diff --git a/src/MiniExcel.OpenXml/Templates/OpenXmlTemplate.Impl.cs b/src/MiniExcel.OpenXml/Templates/OpenXmlTemplate.Impl.cs
index 09009ffe..9571e9eb 100644
--- a/src/MiniExcel.OpenXml/Templates/OpenXmlTemplate.Impl.cs
+++ b/src/MiniExcel.OpenXml/Templates/OpenXmlTemplate.Impl.cs
@@ -936,8 +936,17 @@ private void ProcessFormulas(StringBuilder rowXml, int rowIndex)
                     fNode.SetValue(str.Value[2..]);
                     str.AddBeforeSelf(fNode);
                     str.Remove();
-
-                    var celRef = CellReferenceConverter.GetCellFromCoordinates(index, rowIndex);
+                    // the cell no longer holds an inline string; keeping t="inlineStr" without an <is>
+                    // child is schema-invalid and Excel rejects the package
+                    cell.Attribute("t")?.Remove();
+
+                    // take the column from the cell's own reference — the running index is wrong for
+                    // sparse rows (cells without content are not emitted, so position != column)
+                    var cellRef = cell.Attribute("r")?.Value;
+                    var columnLetters = cellRef is null ? "" : new string(cellRef.TakeWhile(char.IsLetter).ToArray());
+                    var celRef = string.IsNullOrEmpty(columnLetters)
+                        ? CellReferenceConverter.GetCellFromCoordinates(index, rowIndex)
+                        : $"{columnLetters}{rowIndex}";
                     _calcChainCellRefs.Add(celRef);
                 }
             }
diff --git a/src/MiniExcel.OpenXml/Templates/OpenXmlTemplate.cs b/src/MiniExcel.OpenXml/Templates/OpenXmlTemplate.cs
index 60888c6d..09b76f20 100644
--- a/src/MiniExcel.OpenXml/Templates/OpenXmlTemplate.cs
+++ b/src/MiniExcel.OpenXml/Templates/OpenXmlTemplate.cs
@@ -158,11 +158,16 @@ await originalEntryStream.CopyToAsync(newEntryStream
         // batch add sheet
         await BatchAddSheetsToWorkbookAsync(outputFileArchive.ZipFile, originalArchive, allSheetInfos, cancellationToken).ConfigureAwait(false);
 
-        // create mode we need to not create first then create here
-        var calcChain = outputFileArchive.EntryCollection.FirstOrDefault(e 
+        // The template's own calcChain cannot be reused: row insertion shifts formula cells and its
+        // entries would point at the old addresses. It is regenerated from the rendered formulas —
+        // and when none were rendered, dropped entirely, because a calcChain with no <c> entries is
+        // schema-invalid and Excel rejects the whole package. Excel rebuilds the chain on open, so
+        // dropping it is always safe. (The stale-template copy that used to run when no chain entry
+        // was created here is intentionally gone for the same reason.)
+        var calcChain = outputFileArchive.EntryCollection.FirstOrDefault(e
             => e.FullName.TrimStart('/').Equals(ExcelFileNames.CalcChain, StringComparison.OrdinalIgnoreCase));
 
-        if (calcChain is not null)
+        if (calcChain is not null && _calcChainContent.Length > 0)
         {
             var calcChainEntry = outputFileArchive.ZipFile.CreateEntry(calcChain.FullName);
             var calcChainStream = await calcChainEntry.OpenAsync(cancellationToken).ConfigureAwait(false);
@@ -170,29 +175,6 @@ await originalEntryStream.CopyToAsync(newEntryStream
 
             await CalcChainHelper.GenerateCalcChainSheetAsync(calcChainStream, _calcChainContent.ToString(), cancellationToken).ConfigureAwait(false);
         }
-        else
-        {
-            foreach (var entry in originalArchive.Entries)
-            {
-                if (entry.FullName.TrimStart('/').Equals(ExcelFileNames.CalcChain, StringComparison.OrdinalIgnoreCase))
-                {
-                    var newEntry = outputFileArchive.ZipFile.CreateEntry(entry.FullName);
-
-                    // Copy the content of the original entry to the new entry
-                    var originalEntryStream = await entry.OpenAsync(cancellationToken).ConfigureAwait(false);
-                    await using var disposableEntryStream = originalEntryStream.ConfigureAwait(false);
-
-                    var newEntryStream = await newEntry.OpenAsync(cancellationToken).ConfigureAwait(false);
-                    await using var disposableNewEntryStream = newEntryStream.ConfigureAwait(false);
-
-                    await originalEntryStream.CopyToAsync(newEntryStream
-#if NET
-                        , cancellationToken
-#endif
-                    ).ConfigureAwait(false);
-                }
-            }
-        }
 
 #if NET10_0_OR_GREATER
         await outputFileArchive.ZipFile.DisposeAsync().ConfigureAwait(false);