chore: import upstream snapshot with attribution

dotnet/tests/Foundry.Hosting.IntegrationTests/UnsupportedProtocolHostedAgentTests.cs

@@ -0,0 +1,52 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using System;
+using System.ClientModel;
+using System.Threading.Tasks;
+using Foundry.Hosting.IntegrationTests.Fixtures;
+
+namespace Foundry.Hosting.IntegrationTests;
+
+/// <summary>
+/// Provokes the protocol-compatibility failure on purpose: the test container (which targets responses
+/// protocol <c>2.0.0</c> only) is deployed under responses protocol <c>1.0.0</c>. Invoking it must
+/// surface the clear <c>501</c> error the container emits (see <c>HostedProtocolCompatibility</c>),
+/// rather than an opaque 500.
+/// </summary>
+[Trait("Category", "FoundryHostedAgents")]
+public sealed class UnsupportedProtocolHostedAgentTests(UnsupportedProtocolHostedAgentFixture fixture) : IClassFixture<UnsupportedProtocolHostedAgentFixture>
+{
+    private readonly UnsupportedProtocolHostedAgentFixture _fixture = fixture;
+
+    [Fact]
+    public async Task RunAsync_OnProtocol1_0_0_FailsWith501UnsupportedProtocolAsync()
+    {
+        // Arrange
+        var agent = this._fixture.Agent;
+
+        // Act: a 1.0.0 deployment sends no x-agent-foundry-call-id header, so the container detects the
+        // unsupported protocol and fails fast. The OpenAI responses client surfaces the container's HTTP
+        // error as a ClientResultException.
+        var ex = await Assert.ThrowsAnyAsync<Exception>(() => agent.RunAsync("Reply with a short greeting."));
+
+        // Assert: the failure is the deliberate 501, not an opaque 500, and the body names the required
+        // protocol so the operator knows the fix.
+        var clientError = FindClientResultException(ex);
+        Assert.NotNull(clientError);
+        Assert.Equal(501, clientError!.Status);
+        Assert.Contains("2.0.0", clientError.Message, StringComparison.OrdinalIgnoreCase);
+    }
+
+    private static ClientResultException? FindClientResultException(Exception? ex)
+    {
+        for (var current = ex; current is not null; current = current.InnerException)
+        {
+            if (current is ClientResultException clientResultException)
+            {
+                return clientResultException;
+            }
+        }
+
+        return null;
+    }
+}