diff --git a/src/lib/smartsheet.ts b/src/lib/smartsheet.ts
index 9cacc05..f973095 100644
--- a/src/lib/smartsheet.ts
+++ b/src/lib/smartsheet.ts
@@ -279,12 +279,16 @@ export async function addRow(
     return v;
   };
 
-  // NOTE: POST /2.0/sheets/{id}/rows wraps the created row(s) in
-  // `{ result: [{id, rowNumber}, ...] }` — different shape from the
-  // flat GET /2.0/sheets/{id} response. See
-  // https://smartsheet.redoc.ly/#operation/addRows
+  // NOTE: POST /2.0/sheets/{id}/rows response shape varies:
+  //   - One row in request  →  result: { id, rowNumber, ... }  (single object)
+  //   - Multiple rows        →  result: [{ id, rowNumber, ... }, ...]  (array)
+  // We always post exactly one row, but handle both defensively. Different
+  // from the flat GET /2.0/sheets/{id} response.
+  // See https://smartsheet.redoc.ly/#operation/addRows
   type ApiResponse = {
-    result: Array<{ id: number; rowNumber: number }>;
+    result:
+      | { id: number; rowNumber: number; [k: string]: unknown }
+      | Array<{ id: number; rowNumber: number; [k: string]: unknown }>;
     resultCode?: number;
     message?: string;
   };
@@ -305,7 +309,8 @@ export async function addRow(
     },
   );
 
-  const row = data?.result?.[0];
+  const result = data?.result;
+  const row = Array.isArray(result) ? result[0] : result;
   if (!row || row.id == null) {
     throw new SmartsheetApiError(
       502,