.NET: Preserve non-ASCII text in hosting tool payloads

dotnet/src/Microsoft.Agents.AI.Foundry.Hosting/OutputConverter.cs

@@ -7,7 +7,9 @@
 using System.Runtime.CompilerServices;
 using System.Security.Cryptography;
 using System.Text;
+using System.Text.Encodings.Web;
 using System.Text.Json;
+using System.Text.Unicode;
 using System.Threading;
 using System.Threading.Tasks;
 using Azure.AI.AgentServer.Responses;
@@ -46,6 +48,9 @@ public static implicit operator OutputConverterItem(ResponseStreamEvent value) =
 /// </summary>
 internal static class OutputConverter
 {
+    // Keep non-ASCII characters as-is while continuing to escape HTML-sensitive characters.
+    private static readonly JsonSerializerOptions s_jsonOptions = new() { Encoder = JavaScriptEncoder.Create(UnicodeRanges.All) };
+
     /// <summary>
     /// Converts a stream of <see cref="AgentResponseUpdate"/> into a stream of
     /// <see cref="ResponseStreamEvent"/> using the SDK builder pattern.
@@ -209,7 +214,7 @@ public static async IAsyncEnumerable<OutputConverterItem> ConvertUpdatesToItemsA
                         previousMessageId = null;
 
                         var arguments = functionCall.Arguments is not null
-                            ? JsonSerializer.Serialize(functionCall.Arguments)
+                            ? JsonSerializer.Serialize(functionCall.Arguments, s_jsonOptions)
                             : "{}";
 
                         var fcBuilder = stream.AddOutputItemFunctionCall(functionCall.Name, functionCall.CallId);
@@ -328,7 +333,7 @@ public static async IAsyncEnumerable<OutputConverterItem> ConvertUpdatesToItemsA
                         var wireId = ToolApprovalIdMap.ComputeWireId(approvalRequest.RequestId);
 
                         var approvalArguments = approvalFunctionCall.Arguments is not null
-                            ? JsonSerializer.Serialize(approvalFunctionCall.Arguments)
+                            ? JsonSerializer.Serialize(approvalFunctionCall.Arguments, s_jsonOptions)
                             : "{}";
 
                         ToolApprovalIdMap.Record(
@@ -763,13 +768,13 @@ internal static string EncodeFunctionResultAsJsonStringPayload(object? result)
             string s => s,
             JsonElement je => je.ValueKind == JsonValueKind.String
                 ? (je.GetString() ?? string.Empty)
-                : je.GetRawText(),
+                : JsonSerializer.Serialize(je, s_jsonOptions),
             JsonDocument jd => jd.RootElement.ValueKind == JsonValueKind.String
                 ? (jd.RootElement.GetString() ?? string.Empty)
-                : jd.RootElement.GetRawText(),
-            _ => JsonSerializer.Serialize(result),
+                : JsonSerializer.Serialize(jd.RootElement, s_jsonOptions),
+            _ => JsonSerializer.Serialize(result, s_jsonOptions),
         };
 
-        return JsonSerializer.Serialize(innerText);
+        return JsonSerializer.Serialize(innerText, s_jsonOptions);
     }
 }

dotnet/src/Microsoft.Agents.AI.Hosting.OpenAI/ChatCompletions/AgentResponseExtensions.cs

@@ -200,7 +200,7 @@ public static ChoiceMessageToolCall ToChoiceMessageToolCall(this FunctionCallCon
             Function = new()
             {
                 Name = functionCall.Name,
-                Arguments = JsonSerializer.Serialize(functionCall.Arguments, ChatCompletionsJsonContext.Default.DictionaryStringObject)
+                Arguments = JsonSerializer.Serialize(functionCall.Arguments, OpenAIHostingJsonUtilities.DefaultOptions.GetTypeInfo(typeof(IDictionary<string, object?>)))
             }
         };
     }

dotnet/src/Microsoft.Agents.AI.Hosting.OpenAI/OpenAIHostingJsonUtilities.cs

@@ -2,8 +2,10 @@
 
 using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
+using System.Text.Encodings.Web;
 using System.Text.Json;
 using System.Text.Json.Serialization;
+using System.Text.Unicode;
 using Microsoft.Agents.AI.Hosting.OpenAI.Conversations.Models;
 using Microsoft.Agents.AI.Hosting.OpenAI.Models;
 using Microsoft.Agents.AI.Hosting.OpenAI.Responses.Models;
@@ -31,6 +33,9 @@ private static JsonSerializerOptions CreateDefaultOptions()
         options.TypeInfoResolverChain.Add(AgentAbstractionsJsonUtilities.DefaultOptions.TypeInfoResolver!);
         options.TypeInfoResolverChain.Add(OpenAIHostingJsonContext.Default.Options.TypeInfoResolver!);
 
+        // Keep non-ASCII characters as-is while continuing to escape HTML-sensitive characters.
+        options.Encoder = JavaScriptEncoder.Create(UnicodeRanges.All);
+
         options.MakeReadOnly();
         return options;
     }

dotnet/tests/Microsoft.Agents.AI.Foundry.Hosting.UnitTests/OutputConverterTests.cs

@@ -443,6 +443,110 @@ public async Task ConvertUpdatesToEventsAsync_FunctionCallWithNullArguments_Emit
         Assert.IsType<ResponseCompletedEvent>(events[^1]);
     }
 
+    [Fact]
+    public async Task ConvertUpdatesToEventsAsync_FunctionCallNonAsciiArguments_PreservesCharactersAsync()
+    {
+        // Arrange
+        var (stream, _) = CreateTestStream();
+        var update = new AgentResponseUpdate
+        {
+            Contents = [new FunctionCallContent("call_1", "get_weather", new Dictionary<string, object?> { ["location"] = "Ереван" })]
+        };
+
+        // Act
+        var events = new List<ResponseStreamEvent>();
+        await foreach (var evt in OutputConverter.ConvertUpdatesToEventsAsync(ToAsync(new[] { update }), stream))
+        {
+            events.Add(evt);
+        }
+
+        // Assert
+        var done = Assert.Single(events.OfType<ResponseFunctionCallArgumentsDoneEvent>());
+        Assert.Equal("""{"location":"Ереван"}""", done.Arguments);
+    }
+
+    [Fact]
+    public async Task ConvertUpdatesToEventsAsync_FunctionCallHtmlSensitiveArguments_EscapesCharactersAsync()
+    {
+        // Arrange
+        var (stream, _) = CreateTestStream();
+        var update = new AgentResponseUpdate
+        {
+            Contents = [new FunctionCallContent("call_1", "search", new Dictionary<string, object?> { ["query"] = "<tag>&" })]
+        };
+
+        // Act
+        var events = new List<ResponseStreamEvent>();
+        await foreach (var evt in OutputConverter.ConvertUpdatesToEventsAsync(ToAsync(new[] { update }), stream))
+        {
+            events.Add(evt);
+        }
+
+        // Assert
+        var done = Assert.Single(events.OfType<ResponseFunctionCallArgumentsDoneEvent>());
+        Assert.Equal("""{"query":"\u003Ctag\u003E\u0026"}""", done.Arguments);
+    }
+
+    [Fact]
+    public async Task ConvertUpdatesToEventsAsync_ToolApprovalRequestNonAsciiArguments_PreservesCharactersAsync()
+    {
+        // Arrange
+        var (stream, _) = CreateTestStream();
+        var functionCall = new FunctionCallContent("call_1", "get_weather", new Dictionary<string, object?> { ["location"] = "Ереван" });
+        var update = new AgentResponseUpdate { Contents = [new ToolApprovalRequestContent("af_request_1", functionCall)] };
+
+        // Act
+        var events = new List<ResponseStreamEvent>();
+        await foreach (var evt in OutputConverter.ConvertUpdatesToEventsAsync(ToAsync(new[] { update }), stream, new AgentSessionStateBag()))
+        {
+            events.Add(evt);
+        }
+
+        // Assert
+        var added = Assert.Single(events.OfType<ResponseOutputItemAddedEvent>());
+        var item = Assert.IsType<OutputItemMcpApprovalRequest>(added.Item);
+        Assert.Equal("""{"location":"Ереван"}""", item.Arguments);
+    }
+
+    [Fact]
+    public void EncodeFunctionResultAsJsonStringPayload_NonAsciiObject_PreservesCharacters()
+    {
+        // Arrange
+        var result = new { city = "Ереван" };
+
+        // Act
+        string payload = OutputConverter.EncodeFunctionResultAsJsonStringPayload(result);
+
+        // Assert
+        Assert.Equal("""{"city":"Ереван"}""", System.Text.Json.JsonSerializer.Deserialize<string>(payload));
+    }
+
+    [Fact]
+    public void EncodeFunctionResultAsJsonStringPayload_JsonElementWithEscapedUnicode_DecodesCharacters()
+    {
+        // Arrange
+        using System.Text.Json.JsonDocument document = System.Text.Json.JsonDocument.Parse("""{"city":"\u0415"}""");
+
+        // Act
+        string payload = OutputConverter.EncodeFunctionResultAsJsonStringPayload(document.RootElement);
+
+        // Assert
+        Assert.Equal("""{"city":"Е"}""", System.Text.Json.JsonSerializer.Deserialize<string>(payload));
+    }
+
+    [Fact]
+    public void EncodeFunctionResultAsJsonStringPayload_JsonDocumentWithEscapedUnicode_DecodesCharacters()
+    {
+        // Arrange
+        using System.Text.Json.JsonDocument document = System.Text.Json.JsonDocument.Parse("""{"city":"\u0415"}""");
+
+        // Act
+        string payload = OutputConverter.EncodeFunctionResultAsJsonStringPayload(document);
+
+        // Assert
+        Assert.Equal("""{"city":"Е"}""", System.Text.Json.JsonSerializer.Deserialize<string>(payload));
+    }
+
     // G-04
     [Fact]
     public async Task ConvertUpdatesToEventsAsync_FunctionCallWithEmptyCallId_DoesNotEmitWireItemAsync()

dotnet/tests/Microsoft.Agents.AI.Hosting.OpenAI.UnitTests/OpenAIChatCompletionsSerializationTests.cs

@@ -6,6 +6,8 @@
 using System.Text.Json;
 using Microsoft.Agents.AI.Hosting.OpenAI.ChatCompletions.Models;
 using Microsoft.Agents.AI.Hosting.OpenAI.Tests;
+using Microsoft.Extensions.AI;
+using ChatCompletionsAgentResponseExtensions = Microsoft.Agents.AI.Hosting.OpenAI.ChatCompletions.AgentResponseExtensions;
 
 namespace Microsoft.Agents.AI.Hosting.OpenAI.UnitTests;
 
@@ -385,6 +387,24 @@ public void Deserialize_ResponseRoundTrip_PreservesData()
 
     #endregion
 
+    #region Function Call Conversion Tests
+
+    [Fact]
+    public void ToChoiceMessageToolCall_NonAsciiArguments_PreservesCharacters()
+    {
+        // Arrange
+        var functionCall = new FunctionCallContent("call_1", "get_weather", new Dictionary<string, object?> { ["location"] = "Ереван" });
+
+        // Act
+        ChoiceMessageToolCall toolCall = ChatCompletionsAgentResponseExtensions.ToChoiceMessageToolCall(functionCall);
+
+        // Assert
+        Assert.NotNull(toolCall.Function);
+        Assert.Equal("""{"location":"Ереван"}""", toolCall.Function.Arguments);
+    }
+
+    #endregion
+
     #region Streaming Chunk Deserialization Tests
 
     [Fact]

dotnet/tests/Microsoft.Agents.AI.Hosting.OpenAI.UnitTests/OpenAIResponsesSerializationTests.cs

@@ -6,6 +6,8 @@
 using System.Text.Json;
 using Microsoft.Agents.AI.Hosting.OpenAI.Responses.Models;
 using Microsoft.Agents.AI.Hosting.OpenAI.Tests;
+using Microsoft.Extensions.AI;
+using ResponsesAgentResponseExtensions = Microsoft.Agents.AI.Hosting.OpenAI.Responses.AgentResponseExtensions;
 
 namespace Microsoft.Agents.AI.Hosting.OpenAI.UnitTests;
 
@@ -766,6 +768,36 @@ public void Deserialize_ResponseRoundTrip_PreservesData()
 
     #endregion
 
+    #region Function Call Conversion Tests
+
+    [Fact]
+    public void ToFunctionToolCallItemResource_NonAsciiArguments_PreservesCharacters()
+    {
+        // Arrange
+        var functionCall = new FunctionCallContent("call_1", "get_weather", new Dictionary<string, object?> { ["location"] = "Ереван" });
+
+        // Act
+        FunctionToolCallItemResource resource = ResponsesAgentResponseExtensions.ToFunctionToolCallItemResource(functionCall, "fc_1", OpenAIHostingJsonUtilities.DefaultOptions);
+
+        // Assert
+        Assert.Equal("""{"location":"Ереван"}""", resource.Arguments);
+    }
+
+    [Fact]
+    public void ToFunctionToolCallItemResource_HtmlSensitiveArguments_EscapesCharacters()
+    {
+        // Arrange
+        var functionCall = new FunctionCallContent("call_1", "search", new Dictionary<string, object?> { ["query"] = "<tag>&" });
+
+        // Act
+        FunctionToolCallItemResource resource = ResponsesAgentResponseExtensions.ToFunctionToolCallItemResource(functionCall, "fc_1", OpenAIHostingJsonUtilities.DefaultOptions);
+
+        // Assert
+        Assert.Equal("""{"query":"\u003Ctag\u003E\u0026"}""", resource.Arguments);
+    }
+
+    #endregion
+
     #region Streaming Event Deserialization Tests
 
     [Fact]