dotnet: MapAGUI supports per-request agent selection

Author: Manuel Naujoks

dotnet/samples/AGUIClientServer/AGUIDojoServer/Program.cs

@@ -40,6 +40,21 @@
 var jsonOptions = app.Services.GetRequiredService<IOptions<Microsoft.AspNetCore.Http.Json.JsonOptions>>();
 app.MapAGUI("/shared_state", ChatClientAgentFactory.CreateSharedState(jsonOptions.Value.SerializerOptions));
 
+app.MapAGUI("/agents/{agentId}", async (context) =>
+{
+    var agentId = context.Request.RouteValues["agentId"]?.ToString() ?? string.Empty;
+    return agentId switch
+    {
+        "agentic_chat" => ChatClientAgentFactory.CreateAgenticChat(),
+        "backend_tool_rendering" => ChatClientAgentFactory.CreateBackendToolRendering(),
+        "human_in_the_loop" => ChatClientAgentFactory.CreateHumanInTheLoop(),
+        "tool_based_generative_ui" => ChatClientAgentFactory.CreateToolBasedGenerativeUI(),
+        "agentic_generative_ui" => ChatClientAgentFactory.CreateAgenticUI(),
+        "shared_state" => ChatClientAgentFactory.CreateSharedState(jsonOptions.Value.SerializerOptions),
+        _ => throw new ArgumentException($"Unknown agent ID: {agentId}"),
+    };
+});
+
 await app.RunAsync();
 
 public partial class Program { }

dotnet/samples/AGUIClientServer/AGUIServer/Program.cs

@@ -48,4 +48,14 @@
 // Map the AG-UI agent endpoint
 app.MapAGUI("/", agent);
 
+app.MapAGUI("/agents/{agentId}", async (context) =>
+{
+    var agentId = context.Request.RouteValues["agentId"]?.ToString() ?? string.Empty;
+    return agentId switch
+    {
+        "0" => agent,
+        _ => throw new ArgumentException($"Unknown agent ID: {agentId}"),
+    };
+});
+
 await app.RunAsync();

dotnet/src/Microsoft.Agents.AI.Hosting.AGUI.AspNetCore/AGUIEndpointRouteBuilderExtensions.cs

@@ -1,9 +1,11 @@
 // Copyright (c) Microsoft. All rights reserved.
 
+using System;
 using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using System.Threading;
+using System.Threading.Tasks;
 using Microsoft.Agents.AI.Hosting.AGUI.AspNetCore.Shared;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Http;
@@ -32,6 +34,21 @@ public static IEndpointConventionBuilder MapAGUI(
         this IEndpointRouteBuilder endpoints,
         [StringSyntax("route")] string pattern,
         AIAgent aiAgent)
+    {
+        return endpoints.MapAGUI(pattern, _ => ValueTask.FromResult(aiAgent));
+    }
+
+    /// <summary>
+    /// Maps an AG-UI agent endpoint.
+    /// </summary>
+    /// <param name="endpoints">The endpoint route builder.</param>
+    /// <param name="pattern">The URL pattern for the endpoint.</param>
+    /// <param name="aiAgentSelector">A function to select the agent instance based on the HTTP context.</param>
+    /// <returns>An <see cref="IEndpointConventionBuilder"/> for the mapped endpoint.</returns>
+    public static IEndpointConventionBuilder MapAGUI(
+        this IEndpointRouteBuilder endpoints,
+        [StringSyntax("route")] string pattern,
+        Func<HttpContext, ValueTask<AIAgent>> aiAgentSelector)
     {
         return endpoints.MapPost(pattern, async ([FromBody] RunAgentInput? input, HttpContext context, CancellationToken cancellationToken) =>
         {
@@ -63,6 +80,9 @@ public static IEndpointConventionBuilder MapAGUI(
                 }
             };
 
+            // Determine the agent to use
+            var aiAgent = await aiAgentSelector(context).ConfigureAwait(false);
+
             // Run the agent and convert to AG-UI events
             var events = aiAgent.RunStreamingAsync(
                 messages,

dotnet/tests/Microsoft.Agents.AI.Hosting.AGUI.AspNetCore.UnitTests/AGUIEndpointRouteBuilderExtensionsTests.cs

@@ -44,6 +44,26 @@ public void MapAGUIAgent_MapsEndpoint_AtSpecifiedPattern()
         Assert.NotNull(result);
     }
 
+    [Fact]
+    public void MapAGUIAgent_MapsEndpoint_WithOnDemandAgentSelection()
+    {
+        // Arrange
+        Mock<IEndpointRouteBuilder> endpointsMock = new();
+        Mock<IServiceProvider> serviceProviderMock = new();
+
+        endpointsMock.Setup(e => e.ServiceProvider).Returns(serviceProviderMock.Object);
+        endpointsMock.Setup(e => e.DataSources).Returns([]);
+
+        const string Pattern = "/api/agent";
+        AIAgent agent = new TestAgent();
+
+        // Act
+        IEndpointConventionBuilder? result = AGUIEndpointRouteBuilderExtensions.MapAGUI(endpointsMock.Object, Pattern, (httpContext) => ValueTask.FromResult(agent));
+
+        // Assert
+        Assert.NotNull(result);
+    }
+
     [Fact]
     public async Task MapAGUIAgent_WithNullOrInvalidInput_Returns400BadRequestAsync()
     {