Add message persistence via grok options

See https://docs.x.ai/docs/guides/responses-api#chaining-the-conversation

Author: kzu

src/Extensions.Grok/GrokChatClient.cs

@@ -95,6 +95,7 @@ public async Task<ChatResponse> GetResponseAsync(IEnumerable<ChatMessage> messag
 
         return new ChatResponse(message)
         {
+            ConversationId = options is GrokChatOptions { StoreMessages: true } ? response.Id : null,
             ResponseId = response.Id,
             ModelId = response.Model,
             CreatedAt = response.Created.ToDateTimeOffset(),
@@ -298,6 +299,11 @@ codeResult.RawRepresentation is ToolCall codeToolCall &&
         IList<IncludeOption> includes = [IncludeOption.InlineCitations];
         if (options is GrokChatOptions grokOptions)
         {
+            request.StoreMessages = grokOptions.StoreMessages == true;
+            // TODO: should we throw if we find a conversation id but not StoreMessages=true as it might be a user error?
+            if (request.StoreMessages && options.ConversationId is not null)
+                request.PreviousResponseId = options.ConversationId;
+
             // NOTE: overrides our default include for inline citations, potentially.
             request.Include.Clear();
             request.Include.AddRange(grokOptions.Include);

src/Extensions.Grok/GrokChatOptions.cs

@@ -38,4 +38,7 @@ public class GrokChatOptions : ChatOptions
     /// <summary>Additional outputs to include in responses.</summary>
     /// <remarks>Defaults to including <see cref="IncludeOption.InlineCitations"/>.</remarks>
     public IList<IncludeOption> Include { get; set; } = [IncludeOption.InlineCitations];
+
+    /// <summary>Whether to store request and responses.</summary>
+    public bool? StoreMessages { get; set; }
 }

src/Tests/GrokTests.cs

@@ -1,17 +1,35 @@
 using System.Text.Json;
-using System.Text.Json.Nodes;
-using Azure;
 using Devlooped.Extensions.AI.Grok;
 using Devlooped.Grok;
 using Microsoft.Extensions.AI;
-using OpenAI.Realtime;
 using static ConfigurationExtensions;
-using OpenAIClientOptions = OpenAI.OpenAIClientOptions;
 
 namespace Devlooped.Extensions.AI;
 
 public class GrokTests(ITestOutputHelper output)
 {
+    [SecretsFact("XAI_API_KEY")]
+    public async Task GrokRemembersConversation()
+    {
+        var chat = new GrokClient(Configuration["XAI_API_KEY"]!).AsIChatClient("grok-4-1-fast-non-reasoning")
+            .AsBuilder()
+            .UseLogging(output.AsLoggerFactory())
+            .Build();
+
+        var options = new GrokChatOptions { StoreMessages = true };
+        var response = await chat.GetResponseAsync("Hey, my alias is kzu. Keep that in mind.", options);
+
+        Assert.NotNull(response.ConversationId);
+
+        var id = response.ConversationId;
+        options.ConversationId = id;
+
+        response = await chat.GetResponseAsync("What is my alias?", options);
+
+        Assert.Contains("kzu", response.Text);
+    }
+
+
     [SecretsFact("XAI_API_KEY")]
     public async Task GrokInvokesTools()
     {