fix: preserve agent authorship across projections

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

sidecar/src/Eryx.AgentHost/Services/WorkflowTranscriptProjector.cs

@@ -32,7 +32,9 @@ internal static class WorkflowTranscriptProjector
         List<ChatMessageDto> mapped = [];
         int fallbackOutputIndex = 0;
         string createdAt = DateTimeOffset.UtcNow.ToString("O");
-        List<(string MessageId, string AuthorName, string Content)> remainingSegments = segments.ToList();
+        List<(string MessageId, string AuthorName, string Content)> preparedSegments =
+            PrepareSegmentsForProjection(command.Pattern, segments);
+        List<(string MessageId, string AuthorName, string Content)> remainingSegments = preparedSegments.ToList();
         List<ChatMessage> assistantMessages = newMessages.Where(message => message.Role != ChatRole.User).ToList();
 
         for (int messageIndex = 0; messageIndex < assistantMessages.Count; messageIndex++)
@@ -71,9 +73,9 @@ internal static class WorkflowTranscriptProjector
             });
         }
 
-        if (mapped.Count == 0 && segments.Count > 0)
+        if (mapped.Count == 0 && preparedSegments.Count > 0)
         {
-            mapped.AddRange(segments.Select(segment => new ChatMessageDto
+            mapped.AddRange(preparedSegments.Select(segment => new ChatMessageDto
             {
                 Id = segment.MessageId,
                 Role = "assistant",
@@ -86,6 +88,35 @@ internal static class WorkflowTranscriptProjector
         return mapped;
     }
 
+    private static List<(string MessageId, string AuthorName, string Content)> PrepareSegmentsForProjection(
+        PatternDefinitionDto pattern,
+        IReadOnlyList<(string MessageId, string AuthorName, string Content)> segments)
+    {
+        if (!string.Equals(pattern.Mode, "concurrent", StringComparison.Ordinal)
+            || segments.Count <= 1)
+        {
+            return segments.ToList();
+        }
+
+        // Agent Framework concurrent workflows aggregate the last message emitted by each agent.
+        // Collapse streamed segments to the most recent segment per author, preserving the order
+        // in which those authors most recently completed so positional fallback stays aligned.
+        Dictionary<string, ((string MessageId, string AuthorName, string Content) Segment, int LastIndex)> latestSegmentByAuthor =
+            new(StringComparer.Ordinal);
+
+        for (int index = 0; index < segments.Count; index++)
+        {
+            (string MessageId, string AuthorName, string Content) segment = segments[index];
+            string authorKey = AgentIdentityResolver.ResolveDisplayAuthorName(pattern, segment.AuthorName);
+            latestSegmentByAuthor[authorKey] = (segment, index);
+        }
+
+        return latestSegmentByAuthor.Values
+            .OrderBy(entry => entry.LastIndex)
+            .Select(entry => entry.Segment)
+            .ToList();
+    }
+
     private static (string MessageId, string AuthorName, string Content)? TryMatchSegment(
         ChatMessage message,
         IReadOnlyList<(string MessageId, string AuthorName, string Content)> remainingSegments,
@@ -107,22 +138,24 @@ internal static class WorkflowTranscriptProjector
                 fallbackIdentifier: null,
                 fallbackAgent);
 
-            (string MessageId, string AuthorName, string Content)? authorMatchedSegment = remainingSegments.FirstOrDefault(
-                segment => string.Equals(segment.Content, messageText, StringComparison.Ordinal)
-                    && string.Equals(
-                        AgentIdentityResolver.ResolveDisplayAuthorName(pattern, segment.AuthorName),
-                        resolvedAuthorName,
-                        StringComparison.Ordinal));
-            if (authorMatchedSegment.HasValue)
+            if (TryFindSegment(
+                    remainingSegments,
+                    segment => string.Equals(segment.Content, messageText, StringComparison.Ordinal)
+                        && string.Equals(
+                            AgentIdentityResolver.ResolveDisplayAuthorName(pattern, segment.AuthorName),
+                            resolvedAuthorName,
+                            StringComparison.Ordinal),
+                    out (string MessageId, string AuthorName, string Content) authorMatchedSegment))
             {
-                return authorMatchedSegment.Value;
+                return authorMatchedSegment;
             }
 
-            (string MessageId, string AuthorName, string Content)? contentMatchedSegment = remainingSegments.FirstOrDefault(
-                segment => string.Equals(segment.Content, messageText, StringComparison.Ordinal));
-            if (contentMatchedSegment.HasValue)
+            if (TryFindSegment(
+                    remainingSegments,
+                    segment => string.Equals(segment.Content, messageText, StringComparison.Ordinal),
+                    out (string MessageId, string AuthorName, string Content) contentMatchedSegment))
             {
-                return contentMatchedSegment.Value;
+                return contentMatchedSegment;
             }
         }
 
@@ -131,6 +164,24 @@ internal static class WorkflowTranscriptProjector
             : null;
     }
 
+    private static bool TryFindSegment(
+        IReadOnlyList<(string MessageId, string AuthorName, string Content)> segments,
+        Func<(string MessageId, string AuthorName, string Content), bool> predicate,
+        out (string MessageId, string AuthorName, string Content) matchedSegment)
+    {
+        foreach ((string MessageId, string AuthorName, string Content) segment in segments)
+        {
+            if (predicate(segment))
+            {
+                matchedSegment = segment;
+                return true;
+            }
+        }
+
+        matchedSegment = default;
+        return false;
+    }
+
     public static List<ChatMessage> SelectNewOutputMessages(
         IReadOnlyList<ChatMessage> outputMessages,
         IReadOnlyList<ChatMessage> inputMessages)

sidecar/tests/Eryx.AgentHost.Tests/CopilotWorkflowRunnerTests.cs

@@ -244,6 +244,75 @@ public sealed class CopilotWorkflowRunnerTests
             implementer => Assert.Equal("Implementer", implementer.AuthorName));
     }
 
+    [Fact]
+    public void ProjectCompletedMessages_ConcurrentUsesLastStreamedMessagePerAgentForGenericOutput()
+    {
+        RunTurnCommandDto command = new()
+        {
+            RequestId = "turn-1",
+            SessionId = "session-1",
+            Pattern = new PatternDefinitionDto
+            {
+                Id = "pattern-concurrent",
+                Name = "Concurrent Brainstorm",
+                Mode = "concurrent",
+                Availability = "available",
+                Agents =
+                [
+                    CreateAgent(id: "agent-concurrent-architect", name: "Architect"),
+                    CreateAgent(id: "agent-concurrent-product", name: "Product"),
+                    CreateAgent(id: "agent-concurrent-implementer", name: "Implementer"),
+                ],
+            },
+        };
+
+        IReadOnlyList<ChatMessageDto> messages = WorkflowTranscriptProjector.ProjectCompletedMessages(
+            command,
+            [
+                new ChatMessage(ChatRole.Assistant, "Architecture concerns with cleaner wording.")
+                {
+                    AuthorName = "assistant",
+                },
+                new ChatMessage(ChatRole.Assistant, "Product trade-offs with cleaned bullets.")
+                {
+                    AuthorName = "assistant",
+                },
+                new ChatMessage(ChatRole.Assistant, "Implementation details with cleaned formatting.")
+                {
+                    AuthorName = "assistant",
+                },
+            ],
+            [
+                ("msg-arch-1", "Architect", "Architecture concerns."),
+                ("msg-prod-1", "Product", "Product trade-offs."),
+                ("msg-impl-1", "Implementer", "Implementation details."),
+                ("msg-arch-2", "Architect", "Architecture concerns with extra draft spacing."),
+                ("msg-prod-2", "Product", "Product trade-offs with extra draft bullets."),
+                ("msg-impl-2", "Implementer", "Implementation details with extra draft formatting."),
+            ]);
+
+        Assert.Collection(
+            messages,
+            architect =>
+            {
+                Assert.Equal("msg-arch-2", architect.Id);
+                Assert.Equal("Architect", architect.AuthorName);
+                Assert.Equal("Architecture concerns with cleaner wording.", architect.Content);
+            },
+            product =>
+            {
+                Assert.Equal("msg-prod-2", product.Id);
+                Assert.Equal("Product", product.AuthorName);
+                Assert.Equal("Product trade-offs with cleaned bullets.", product.Content);
+            },
+            implementer =>
+            {
+                Assert.Equal("msg-impl-2", implementer.Id);
+                Assert.Equal("Implementer", implementer.AuthorName);
+                Assert.Equal("Implementation details with cleaned formatting.", implementer.Content);
+            });
+    }
+
     [Fact]
     public void ProjectCompletedMessages_PreservesGroupChatConversationHistory()
     {
@@ -293,6 +362,60 @@ public sealed class CopilotWorkflowRunnerTests
             });
     }
 
+    [Fact]
+    public void ProjectCompletedMessages_FallsBackToPositionWhenOutputTextDiffers()
+    {
+        RunTurnCommandDto command = new()
+        {
+            RequestId = "turn-1",
+            SessionId = "session-1",
+            Pattern = new PatternDefinitionDto
+            {
+                Id = "pattern-group-chat",
+                Name = "Collaborative Group Chat",
+                Mode = "group-chat",
+                Availability = "available",
+                Agents =
+                [
+                    CreateAgent(id: "agent-group-writer", name: "Writer"),
+                    CreateAgent(id: "agent-group-reviewer", name: "Reviewer"),
+                ],
+            },
+        };
+
+        IReadOnlyList<ChatMessageDto> messages = WorkflowTranscriptProjector.ProjectCompletedMessages(
+            command,
+            [
+                new ChatMessage(ChatRole.Assistant, "Initial draft with cleaner wording.")
+                {
+                    AuthorName = "assistant",
+                },
+                new ChatMessage(ChatRole.Assistant, "Review feedback with cleaner wording.")
+                {
+                    AuthorName = "assistant",
+                },
+            ],
+            [
+                ("msg-1", "Writer", "Initial draft with extra draft wording."),
+                ("msg-2", "Reviewer", "Review feedback with extra draft wording."),
+            ]);
+
+        Assert.Collection(
+            messages,
+            writer =>
+            {
+                Assert.Equal("msg-1", writer.Id);
+                Assert.Equal("Writer", writer.AuthorName);
+                Assert.Equal("Initial draft with cleaner wording.", writer.Content);
+            },
+            reviewer =>
+            {
+                Assert.Equal("msg-2", reviewer.Id);
+                Assert.Equal("Reviewer", reviewer.AuthorName);
+                Assert.Equal("Review feedback with cleaner wording.", reviewer.Content);
+            });
+    }
+
     [Fact]
     public void ProjectCompletedMessages_UsesFallbackAgentForGenericAssistantOutput()
     {