.NET: fix: preserve Responses logprobs field

[Yufeng He (he-yufeng)]

Summary

• add the missing logprobs field to the Responses CreateResponse and Response models
• keep logprobs alongside top_logprobs during JSON deserialize / reserialize round trips
• cover request and response payloads in OpenAI hosting serialization tests

Fixes #5854.

To verify

• dotnet test --project tests\Microsoft.Agents.AI.Hosting.OpenAI.UnitTests\Microsoft.Agents.AI.Hosting.OpenAI.UnitTests.csproj -f net10.0 --no-restore --filter-class Microsoft.Agents.AI.Hosting.OpenAI.UnitTests.OpenAIResponsesSerializationTests
• dotnet build src\Microsoft.Agents.AI.Hosting.OpenAI\Microsoft.Agents.AI.Hosting.OpenAI.csproj -f net10.0 --no-restore --tl:off
• dotnet build tests\Microsoft.Agents.AI.Hosting.OpenAI.UnitTests\Microsoft.Agents.AI.Hosting.OpenAI.UnitTests.csproj -f net10.0 --no-restore --tl:off
• dotnet format src\Microsoft.Agents.AI.Hosting.OpenAI\Microsoft.Agents.AI.Hosting.OpenAI.csproj --verify-no-changes --no-restore
• dotnet format tests\Microsoft.Agents.AI.Hosting.OpenAI.UnitTests\Microsoft.Agents.AI.Hosting.OpenAI.UnitTests.csproj --verify-no-changes --no-restore

[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

This PR fixes loss of the logprobs field during .NET Responses request/response JSON serialization round-trips by adding the missing model properties and extending serialization tests to cover the behavior.

Changes:

• Add nullable logprobs to CreateResponse and Response models.
• Add unit tests to validate logprobs + top_logprobs deserialize/reserialize round trips.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 4 comments.

File	Description
dotnet/tests/Microsoft.Agents.AI.Hosting.OpenAI.UnitTests/OpenAIResponsesSerializationTests.cs	Adds round-trip serialization tests for logprobs and top_logprobs in request/response payloads.
dotnet/src/Microsoft.Agents.AI.Hosting.OpenAI/Responses/Models/Response.cs	Adds Logprobs JSON-mapped property to preserve response payload field.
dotnet/src/Microsoft.Agents.AI.Hosting.OpenAI/Responses/Models/CreateResponse.cs	Adds Logprobs JSON-mapped property to preserve request payload field.

[Justin Yoo (justinyoo)]

Hi, Team. Just follow up for the catch up on the current status of this.

[Yufeng He (he-yufeng)]

Addressed the remaining propagation gap in 5ead97d. Logprobs is now copied alongside TopLogprobs in all three CreateResponse -> Response synthesis paths: non-streaming agent responses, streaming response snapshots, and the in-memory response service.

Validation on Windows: project restore/build succeeded, OpenAIResponsesSerializationTests passed, all 38 OpenAIResponsesIntegrationTests passed, targeted dotnet format verification passed with the existing workspace-load warning, and git diff --check passed.

[Yufeng He (he-yufeng)]

Rebased the logprobs propagation fix onto current main. The final six-file behavior diff is unchanged, the hosting project builds with zero warnings/errors, and the earlier focused serialization/integration test results remain applicable.

[Yufeng He (he-yufeng)]

Updated and rebased the branch onto current main.

This addresses the remaining review threads:

• renamed the create-side logprobs test/variable to match the CreateResponse model being deserialized
• changed the nullable bool assertions to check HasValue and then Value
• kept the earlier Logprobs propagation fix across all three CreateResponse -> Response synthesis paths

Validation:

• dotnet build .\dotnet\tests\Microsoft.Agents.AI.Hosting.OpenAI.UnitTests\Microsoft.Agents.AI.Hosting.OpenAI.UnitTests.csproj -f net10.0 --tl:off (0 warnings, 0 errors)
• dotnet .\dotnet\tests\Microsoft.Agents.AI.Hosting.OpenAI.UnitTests\bin\Debug\net10.0\Microsoft.Agents.AI.Hosting.OpenAI.UnitTests.dll --filter-class Microsoft.Agents.AI.Hosting.OpenAI.UnitTests.OpenAIResponsesSerializationTests --no-progress (53 passed)
• dotnet format dotnet\agent-framework-dotnet.slnx --verify-no-changes --no-restore --include ... (passed; existing workspace-load warning only)
• git diff --check upstream/main..HEAD

[Yufeng He (he-yufeng)]

Rebased this branch onto current main and pushed the updated head facab905.

Validation run locally from dotnet/:

• dotnet build .\src\Microsoft.Agents.AI.Hosting.OpenAI\Microsoft.Agents.AI.Hosting.OpenAI.csproj -f net10.0 --tl:off -> passed, 0 warnings/errors
• dotnet run --project .\tests\Microsoft.Agents.AI.Hosting.OpenAI.UnitTests\Microsoft.Agents.AI.Hosting.OpenAI.UnitTests.csproj -f net10.0 -> passed, 390 tests
• git diff --check upstream/main..HEAD -> passed

Note: I used dotnet run --project for the test project because the local .NET 10 dotnet test runner rejected this project under the repository's MTP global runner setting before executing tests.

[Yufeng He (he-yufeng)]

Rebased this branch onto current main and pushed the updated head c2e48bd.

Validation run locally from dotnet/:

• dotnet build .\src\Microsoft.Agents.AI.Hosting.OpenAI\Microsoft.Agents.AI.Hosting.OpenAI.csproj -f net10.0 --tl:off -> passed, 0 warnings/errors
• dotnet run --project .\tests\Microsoft.Agents.AI.Hosting.OpenAI.UnitTests\Microsoft.Agents.AI.Hosting.OpenAI.UnitTests.csproj -f net10.0 -> passed, 390 tests
• git diff --check upstream/main..HEAD -> passed

The PR diff remains scoped to the six .NET OpenAI hosting/logprobs files after the rebase.

[Yufeng He (he-yufeng)]

Rebased this branch onto current main and pushed head 766e32e67.

Validation run locally from dotnet/:

• git diff --check upstream/main..HEAD -> passed
• dotnet build .\src\Microsoft.Agents.AI.Hosting.OpenAI\Microsoft.Agents.AI.Hosting.OpenAI.csproj -f net10.0 --tl:off -> passed, 0 warnings/errors
• dotnet run --project .\tests\Microsoft.Agents.AI.Hosting.OpenAI.UnitTests\Microsoft.Agents.AI.Hosting.OpenAI.UnitTests.csproj -f net10.0 -- --no-progress -> passed, 390 tests

[Evan Mattson (moonbox3)]

Yufeng He (@he-yufeng) going forward, please post replies on the actual PR comments, not as follow up comments. It's hard for us to know which comments are actually resolved.

[Yufeng He (he-yufeng)]

Nudge on this one: every review point from June is addressed and the branch is still mergeable with green checks. The Responses logprobs field now survives serialization both directions. Could use another pass when you have a minute.