feat: add support for citations when streaming

src/AnthropicClient/AnthropicApiClient.cs

@@ -124,10 +124,37 @@ public class AnthropicApiClient : IAnthropicApiClient
       // current content type and delta type
       if (currentEvent.Type is EventType.ContentBlockDelta && currentEvent.Data is ContentDeltaEventData contentDeltaData)
       {
-        if (content is TextContent textContent && contentDeltaData.Delta is TextDelta textDelta)
+        if (content is TextContent textContent)
         {
-          var newText = textContent.Text + textDelta.Text;
-          content = new TextContent(newText);
+          if (contentDeltaData.Delta is TextDelta textDelta)
+          {
+            var newText = textContent.Text + textDelta.Text;
+
+            content = new TextContent(newText)
+            {
+              Citations = textContent.Citations,
+            };
+          }
+
+          if (contentDeltaData.Delta is CitationDelta citationDelta)
+          {
+            var citations = new List<Citation>()
+            {
+              citationDelta.Citation,
+            };
+
+            if (textContent.Citations is not null)
+            {
+              citations.AddRange(textContent.Citations);
+            }
+
+            var newContent = new TextContent(textContent.Text)
+            {
+              Citations = [.. citations],
+            };
+
+            content = newContent;
+          }
         }
 
         if (content is ToolUseContent toolUseContent && contentDeltaData.Delta is JsonDelta jsonDelta)

src/AnthropicClient/Json/ContentDeltaConverter.cs

@@ -16,6 +16,7 @@ class ContentDeltaConverter : JsonConverter<ContentDelta>
     {
       ContentDeltaType.TextDelta => JsonSerializer.Deserialize<TextDelta>(root.GetRawText(), options)!,
       ContentDeltaType.JsonDelta => JsonSerializer.Deserialize<JsonDelta>(root.GetRawText(), options)!,
+      ContentDeltaType.CitationDelta => JsonSerializer.Deserialize<CitationDelta>(root.GetRawText(), options)!,
       _ => throw new JsonException($"Unknown content type: {type}")
     };
   }

src/AnthropicClient/Models/CitationDelta.cs

@@ -0,0 +1,30 @@
+using System.Text.Json.Serialization;
+
+using AnthropicClient.Utils;
+
+namespace AnthropicClient.Models;
+
+/// <summary>
+/// Represents a citation delta.
+/// </summary>
+public class CitationDelta : ContentDelta
+{
+  /// <summary>
+  /// Gets the citation associated with this delta.
+  /// </summary>
+  public Citation Citation { get; init; } = new CharacterLocationCitation();
+
+  [JsonConstructor]
+  internal CitationDelta() : base(ContentDeltaType.CitationDelta)
+  {
+  }
+
+  /// <summary>
+  /// Initializes a new instance of the <see cref="CitationDelta"/> class.
+  /// </summary>
+  public CitationDelta(Citation citation) : base(ContentDeltaType.CitationDelta)
+  {
+    ArgumentValidator.ThrowIfNull(citation, nameof(citation));
+    Citation = citation;
+  }
+}

src/AnthropicClient/Models/ContentDeltaType.cs

@@ -14,4 +14,9 @@ public static class ContentDeltaType
   /// The input_json_delta.
   /// </summary>
   public const string JsonDelta = "input_json_delta";
+
+  /// <summary>
+  /// The citation_delta.
+  /// </summary>
+  public const string CitationDelta = "citations_delta";
 }

tests/AnthropicClient.Tests/EndToEnd/AnthropicApiClientTests.cs

@@ -316,10 +316,7 @@ public class AnthropicApiClientTests(ConfigurationFixture configFixture) : EndTo
     var citations = result.Value
       .Content
       .OfType<TextContent>()
-      .SelectMany(static c =>
-      {
-        return c.Citations is null ? [] : c.Citations;
-      });
+      .SelectMany(static c => c.Citations is null ? [] : c.Citations);
 
     citations.OfType<CharacterLocationCitation>().Should().NotBeEmpty();
   }
@@ -398,6 +395,127 @@ public class AnthropicApiClientTests(ConfigurationFixture configFixture) : EndTo
     citations.OfType<ContentBlockLocationCitation>().Should().NotBeEmpty();
   }
 
+  [Fact]
+  public async Task CreateMessageAsync_WhenStreamingAndCitationsAreEnabledForTextDocumentSource_ItShouldReturnCitationsInResponse()
+  {
+    var request = new StreamMessageRequest(
+      model: AnthropicModels.Claude35HaikuLatest,
+      messages: [
+        new(
+          MessageRole.User,
+          [
+            new DocumentContent(
+              new TextSource("The grass is green. The sky is blue.")
+            )
+            {
+              Title = "My Document",
+              Context = "This is a trustworthy document.",
+              Citations = new() { Enabled = true }
+            },
+            new TextContent("What color is the grass and sky?"),
+          ]
+        )
+      ]
+    );
+
+    var result = _client.CreateMessageAsync(request);
+
+    var messageCompleteEvent = await result
+      .Where(e => e.Type is EventType.MessageComplete)
+      .FirstAsync();
+
+    var citations = messageCompleteEvent.Data
+      .As<MessageCompleteEventData>()
+      .Message
+      .Content
+      .OfType<TextContent>()
+      .SelectMany(static c => c.Citations is null ? [] : c.Citations);
+
+    citations.OfType<CharacterLocationCitation>().Should().NotBeEmpty();
+  }
+
+  [Fact]
+  public async Task CreateMessageAsync_WhenStreamingAndCitationsAreEnabledForPDFDocumentSource_ItShouldReturnCitationsInResponse()
+  {
+    var pdfPath = TestFileHelper.GetTestFilePath("addendum.pdf");
+    var bytes = await File.ReadAllBytesAsync(pdfPath);
+    var base64Data = Convert.ToBase64String(bytes);
+
+    var request = new StreamMessageRequest(
+      model: AnthropicModels.Claude35HaikuLatest,
+      messages: [
+        new(
+          MessageRole.User,
+          [
+            new DocumentContent("application/pdf", base64Data)
+            {
+              Title = "My PDF Document",
+              Context = "This is a trustworthy document.",
+              Citations = new() { Enabled = true }
+            },
+            new TextContent("What is the title of this paper?"),
+          ]
+        )
+      ]
+    );
+
+    var result = _client.CreateMessageAsync(request);
+
+    var messageCompleteEvent = await result
+      .Where(e => e.Type is EventType.MessageComplete)
+      .FirstAsync();
+
+    var citations = messageCompleteEvent.Data
+      .As<MessageCompleteEventData>()
+      .Message
+      .Content
+      .OfType<TextContent>()
+      .SelectMany(static c => c.Citations is null ? [] : c.Citations);
+
+    citations.OfType<PageLocationCitation>().Should().NotBeEmpty();
+  }
+
+  [Fact]
+  public async Task CreateMessageAsync_WhenStreamingAndCitationsAreEnabledForCustomDocumentSource_ItShouldReturnCitationsInResponse()
+  {
+    var request = new StreamMessageRequest(
+      model: AnthropicModels.Claude35HaikuLatest,
+      messages: [
+        new(
+          MessageRole.User,
+          [
+            new DocumentContent(
+              new CustomSource([
+                new TextContent("The grass is green. The sky is blue.")
+              ])
+            )
+            {
+              Title = "My Custom Document",
+              Context = "This is a trustworthy document.",
+              Citations = new() { Enabled = true }
+            },
+            new TextContent("What color is the grass and sky?"),
+          ]
+        )
+      ]
+    );
+
+    var result = _client.CreateMessageAsync(request);
+
+    var messageCompleteEvent = await result
+      .Where(e => e.Type is EventType.MessageComplete)
+      .FirstAsync();
+
+    var citations = messageCompleteEvent.Data
+      .As<MessageCompleteEventData>()
+      .Message
+      .Content
+      .OfType<TextContent>()
+      .SelectMany(static c => c.Citations is null ? [] : c.Citations);
+
+    citations.OfType<ContentBlockLocationCitation>().Should().NotBeEmpty();
+  }
+
   [Fact]
   public async Task CountMessageTokensAsync_WhenCalled_ItShouldReturnResponse()
   {