Flip default on FunctionInvokingChatClient.ConcurrentInvocation (#5485)

* Flip default on FunctionInvokingChatClient.ConcurrentInvocation

For better reliability, default ConcurrentInvocation to false, so that it doesn't introduce concurrency / parallelism where there wasn't any.

* Update src/Libraries/Microsoft.Extensions.AI/ChatCompletion/FunctionInvokingChatClient.cs

Co-authored-by: Igor Velikorossov <RussKie@users.noreply.github.com>

---------

Co-authored-by: Igor Velikorossov <RussKie@users.noreply.github.com>

src/Libraries/Microsoft.Extensions.AI/ChatCompletion/FunctionInvokingChatClient.cs

@@ -82,15 +82,14 @@ public class FunctionInvokingChatClient : DelegatingChatClient
     /// <remarks>
     /// <para>
     /// An individual response from the inner client may contain multiple function call requests.
-    /// By default, such function calls may be issued to execute concurrently with each other. Set
+    /// By default, such function calls are processed serially. Set <see cref="ConcurrentInvocation"/> to
-    /// <see cref="ConcurrentInvocation"/> to false to disable such concurrent invocation and force
+    /// <see langword="true"/> to enable concurrent invocation such that multiple function calls may execute in parallel.
-    /// the functions to be invoked serially.
     /// </para>
     /// <para>
-    /// The default value is <see langword="true"/>.
+    /// The default value is <see langword="false"/>.
     /// </para>
     /// </remarks>
-    public bool ConcurrentInvocation { get; set; } = true;
+    public bool ConcurrentInvocation { get; set; }
 
     /// <summary>
     /// Gets or sets a value indicating whether to keep intermediate messages in the chat history.

test/Libraries/Microsoft.Extensions.AI.Tests/ChatCompletion/FunctionInvokingChatClientTests.cs

@@ -12,6 +12,19 @@ namespace Microsoft.Extensions.AI;
 
 public class FunctionInvokingChatClientTests
 {
+    [Fact]
+    public void Ctor_HasExpectedDefaults()
+    {
+        using TestChatClient innerClient = new();
+        using FunctionInvokingChatClient client = new(innerClient);
+
+        Assert.False(client.ConcurrentInvocation);
+        Assert.False(client.DetailedErrors);
+        Assert.True(client.KeepFunctionCallingMessages);
+        Assert.Null(client.MaximumIterationsPerRequest);
+        Assert.False(client.RetryOnError);
+    }
+
     [Fact]
     public async Task SupportsSingleFunctionCallPerRequestAsync()
     {
@@ -71,7 +84,7 @@ public class FunctionInvokingChatClientTests
     }
 
     [Fact]
-    public async Task ParallelFunctionCallsInvokedConcurrentlyByDefaultAsync()
+    public async Task ParallelFunctionCallsMayBeInvokedConcurrentlyAsync()
     {
         using var barrier = new Barrier(2);
 
@@ -97,11 +110,11 @@ public class FunctionInvokingChatClientTests
                 new FunctionResultContent("callId2", "Func", result: "worldworld"),
             ]),
             new ChatMessage(ChatRole.Assistant, "done"),
-        ]);
+        ], configurePipeline: b => b.Use(s => new FunctionInvokingChatClient(s) { ConcurrentInvocation = true }));
     }
 
     [Fact]
-    public async Task ConcurrentInvocationOfParallelCallsCanBeDisabledAsync()
+    public async Task ConcurrentInvocationOfParallelCallsDisabledByDefaultAsync()
     {
         int activeCount = 0;
 
@@ -130,7 +143,7 @@ public class FunctionInvokingChatClientTests
                 new FunctionResultContent("callId2", "Func", result: "worldworld"),
             ]),
             new ChatMessage(ChatRole.Assistant, "done"),
-        ], configurePipeline: b => b.Use(s => new FunctionInvokingChatClient(s) { ConcurrentInvocation = false }));
+        ]);
     }
 
     [Theory]