.NET: Add Invocations protocol samples (hosted echo agent + client)

dotnet/samples/04-hosting/FoundryHostedAgents/HostedAgentsV2/Hosted-Invocations-EchoAgent/Dockerfile

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+# Use the official .NET 10.0 ASP.NET runtime as a parent image
+FROM mcr.microsoft.com/dotnet/aspnet:10.0 AS base
+WORKDIR /app
+
+FROM mcr.microsoft.com/dotnet/sdk:10.0 AS build
+WORKDIR /src
+COPY . .
+RUN dotnet restore
+RUN dotnet publish -c Release -o /app/publish
+
+# Final stage
+FROM base AS final
+WORKDIR /app
+COPY --from=build /app/publish .
+EXPOSE 8088
+ENV ASPNETCORE_URLS=http://+:8088
+ENTRYPOINT ["dotnet", "HostedInvocationsEchoAgent.dll"]

dotnet/samples/04-hosting/FoundryHostedAgents/HostedAgentsV2/Hosted-Invocations-EchoAgent/Dockerfile.contributor

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+# Dockerfile for contributors building from the agent-framework repository source.
+#
+# This project uses ProjectReference to the local Microsoft.Agents.AI.Abstractions source,
+# which means a standard multi-stage Docker build cannot resolve dependencies outside
+# this folder. Instead, pre-publish the app targeting the container runtime and copy
+# the output into the container:
+#
+#   dotnet publish -c Debug -f net10.0 -r linux-musl-x64 --self-contained false -o out
+#   docker build -f Dockerfile.contributor -t hosted-invocations-echo-agent .
+#   docker run --rm -p 8088:8088 hosted-invocations-echo-agent
+#
+# For end-users consuming the NuGet package (not ProjectReference), use the standard
+# Dockerfile which performs a full dotnet restore + publish inside the container.
+FROM mcr.microsoft.com/dotnet/aspnet:10.0-alpine AS final
+WORKDIR /app
+COPY out/ .
+EXPOSE 8088
+ENV ASPNETCORE_URLS=http://+:8088
+ENTRYPOINT ["dotnet", "HostedInvocationsEchoAgent.dll"]

dotnet/samples/04-hosting/FoundryHostedAgents/HostedAgentsV2/Hosted-Invocations-EchoAgent/EchoAIAgent.cs

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+// Copyright (c) Microsoft. All rights reserved.
+
+using System.Runtime.CompilerServices;
+using System.Text.Json;
+using Microsoft.Extensions.AI;
+
+namespace Microsoft.Agents.AI;
+
+/// <summary>
+/// A minimal <see cref="AIAgent"/> that echoes the user's input text back as the response.
+/// No LLM or external service is required.
+/// </summary>
+public sealed class EchoAIAgent : AIAgent
+{
+    /// <inheritdoc/>
+    public override string Name => "echo-agent";
+
+    /// <inheritdoc/>
+    public override string Description => "An agent that echoes back the input message.";
+
+    /// <inheritdoc/>
+    protected override Task<AgentResponse> RunCoreAsync(
+        IEnumerable<ChatMessage> messages,
+        AgentSession? session = null,
+        AgentRunOptions? options = null,
+        CancellationToken cancellationToken = default)
+    {
+        var inputText = GetInputText(messages);
+        var response = new AgentResponse(new ChatMessage(ChatRole.Assistant, $"Echo: {inputText}"));
+        return Task.FromResult(response);
+    }
+
+    /// <inheritdoc/>
+    protected override async IAsyncEnumerable<AgentResponseUpdate> RunCoreStreamingAsync(
+        IEnumerable<ChatMessage> messages,
+        AgentSession? session = null,
+        AgentRunOptions? options = null,
+        [EnumeratorCancellation] CancellationToken cancellationToken = default)
+    {
+        var inputText = GetInputText(messages);
+        yield return new AgentResponseUpdate
+        {
+            Role = ChatRole.Assistant,
+            Contents = [new TextContent($"Echo: {inputText}")],
+        };
+
+        await Task.CompletedTask;
+    }
+
+    /// <inheritdoc/>
+    protected override ValueTask<AgentSession> CreateSessionCoreAsync(CancellationToken cancellationToken = default)
+        => new(new EchoAgentSession());
+
+    /// <inheritdoc/>
+    protected override ValueTask<JsonElement> SerializeSessionCoreAsync(
+        AgentSession session,
+        JsonSerializerOptions? jsonSerializerOptions = null,
+        CancellationToken cancellationToken = default)
+        => new(JsonSerializer.SerializeToElement(new { }, jsonSerializerOptions));
+
+    /// <inheritdoc/>
+    protected override ValueTask<AgentSession> DeserializeSessionCoreAsync(
+        JsonElement serializedState,
+        JsonSerializerOptions? jsonSerializerOptions = null,
+        CancellationToken cancellationToken = default)
+        => new(new EchoAgentSession());
+
+    private static string GetInputText(IEnumerable<ChatMessage> messages)
+    {
+        foreach (var message in messages)
+        {
+            if (message.Role == ChatRole.User)
+            {
+                return message.Text ?? string.Empty;
+            }
+        }
+
+        return string.Empty;
+    }
+
+    /// <summary>
+    /// Minimal session for the echo agent. No state is persisted.
+    /// </summary>
+    private sealed class EchoAgentSession : AgentSession;
+}

dotnet/samples/04-hosting/FoundryHostedAgents/HostedAgentsV2/Hosted-Invocations-EchoAgent/EchoInvocationHandler.cs

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+// Copyright (c) Microsoft. All rights reserved.
+
+using Azure.AI.AgentServer.Invocations;
+using Microsoft.Agents.AI;
+using Microsoft.AspNetCore.Http;
+
+namespace HostedInvocationsEchoAgent;
+
+/// <summary>
+/// An <see cref="InvocationHandler"/> that reads the request body as plain text,
+/// passes it to the <see cref="EchoAIAgent"/>, and writes the response back.
+/// </summary>
+public sealed class EchoInvocationHandler(EchoAIAgent agent) : InvocationHandler
+{
+    /// <inheritdoc/>
+    public override async Task HandleAsync(
+        HttpRequest request,
+        HttpResponse response,
+        InvocationContext context,
+        CancellationToken cancellationToken)
+    {
+        // Read the raw text from the request body.
+        using var reader = new StreamReader(request.Body);
+        var input = await reader.ReadToEndAsync(cancellationToken);
+
+        // Run the echo agent with the input text.
+        var agentResponse = await agent.RunAsync(input, cancellationToken: cancellationToken);
+
+        // Write the agent response text back to the HTTP response.
+        response.ContentType = "text/plain";
+        await response.WriteAsync(agentResponse.Text, cancellationToken);
+    }
+}

dotnet/samples/04-hosting/FoundryHostedAgents/HostedAgentsV2/Hosted-Invocations-EchoAgent/Hosted-Invocations-EchoAgent.csproj

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+<Project Sdk="Microsoft.NET.Sdk.Web">
+
+  <PropertyGroup>
+    <TargetFrameworks>net10.0</TargetFrameworks>
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <CentralPackageTransitivePinningEnabled>false</CentralPackageTransitivePinningEnabled>
+    <RootNamespace>HostedInvocationsEchoAgent</RootNamespace>
+    <AssemblyName>HostedInvocationsEchoAgent</AssemblyName>
+    <NoWarn>$(NoWarn);</NoWarn>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Azure.AI.AgentServer.Invocations" />
+  </ItemGroup>
+
+  <!-- For contributors: uses ProjectReference to build against local source -->
+  <ItemGroup>
+    <ProjectReference Include="..\..\..\..\..\src\Microsoft.Agents.AI.Abstractions\Microsoft.Agents.AI.Abstractions.csproj" />
+  </ItemGroup>
+
+  <!-- For end-users: uncomment the PackageReference below and remove the ProjectReference above
+  <ItemGroup>
+    <PackageReference Include="Microsoft.Agents.AI.Abstractions" Version="1.0.0" />
+    <PackageReference Include="Azure.AI.AgentServer.Invocations" />
+  </ItemGroup>
+  -->
+
+</Project>

dotnet/samples/04-hosting/FoundryHostedAgents/HostedAgentsV2/Hosted-Invocations-EchoAgent/Program.cs

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+// Copyright (c) Microsoft. All rights reserved.
+
+using Azure.AI.AgentServer.Invocations;
+using HostedInvocationsEchoAgent;
+using Microsoft.Agents.AI;
+
+var builder = WebApplication.CreateBuilder(args);
+
+// Register the echo agent as a singleton (no LLM needed).
+builder.Services.AddSingleton<EchoAIAgent>();
+
+// Register the Invocations SDK services and wire the handler.
+builder.Services.AddInvocationsServer();
+builder.Services.AddScoped<InvocationHandler, EchoInvocationHandler>();
+
+var app = builder.Build();
+
+// Map the Invocations protocol endpoints:
+//   POST /invocations              — invoke the agent
+//   GET  /invocations/{id}         — get result (not used by this sample)
+//   POST /invocations/{id}/cancel  — cancel (not used by this sample)
+app.MapInvocationsServer();
+
+app.Run();

dotnet/samples/04-hosting/FoundryHostedAgents/HostedAgentsV2/Hosted-Invocations-EchoAgent/Properties/launchSettings.json

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+{
+  "profiles": {
+    "Hosted-Invocations-EchoAgent": {
+      "commandName": "Project",
+      "environmentVariables": {
+        "ASPNETCORE_ENVIRONMENT": "Development"
+      },
+      "applicationUrl": "http://localhost:8088"
+    }
+  }
+}

dotnet/samples/04-hosting/FoundryHostedAgents/HostedAgentsV2/Hosted-Invocations-EchoAgent/README.md

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+# Hosted-Invocations-EchoAgent
+
+A minimal echo agent hosted as a Foundry Hosted Agent using the **Invocations protocol**. The agent reads the request body as plain text, passes it through a custom `EchoAIAgent`, and writes the echoed text back in the response. No LLM or Azure credentials are required.
+
+## Prerequisites
+
+- [.NET 10 SDK](https://dotnet.microsoft.com/download/dotnet/10.0)
+
+## Running directly (contributors)
+
+This project uses `ProjectReference` to build against the local Agent Framework source.
+
+```bash
+cd dotnet/samples/04-hosting/FoundryHostedAgents/HostedAgentsV2/Hosted-Invocations-EchoAgent
+dotnet run
+```
+
+The agent will start on `http://localhost:8088`.
+
+### Test it
+
+```bash
+curl -X POST http://localhost:8088/invocations \
+  -H "Content-Type: text/plain" \
+  -d "Hello, world!"
+```
+
+Expected response:
+
+```
+Echo: Hello, world!
+```
+
+## Running with Docker
+
+Since this project uses `ProjectReference`, the standard `Dockerfile` cannot resolve dependencies outside this folder. Use `Dockerfile.contributor` which takes a pre-published output.
+
+### 1. Publish for the container runtime (Linux Alpine)
+
+```bash
+dotnet publish -c Debug -f net10.0 -r linux-musl-x64 --self-contained false -o out
+```
+
+### 2. Build the Docker image
+
+```bash
+docker build -f Dockerfile.contributor -t hosted-invocations-echo-agent .
+```
+
+### 3. Run the container
+
+```bash
+docker run --rm -p 8088:8088 hosted-invocations-echo-agent
+```
+
+### 4. Test it
+
+```bash
+curl -X POST http://localhost:8088/invocations \
+  -H "Content-Type: text/plain" \
+  -d "Hello from Docker!"
+```
+
+## NuGet package users
+
+If you are consuming the Agent Framework as a NuGet package (not building from source), use the standard `Dockerfile` instead of `Dockerfile.contributor`. See the commented section in `Hosted-Invocations-EchoAgent.csproj` for the `PackageReference` alternative.

dotnet/samples/04-hosting/FoundryHostedAgents/HostedAgentsV2/Hosted-Invocations-EchoAgent/agent.manifest.yaml

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+# yaml-language-server: $schema=https://raw.githubusercontent.com/microsoft/AgentSchema/refs/heads/main/schemas/v1.0/AgentManifest.yaml
+name: hosted-invocations-echo-agent
+displayName: "Hosted Invocations Echo Agent"
+
+description: >
+  A minimal echo agent hosted as a Foundry Hosted Agent using the Invocations
+  protocol. Reads the request body as plain text, echoes it back in the response.
+
+metadata:
+  tags:
+    - AI Agent Hosting
+    - Azure AI AgentServer
+    - Invocations Protocol
+    - Agent Framework
+
+template:
+  name: hosted-invocations-echo-agent
+  kind: hosted
+  protocols:
+    - protocol: invocations
+      version: 1.0.0
+  resources:
+    cpu: "0.25"
+    memory: 0.5Gi
+parameters:
+  properties: []
+resources: []

dotnet/samples/04-hosting/FoundryHostedAgents/HostedAgentsV2/Hosted-Invocations-EchoAgent/agent.yaml

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+# yaml-language-server: $schema=https://raw.githubusercontent.com/microsoft/AgentSchema/refs/heads/main/schemas/v1.0/ContainerAgent.yaml
+kind: hosted
+name: hosted-invocations-echo-agent
+protocols:
+  - protocol: invocations
+    version: 1.0.0
+resources:
+  cpu: "0.25"
+  memory: 0.5Gi