diff --git a/dotnet/src/Microsoft.Agents.AI.Hosting.OpenAI/ChatCompletions/Converters/ChatClientAgentRunOptionsConverter.cs b/dotnet/src/Microsoft.Agents.AI.Hosting.OpenAI/ChatCompletions/Converters/ChatClientAgentRunOptionsConverter.cs
index 0878ad8bcb..8e9ca91267 100644
--- a/dotnet/src/Microsoft.Agents.AI.Hosting.OpenAI/ChatCompletions/Converters/ChatClientAgentRunOptionsConverter.cs
+++ b/dotnet/src/Microsoft.Agents.AI.Hosting.OpenAI/ChatCompletions/Converters/ChatClientAgentRunOptionsConverter.cs
@@ -29,6 +29,7 @@ internal static class ChatClientAgentRunOptionsConverter
         Model = request.Model,
         ToolChoice = request.ToolChoice?.ToChatToolMode(),
         Tools = request.Tools is { Count: > 0 } tools ? tools.Select(x => x.ToAITool()).ToList() : null,
+        WebSearchOptions = request.WebSearchOptions,
     };
 
     private static ChatResponseFormat ToChatResponseFormat(this ResponseFormat responseFormat)
diff --git a/dotnet/src/Microsoft.Agents.AI.Hosting.OpenAI/OpenAIChatCompletionRequestInfo.cs b/dotnet/src/Microsoft.Agents.AI.Hosting.OpenAI/OpenAIChatCompletionRequestInfo.cs
index e345f18404..299dd4b382 100644
--- a/dotnet/src/Microsoft.Agents.AI.Hosting.OpenAI/OpenAIChatCompletionRequestInfo.cs
+++ b/dotnet/src/Microsoft.Agents.AI.Hosting.OpenAI/OpenAIChatCompletionRequestInfo.cs
@@ -84,4 +84,9 @@ public sealed class OpenAIChatCompletionRequestInfo
     /// Gets or sets the tools supplied on the request, if any.
     /// </summary>
     public IReadOnlyList<AITool>? Tools { get; set; }
+
+    /// <summary>
+    /// Gets or sets the web search options (<c>web_search_options</c>) supplied on the request, if any.
+    /// </summary>
+    public object? WebSearchOptions { get; set; }
 }
diff --git a/dotnet/src/Microsoft.Agents.AI.Hosting.OpenAI/OpenAIChatCompletionsMapOptions.cs b/dotnet/src/Microsoft.Agents.AI.Hosting.OpenAI/OpenAIChatCompletionsMapOptions.cs
index ba7f2f33d4..2aa33d64b1 100644
--- a/dotnet/src/Microsoft.Agents.AI.Hosting.OpenAI/OpenAIChatCompletionsMapOptions.cs
+++ b/dotnet/src/Microsoft.Agents.AI.Hosting.OpenAI/OpenAIChatCompletionsMapOptions.cs
@@ -109,6 +109,11 @@ public sealed class OpenAIChatCompletionsMapOptions
             LocalAdd("tool_choice");
         }
 
+        if (request.WebSearchOptions is not null)
+        {
+            LocalAdd("web_search_options");
+        }
+
         if (unsupported is not null)
         {
             throw new NotSupportedException(
diff --git a/dotnet/tests/Microsoft.Agents.AI.Hosting.OpenAI.UnitTests/OpenAIMapOptionsTests.cs b/dotnet/tests/Microsoft.Agents.AI.Hosting.OpenAI.UnitTests/OpenAIMapOptionsTests.cs
index b0ce53eaa0..67c3683ec6 100644
--- a/dotnet/tests/Microsoft.Agents.AI.Hosting.OpenAI.UnitTests/OpenAIMapOptionsTests.cs
+++ b/dotnet/tests/Microsoft.Agents.AI.Hosting.OpenAI.UnitTests/OpenAIMapOptionsTests.cs
@@ -181,6 +181,25 @@ public async Task ChatCompletions_DefaultEndpoint_RejectsRequestWithSettingsAsyn
         Assert.Contains("invalid_request_error", body, StringComparison.Ordinal);
     }
 
+    [Fact]
+    public async Task ChatCompletions_DefaultEndpoint_RejectsWebSearchOptionsAsync()
+    {
+        // Arrange
+        using var app = await CreateChatCompletionsServerAsync("reject-agent", mapOptions: null);
+        HttpClient client = GetClient(app);
+
+        // Act
+        HttpResponseMessage response = await client.PostAsync(
+            new Uri("/reject-agent/v1/chat/completions", UriKind.Relative),
+            new StringContent("""{"model":"myModel","messages":[{"role":"user","content":"hello"}],"web_search_options":{}}""", Encoding.UTF8, "application/json"));
+
+        // Assert
+        Assert.Equal(HttpStatusCode.BadRequest, response.StatusCode);
+        string body = await response.Content.ReadAsStringAsync();
+        Assert.Contains("web_search_options", body, StringComparison.Ordinal);
+        Assert.Contains("invalid_request_error", body, StringComparison.Ordinal);
+    }
+
     [Fact]
     public async Task ChatCompletions_ConfiguredEndpoint_HonorsRequestSettingsAsync()
     {