diff --git a/src/io/excellOffice.test.ts b/src/io/excellOffice.test.ts
index 0449133..012e8d1 100644
--- a/src/io/excellOffice.test.ts
+++ b/src/io/excellOffice.test.ts
@@ -37,6 +37,7 @@ import {
   worksheetXmlToZoomScale,
   xlsxStylesXmlToCellFormatTable,
   xlsxThemeXmlToColors,
+  xlsxSafeSheetNames,
   xlsxCellToText
 } from "./excellOffice";
 
@@ -633,6 +634,38 @@ describe("excellOffice OOXML helpers", () => {
     expect(imported.activeSheet).toBe("sheet-2");
   });
 
+  it("normalizes XLSX sheet names to Excel-safe unique names on export", async () => {
+    expect(
+      xlsxSafeSheetNames([
+        { name: "Sales/2026:Q1*?" },
+        { name: "'Very long worksheet name that exceeds thirty one characters'" },
+        { name: "Sales 2026 Q1" },
+        { name: "'[]:*?/\\'" },
+        { name: "History" }
+      ])
+    ).toEqual(["Sales 2026 Q1", "Very long worksheet name that e", "Sales 2026 Q1 (2)", "Лист 4", "History 1"]);
+
+    const blob = await exportXlsxBlob({
+      id: "book-1",
+      title: "Safe sheet names.xlsx",
+      updatedAt: "2026-06-01T00:00:00.000Z",
+      activeSheet: "sheet-1",
+      sheets: [
+        { id: "sheet-1", name: "Sales/2026:Q1*?", printArea: "A1:B2", cells: { A1: "Sales" } },
+        { id: "sheet-2", name: "Sales 2026 Q1", cells: { A1: "Duplicate" } }
+      ]
+    });
+    const zip = await JSZip.loadAsync(await blob.arrayBuffer());
+    const workbookXml = await zip.file("xl/workbook.xml")?.async("string");
+    const imported = await importXlsxFile(new File([blob], "Safe sheet names.xlsx", { type: blob.type }));
+
+    expect(workbookXml).toContain('<sheet name="Sales 2026 Q1" sheetId="1" r:id="rId1"/>');
+    expect(workbookXml).toContain('<sheet name="Sales 2026 Q1 (2)" sheetId="2" r:id="rId2"/>');
+    expect(workbookXml).toContain('<definedName name="_xlnm.Print_Area" localSheetId="0">\'Sales 2026 Q1\'!$A$1:$B$2</definedName>');
+    expect(imported.sheets.map((sheet) => sheet.name)).toEqual(["Sales 2026 Q1", "Sales 2026 Q1 (2)"]);
+    expect(imported.sheets[0].printArea).toBe("A1:B2");
+  });
+
   it("сохраняет и импортирует область печати XLSX через definedName _xlnm.Print_Area", async () => {
     expect(
       workbookPrintAreas(
diff --git a/src/io/excellOffice.ts b/src/io/excellOffice.ts
index 937cbb5..9814498 100644
--- a/src/io/excellOffice.ts
+++ b/src/io/excellOffice.ts
@@ -267,11 +267,13 @@ export async function exportXlsxBlob(workbook: Workbook): Promise<Blob> {
   const JSZip = await loadJsZip();
   const zip = new JSZip();
   const sheets = workbook.sheets.length > 0 ? workbook.sheets : [{ id: "sheet-1", name: "Лист 1", cells: {}, mergedCells: [], hyperlinks: {} }];
+  const safeSheetNames = xlsxSafeSheetNames(sheets);
+  const safeSheets = sheets.map((sheet, index) => ({ ...sheet, name: safeSheetNames[index] }));
 
-  const styleRegistry = createCellStyleRegistry(sheets.map((sheet) => sheet.cellFormats));
-  const chartParts = chartPartRefsForSheets(sheets);
-  const commentParts = commentPartRefsForSheets(sheets);
-  const activeSheetIndex = Math.max(0, sheets.findIndex((sheet) => sheet.id === workbook.activeSheet));
+  const styleRegistry = createCellStyleRegistry(safeSheets.map((sheet) => sheet.cellFormats));
+  const chartParts = chartPartRefsForSheets(safeSheets);
+  const commentParts = commentPartRefsForSheets(safeSheets);
+  const activeSheetIndex = Math.max(0, safeSheets.findIndex((sheet) => sheet.id === workbook.activeSheet));
 
   zip.file("[Content_Types].xml", buildContentTypesXml(sheets.length, chartParts, commentParts));
   zip.file("_rels/.rels", buildRootRelationshipsXml());
@@ -280,8 +282,8 @@ export async function exportXlsxBlob(workbook: Workbook): Promise<Blob> {
   zip.file(
     "xl/workbook.xml",
     buildWorkbookXml(
-      sheets.map((sheet, index) => ({
-        name: sheet.name.trim() || `Лист ${index + 1}`,
+      safeSheets.map((sheet) => ({
+        name: sheet.name,
         ...(sheet.visibility ? { visibility: sheet.visibility } : {}),
         ...(sheet.printArea ? { printArea: sheet.printArea } : {})
       })),
@@ -291,7 +293,7 @@ export async function exportXlsxBlob(workbook: Workbook): Promise<Blob> {
   zip.file("xl/_rels/workbook.xml.rels", buildWorkbookRelationshipsXml(sheets.length));
   zip.file("xl/styles.xml", buildStylesXml(styleRegistry));
 
-  sheets.forEach((sheet, index) => {
+  safeSheets.forEach((sheet, index) => {
     const sheetChartParts = chartParts.filter((part) => part.sheetIndex === index);
     const sheetCommentPart = commentParts.find((part) => part.sheetIndex === index);
     const externalHyperlinkCount = sortedExternalHyperlinkEntries(sheet.hyperlinks).length;
@@ -1109,6 +1111,45 @@ function buildRootRelationshipsXml() {
   );
 }
 
+export function xlsxSafeSheetNames(sheets: Array<{ name: string }>) {
+  const usedNames = new Set<string>();
+  return sheets.map((sheet, index) => uniqueXlsxSheetName(sheet.name, index, usedNames));
+}
+
+function uniqueXlsxSheetName(value: string, index: number, usedNames: Set<string>) {
+  const fallback = `Лист ${index + 1}`;
+  const normalizedName = normalizedXlsxSheetName(value);
+  const baseName = xlsxReservedSheetName(normalizedName) ? `${normalizedName} 1` : normalizedName || fallback;
+  let suffixNumber = 1;
+  let candidate = truncateXlsxSheetName(baseName);
+
+  while (usedNames.has(candidate.toLowerCase())) {
+    suffixNumber += 1;
+    const suffix = ` (${suffixNumber})`;
+    candidate = `${truncateXlsxSheetName(baseName, 31 - suffix.length)}${suffix}`;
+  }
+
+  usedNames.add(candidate.toLowerCase());
+  return candidate;
+}
+
+function normalizedXlsxSheetName(value: string) {
+  return value
+    .replace(/[\u0000-\u001f\\/?*:[\]]+/g, " ")
+    .replace(/\s+/g, " ")
+    .trim()
+    .replace(/^'+|'+$/g, "")
+    .trim();
+}
+
+function xlsxReservedSheetName(value: string) {
+  return value.trim().toLowerCase() === "history";
+}
+
+function truncateXlsxSheetName(value: string, maxLength = 31) {
+  return Array.from(value).slice(0, Math.max(1, maxLength)).join("");
+}
+
 function buildWorkbookXml(sheets: Array<{ name: string; visibility?: WorkbookSheetRef["visibility"]; printArea?: string }>, activeSheetIndex = 0) {
   const activeTab = Math.min(Math.max(0, activeSheetIndex), Math.max(0, sheets.length - 1));
   const bookViews = `<bookViews><workbookView activeTab="${activeTab}"/></bookViews>`;