.NET: Bump MEAI to 10.5.1 and add Foundry per-call x-client header support

dotnet/Directory.Packages.props

@@ -71,12 +71,12 @@
     <PackageVersion Include="Microsoft.AspNetCore.OpenApi" Version="10.0.0" />
     <PackageVersion Include="Swashbuckle.AspNetCore.SwaggerUI" Version="10.0.0" />
     <!-- Microsoft.Extensions.* -->
-    <PackageVersion Include="Microsoft.Extensions.AI" Version="10.5.0" />
-    <PackageVersion Include="Microsoft.Extensions.AI.Abstractions" Version="10.5.0" />
+    <PackageVersion Include="Microsoft.Extensions.AI" Version="10.5.1" />
+    <PackageVersion Include="Microsoft.Extensions.AI.Abstractions" Version="10.5.1" />
     <PackageVersion Include="Microsoft.Extensions.AI.Evaluation" Version="10.4.0" />
     <PackageVersion Include="Microsoft.Extensions.AI.Evaluation.Quality" Version="10.4.0" />
     <PackageVersion Include="Microsoft.Extensions.AI.Evaluation.Safety" Version="10.3.0-preview.1.26109.11" />
-    <PackageVersion Include="Microsoft.Extensions.AI.OpenAI" Version="10.5.0" />
+    <PackageVersion Include="Microsoft.Extensions.AI.OpenAI" Version="10.5.1" />
     <PackageVersion Include="Microsoft.Extensions.Caching.Memory" Version="10.0.0" />
     <PackageVersion Include="Microsoft.Extensions.Compliance.Abstractions" Version="10.5.0" />
     <PackageVersion Include="Microsoft.Extensions.Configuration" Version="10.0.1" />

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

@@ -4,6 +4,7 @@
 using System.Collections.Generic;
 using System.Reflection;
 using System.Threading.Tasks;
+using Microsoft.Extensions.AI;
 
 namespace Microsoft.Agents.AI.Foundry.Hosting;
 
@@ -18,10 +19,9 @@ namespace Microsoft.Agents.AI.Foundry.Hosting;
 /// is already present in the <c>User-Agent</c> header, the policy does not append it again.
 /// </para>
 /// <para>
-/// This policy is added at request time (per-call <see cref="PipelinePosition"/>)
-/// by <see cref="UserAgentResponsesClient"/> when invoking the wrapped
-/// <see cref="OpenAI.Responses.ResponsesClient"/>. It is only registered when an agent is
-/// resolved by the Foundry hosting layer.
+/// This policy is added at hosted-agent resolution time via the MEAI 10.5.1
+/// <see cref="OpenAIRequestPolicies"/> hook on the agent's underlying chat client. It is only
+/// registered when an agent is resolved by the Foundry hosting layer.
 /// </para>
 /// </remarks>
 internal sealed class HostedAgentUserAgentPolicy : PipelinePolicy

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

@@ -1,8 +1,9 @@
 // Copyright (c) Microsoft. All rights reserved.
 
 using System;
+using System.ClientModel.Primitives;
 using System.Diagnostics.CodeAnalysis;
-using System.Reflection;
+using System.Runtime.CompilerServices;
 using Azure.AI.AgentServer.Responses;
 using Azure.Core;
 using Azure.Identity;
@@ -11,7 +12,6 @@
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.DependencyInjection.Extensions;
 using Microsoft.Shared.DiagnosticIds;
-using OpenAI.Responses;
 
 namespace Microsoft.Agents.AI.Foundry.Hosting;
 
@@ -207,84 +207,45 @@ internal static AIAgent ApplyOpenTelemetry(AIAgent agent)
     }
 
     /// <summary>
-    /// Attempts to wrap the agent's underlying <see cref="ResponsesClient"/>
-    /// with a <see cref="UserAgentResponsesClient"/> so every outgoing Responses-API request
-    /// carries the hosted-agent <c>User-Agent</c> segment.
+    /// Registers the hosted-agent <c>User-Agent</c> supplement policy
+    /// (<see cref="HostedAgentUserAgentPolicy"/>) on the agent's underlying chat client via the
+    /// MEAI 10.5.1 <see cref="OpenAIRequestPolicies"/> hook so every outgoing OpenAI Responses
+    /// request carries the segment <c>foundry-hosting/agent-framework-dotnet/{version}</c>.
     /// </summary>
     /// <remarks>
     /// <para>
     /// Best-effort and idempotent. The method is a no-op when:
     /// <list type="bullet">
     /// <item><description><paramref name="agent"/> exposes no <see cref="IChatClient"/>;</description></item>
-    /// <item><description>the chat client is not backed by MEAI's internal <c>OpenAIResponsesChatClient</c> (e.g., a non-OpenAI provider or a custom impl);</description></item>
-    /// <item><description>the inner <see cref="ResponsesClient"/> is already a <see cref="UserAgentResponsesClient"/>.</description></item>
+    /// <item><description>the chat client is not OpenAI-backed (the <see cref="OpenAIRequestPolicies"/> service lookup returns <see langword="null"/>);</description></item>
+    /// <item><description>the policy was already registered on this client by a prior invocation (deduped via reflection on <c>OpenAIRequestPolicies._entries</c>).</description></item>
     /// </list>
     /// </para>
     /// <para>
-    /// Works for any <see cref="ResponsesClient"/>-derived inner client — both the Foundry-specific
-    /// <see cref="Azure.AI.Extensions.OpenAI.ProjectResponsesClient"/> and the native OpenAI
-    /// <see cref="ResponsesClient"/> obtained from <see cref="OpenAI.OpenAIClient"/>. The wrapper preserves
-    /// the inner client's pipeline (Transport, RetryPolicy, NetworkTimeout, OrganizationId / ProjectId /
-    /// UserAgentApplicationId, custom policies) because every override delegates to the inner instance.
-    /// </para>
-    /// <para>
-    /// Returns the same <paramref name="agent"/> instance unchanged. Mutation happens via
-    /// reflection on MEAI's private <c>_responseClient</c> field; the agent itself is not wrapped.
+    /// Returns the same <paramref name="agent"/> instance unchanged. The policy is installed
+    /// on the chat client; the agent itself is not wrapped.
     /// </para>
     /// </remarks>
     internal static AIAgent TryApplyUserAgent(AIAgent agent)
     {
         var chatClient = agent.GetService<IChatClient>();
-        if (chatClient is null)
-        {
-            return agent;
-        }
-
-        var meaiType = s_meaiResponsesChatClientType;
-        if (meaiType is null)
-        {
-            return agent;
-        }
-
-        var meaiInstance = chatClient.GetService(meaiType);
-        if (meaiInstance is null)
-        {
-            return agent;
-        }
-
-        var field = s_meaiResponseClientField;
-        if (field is null)
+        if (chatClient?.GetService<OpenAIRequestPolicies>() is { } policies)
         {
-            return agent;
-        }
-
-        var current = field.GetValue(meaiInstance) as ResponsesClient;
-        if (current is null or UserAgentResponsesClient)
-        {
-            return agent;
+            // Hosted agents are typically singletons resolved per request, so AddPolicy must be
+            // called at most once per OpenAIRequestPolicies instance to avoid unbounded growth of
+            // the policy list (each entry adds per-request CPU work even though the User-Agent
+            // value stays stable). Track which instances we have already wired with a
+            // ConditionalWeakTable keyed on the OpenAIRequestPolicies reference; the table holds
+            // weak references so it does not extend the lifetime of the chat client.
+            if (s_userAgentRegistrations.TryAdd(policies, s_boxedTrue))
+            {
+                policies.AddPolicy(HostedAgentUserAgentPolicy.Instance, PipelinePosition.PerCall);
+            }
         }
 
-        field.SetValue(meaiInstance, new UserAgentResponsesClient(current));
         return agent;
     }
 
-    /// <summary>
-    /// MEAI's internal <c>OpenAIResponsesChatClient</c> type, resolved once via reflection.
-    /// <see langword="null"/> if the type cannot be found (e.g., MEAI version drift).
-    /// </summary>
-    [UnconditionalSuppressMessage("Trimming", "IL2026:RequiresUnreferencedCode",
-        Justification = "MEAI's OpenAIResponsesChatClient is referenced through MicrosoftExtensionsAIResponsesExtensions and survives trimming.")]
-    [UnconditionalSuppressMessage("Trimming", "IL2073:RequiresUnreferencedCode",
-        Justification = "MEAI's OpenAIResponsesChatClient is referenced through MicrosoftExtensionsAIResponsesExtensions and survives trimming.")]
-    private static readonly Type? s_meaiResponsesChatClientType =
-        typeof(MicrosoftExtensionsAIResponsesExtensions).Assembly.GetType("Microsoft.Extensions.AI.OpenAIResponsesChatClient");
-
-    /// <summary>
-    /// MEAI's internal <c>_responseClient</c> field on <c>OpenAIResponsesChatClient</c>,
-    /// resolved once via reflection. <see langword="null"/> if the field cannot be found.
-    /// </summary>
-    [UnconditionalSuppressMessage("Trimming", "IL2080:RequiresDynamicallyAccessedMembers",
-        Justification = "OpenAIResponsesChatClient and its private fields are preserved by the polyfill design; MEAI does the same reflection internally.")]
-    private static readonly FieldInfo? s_meaiResponseClientField =
-        s_meaiResponsesChatClientType?.GetField("_responseClient", BindingFlags.NonPublic | BindingFlags.Instance);
+    private static readonly object s_boxedTrue = new();
+    private static readonly ConditionalWeakTable<OpenAIRequestPolicies, object> s_userAgentRegistrations = new();
 }

dotnet/src/Microsoft.Agents.AI.Foundry/ClientHeadersAgent.cs

@@ -0,0 +1,103 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using System.Collections.Generic;
+using System.Runtime.CompilerServices;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.Extensions.AI;
+
+namespace Microsoft.Agents.AI.Foundry;
+
+/// <summary>
+/// Delegating <see cref="AIAgent"/> that captures any <c>x-client-*</c> headers stored on
+/// <see cref="ChatClientAgentRunOptions.ChatOptions"/> by callers of
+/// <see cref="ClientHeadersExtensions.WithClientHeader(ChatOptions, string, string)"/> and pushes
+/// them onto a <see cref="ClientHeadersScope"/> for the lifetime of the run. The scope is read by
+/// <see cref="ClientHeadersPolicy"/> inside the SCM transport pipeline and stamped onto the
+/// outbound request.
+/// </summary>
+/// <remarks>
+/// <para>
+/// The decorator snapshots the header dictionary at scope-push time so concurrent runs that share
+/// the same <see cref="ChatOptions"/> reference are isolated; mutating the source dictionary after
+/// <c>RunAsync</c> begins does not leak into in-flight requests.
+/// </para>
+/// <para>
+/// Streaming uses the async-iterator pattern so the AsyncLocal scope stays alive across yields,
+/// which is required because the underlying HTTP send happens during enumeration.
+/// </para>
+/// </remarks>
+internal sealed class ClientHeadersAgent : DelegatingAIAgent
+{
+    public ClientHeadersAgent(AIAgent innerAgent)
+        : base(innerAgent)
+    {
+    }
+
+    /// <inheritdoc/>
+    protected override Task<AgentResponse> RunCoreAsync(
+        IEnumerable<ChatMessage> messages,
+        AgentSession? session = null,
+        AgentRunOptions? options = null,
+        CancellationToken cancellationToken = default)
+    {
+        var snapshot = TrySnapshot(options);
+        if (snapshot is null)
+        {
+            return this.InnerAgent.RunAsync(messages, session, options, cancellationToken);
+        }
+
+        return RunAsyncCoreAsync(messages, session, options, snapshot, cancellationToken);
+
+        async Task<AgentResponse> RunAsyncCoreAsync(
+            IEnumerable<ChatMessage> innerMessages,
+            AgentSession? innerSession,
+            AgentRunOptions? innerOptions,
+            Dictionary<string, string> innerSnapshot,
+            CancellationToken innerCt)
+        {
+            using var _ = ClientHeadersScope.Push(innerSnapshot);
+            return await this.InnerAgent.RunAsync(innerMessages, innerSession, innerOptions, innerCt).ConfigureAwait(false);
+        }
+    }
+
+    /// <inheritdoc/>
+    protected override async IAsyncEnumerable<AgentResponseUpdate> RunCoreStreamingAsync(
+        IEnumerable<ChatMessage> messages,
+        AgentSession? session = null,
+        AgentRunOptions? options = null,
+        [EnumeratorCancellation] CancellationToken cancellationToken = default)
+    {
+        var snapshot = TrySnapshot(options);
+        using var _ = snapshot is null ? default : ClientHeadersScope.Push(snapshot);
+
+        await foreach (var update in this.InnerAgent.RunStreamingAsync(messages, session, options, cancellationToken).ConfigureAwait(false))
+        {
+            yield return update;
+        }
+    }
+
+    /// <summary>Reads the header dictionary stamped by <c>WithClientHeader(s)</c> and returns an immutable snapshot, or <see langword="null"/> if none.</summary>
+    private static Dictionary<string, string>? TrySnapshot(AgentRunOptions? options)
+    {
+        if (options is not ChatClientAgentRunOptions { ChatOptions: { } chatOptions })
+        {
+            return null;
+        }
+
+        var headers = chatOptions.GetClientHeaders();
+        if (headers is null || headers.Count == 0)
+        {
+            return null;
+        }
+
+        // Copy to defeat caller mutation after RunAsync starts.
+        var copy = new Dictionary<string, string>(headers.Count, System.StringComparer.OrdinalIgnoreCase);
+        foreach (var kvp in headers)
+        {
+            copy[kvp.Key] = kvp.Value;
+        }
+
+        return copy;
+    }
+}