Make it possible to construct the raw completion request from gRPC

This is the pattern followed by the OpenAI implementation too. Allows exposing ALL the underlying options, albeit quite a bit less discoverable.

This should be sufficient fallback for any new (auto-updated) features in the upstream GrokClient generated from .proto files if we ever lag behind it on this library.

We make the test fully isolated from xAI calls to avoid spending tokens on a test that doesn't really require hitting the backend (unlike most of the others).

Author: kzu

.netconfig

@@ -165,4 +165,9 @@
     url = https://github.com/andrewlock/NetEscapades.Configuration/blob/master/src/NetEscapades.Configuration.Yaml/YamlConfigurationStreamParser.cs
     weak
 	sha = a1ec2c6746d96b4f6f140509aa68dcff09271146
-	etag = 9e5c6908edc34eb661d647671f79153d8f3a54ebdc848c8765c78d2715f2f657
+	etag = 9e5c6908edc34eb661d647671f79153d8f3a54ebdc848c8765c78d2715f2f657
+[file "src/Tests/Extensions/CallHelpers.cs"]
+	url = https://github.com/grpc/grpc-dotnet/blob/master/examples/Tester/Tests/Client/Helpers/CallHelpers.cs
+	sha = a04684ab2306e5a17bad26d3da69636b326cce14
+	etag = 7faacded709d2bede93356fd58b93af84884949f3bab098b8b8d121a03696449
+	weak

src/Extensions.Grok/Extensions.Grok.csproj

@@ -26,6 +26,7 @@
   <ItemGroup>
     <Compile Include="..\Extensions\Extensions\ChatOptionsExtensions.cs" Link="Extensions\ChatOptionsExtensions.cs" />
     <None Include="..\..\osmfeula.txt" Link="osmfeula.txt" PackagePath="OSMFEULA.txt" />
+    <InternalsVisibleTo Include="Tests"/>
   </ItemGroup>
 
 </Project>

src/Extensions.Grok/GrokChatClient.cs

@@ -15,8 +15,19 @@ class GrokChatClient : IChatClient
     readonly GrokClientOptions clientOptions;
 
     internal GrokChatClient(GrpcChannel channel, GrokClientOptions clientOptions, string defaultModelId)
+        : this(new ChatClient(channel), clientOptions, defaultModelId)
+    { }
+
+    /// <summary>
+    /// Test constructor.
+    /// </summary>
+    internal GrokChatClient(ChatClient client, string defaultModelId)
+        : this(client, new(), defaultModelId)
+    { }
+
+    GrokChatClient(ChatClient client, GrokClientOptions clientOptions, string defaultModelId)
     {
-        client = new ChatClient(channel);
+        this.client = client;
         this.clientOptions = clientOptions;
         this.defaultModelId = defaultModelId;
         metadata = new ChatClientMetadata("xai", clientOptions.Endpoint, defaultModelId);
@@ -97,7 +108,7 @@ public async Task<ChatResponse> GetResponseAsync(IEnumerable<ChatMessage> messag
         {
             ResponseId = response.Id,
             ModelId = response.Model,
-            CreatedAt = response.Created.ToDateTimeOffset(),
+            CreatedAt = response.Created?.ToDateTimeOffset(),
             FinishReason = lastOutput != null ? MapFinishReason(lastOutput.FinishReason) : null,
             Usage = MapToUsage(response.Usage),
         };
@@ -210,13 +221,16 @@ static CitationAnnotation MapCitation(string citation)
 
     GetCompletionsRequest MapToRequest(IEnumerable<ChatMessage> messages, ChatOptions? options)
     {
-        var request = new GetCompletionsRequest
+        var request = options?.RawRepresentationFactory?.Invoke(this) as GetCompletionsRequest ?? new GetCompletionsRequest()
         {
             // By default always include citations in the final output if available
             Include = { IncludeOption.InlineCitations },
             Model = options?.ModelId ?? defaultModelId,
         };
 
+        if (string.IsNullOrEmpty(request.Model))
+            request.Model = options?.ModelId ?? defaultModelId;
+
         if ((options?.EndUserId ?? clientOptions.EndUserId) is { } user) request.User = user;
         if (options?.MaxOutputTokens is { } maxTokens) request.MaxTokens = maxTokens;
         if (options?.Temperature is { } temperature) request.Temperature = temperature;

src/Tests/Extensions/CallHelpers.cs

@@ -0,0 +1,46 @@
+#region Copyright notice and license
+
+// Copyright 2019 The gRPC Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#endregion
+
+using Grpc.Core;
+
+namespace Tests.Client.Helpers
+{
+    static class CallHelpers
+    {
+        public static AsyncUnaryCall<TResponse> CreateAsyncUnaryCall<TResponse>(TResponse response)
+        {
+            return new AsyncUnaryCall<TResponse>(
+                Task.FromResult(response),
+                Task.FromResult(new Metadata()),
+                () => Status.DefaultSuccess,
+                () => new Metadata(),
+                () => { });
+        }
+
+        public static AsyncUnaryCall<TResponse> CreateAsyncUnaryCall<TResponse>(StatusCode statusCode)
+        {
+            var status = new Status(statusCode, string.Empty);
+            return new AsyncUnaryCall<TResponse>(
+                Task.FromException<TResponse>(new RpcException(status)),
+                Task.FromResult(new Metadata()),
+                () => status,
+                () => new Metadata(),
+                () => { });
+        }
+    }
+}

src/Tests/GrokTests.cs

@@ -4,7 +4,8 @@
 using Devlooped.Extensions.AI.Grok;
 using Devlooped.Grok;
 using Microsoft.Extensions.AI;
-using OpenAI.Realtime;
+using Moq;
+using Tests.Client.Helpers;
 using static ConfigurationExtensions;
 using OpenAIClientOptions = OpenAI.OpenAIClientOptions;
 
@@ -466,5 +467,40 @@ public async Task GrokStreamsUpdatesFromAllTools()
         Assert.True(typed.Price > 100);
     }
 
+    [Fact]
+    public async Task GrokCustomFactoryInvokedFromOptions()
+    {
+        var invoked = false;
+        var client = new Mock<Devlooped.Grok.Chat.ChatClient>(MockBehavior.Strict);
+        client.Setup(x => x.GetCompletionAsync(It.IsAny<GetCompletionsRequest>(), null, null, CancellationToken.None))
+            .Returns(CallHelpers.CreateAsyncUnaryCall(new GetChatCompletionResponse
+            {
+                Outputs =
+                {
+                    new CompletionOutput
+                    {
+                        Message = new CompletionMessage
+                        {
+                            Content = "Hey Cazzulino!"
+                        }
+                    }
+                }
+            }));
+
+        var grok = new GrokChatClient(client.Object, "grok-4-1-fast");
+        var response = await grok.GetResponseAsync("Hi, my internet alias is kzu. Lookup my real full name online.",
+            new GrokChatOptions
+            {
+                RawRepresentationFactory = (client) =>
+                {
+                    invoked = true;
+                    return new GetCompletionsRequest();
+                }
+            });
+
+        Assert.True(invoked);
+        Assert.Equal("Hey Cazzulino!", response.Text);
+    }
+
     record Response(DateOnly Today, string Release, decimal Price);
 }