seamapi · razor-x · Aug 6, 2026 · Aug 6, 2026
diff --git a/codegen/layouts/partials/route-methods.hbs b/codegen/layouts/partials/route-methods.hbs
@@ -6,7 +6,7 @@ requestOptions.Data = request;
 {{#if isVoid}}
 _seam.Post<object>("{{path}}", requestOptions);
 {{else}}
-return _seam.Post<{{responseTypeArg}}>("{{path}}", requestOptions).Data.{{returnProp}};
+return _seam.Post<{{responseTypeArg}}>("{{path}}", requestOptions).EnsureData("{{path}}").{{returnProp}};
 {{/if}}
 }
 
@@ -28,7 +28,7 @@ requestOptions.Data = request;
 {{#if isVoid}}
 await _seam.PostAsync<object>("{{path}}", requestOptions);
 {{else}}
-return (await _seam.PostAsync<{{responseTypeArg}}>("{{path}}", requestOptions)).Data.{{returnProp}};
+return (await _seam.PostAsync<{{responseTypeArg}}>("{{path}}", requestOptions)).EnsureData("{{path}}").{{returnProp}};
 {{/if}}
 }
 

diff --git a/output/csharp/src/Seam.Test/Client/ApiResponseTests.cs b/output/csharp/src/Seam.Test/Client/ApiResponseTests.cs
@@ -0,0 +1,50 @@
+namespace Seam.Test;
+
+using System.Net;
+using Seam.Client;
+
+public class ApiResponseTests
+{
+    [Fact]
+    public void EnsureDataReturnsDataWhenPresent()
+    {
+        var data = new Api.Locks.ListResponse(devices: new List<Model.Device>());
+        var response = new ApiResponse<Api.Locks.ListResponse>(HttpStatusCode.OK, data, "{}");
+
+        Assert.Same(data, response.EnsureData("/locks/list"));
+    }
+
+    [Fact]
+    public void EnsureDataThrowsSeamExceptionWhenDataIsNull()
+    {
+        var headers = new Multimap<string, string> { { "seam-request-id", "req-123" } };
+        var response = new ApiResponse<Api.Locks.ListResponse>(
+            HttpStatusCode.OK,
+            headers,
+            null!,
+            "<html>unexpected body</html>"
+        );
+
+        var exception = Assert.Throws<SeamException>(() => response.EnsureData("/locks/list"));
+
+        Assert.Equal(200, exception.ErrorCode);
+        Assert.Contains("/locks/list", exception.Message);
+        Assert.Contains("HTTP 200", exception.Message);
+        Assert.Equal("<html>unexpected body</html>", exception.ErrorContent);
+        Assert.Equal(headers, exception.Headers);
+    }
+
+    [Fact]
+    public void EnsureDataIncludesErrorTextInMessageWhenSet()
+    {
+        var response = new ApiResponse<Api.Locks.ListResponse>(HttpStatusCode.OK, null!, "not json")
+        {
+            ErrorText = "Error deserializing response",
+        };
+
+        var exception = Assert.Throws<SeamException>(() => response.EnsureData("/locks/list"));
+
+        Assert.Contains("Error deserializing response", exception.Message);
+        Assert.Equal("not json", exception.ErrorContent);
+    }
+}
diff --git a/output/csharp/src/Seam/Api/AccessCodes.cs b/output/csharp/src/Seam/Api/AccessCodes.cs
diff --git a/output/csharp/src/Seam/Api/AccessGrants.cs b/output/csharp/src/Seam/Api/AccessGrants.cs
diff --git a/output/csharp/src/Seam/Api/AccessGroupsAcs.cs b/output/csharp/src/Seam/Api/AccessGroupsAcs.cs