[valkiara]

Chat Completions sends tool arguments and structured tool results as JSON strings. The default serializer indents both strings, adding whitespace to the request.

Use compact JSON for those payloads while retaining the existing serializer settings. String tool results still pass through unchanged.

Fixes #7921.

Both regression tests failed on the indented payloads before the fix. Afterward, the .NET 11 adapter suite passed (398 passed, 163 live integration tests skipped). Both regression tests also passed with reflection-based JSON serialization disabled. The adapter built for all six target frameworks with zero warnings or errors.

Microsoft Reviewers: Open in CodeFlow

[dotnet-comment-bot]

‼️ Found issues ‼️

Project	Coverage Type	Expected	Actual
Microsoft.Extensions.AI	Line	89	87.81 🔻
Microsoft.Extensions.AI	Branch	89	79.23 🔻
Microsoft.Extensions.AI.OpenAI	Line	75	68.83 🔻
Microsoft.Extensions.AI.OpenAI	Branch	75	60.34 🔻
Microsoft.Extensions.DataIngestion.MarkItDown	Line	75	4.46 🔻
Microsoft.Extensions.DataIngestion.MarkItDown	Branch	75	0.75 🔻
Microsoft.Extensions.Diagnostics.ResourceMonitoring	Line	99	96.06 🔻
Microsoft.Extensions.Diagnostics.ResourceMonitoring	Branch	99	92.28 🔻
Microsoft.Extensions.Diagnostics.ResourceMonitoring.Kubernetes	Line	99	97.73 🔻
Microsoft.Extensions.Diagnostics.ResourceMonitoring.Kubernetes	Branch	99	92.86 🔻
Microsoft.Extensions.Diagnostics.Testing	Line	99	98.22 🔻
Microsoft.Extensions.Diagnostics.Testing	Branch	99	93.66 🔻
Microsoft.Extensions.ServiceDiscovery	Line	75	59.18 🔻
Microsoft.Extensions.ServiceDiscovery	Branch	75	64.41 🔻
Microsoft.Extensions.ServiceDiscovery.Abstractions	Line	75	41.14 🔻
Microsoft.Extensions.ServiceDiscovery.Abstractions	Branch	75	45.1 🔻
Microsoft.Extensions.ServiceDiscovery.Dns	Line	75	62.53 🔻
Microsoft.Extensions.ServiceDiscovery.Dns	Branch	75	74.08 🔻
Microsoft.Extensions.ServiceDiscovery.Yarp	Line	75	73.85 🔻
Microsoft.Extensions.ServiceDiscovery.Yarp	Branch	75	60 🔻
Microsoft.Extensions.Telemetry	Line	93	90.47 🔻
Microsoft.Extensions.Telemetry	Branch	93	86.83 🔻
Microsoft.Extensions.VectorData.Abstractions	Line	75	32.15 🔻
Microsoft.Extensions.VectorData.Abstractions	Branch	75	26.31 🔻

🎉 Good job! The coverage increased 🎉
Update MinCodeCoverage in the project files.

Project	Expected	Actual
Microsoft.Extensions.AI.Evaluation.NLP	0	74
Microsoft.Extensions.Caching.Hybrid	81	83
Microsoft.Extensions.DataIngestion	75	77
Microsoft.Extensions.DataIngestion.Markdig	75	88
Microsoft.Extensions.DocumentExtraction	80	94
Microsoft.Extensions.DocumentExtraction.Abstractions	80	100
Microsoft.Extensions.Documents.Abstractions	80	98
Microsoft.Gen.MetadataExtractor	57	72
Microsoft.Gen.MetricsReports	67	69

Full code coverage report: https://dev.azure.com/dnceng-public/public/_build/results?buildId=1675454&view=codecoverage-tab

[dfedoryshchev]

You fixed Chat Completions, but the Responses client still sends the same payloads indented: OpenAIResponsesChatClient.ToOpenAIResponseItems serializes FunctionResultContent.Result with AIJsonUtilities.DefaultOptions (L1528) and FunctionCallContent.Arguments the same way (L1596), so a tool loop on GetResponsesClient().AsIChatClient() pays the whitespace from #7921 on every turn. The MCP call and approval arguments (L1606, L1618) and the realtime function result (OpenAIRealtimeClientSession.cs L639) go through DefaultOptions too.

Minor: _toolJsonOptions could live somewhere both clients share, so the two adapters don't drift again.