.NET: BugFix #3433 ChatClientAgent streaming responses missing messageid#4615
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Pull request overview
Fixes .NET streaming MessageId propagation for ChatClientAgent so AGUI/CopilotKit event conversion doesn’t emit messageId: null (Issue #3433).
Changes:
- Add fallback
MessageIdgeneration for streaming chunks when providers omit it. - Sync
MessageIdfromAgentResponseUpdateback into aChatResponseUpdateRawRepresentationduring conversion. - Add unit tests for
ChatClientAgent,AgentResponseUpdateconversion, and an AGUI pipeline coverage test.
Reviewed changes
Copilot reviewed 5 out of 5 changed files in this pull request and generated 4 comments.
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| File | Description |
|---|---|
| dotnet/src/Microsoft.Agents.AI/ChatClient/ChatClientAgent.cs | Adds per-stream fallback MessageId assignment for streaming updates. |
| dotnet/src/Microsoft.Agents.AI.Abstractions/AgentResponseExtensions.cs | Ensures AsChatResponseUpdate() can recover MessageId into RawRepresentation when missing. |
| dotnet/tests/Microsoft.Agents.AI.UnitTests/ChatClient/ChatClientAgentTests.cs | Adds tests for fallback MessageId generation and preserving provider IDs. |
| dotnet/tests/Microsoft.Agents.AI.Abstractions.UnitTests/AgentResponseUpdateExtensionsTests.cs | Adds tests verifying MessageId syncing behavior in AsChatResponseUpdate(). |
| dotnet/tests/Microsoft.Agents.AI.AGUI.UnitTests/AGUIStreamingMessageIdTests.cs | Adds an end-to-end pipeline test verifying AGUI events include non-null messageId. |
dotnet/tests/Microsoft.Agents.AI.AGUI.UnitTests/AGUIStreamingMessageIdTests.cs
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dotnet/tests/Microsoft.Agents.AI.UnitTests/ChatClient/ChatClientAgentTests.cs
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dotnet/tests/Microsoft.Agents.AI.AGUI.UnitTests/AGUIStreamingMessageIdTests.cs
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- Fix MessageId seeding: use first-seen provider MessageId (or generate fallback) and apply consistently to all chunks in the stream, preventing message splitting when providers set MessageId only on the first chunk - Add test for mixed MessageId scenario (first chunk only) - Fix skipped TextStreaming test: assert Empty (not NotEmpty) to match actual null==null behavior - Fix skipped ToolCalls test: assert empty ParentMessageId to match actual empty-string passthrough behavior
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- Fix MessageId seeding: use first-seen provider MessageId (or generate fallback) and apply consistently to all chunks in the stream, preventing message splitting when providers set MessageId only on the first chunk - Add test for mixed MessageId scenario (first chunk only) - Fix skipped TextStreaming test: assert Empty (not NotEmpty) to match actual null==null behavior - Fix skipped ToolCalls test: assert empty ParentMessageId to match actual empty-string passthrough behavior
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dotnet/src/Microsoft.Agents.AI.Abstractions/AgentResponseExtensions.cs
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Generate fallback MessageId in ChatClientAgent.RunCoreStreamingAsync when
the underlying LLM provider does not set ChatResponseUpdate.MessageId.
Without a MessageId the AGUI converter's null==null check silently drops
all text content, causing CopilotKit Zod validation errors.
Changes:
- ChatClientAgent: generate msg_{Guid} fallback via ??= in streaming loop
- AgentResponseExtensions: sync wrapper MessageId back to RawRepresentation
in AsChatResponseUpdate() so downstream consumers see the value
- Add unit tests for both fixes and AGUI streaming MessageId scenarios
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
- Fix MessageId seeding: use first-seen provider MessageId (or generate fallback) and apply consistently to all chunks in the stream, preventing message splitting when providers set MessageId only on the first chunk - Add test for mixed MessageId scenario (first chunk only) - Fix skipped TextStreaming test: assert Empty (not NotEmpty) to match actual null==null behavior - Fix skipped ToolCalls test: assert empty ParentMessageId to match actual empty-string passthrough behavior
Treat empty/whitespace MessageId the same as null when syncing from the AgentResponseUpdate wrapper back to RawRepresentation. Providers that return empty string MessageId (e.g. tool call responses) now get the wrapper value recovered correctly. Add test for empty string MessageId recovery scenario.
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westey-m
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Mar 13, 2026
Move fallback MessageId generation from ChatClientAgent to AsAGUIEventStreamAsync, addressing the architectural concern that MessageId is nullable in the AIAgent abstraction and the requirement for non-null values is specific to the AGUI protocol. The AGUI layer now generates a fallback MessageId for null or empty/whitespace values, covering all agent types (not just ChatClientAgent) including external implementations. Changes: - Revert MessageId generation from ChatClientAgent.RunCoreStreamingAsync - Add fallback MessageId generation in AsAGUIEventStreamAsync for null/empty MessageId values (handles both null and whitespace) - Unskip and update AGUI tests to verify fallback generation - Update ChatClientAgent tests to reflect passthrough behavior
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dotnet/src/Microsoft.Agents.AI.Abstractions/AgentResponseExtensions.cs
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westey-m
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Mar 13, 2026
Remove the MessageId sync-back logic from AsChatResponseUpdate() as it is no longer needed. With fallback generation moved to the AGUI layer, the abstraction layer should not mutate the RawRepresentation object. Revert to the original passthrough behavior for AsChatResponseUpdate() and update tests accordingly.
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SergeyMenshykh
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