.NET: [Bug]: Approval response false throwing error in AGUI Client

[Mohanr1122]

Description

if we sending approval response as false, getting error "System.Text.Json.JsonException: ''T' is an invalid start of a value. Path: $ | LineNumber: 0 | BytePositionInLine: 0.'" in AGUI Client

Code Sample

Error Messages / Stack Traces

System.Text.Json.JsonException
  HResult=0x80131500
  Message='T' is an invalid start of a value. Path: $ | LineNumber: 0 | BytePositionInLine: 0.
  Source=System.Text.Json
  StackTrace:
   at System.Text.Json.ThrowHelper.ReThrowWithPath(ReadStack& state, JsonReaderException ex)
   at System.Text.Json.Serialization.JsonConverter`1.ReadCore(Utf8JsonReader& reader, T& value, JsonSerializerOptions options, ReadStack& state)
   at System.Text.Json.Serialization.Metadata.JsonTypeInfo`1.Deserialize(Utf8JsonReader& reader, ReadStack& state)
   at System.Text.Json.Serialization.Metadata.JsonTypeInfo`1.DeserializeAsObject(Utf8JsonReader& reader, ReadStack& state)
   at System.Text.Json.JsonSerializer.ReadFromSpanAsObject(ReadOnlySpan`1 utf8Json, JsonTypeInfo jsonTypeInfo, Nullable`1 actualByteCount)
   at System.Text.Json.JsonSerializer.ReadFromSpanAsObject(ReadOnlySpan`1 json, JsonTypeInfo jsonTypeInfo)
   at System.Text.Json.JsonSerializer.Deserialize(String json, JsonTypeInfo jsonTypeInfo)
   at Microsoft.Agents.AI.AGUI.Shared.ChatResponseUpdateAGUIExtensions.DeserializeResultIfAvailable(ToolCallResultEvent toolCallResult, JsonSerializerOptions options)
   at Microsoft.Agents.AI.AGUI.Shared.ChatResponseUpdateAGUIExtensions.ToolCallBuilder.EmitToolCallResult(ToolCallResultEvent toolCallResult, JsonSerializerOptions options)
   at Microsoft.Agents.AI.AGUI.Shared.ChatResponseUpdateAGUIExtensions.<AsChatResponseUpdatesAsync>d__2.MoveNext()
   at Microsoft.Agents.AI.AGUI.Shared.ChatResponseUpdateAGUIExtensions.<AsChatResponseUpdatesAsync>d__2.MoveNext()
   at Microsoft.Agents.AI.AGUI.Shared.ChatResponseUpdateAGUIExtensions.<AsChatResponseUpdatesAsync>d__2.System.Threading.Tasks.Sources.IValueTaskSource<System.Boolean>.GetResult(Int16 token)
   at Microsoft.Agents.AI.AGUI.AGUIChatClient.AGUIChatClientHandler.<GetStreamingResponseAsync>d__9.MoveNext()
   at Microsoft.Agents.AI.AGUI.AGUIChatClient.AGUIChatClientHandler.<GetStreamingResponseAsync>d__9.MoveNext()
   at Microsoft.Agents.AI.AGUI.AGUIChatClient.AGUIChatClientHandler.<GetStreamingResponseAsync>d__9.System.Threading.Tasks.Sources.IValueTaskSource<System.Boolean>.GetResult(Int16 token)
   at Microsoft.Extensions.AI.FunctionInvokingChatClient.<GetStreamingResponseAsync>d__42.MoveNext()
   at Microsoft.Extensions.AI.FunctionInvokingChatClient.<GetStreamingResponseAsync>d__42.MoveNext()
   at Microsoft.Extensions.AI.FunctionInvokingChatClient.<GetStreamingResponseAsync>d__42.System.Threading.Tasks.Sources.IValueTaskSource<System.Boolean>.GetResult(Int16 token)
   at Microsoft.Agents.AI.AGUI.AGUIChatClient.<GetStreamingResponseAsync>d__4.MoveNext()
   at Microsoft.Agents.AI.AGUI.AGUIChatClient.<GetStreamingResponseAsync>d__4.MoveNext()
   at Microsoft.Agents.AI.AGUI.AGUIChatClient.<GetStreamingResponseAsync>d__4.System.Threading.Tasks.Sources.IValueTaskSource<System.Boolean>.GetResult(Int16 token)
   at Microsoft.Agents.AI.ChatClientAgent.<RunCoreStreamingAsync>d__29.MoveNext()
   at Microsoft.Agents.AI.ChatClientAgent.<RunCoreStreamingAsync>d__29.MoveNext()
   at Microsoft.Agents.AI.ChatClientAgent.<RunCoreStreamingAsync>d__29.MoveNext()
   at Microsoft.Agents.AI.ChatClientAgent.<RunCoreStreamingAsync>d__29.System.Threading.Tasks.Sources.IValueTaskSource<System.Boolean>.GetResult(Int16 token)
   at Microsoft.Agents.AI.AIAgent.<RunStreamingAsync>d__33.MoveNext()
   at Microsoft.Agents.AI.AIAgent.<RunStreamingAsync>d__33.MoveNext()
   at Microsoft.Agents.AI.AIAgent.<RunStreamingAsync>d__33.System.Threading.Tasks.Sources.IValueTaskSource<System.Boolean>.GetResult(Int16 token)
   at ServerFunctionApprovalClientAgent.<RunCoreStreamingAsync>d__3.MoveNext() in \agent-framework-main\dotnet\samples\02-agents\AGUI\Step04_HumanInLoop\Client\ServerFunctionApprovalClientAgent.cs:line 45
   at ServerFunctionApprovalClientAgent.<RunCoreStreamingAsync>d__3.MoveNext() in agent-framework-main\dotnet\samples\02-agents\AGUI\Step04_HumanInLoop\Client\ServerFunctionApprovalClientAgent.cs:line 45
   at ServerFunctionApprovalClientAgent.<RunCoreStreamingAsync>d__3.System.Threading.Tasks.Sources.IValueTaskSource<System.Boolean>.GetResult(Int16 token)
   at Microsoft.Agents.AI.AIAgent.<RunStreamingAsync>d__33.MoveNext()
   at Microsoft.Agents.AI.AIAgent.<RunStreamingAsync>d__33.MoveNext()
   at Microsoft.Agents.AI.AIAgent.<RunStreamingAsync>d__33.System.Threading.Tasks.Sources.IValueTaskSource<System.Boolean>.GetResult(Int16 token)
   at Program.<<Main>$>d__0.MoveNext() in agent-framework-main (1)\agent-framework-main\dotnet\samples\02-agents\AGUI\Step04_HumanInLoop\Client\Program.cs:line 55
   at Program.<<Main>$>d__0.MoveNext() in agent-framework-main (1)\agent-framework-main\dotnet\samples\02-agents\AGUI\Step04_HumanInLoop\Client\Program.cs:line 55

  This exception was originally thrown at this call stack:
    [External Code]

Inner Exception 1:
JsonReaderException: 'T' is an invalid start of a value. LineNumber: 0 | BytePositionInLine: 0.

Package Versions

Microsoft.Agents.AI 1.6.2

.NET Version

No response

Additional Context

No response

[github-actions]

🤖 Automated triage reproduction notes (agent-authored — trust but verify)

Agent analysis

Repro: DeserializeResultIfAvailable() in dotnet/src/Microsoft.Agents.AI.AGUI/Shared/ChatResponseUpdateAGUIExtensions.cs:431 throws JsonException when ToolCallResultEvent.Content is a non-JSON string like "True" or "False". The mismatch is with SerializeResultContent() at line 742 which passes strings through as-is (string str => str) without JSON-encoding them. Minimal repro: send a ToolCallResultEvent with Content="True" through AsChatResponseUpdatesAsync; the fix should either JSON-encode strings in SerializeResultContent or gracefully handle non-JSON strings in DeserializeResultIfAvailable (e.g., wrap as a JSON string or return the raw string).

• Failing test: dotnet/tests/Microsoft.Agents.AI.AGUI.UnitTests/ToolCallResultDeserializationTests.cs
• Files examined: dotnet/src/Microsoft.Agents.AI.AGUI/Shared/ChatResponseUpdateAGUIExtensions.cs, dotnet/src/Microsoft.Agents.AI.AGUI/Shared/ToolCallResultEvent.cs, dotnet/samples/02-agents/AGUI/Step04_HumanInLoop/Client/ServerFunctionAprovalClientAgent.cs, dotnet/samples/02-agents/AGUI/Step04_HumanInLoop/ServerFunctionApprovalServerAgent.cs, dotnet/tests/Microsoft.Agents.AI.AGUI.UnitTests/AGUIChatClientTests.cs
• Tests run: ToolCallResultDeserializationTests.ToolCallResult_WithBooleanToStringContent_ThrowsJsonException(True), ToolCallResultDeserializationTests.ToolCallResult_WithBooleanToStringContent_ThrowsJsonException(False), ToolCallResultDeserializationTests.ToolCallResult_WithValidJsonContent_DoesNotThrow(true), ToolCallResultDeserializationTests.ToolCallResult_WithValidJsonContent_DoesNotThrow(false), ToolCallResultDeserializationTests.ToolCallResult_WithValidJsonContent_DoesNotThrow(json_object), ToolCallResultDeserializationTests.ToolCallResult_WithValidJsonContent_DoesNotThrow(json_string), ToolCallResultDeserializationTests.SerializeResultContent_WithStringResult_ProducesInvalidJsonForDeserialization
• Reported version: 1.6.2
• Current version: 1.8.0

[Mohanr1122]

Same issue when adding handoffbuillder as agent

[javiercn]

This was resolved by the AGUI.Client migration in #6653. The old in-tree result deserializer that attempted to parse True/False as JSON was removed; current AGUI.Client carries the tool result content directly. Closing as resolved.