Fix model override bug and add client REPL sample

- InputConverter: stop propagating request.Model to ChatOptions.ModelId
  Hosted agents use their own model; client-provided model values like
  'hosted-agent' were being passed through and causing server errors.
- Add FoundryResponsesRepl sample: interactive CLI client that connects
  to a Foundry Responses endpoint using ResponsesClient.AsAIAgent()
- Bump package version to 0.9.0-hosted.260403.1

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

dotnet/agent-framework-dotnet.slnx

@@ -1,4 +1,4 @@
-<Solution>
+<Solution>
   <Configurations>
     <BuildType Name="Debug" />
     <BuildType Name="Publish" />
@@ -260,7 +260,9 @@
     <Project Path="samples/03-workflows/_StartHere/06_MixedWorkflowAgentsAndExecutors/06_MixedWorkflowAgentsAndExecutors.csproj" />
     <Project Path="samples/03-workflows/_StartHere/07_WriterCriticWorkflow/07_WriterCriticWorkflow.csproj" />
   </Folder>
-  <Folder Name="/Samples/04-hosting/" />
+  <Folder Name="/Samples/04-hosting/">
+    <Project Path="samples/04-hosting/FoundryResponsesRepl/FoundryResponsesRepl.csproj" />
+  </Folder>
   <Folder Name="/Samples/04-hosting/FoundryResponsesHosting/">
     <Project Path="samples/04-hosting/FoundryResponsesHosting/FoundryResponsesHosting.csproj" />
   </Folder>

dotnet/nuget/nuget-package.props

@@ -8,7 +8,7 @@
     <PackageVersion Condition="'$(IsReleaseCandidate)' != 'true' AND '$(VersionSuffix)' == ''">$(VersionPrefix)-preview.260402.1</PackageVersion>
     <PackageVersion Condition="'$(IsReleased)' == 'true'">$(VersionPrefix)</PackageVersion>
     <!-- Branch-specific override to distinguish from mainline packages -->
-    <PackageVersion>0.9.0-hosted.260402.2</PackageVersion>
+    <PackageVersion>0.9.0-hosted.260403.1</PackageVersion>
     <GitTag>1.0.0</GitTag>
 
     <Configurations>Debug;Release;Publish</Configurations>

dotnet/samples/04-hosting/FoundryResponsesRepl/FoundryResponsesRepl.csproj

@@ -0,0 +1,21 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFrameworks>net10.0</TargetFrameworks>
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <CentralPackageTransitivePinningEnabled>false</CentralPackageTransitivePinningEnabled>
+    <NoWarn>$(NoWarn);NU1903;NU1605</NoWarn>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Azure.Core" />
+    <PackageReference Include="OpenAI" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\..\..\src\Microsoft.Agents.AI.OpenAI\Microsoft.Agents.AI.OpenAI.csproj" />
+  </ItemGroup>
+
+</Project>

dotnet/samples/04-hosting/FoundryResponsesRepl/Program.cs

@@ -0,0 +1,98 @@
+// Foundry Responses Client REPL
+//
+// Connects to a Foundry Responses agent running on a given endpoint
+// and provides an interactive multi-turn chat REPL.
+//
+// Usage:
+//   dotnet run                                    (connects to http://localhost:8088)
+//   dotnet run -- --endpoint http://localhost:9090
+//   dotnet run -- --endpoint https://my-foundry-project.services.ai.azure.com
+//
+// The endpoint should be running a Foundry Responses server (POST /responses).
+
+using System.ClientModel;
+using Microsoft.Agents.AI;
+using OpenAI;
+using OpenAI.Responses;
+
+// ── Parse args ────────────────────────────────────────────────────────────────
+
+string endpointUrl = "http://localhost:8088";
+for (int i = 0; i < args.Length - 1; i++)
+{
+    if (args[i] is "--endpoint" or "-e")
+    {
+        endpointUrl = args[i + 1];
+    }
+}
+
+// ── Create an agent-framework agent backed by the remote Responses endpoint ──
+
+// The OpenAI SDK's ResponsesClient can target any OpenAI-compatible endpoint.
+// We use a dummy API key since our local server doesn't require auth.
+var credential = new ApiKeyCredential(
+    Environment.GetEnvironmentVariable("RESPONSES_API_KEY") ?? "no-key-needed");
+
+var openAiClient = new OpenAIClient(
+    credential,
+    new OpenAIClientOptions { Endpoint = new Uri(endpointUrl) });
+
+ResponsesClient responsesClient = openAiClient.GetResponsesClient();
+
+// Wrap as an agent-framework AIAgent via the OpenAI extensions.
+// We pass an empty model since hosted agents use their own model configuration.
+AIAgent agent = responsesClient.AsAIAgent(
+    model: "",
+    name: "remote-agent");
+
+// Create a session so multi-turn context is preserved via previous_response_id
+AgentSession session = await agent.CreateSessionAsync();
+
+// ── REPL ──────────────────────────────────────────────────────────────────────
+
+Console.ForegroundColor = ConsoleColor.Cyan;
+Console.WriteLine("╔══════════════════════════════════════════════════════════╗");
+Console.WriteLine("║  Foundry Responses Client REPL                          ║");
+Console.WriteLine($"║  Connected to: {endpointUrl,-41}║");
+Console.WriteLine("║  Type a message or 'quit' to exit                       ║");
+Console.WriteLine("╚══════════════════════════════════════════════════════════╝");
+Console.ResetColor();
+Console.WriteLine();
+
+while (true)
+{
+    Console.ForegroundColor = ConsoleColor.Green;
+    Console.Write("You> ");
+    Console.ResetColor();
+
+    string? input = Console.ReadLine();
+    if (string.IsNullOrWhiteSpace(input)) continue;
+    if (input.Equals("quit", StringComparison.OrdinalIgnoreCase) ||
+        input.Equals("exit", StringComparison.OrdinalIgnoreCase))
+        break;
+
+    try
+    {
+        Console.ForegroundColor = ConsoleColor.Yellow;
+        Console.Write("Agent> ");
+        Console.ResetColor();
+
+        // Stream the response token-by-token
+        await foreach (var update in agent.RunStreamingAsync(input, session))
+        {
+            Console.Write(update);
+        }
+
+        Console.WriteLine();
+    }
+    catch (Exception ex)
+    {
+        Console.ForegroundColor = ConsoleColor.Red;
+        Console.WriteLine($"Error: {ex.Message}");
+        Console.ResetColor();
+    }
+
+    Console.WriteLine();
+}
+
+Console.WriteLine("Goodbye!");

dotnet/samples/04-hosting/FoundryResponsesRepl/Properties/launchSettings.json

@@ -0,0 +1,12 @@
+{
+  "profiles": {
+    "FoundryResponsesRepl": {
+      "commandName": "Project",
+      "launchBrowser": true,
+      "environmentVariables": {
+        "ASPNETCORE_ENVIRONMENT": "Development"
+      },
+      "applicationUrl": "https://localhost:61980;http://localhost:61981"
+    }
+  }
+}

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

@@ -69,7 +69,10 @@ internal static class InputConverter
             Temperature = (float?)request.Temperature,
             TopP = (float?)request.TopP,
             MaxOutputTokens = (int?)request.MaxOutputTokens,
-            ModelId = request.Model,
+            // Note: We intentionally do NOT set ModelId from request.Model here.
+            // The hosted agent already has its own model configured, and passing
+            // the client-provided model would override it (causing failures when
+            // clients send placeholder values like "hosted-agent").
         };
     }
 

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

@@ -157,7 +157,7 @@ public class InputConverterTests
         Assert.Equal(0.7f, options.Temperature);
         Assert.Equal(0.9f, options.TopP);
         Assert.Equal(1000, options.MaxOutputTokens);
-        Assert.Equal("gpt-4o", options.ModelId);
+        Assert.Null(options.ModelId);
     }
 
     [Fact]
@@ -659,12 +659,13 @@ public class InputConverterTests
     }
 
     [Fact]
-    public void ConvertToChatOptions_ModelId_SetFromRequest()
+    public void ConvertToChatOptions_ModelId_NotSetFromRequest()
     {
         var request = AzureAIAgentServerResponsesModelFactory.CreateResponse(model: "my-model");
 
         var options = InputConverter.ConvertToChatOptions(request);
 
-        Assert.Equal("my-model", options.ModelId);
+        // Model from the request is intentionally NOT propagated — the hosted agent uses its own model.
+        Assert.Null(options.ModelId);
     }
 }