iOfficeAI/OfficeCLI · error · ArgumentException

Import exceeds Excel's column limit: data would reach column

Error message

Import exceeds Excel's column limit: data would reach column {endColIdx} (maximum {ExcelMaxCol} / XFD). Reduce the CSV width or change the start cell.

What it means

Thrown by ExcelHandler.Import as a DOS-hardening guard BEFORE writing any cells, when startColIdx + maxCols - 1 would exceed Excel's maximum of 16,384 columns (XFD). The check uses the widest row in the parsed CSV.

Source

Thrown at src/officecli/Handlers/Excel/ExcelHandler.Import.cs:59

            return "No data to import";

        int maxCols = 0;
        for (int r = 0; r < rows.Count; r++)
            if (rows[r].Count > maxCols) maxCols = rows[r].Count;

        // DOS-hardening: reject imports that exceed Excel's sheet dimensions
        // BEFORE writing anything. Without this an over-sized CSV (e.g. >XFD
        // columns or >1048576 rows) spun indefinitely instead of erroring.
        const int ExcelMaxRow = 1048576;
        const int ExcelMaxCol = 16384; // XFD (ColumnNameToIndex is 1-based)
        long endRowReq = (long)startRow + rows.Count - 1;
        if (endRowReq > ExcelMaxRow)
            throw new ArgumentException(
                $"Import exceeds Excel's row limit: data would reach row {endRowReq} " +
                $"(maximum {ExcelMaxRow}). Reduce the CSV or change the start cell.");
        long endColIdx = (long)startColIdx + maxCols - 1;
        if (endColIdx > ExcelMaxCol)
            throw new ArgumentException(
                $"Import exceeds Excel's column limit: data would reach column {endColIdx} " +
                $"(maximum {ExcelMaxCol} / XFD). Reduce the CSV width or change the start cell.");

        // BUG-R11-import-dup-row BUG-11: import previously always appended a
        // brand-new <row r="N">, producing duplicate row entries when the
        // target rows already existed (Excel auto-repaired by keeping the
        // first one, silently losing imported data). Upsert by RowIndex —
        // reuse an existing row, otherwise insert a new one in sorted position.
        //
        // PERF(dos-hardening): the previous implementation re-scanned the whole
        // SheetData (LINQ FirstOrDefault) for every imported row AND every cell,
        // making a bulk import O(rows*cells * existing) — a 100k-row CSV took
        // 9+ minutes. Pre-index existing rows once and walk them with an
        // ascending cursor for sorted insertion; build a per-row cell index
        // only when reusing a pre-existing row. Bulk-append into a fresh sheet
        // is now linear.
        var existingRows = sheetData.Elements<Row>()
            .Where(rr => rr.RowIndex?.Value != null)

View on GitHub (pinned to 1ced45e900)

Solutions

1. Reduce the CSV width to at most (16384 - startColIdx + 1) columns.
2. Start at A1 to use the full column budget.
3. Drop unused columns or split wide data across multiple sheets/tables.

Example fix

// before
var csv = WideExport();          // 17,000 columns
excel.Import("/Sheet1", csv, ',', false, "A1");

// after
var maxCols = 16384 - ColumnNameToIndex("A");
var csv = TrimToWidth(WideExport(), maxCols);
excel.Import("/Sheet1", csv, ',', false, "A1");

const int ExcelMaxCol = 16384;
var (startCol, startRow) = ExcelHandler.ParseCellReference(startCell.ToUpperInvariant());
long endCol = (long)ExcelHandler.ColumnNameToIndex(startCol) + maxCols - 1;
if (endCol > ExcelMaxCol)
    throw new ArgumentException($"Import would reach column {endCol} (max {ExcelMaxCol}/XFD).");

When it happens

Trigger: Importing a CSV wider than Excel's column limit from the given startCell, e.g. startCell=A1 with a 17,000-column CSV, or startCell=Z1 (column 26) with a 16,400-column CSV.

Common situations: Wide exports from data tools (pandas to_csv with hundreds of columns is fine, but a transposed or mis-shaped export can exceed 16k); starting at a non-A column and underestimating the offset.

Related errors

• Import exceeds Excel's row limit: data would reach row {endR
• unsupported_type
• Property 'sqref' (or 'range'/'ref') is required for validati
• Invalid 'height' value: '{value}'. Row height must be betwee
• Invalid 'width' value: '{value}'. Column width must be betwe

AI-assisted analysis of iOfficeAI/OfficeCLI@1ced45e900 (2026-08-13). Data as JSON: /api/errors/e64a1278d90c0f8a. Report an issue: GitHub.