Add reasoning text content for OpenAI Responses ChatClient Streaming (#6761)

* Add reasoning text content for OpenAI Responses ChatClient Streaming

---------

Co-authored-by: Stephen Toub <[email protected]>

Author: rogerbarreto

src/Libraries/Microsoft.Extensions.AI.OpenAI/OpenAIResponsesChatClient.cs

@@ -4,6 +4,7 @@
 using System;
 using System.ClientModel.Primitives;
 using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using System.Reflection;
 using System.Runtime.CompilerServices;
@@ -26,6 +27,11 @@ namespace Microsoft.Extensions.AI;
 /// <summary>Represents an <see cref="IChatClient"/> for an <see cref="OpenAIResponseClient"/>.</summary>
 internal sealed class OpenAIResponsesChatClient : IChatClient
 {
+    // Fix this to not use reflection once https://github.com/openai/openai-dotnet/issues/643 is addressed.
+    [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicProperties)]
+    private static readonly Type? _internalResponseReasoningSummaryTextDeltaEventType = Type.GetType("OpenAI.Responses.InternalResponseReasoningSummaryTextDeltaEvent, OpenAI");
+    private static readonly PropertyInfo? _summaryTextDeltaProperty = _internalResponseReasoningSummaryTextDeltaEventType?.GetProperty("Delta");
+
     /// <summary>Metadata about the client.</summary>
     private readonly ChatClientMetadata _metadata;
 
@@ -324,8 +330,17 @@ ChatResponseUpdate CreateUpdate(AIContent? content = null) =>
                     break;
 
                 default:
+                {
+                    if (streamingUpdate.GetType() == _internalResponseReasoningSummaryTextDeltaEventType &&
+                        _summaryTextDeltaProperty?.GetValue(streamingUpdate) is string delta)
+                    {
+                        yield return CreateUpdate(new TextReasoningContent(delta));
+                        break;
+                    }
+
                     yield return CreateUpdate();
                     break;
+                }
             }
         }
     }

test/Libraries/Microsoft.Extensions.AI.OpenAI.Tests/OpenAIResponseClientTests.cs

@@ -168,6 +168,186 @@ public async Task BasicRequestResponse_NonStreaming()
         Assert.Equal(36, response.Usage.TotalTokenCount);
     }
 
+    [Fact]
+    public async Task BasicReasoningResponse_Streaming()
+    {
+        const string Input = """
+            {
+              "input":[{
+                "type":"message",
+                "role":"user",
+                "content":[{
+                  "type":"input_text",
+                  "text":"Calculate the sum of the first 5 positive integers."
+                }]
+              }],
+              "reasoning": {
+                "summary": "detailed",
+                "effort": "low"
+              },
+              "model": "o4-mini",
+              "stream": true
+            }
+            """;
+
+        // Compressed down for testing purposes; real-world output would be larger.
+        const string Output = """
+            event: response.created
+            data: {"type":"response.created","sequence_number":0,"response":{"id":"resp_68b5ebab461881969ed94149372c2a530698ecbf1b9f2704","object":"response","created_at":1756752811,"status":"in_progress","background":false,"error":null,"incomplete_details":null,"instructions":null,"max_output_tokens":null,"max_tool_calls":null,"model":"o4-mini-2025-04-16","output":[],"parallel_tool_calls":true,"previous_response_id":null,"prompt_cache_key":null,"reasoning":{"effort":"low","summary":"detailed"},"safety_identifier":null,"service_tier":"auto","store":true,"temperature":1.0,"text":{"format":{"type":"text"},"verbosity":"medium"},"tool_choice":"auto","tools":[],"top_logprobs":0,"top_p":1.0,"truncation":"disabled","usage":null,"user":null,"metadata":{}}}
+
+            event: response.in_progress
+            data: {"type":"response.in_progress","sequence_number":1,"response":{"id":"resp_68b5ebab461881969ed94149372c2a530698ecbf1b9f2704","object":"response","created_at":1756752811,"status":"in_progress","background":false,"error":null,"incomplete_details":null,"instructions":null,"max_output_tokens":null,"max_tool_calls":null,"model":"o4-mini-2025-04-16","output":[],"parallel_tool_calls":true,"previous_response_id":null,"prompt_cache_key":null,"reasoning":{"effort":"low","summary":"detailed"},"safety_identifier":null,"service_tier":"auto","store":true,"temperature":1.0,"text":{"format":{"type":"text"},"verbosity":"medium"},"tool_choice":"auto","tools":[],"top_logprobs":0,"top_p":1.0,"truncation":"disabled","usage":null,"user":null,"metadata":{}}}
+
+            event: response.output_item.added
+            data: {"type":"response.output_item.added","sequence_number":2,"output_index":0,"item":{"id":"rs_68b5ebabc0088196afb9fa86b487732d0698ecbf1b9f2704","type":"reasoning","summary":[]}}
+
+            event: response.reasoning_summary_part.added
+            data: {"type":"response.reasoning_summary_part.added","sequence_number":3,"item_id":"rs_68b5ebabc0088196afb9fa86b487732d0698ecbf1b9f2704","output_index":0,"summary_index":0,"part":{"type":"summary_text","text":""}}
+
+            event: response.reasoning_summary_text.delta
+            data: {"type":"response.reasoning_summary_text.delta","sequence_number":4,"item_id":"rs_68b5ebabc0088196afb9fa86b487732d0698ecbf1b9f2704","output_index":0,"summary_index":0,"delta":"**Calcul","obfuscation":"sLkbFySM"}
+
+            event: response.reasoning_summary_text.delta
+            data: {"type":"response.reasoning_summary_text.delta","sequence_number":5,"item_id":"rs_68b5ebabc0088196afb9fa86b487732d0698ecbf1b9f2704","output_index":0,"summary_index":0,"delta":"ating","obfuscation":"dkm1f6DKqUj"}
+
+            event: response.reasoning_summary_text.delta
+            data: {"type":"response.reasoning_summary_text.delta","sequence_number":6,"item_id":"rs_68b5ebabc0088196afb9fa86b487732d0698ecbf1b9f2704","output_index":0,"summary_index":0,"delta":" a","obfuscation":"X8ahc2lfCf9eA1"}
+
+            event: response.reasoning_summary_text.delta
+            data: {"type":"response.reasoning_summary_text.delta","sequence_number":7,"item_id":"rs_68b5ebabc0088196afb9fa86b487732d0698ecbf1b9f2704","output_index":0,"summary_index":0,"delta":" simple","obfuscation":"1rLVyIaNl"}
+
+            event: response.reasoning_summary_text.delta
+            data: {"type":"response.reasoning_summary_text.delta","sequence_number":8,"item_id":"rs_68b5ebabc0088196afb9fa86b487732d0698ecbf1b9f2704","output_index":0,"summary_index":0,"delta":" sum","obfuscation":"jCK7mgNR80Re"}
+
+            event: response.reasoning_summary_text.done
+            data: {"type":"response.reasoning_summary_text.done","sequence_number":9,"item_id":"rs_68b5ebabc0088196afb9fa86b487732d0698ecbf1b9f2704","output_index":0,"summary_index":0,"text":"**Calculating a simple sum**"}
+
+            event: response.reasoning_summary_part.done
+            data: {"type":"response.reasoning_summary_part.done","sequence_number":10,"item_id":"rs_68b5ebabc0088196afb9fa86b487732d0698ecbf1b9f2704","output_index":0,"summary_index":0,"part":{"type":"summary_text","text":"**Calculating a simple sum**"}}
+
+            event: response.output_item.done
+            data: {"type":"response.output_item.done","sequence_number":11,"output_index":0,"item":{"id":"rs_68b5ebabc0088196afb9fa86b487732d0698ecbf1b9f2704","type":"reasoning","summary":[{"type":"summary_text","text":"**Calculating a simple sum**"}]}}
+
+            event: response.output_item.added
+            data: {"type":"response.output_item.added","sequence_number":12,"output_index":1,"item":{"id":"msg_68b5ebae5a708196b74b94f22ca8995e0698ecbf1b9f2704","type":"message","status":"in_progress","content":[],"role":"assistant"}}
+
+            event: response.content_part.added
+            data: {"type":"response.content_part.added","sequence_number":13,"item_id":"msg_68b5ebae5a708196b74b94f22ca8995e0698ecbf1b9f2704","output_index":1,"content_index":0,"part":{"type":"output_text","annotations":[],"logprobs":[],"text":""}}
+
+            event: response.output_text.delta
+            data: {"type":"response.output_text.delta","sequence_number":14,"item_id":"msg_68b5ebae5a708196b74b94f22ca8995e0698ecbf1b9f2704","output_index":1,"content_index":0,"delta":"The","logprobs":[],"obfuscation":"japg2KaCkjNsp"}
+
+            event: response.output_text.delta
+            data: {"type":"response.output_text.delta","sequence_number":15,"item_id":"msg_68b5ebae5a708196b74b94f22ca8995e0698ecbf1b9f2704","output_index":1,"content_index":0,"delta":" sum","logprobs":[],"obfuscation":"1BEqjKQ0KU41"}
+
+            event: response.output_text.delta
+            data: {"type":"response.output_text.delta","sequence_number":16,"item_id":"msg_68b5ebae5a708196b74b94f22ca8995e0698ecbf1b9f2704","output_index":1,"content_index":0,"delta":" of","logprobs":[],"obfuscation":"GUqom1rsdZsnT"}
+
+            event: response.output_text.delta
+            data: {"type":"response.output_text.delta","sequence_number":17,"item_id":"msg_68b5ebae5a708196b74b94f22ca8995e0698ecbf1b9f2704","output_index":1,"content_index":0,"delta":" the","logprobs":[],"obfuscation":"UmCms91yrTlg"}
+
+            event: response.output_text.delta
+            data: {"type":"response.output_text.delta","sequence_number":18,"item_id":"msg_68b5ebae5a708196b74b94f22ca8995e0698ecbf1b9f2704","output_index":1,"content_index":0,"delta":" first","logprobs":[],"obfuscation":"AyNbZpfTXo"}
+
+            event: response.output_text.delta
+            data: {"type":"response.output_text.delta","sequence_number":19,"item_id":"msg_68b5ebae5a708196b74b94f22ca8995e0698ecbf1b9f2704","output_index":1,"content_index":0,"delta":" ","logprobs":[],"obfuscation":"tuyz4HkKODFQRtk"}
+
+            event: response.output_text.delta
+            data: {"type":"response.output_text.delta","sequence_number":20,"item_id":"msg_68b5ebae5a708196b74b94f22ca8995e0698ecbf1b9f2704","output_index":1,"content_index":0,"delta":"5","logprobs":[],"obfuscation":"QAwyISolmjXfTlc"}
+
+            event: response.output_text.delta
+            data: {"type":"response.output_text.delta","sequence_number":21,"item_id":"msg_68b5ebae5a708196b74b94f22ca8995e0698ecbf1b9f2704","output_index":1,"content_index":0,"delta":" positive","logprobs":[],"obfuscation":"2Euge1H"}
+
+            event: response.output_text.delta
+            data: {"type":"response.output_text.delta","sequence_number":22,"item_id":"msg_68b5ebae5a708196b74b94f22ca8995e0698ecbf1b9f2704","output_index":1,"content_index":0,"delta":" integers","logprobs":[],"obfuscation":"ih0Znt8"}
+
+            event: response.output_text.delta
+            data: {"type":"response.output_text.delta","sequence_number":23,"item_id":"msg_68b5ebae5a708196b74b94f22ca8995e0698ecbf1b9f2704","output_index":1,"content_index":0,"delta":" is","logprobs":[],"obfuscation":"oQihR5Pw8jRz5"}
+
+            event: response.output_text.delta
+            data: {"type":"response.output_text.delta","sequence_number":24,"item_id":"msg_68b5ebae5a708196b74b94f22ca8995e0698ecbf1b9f2704","output_index":1,"content_index":0,"delta":" 15","logprobs":[],"obfuscation":"7TdJ1FWlZF8lTd"}
+
+            event: response.output_text.delta
+            data: {"type":"response.output_text.delta","sequence_number":25,"item_id":"msg_68b5ebae5a708196b74b94f22ca8995e0698ecbf1b9f2704","output_index":1,"content_index":0,"delta":".","logprobs":[],"obfuscation":"x2VAJKlWI8qjgYq"}
+
+            event: response.output_text.done
+            data: {"type":"response.output_text.done","sequence_number":26,"item_id":"msg_68b5ebae5a708196b74b94f22ca8995e0698ecbf1b9f2704","output_index":1,"content_index":0,"text":"The sum of the first 5 positive integers is 15.","logprobs":[]}
+
+            event: response.content_part.done
+            data: {"type":"response.content_part.done","sequence_number":27,"item_id":"msg_68b5ebae5a708196b74b94f22ca8995e0698ecbf1b9f2704","output_index":1,"content_index":0,"part":{"type":"output_text","annotations":[],"logprobs":[],"text":"The sum of the first 5 positive integers is 15."}}
+
+            event: response.output_item.done
+            data: {"type":"response.output_item.done","sequence_number":28,"output_index":1,"item":{"id":"msg_68b5ebae5a708196b74b94f22ca8995e0698ecbf1b9f2704","type":"message","status":"completed","content":[{"type":"output_text","annotations":[],"logprobs":[],"text":"The sum of the first 5 positive integers is 15."}],"role":"assistant"}}
+
+            event: response.completed
+            data: {"type":"response.completed","sequence_number":29,"response":{"id":"resp_68b5ebab461881969ed94149372c2a530698ecbf1b9f2704","object":"response","created_at":1756752811,"status":"completed","background":false,"error":null,"incomplete_details":null,"instructions":null,"max_output_tokens":null,"max_tool_calls":null,"model":"o4-mini-2025-04-16","output":[{"id":"rs_68b5ebabc0088196afb9fa86b487732d0698ecbf1b9f2704","type":"reasoning","summary":[{"type":"summary_text","text":"**Calculating a simple sum**"}]},{"id":"msg_68b5ebae5a708196b74b94f22ca8995e0698ecbf1b9f2704","type":"message","status":"completed","content":[{"type":"output_text","annotations":[],"logprobs":[],"text":"The sum of the first 5 positive integers is 15."}],"role":"assistant"}],"parallel_tool_calls":true,"previous_response_id":null,"prompt_cache_key":null,"reasoning":{"effort":"low","summary":"detailed"},"safety_identifier":null,"service_tier":"default","store":true,"temperature":1.0,"text":{"format":{"type":"text"},"verbosity":"medium"},"tool_choice":"auto","tools":[],"top_logprobs":0,"top_p":1.0,"truncation":"disabled","usage":{"input_tokens":17,"input_tokens_details":{"cached_tokens":0},"output_tokens":122,"output_tokens_details":{"reasoning_tokens":64},"total_tokens":139},"user":null,"metadata":{}}}
+
+
+            """;
+
+        using VerbatimHttpHandler handler = new(Input, Output);
+        using HttpClient httpClient = new(handler);
+        using IChatClient client = CreateResponseClient(httpClient, "o4-mini");
+
+        List<ChatResponseUpdate> updates = [];
+        await foreach (var update in client.GetStreamingResponseAsync("Calculate the sum of the first 5 positive integers.", new()
+        {
+            RawRepresentationFactory = options => new ResponseCreationOptions
+            {
+                ReasoningOptions = new()
+                {
+                    ReasoningEffortLevel = ResponseReasoningEffortLevel.Low,
+                    ReasoningSummaryVerbosity = ResponseReasoningSummaryVerbosity.Detailed
+                }
+            }
+        }))
+        {
+            updates.Add(update);
+        }
+
+        Assert.Equal("The sum of the first 5 positive integers is 15.", string.Concat(updates.Select(u => u.Text)));
+
+        var createdAt = DateTimeOffset.FromUnixTimeSeconds(1_756_752_811);
+        Assert.Equal(30, updates.Count);
+
+        for (int i = 0; i < updates.Count; i++)
+        {
+            Assert.Equal("resp_68b5ebab461881969ed94149372c2a530698ecbf1b9f2704", updates[i].ResponseId);
+            Assert.Equal("resp_68b5ebab461881969ed94149372c2a530698ecbf1b9f2704", updates[i].ConversationId);
+            Assert.Equal(createdAt, updates[i].CreatedAt);
+            Assert.Equal("o4-mini-2025-04-16", updates[i].ModelId);
+            Assert.Null(updates[i].AdditionalProperties);
+
+            if (i is (>= 4 and <= 8))
+            {
+                // Reasoning updates
+                Assert.Single(updates[i].Contents);
+                Assert.Null(updates[i].Role);
+
+                var reasoning = Assert.IsType<TextReasoningContent>(updates[i].Contents.Single());
+                Assert.NotNull(reasoning);
+                Assert.NotNull(reasoning.Text);
+            }
+            else if (i is (>= 14 and <= 25) or 29)
+            {
+                // Response Complete and Assistant message updates
+                Assert.Single(updates[i].Contents);
+            }
+            else
+            {
+                // Other updates
+                Assert.Empty(updates[i].Contents);
+            }
+
+            Assert.Equal(i < updates.Count - 1 ? null : ChatFinishReason.Stop, updates[i].FinishReason);
+        }
+
+        UsageContent usage = updates.SelectMany(u => u.Contents).OfType<UsageContent>().Single();
+        Assert.Equal(17, usage.Details.InputTokenCount);
+        Assert.Equal(122, usage.Details.OutputTokenCount);
+        Assert.Equal(139, usage.Details.TotalTokenCount);
+    }
+
     [Fact]
     public async Task BasicRequestResponse_Streaming()
     {