From 606f89d95761be435885915b2e59ed83f1300b37 Mon Sep 17 00:00:00 2001
From: dfedoryshchev <dmitriy.fedoryshchev@gmail.com>
Date: Thu, 13 Aug 2026 15:54:27 +0100
Subject: [PATCH] Fix ChatResponseUpdate.Clone dropping ContinuationToken

Clone() copied every settable property except ContinuationToken, so a
cloned update lost the token needed to resume a background streaming
response.

Extended Clone_CreatesShallowCopy to cover the property.
---
 .../ChatCompletion/ChatResponseUpdate.cs                       | 1 +
 .../ChatCompletion/ChatResponseUpdateTests.cs                  | 3 +++
 2 files changed, 4 insertions(+)

diff --git a/src/Libraries/Microsoft.Extensions.AI.Abstractions/ChatCompletion/ChatResponseUpdate.cs b/src/Libraries/Microsoft.Extensions.AI.Abstractions/ChatCompletion/ChatResponseUpdate.cs
index 2637a41cf67..37611996924 100644
--- a/src/Libraries/Microsoft.Extensions.AI.Abstractions/ChatCompletion/ChatResponseUpdate.cs
+++ b/src/Libraries/Microsoft.Extensions.AI.Abstractions/ChatCompletion/ChatResponseUpdate.cs
@@ -71,6 +71,7 @@ public ChatResponseUpdate Clone() =>
             AdditionalProperties = AdditionalProperties,
             AuthorName = AuthorName,
             Contents = Contents,
+            ContinuationToken = ContinuationToken,
             CreatedAt = CreatedAt,
             ConversationId = ConversationId,
             FinishReason = FinishReason,
diff --git a/test/Libraries/Microsoft.Extensions.AI.Abstractions.Tests/ChatCompletion/ChatResponseUpdateTests.cs b/test/Libraries/Microsoft.Extensions.AI.Abstractions.Tests/ChatCompletion/ChatResponseUpdateTests.cs
index fba280aceff..83896c336b4 100644
--- a/test/Libraries/Microsoft.Extensions.AI.Abstractions.Tests/ChatCompletion/ChatResponseUpdateTests.cs
+++ b/test/Libraries/Microsoft.Extensions.AI.Abstractions.Tests/ChatCompletion/ChatResponseUpdateTests.cs
@@ -246,12 +246,14 @@ public void Clone_CreatesShallowCopy()
         var originalContents = new List<AIContent> { new TextContent("text1"), new TextContent("text2") };
         var originalRawRepresentation = new object();
         var originalCreatedAt = new DateTimeOffset(2022, 1, 1, 0, 0, 0, TimeSpan.Zero);
+        var originalContinuationToken = ResponseContinuationToken.FromBytes(new byte[] { 1, 2, 3 });
 
         var original = new ChatResponseUpdate
         {
             AdditionalProperties = originalAdditionalProperties,
             AuthorName = "author",
             Contents = originalContents,
+            ContinuationToken = originalContinuationToken,
             CreatedAt = originalCreatedAt,
             ConversationId = "conv123",
             FinishReason = ChatFinishReason.ContentFilter,
@@ -282,6 +284,7 @@ public void Clone_CreatesShallowCopy()
         Assert.Same(original.AdditionalProperties, clone.AdditionalProperties);
         Assert.Same(original.Contents, clone.Contents);
         Assert.Same(original.RawRepresentation, clone.RawRepresentation);
+        Assert.Same(original.ContinuationToken, clone.ContinuationToken);
     }
 
     [Fact]