.Equal(_testJson, result);
+  }
+
+  [Fact]
+  public void JsonDeserialization_WhenDeserialized_ItShouldHaveExpectedShape()
+  {
+    var source = Deserialize<Source>(_testJson);
+
+    var customSource = source.As<CustomSource>();
+    customSource!.Type.Should().Be("content");
+    customSource.Content.Should().HaveCount(1);
+    customSource.Content[0].Type.Should().Be("text");
+    customSource.Content[0].Text.Should().Be("Sample text");
+  }
 }
\ No newline at end of file
diff --git a/tests/AnthropicClient.Tests/Unit/Models/TextSourceTests.cs b/tests/AnthropicClient.Tests/Unit/Models/TextSourceTests.cs
index eacdff3..dd9780c 100644
--- a/tests/AnthropicClient.Tests/Unit/Models/TextSourceTests.cs
+++ b/tests/AnthropicClient.Tests/Unit/Models/TextSourceTests.cs
@@ -1,7 +1,13 @@
 namespace AnthropicClient.Tests.Unit.Models;
 
-public class TextSourceTests
+public class TextSourceTests : SerializationTest
 {
+  private readonly string _testJson = @"{
+    ""type"": ""text"",
+    ""media_type"": ""text/plain"",
+    ""data"": ""data""
+  }";
+
   [Fact]
   public void Constructor_WhenCalled_ItShouldSetProperties()
   {
@@ -11,4 +17,25 @@ public class TextSourceTests
     result.MediaType.Should().Be("text/plain");
     result.Data.Should().Be("data");
   }
+
+  [Fact]
+  public void JsonSerialization_WhenSerialized_ItShouldHaveExpectedShape()
+  {
+    var source = new TextSource("data");
+
+    var result = Serialize<Source>(source);
+
+    JsonAssert.Equal(_testJson, result);
+  }
+
+  [Fact]
+  public void JsonDeserialization_WhenDeserialized_ItShouldHaveExpectedShape()
+  {
+    var source = Deserialize<Source>(_testJson);
+
+    var textSource = source.As<TextSource>();
+    textSource!.Type.Should().Be("text");
+    textSource.MediaType.Should().Be("text/plain");
+    textSource.Data.Should().Be("data");
+  }
 }
\ No newline at end of file