Skip to content

.NET: [Bug]: Approval response false throwing error in AGUI Client #6220

New issue
New issue
Closed
Bug
Closed
.NET: [Bug]: Approval response false throwing error in AGUI Client#6220
Bug
Assignees
javiercn
Labels
.NETUsage: [Issues, PRs], Target: .Netag-uiUsage: [Issues, PRs], Target: AG-UI protocol integrationbugUsage: [Issues], Target: all issues (Legacy, prefer issue type: bug)reproducedUsage: [Issues], Target: all issues that can be reproduced by the triage workflow

Description

@Mohanr1122
Mohanr1122
opened on May 31, 2026

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

Image

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
Activity
  1. Mohanr1122
    added the
    Bug
    issue type on May 31, 2026
  2. Mohanr1122
    added 
    bugUsage: [Issues], Target: all issues (Legacy, prefer issue type: bug)
     
    .NETUsage: [Issues, PRs], Target: .Net
     on May 31, 2026
  3. github-project-automation
    added this to  Agent Frameworkon May 31, 2026
  4. Evan Mattson (moonbox3)
    added 
    triageUsage: [Issues], Target: All issues that still need to be triaged
     on May 31, 2026
  5. github-actions
    added 
    reproducedUsage: [Issues], Target: all issues that can be reproduced by the triage workflow
     on May 31, 2026
  6. github-actions commented on May 31, 2026 
    @github-actions
    github-actionsBot
    on May 31, 2026 – with GitHub Actions
    Contributor
    🤖 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
      • 

    

    

  7. Mohanr1122 commented on May 31, 2026 
    @Mohanr1122
    Mohanr1122
    on May 31, 2026
    Author
    Same issue when adding handoffbuillder as agent
  8. chetantoshniwal
    assigned 
    Javier Calvarro Nelson (javiercn)
    on Jun 2, 2026
  9. chetantoshniwal
    removed 
    triageUsage: [Issues], Target: All issues that still need to be triaged
     on Jun 9, 2026
  10. Javier Calvarro Nelson (javiercn)
    added 
    ag-uiUsage: [Issues, PRs], Target: AG-UI protocol integration
     on Aug 18, 2026
  11. javiercn commented on Aug 18, 2026 
    @javiercn
    Javier Calvarro Nelson (javiercn)
    on Aug 18, 2026
    Contributor
    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.
  12. Javier Calvarro Nelson (javiercn)
    closed this as completedon Aug 18, 2026
  13. github-project-automation
    moved this to Done in  Agent Frameworkon Aug 18, 2026
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Metadata
Metadata
Assignees
Labels
.NETUsage: [Issues, PRs], Target: .Netag-uiUsage: [Issues, PRs], Target: AG-UI protocol integrationbugUsage: [Issues], Target: all issues (Legacy, prefer issue type: bug)reproducedUsage: [Issues], Target: all issues that can be reproduced by the triage workflow
Type
Bug
Projects
Milestone
No milestone
Relationships
None yet
Development
No branches or pull requests
Issue actions