diff --git a/agents/common/src/test/java/com/dbx/agent/JsonRpcLargeValueTest.java b/agents/common/src/test/java/com/dbx/agent/JsonRpcLargeValueTest.java
index 7af2b2b12c..a09f6cfdda 100644
--- a/agents/common/src/test/java/com/dbx/agent/JsonRpcLargeValueTest.java
+++ b/agents/common/src/test/java/com/dbx/agent/JsonRpcLargeValueTest.java
@@ -46,4 +46,27 @@ class JsonRpcLargeValueTest {
             JsonParser.parseString("{}").getAsJsonObject());
         assertEquals(List.of("invalidate", "commit"), calls);
     }
+
+    @Test
+    void invalidatesBeforeFailedWriteAndRollbackAndOnCancellation() throws Exception {
+        List<String> calls = new ArrayList<>();
+        DatabaseAgent agent = (DatabaseAgent) Proxy.newProxyInstance(DatabaseAgent.class.getClassLoader(),
+            new Class<?>[]{DatabaseAgent.class}, (object, method, args) -> {
+                if (method.getName().equals("supportsQueryTiming")) return false;
+                if (method.getName().equals("invalidateLargeValues")) { calls.add("invalidate"); return null; }
+                if (method.getName().equals("executeBatch")) { calls.add("write"); throw new java.sql.SQLException("concurrent row removed"); }
+                if (method.getName().equals("rollbackManualTransaction")) { calls.add("rollback"); return Map.of("ok", true); }
+                return null;
+            });
+        JsonRpcServer server = new JsonRpcServer(agent);
+        assertThrows(Exception.class, () -> server.dispatchForRuntime(AgentProtocol.METHOD_EXECUTE_BATCH,
+            JsonParser.parseString("{\"statements\":[\"UPDATE T SET C='full original value'\"]}").getAsJsonObject()));
+        assertEquals(List.of("invalidate", "write"), calls);
+        calls.clear();
+        server.dispatchForRuntime(AgentProtocol.METHOD_ROLLBACK_MANUAL_TRANSACTION, JsonParser.parseString("{}").getAsJsonObject());
+        assertEquals(List.of("invalidate", "rollback"), calls);
+        calls.clear();
+        server.cancelActiveStatements();
+        assertEquals(List.of("invalidate"), calls);
+    }
 }
diff --git a/apps/desktop/src/components/grid/DataGrid.vue b/apps/desktop/src/components/grid/DataGrid.vue
index c3cddd2296..eb2338e01e 100644
--- a/apps/desktop/src/components/grid/DataGrid.vue
+++ b/apps/desktop/src/components/grid/DataGrid.vue
@@ -8663,6 +8663,7 @@ const {
   queryResultExportRequest: props.queryResultExportRequest,
   hasCompleteLocalResult,
   completeLocalResult: computed(() => (hasCompleteLocalResult.value ? props.result : undefined)),
+  snapshotResult: computed(() => props.result),
   allExportResults: computed(() => props.allExportResults),
   currentResultLabel: computed(() => props.result.sourceLabel),
   exportFileBaseName: computed(() => props.exportFileBaseName),
diff --git a/apps/desktop/src/composables/__tests__/useDataGridExport.spec.ts b/apps/desktop/src/composables/__tests__/useDataGridExport.spec.ts
index 0abcecf613..f242ac8754 100644
--- a/apps/desktop/src/composables/__tests__/useDataGridExport.spec.ts
+++ b/apps/desktop/src/composables/__tests__/useDataGridExport.spec.ts
@@ -2,13 +2,13 @@ import { computed, ref } from "vue";
 import { createPinia, setActivePinia } from "pinia";
 import { beforeEach, describe, expect, it, vi } from "vitest";
 import { useDataGridExport, type UseDataGridExportOptions } from "@/composables/useDataGridExport";
-import type { DatabaseType } from "@/types/database";
+import type { DatabaseType, QueryResult } from "@/types/database";
 import { buildDataGridCopyUpdateStatements } from "@/lib/dataGrid/dataGridSql";
 import { copyToClipboard } from "@/lib/common/clipboard";
 import type { DataGridTableMeta } from "@/lib/dataGrid/dataGridSql";
 import type { CellSelectionMatrix, SelectionData } from "@/lib/dataGrid/gridSelection";
 import type { CellValue } from "@/lib/dataGrid/cellValue";
-import { extractDataGridSelection, exportQueryResultCsv, exportQueryResultJson } from "@/lib/backend/api";
+import { extractDataGridSelection, exportQueryResultCsv, exportQueryResultJson, exportQueryResultMarkdown, exportSnapshotResult, readLargeValueChunk } from "@/lib/backend/api";
 import { DEFAULT_DATA_GRID_EXTRACTOR_OPTIONS } from "@/lib/dataGrid/dataGridCopyExtractor";
 import { clearDataGridClipboardCopy, parseDataGridClipboard } from "@/lib/dataGrid/dataGridClipboard";
 import { MONGO_DOCUMENT_GRID_NULL, mongoDocumentGridExternalValue } from "@/lib/mongo/mongoDocumentValues";
@@ -52,6 +52,10 @@ vi.mock("@/lib/backend/api", async (importOriginal) => {
     extractDataGridSelection: vi.fn(),
     exportQueryResultCsv: vi.fn(),
     exportQueryResultJson: vi.fn(),
+    exportQueryResultMarkdown: vi.fn(),
+    exportSnapshotResult: vi.fn(),
+    readLargeValueChunk: vi.fn(),
+    cancelQuery: vi.fn(),
   };
 });
 
@@ -143,6 +147,7 @@ function createExportState(
   contextColumn?: number,
   databaseType: DatabaseType = "mysql",
   displayValue?: (value: CellValue, columnIndex: number) => string,
+  overrides: Partial<UseDataGridExportOptions> = {},
 ) {
   const rows = (rowDataList ?? [rowData ?? columns.map((column, index) => (column === "id" ? 1 : `value-${index}`))]).map((data, index) => ({ ...row(data), id: index + 1 }));
   const resolvedContextRowId = contextRowId === undefined ? (rows[0]?.id ?? null) : contextRowId;
@@ -175,9 +180,56 @@ function createExportState(
     selectedRowIds,
     hasRowSelection: computed(() => selectedRowIds.value.size > 0),
   };
-  return useDataGridExport(options);
+  return useDataGridExport({ ...options, ...overrides });
 }
 
+describe("original LOB result exports", () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+    setActivePinia(createPinia());
+    vi.mocked(exportSnapshotResult).mockResolvedValue(undefined);
+  });
+  function snapshotState() {
+    const original = {
+      columns: ["id", "name"], rows: [[1, "preview"]], column_types: ["NUMBER", "CLOB"],
+      large_value_context: { connectionId: "original-connection", database: "original-database", clientSessionId: "original-session" },
+      large_value_cells: [{ row_index: 0, column_index: 1, value_ref: "original-locator", value_kind: "text" }],
+    } as QueryResult;
+    return { original, state: createExportState(editableTable, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, "oracle", undefined, {
+      snapshotResult: computed(() => original), hasCompleteLocalResult: computed(() => true), completeLocalResult: computed(() => original),
+    }) };
+  }
+  it.each(["csv", "json"] as const)("streams export-all %s from captured locators without frontend hydration or requery", async (format) => {
+    const { state } = snapshotState();
+    await (format === "csv" ? state.exportCsv() : state.exportJson());
+    expect(exportSnapshotResult).toHaveBeenCalledWith(expect.objectContaining({
+      format, context: expect.objectContaining({ connectionId: "original-connection", clientSessionId: "original-session" }),
+      cells: [{ rowIndex: 0, columnIndex: 1, valueRef: "original-locator" }],
+    }), expect.any(String));
+    expect(readLargeValueChunk).not.toHaveBeenCalled();
+    expect(exportQueryResultCsv).not.toHaveBeenCalled();
+    expect(exportQueryResultJson).not.toHaveBeenCalled();
+  });
+  it("does not publish a legacy preview export when the snapshot backend fails", async () => {
+    const { state, original } = snapshotState();
+    vi.mocked(exportSnapshotResult).mockRejectedValue(new Error("LOB snapshot expired"));
+    await state.exportJson();
+    expect(exportQueryResultJson).not.toHaveBeenCalled();
+    expect(original.rows[0]![1]).toBe("preview");
+    expect(toast).toHaveBeenCalledWith(expect.stringContaining("LOB snapshot expired"), 5000);
+  });
+  it("materializes export-all for bounded formats rather than passing preview rows", async () => {
+    const { original } = snapshotState();
+    const localState = createExportState(editableTable, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, undefined, "oracle", undefined, {
+      context: computed(() => "results"), snapshotResult: computed(() => original), hasCompleteLocalResult: computed(() => true), completeLocalResult: computed(() => original),
+    });
+    vi.mocked(readLargeValueChunk).mockResolvedValue({ status: "ok", data: "complete original text", next_offset: 22, eof: true, value_kind: "text" });
+    await localState.exportMarkdown();
+    expect(exportQueryResultMarkdown).toHaveBeenCalledWith(expect.any(String), original.columns, [[1, "complete original text"]]);
+    expect(original.rows[0]![1]).toBe("preview");
+  });
+});
+
 const editableTable: DataGridTableMeta = {
   tableName: "users",
   primaryKeys: ["id"],
diff --git a/apps/desktop/src/composables/useDataGridExport.ts b/apps/desktop/src/composables/useDataGridExport.ts
index abc9068fb2..d75f6ce776 100644
--- a/apps/desktop/src/composables/useDataGridExport.ts
+++ b/apps/desktop/src/composables/useDataGridExport.ts
@@ -1,4 +1,4 @@
-import { computed, type ComputedRef, type Ref, createApp } from "vue";
+import { computed, type ComputedRef, type Ref, createApp, watch, getCurrentScope, onScopeDispose } from "vue";
 import { useI18n } from "vue-i18n";
 import { useDataGridExtractor } from "@/composables/useDataGridExtractor";
 import { isTauriRuntime } from "@/lib/backend/tauriRuntime";
@@ -14,6 +14,7 @@ import { useExportTracker } from "@/composables/useExportTracker";
 import { clipboardCellValue, type CellValue } from "@/lib/dataGrid/cellValue";
 import { binaryCellClipboardText } from "@/lib/dataGrid/binaryCellDownload";
 import { materializeSnapshotResultRows } from "@/lib/dataGrid/largeValueSnapshot";
+import { snapshotExportSelection, assertSnapshotXlsxCellLengths } from "@/lib/dataGrid/snapshotExport";
 import { tryStartExclusiveActivation, type ActionActivationGuard } from "@/lib/connection/actionActivation";
 import { clipboardLineEndings, copyToClipboard } from "@/lib/common/clipboard";
 import { clearDataGridClipboardCopy, rememberDataGridClipboardCopy } from "@/lib/dataGrid/dataGridClipboard";
@@ -170,6 +171,7 @@ export interface UseDataGridExportOptions {
    * silently change what "export all data" produces.
    */
   completeLocalResult?: ComputedRef<QueryResult | undefined>;
+  snapshotResult?: ComputedRef<QueryResult>;
   allExportResults?: ComputedRef<Array<{ sheetName: string; result: QueryResult; sql?: string }> | undefined>;
   currentResultLabel?: ComputedRef<string | undefined>;
   exportFileBaseName?: ComputedRef<string | undefined>;
@@ -198,6 +200,8 @@ interface CopyInsertData {
 }
 
 export function useDataGridExport(options: UseDataGridExportOptions) {
+  let activeSnapshotCancel: (() => Promise<void>) | undefined;
+  if (getCurrentScope()) onScopeDispose(() => { void activeSnapshotCancel?.().catch(() => undefined); });
   const { t } = useI18n();
   const { toast } = useToast();
   const tracker = useExportTracker();
@@ -524,7 +528,10 @@ export function useDataGridExport(options: UseDataGridExportOptions) {
     // client-side filters/search and unsaved edits, which would silently
     // change what the export contains.
     if (useFullExport && rowIds === undefined && hasCompleteLocalResult?.value && completeLocalResult?.value) {
-      const normalized = hasColumnSubset || databaseType.value === "mongodb" ? normalizeCompleteLocalResult(completeLocalResult.value, targetColumns, projectionSourceIndexes) : normalizeCompleteLocalResult(completeLocalResult.value);
+      const original = completeLocalResult.value;
+      const rows = await materializeSnapshotResultRows(original, () => completeLocalResult.value === original);
+      const materialized = { ...original, rows };
+      const normalized = hasColumnSubset || databaseType.value === "mongodb" ? normalizeCompleteLocalResult(materialized, targetColumns, projectionSourceIndexes) : normalizeCompleteLocalResult(materialized);
       const columnComments = buildXlsxHeaderOverrides(normalized.columns, normalized.columnComments, headerMode);
       return {
         ...applyGlobalDateTimeExportFormat(
@@ -590,6 +597,7 @@ export function useDataGridExport(options: UseDataGridExportOptions) {
   }
 
   async function writeXlsxResult(outputPath: string, result: { columns: string[]; columnTypes: string[]; columnComments?: (string | null)[]; rows: CellValue[][] }, includeSqlSheet: boolean, autoFilter: boolean, sqlOverride?: string) {
+    if (options.snapshotResult?.value.large_value_refs?.length || options.snapshotResult?.value.large_value_cells?.some((cell) => cell.value_ref)) assertSnapshotXlsxCellLengths(result.rows);
     const effectiveSql = sqlOverride ?? currentExportSql();
     const sqlWorksheet = includeSqlSheet ? buildXlsxSqlWorksheet([{ sql: effectiveSql || "" }]) : undefined;
     const rightAlign = useSettingsStore().editorSettings.numericColumnRightAlign;
@@ -930,10 +938,76 @@ export function useDataGridExport(options: UseDataGridExportOptions) {
     return exported;
   }
 
+  async function exportLocalSnapshot(format: "csv" | "json", rowIds: number[] | undefined, columnIndexes: number[] | undefined, full: boolean): Promise<boolean> {
+    const original = options.snapshotResult?.value;
+    const originalConnectionId = connectionId.value;
+    const originalDatabase = database.value;
+    const isCurrent = () => options.snapshotResult?.value === original && connectionId.value === originalConnectionId && database.value === originalDatabase;
+    if (!original || full && rowIds === undefined && !hasCompleteLocalResult?.value) return false;
+    const exportAll = full && rowIds === undefined && hasCompleteLocalResult?.value;
+    const visibleIndexes = visibleColumnIndexesOption?.value ?? columns.value.map((_, index) => index);
+    const indexes = columnIndexes?.filter((index) => index >= 0 && index < columns.value.length);
+    const sourceIndexes = exportAll && !indexes ? original.columns.map((_, index) => index) : (indexes ?? columns.value.map((_, index) => index)).map((index) => visibleIndexes[index] ?? index);
+    const names = sourceIndexes.map((index) => original.columns[index]!);
+    const items = exportAll
+      ? original.rows.map((row, sourceIndex) => ({ sourceIndex, data: sourceIndexes.map((index) => row[index]) }))
+      : rowsToExport(rowIds).map((item) => ({
+          sourceIndex: item.sourceIndex, isNew: item.isNew,
+          data: externalizeRows([item.data], indexes)[0]!,
+          isDirtyCol: (indexes ?? columns.value.map((_, index) => index)).map((index) => item.isDirtyCol[index] ?? false),
+        }));
+    const selected = snapshotExportSelection(original, names, sourceIndexes, items);
+    if (!selected) return false;
+    const types = sourceIndexes.map((index) => original.column_types?.[index] ?? "");
+    selected.rows = applyGlobalDateTimeExportFormat({ columns: names, columnTypes: types, rows: selected.rows as CellValue[][] }, true).rows;
+    let outputPath = exportFileName(full ? "export" : "export-page", format, { page: !full });
+    if (isTauriRuntime()) {
+      const path = await promptExportSavePath({ defaultFileName: outputPath, filters: [{ name: FORMAT_META[format]!.label, extensions: [format] }], preferredPath: useSettingsStore().editorSettings.preferredExportPath });
+      if (!path) return true;
+      outputPath = path;
+    }
+    if (!isCurrent()) throw new Error("LOB result context changed");
+    const executionId = uuid();
+    const cancel = async () => { await api.cancelQuery(executionId); };
+    activeSnapshotCancel = cancel;
+    const title = currentExportTitle();
+    tracker.addTask(title, format, outputPath, executionId);
+    tracker.registerTaskCancelHandler(executionId, cancel);
+    if (exportProgressState) exportProgressState.value = {
+      title: t("exportProgress.title"), tableName: title, format, rowsExported: 0, totalRows: selected.rows.length,
+      status: "Running", errorMessage: null, filePath: outputPath, startedAt: Date.now(), finishedAt: undefined,
+    };
+    if (exportProgressDialog) exportProgressDialog.value = true;
+    if (exportCanMinimize) exportCanMinimize.value = true;
+    const previousCancel = exportCancelHandler?.value;
+    if (exportCancelHandler) exportCancelHandler.value = cancel;
+    const stop = watch(() => [options.snapshotResult?.value, connectionId.value, database.value], () => { if (!isCurrent()) void cancel().catch(() => undefined); });
+    try {
+      await api.exportSnapshotResult({ ...selected, context: { ...selected.context, executionId }, format, quoteMode: useSettingsStore().editorSettings.csvQuoteMode, nullLiteral: csvNullLiteralForMode(useSettingsStore().editorSettings.csvNullMode) }, outputPath);
+      if (!isCurrent()) throw new Error("LOB result context changed");
+      tracker.updateTableExportTask(executionId, { exportId: executionId, tableName: title, rowsExported: selected.rows.length, totalRows: selected.rows.length, status: "Done" });
+      if (exportProgressState) exportProgressState.value = { ...exportProgressState.value, status: "Done", rowsExported: selected.rows.length, finishedAt: Date.now() };
+      notifyExportSuccess(outputPath);
+    } catch (error) {
+      const errorMessage = error instanceof Error ? error.message : String(error);
+      tracker.updateTableExportTask(executionId, { exportId: executionId, tableName: title, rowsExported: 0, totalRows: selected.rows.length, status: "Error", errorMessage });
+      if (exportProgressState) exportProgressState.value = { ...exportProgressState.value, status: "Error", errorMessage, finishedAt: Date.now() };
+      throw error;
+    } finally {
+      stop();
+      if (activeSnapshotCancel === cancel) activeSnapshotCancel = undefined;
+      tracker.unregisterTaskCancelHandler(executionId);
+      if (exportCanMinimize) exportCanMinimize.value = false;
+      if (exportCancelHandler) exportCancelHandler.value = previousCancel ?? null;
+    }
+    return true;
+  }
+
   async function exportCsv(target?: ExportTargetParam, columnIndexesParam?: number[]) {
     const { rowIds, columnIndexes } = normalizeExportTarget(target, columnIndexesParam);
     await runExclusiveExport(async () => {
       try {
+        if (await exportLocalSnapshot("csv", rowIds, columnIndexes, true)) return;
         if (await exportQueryResultViaBackend("csv", rowIds, false, "name", true, undefined, false, columnIndexes)) return;
         if (await exportFullTableDataViaBackend("csv", rowIds, "name", true, undefined, false, columnIndexes)) return;
 
@@ -1016,6 +1090,7 @@ export function useDataGridExport(options: UseDataGridExportOptions) {
   async function exportCurrentPageCsv(columnIndexes?: number[]) {
     await runExclusiveExport(async () => {
       try {
+        if (await exportLocalSnapshot("csv", undefined, columnIndexes, false)) return;
         let outputPath = exportFileName("export-page", "csv", { page: true });
         if (isTauriRuntime()) {
           const path = await promptExportSavePath({
@@ -1039,6 +1114,7 @@ export function useDataGridExport(options: UseDataGridExportOptions) {
     const { rowIds, columnIndexes } = normalizeExportTarget(target, columnIndexesParam);
     await runExclusiveExport(async () => {
       try {
+        if (await exportLocalSnapshot("json", rowIds, columnIndexes, true)) return;
         if (await exportFullTableDataViaBackend("json", rowIds, "name", true, undefined, false, columnIndexes)) return;
         if (await exportQueryResultViaBackend("json", rowIds, false, "name", true, undefined, false, columnIndexes)) return;
 
@@ -1064,6 +1140,7 @@ export function useDataGridExport(options: UseDataGridExportOptions) {
   async function exportCurrentPageJson(columnIndexes?: number[]) {
     await runExclusiveExport(async () => {
       try {
+        if (await exportLocalSnapshot("json", undefined, columnIndexes, false)) return;
         let outputPath = exportFileName("export-page", "json", { page: true });
         if (isTauriRuntime()) {
           const path = await promptExportSavePath({
@@ -1375,6 +1452,7 @@ export function useDataGridExport(options: UseDataGridExportOptions) {
         for (const sheet of sheets) {
           const sourceRows = sheet.result.rows;
           const rows = await materializeSnapshotResultRows(sheet.result, () => sheet.result.rows === sourceRows);
+          if (sheet.result.large_value_refs?.length || sheet.result.large_value_cells?.some((cell) => cell.value_ref)) assertSnapshotXlsxCellLengths(rows);
           worksheets.push({
           sheetName: sheet.sheetName,
           columns: sheet.result.columns,
diff --git a/apps/desktop/src/composables/useDataGridLargeValues.ts b/apps/desktop/src/composables/useDataGridLargeValues.ts
index 0363f1c8df..07f6680e9a 100644
--- a/apps/desktop/src/composables/useDataGridLargeValues.ts
+++ b/apps/desktop/src/composables/useDataGridLargeValues.ts
@@ -80,6 +80,7 @@ export interface UseDataGridLargeValuesOptions {
 }
 
 type ResolvedLargeValueCells = Map<number, Map<number, CellValue>>;
+const materializedSnapshotBytes = new WeakMap<QueryResult, Map<string, number>>();
 type LargeValueCellRequest = {
   item: LargeValueRowItem;
   sourceIndex: number;
@@ -513,6 +514,7 @@ export function useDataGridLargeValues(options: UseDataGridLargeValuesOptions) {
     const isCurrent = () => options.result.value === sourceResult && options.connectionId.value === connectionId
       && options.executionDatabase.value === executionDatabase && options.resultLifecycle.isCurrent(operation);
     const resolved: ResolvedLargeValueCells = new Map();
+    let snapshotBytes = 0;
     const requestedColumns = new Set(columnIndexes);
     const requestsByColumn = new Map<number, LargeValueCellRequest[]>();
     for (const rowId of new Set(rowIds)) {
@@ -531,6 +533,8 @@ export function useDataGridLargeValues(options: UseDataGridLargeValuesOptions) {
           snapshotExecutionIds.add(executionId);
           try {
             const value = await materializeLargeValueSnapshot({ ...context, valueRef: metadata.value_ref, executionId }, isCurrent);
+            snapshotBytes += new TextEncoder().encode(value).length;
+            if (snapshotBytes > 64 * 1024 * 1024) throw new Error("LOB selection exceeds the 64 MiB view/copy limit; use CSV/JSON export or download individual complete values");
             const rowValues = resolved.get(item.id) ?? new Map<number, CellValue>();
             rowValues.set(columnIndex, value);
             resolved.set(item.id, rowValues);
@@ -598,6 +602,7 @@ export function useDataGridLargeValues(options: UseDataGridLargeValuesOptions) {
     if (!isLargeValuePreview(item, columnIndex) || item?.sourceIndex === undefined) return true;
     const sourceResult = options.result.value;
     const hydrationKey = largeValueCellKey(item.sourceIndex, columnIndex);
+    const ownsSnapshot = !!largeValueCellsByKey.value.get(hydrationKey)?.value_ref;
     const operation = options.resultLifecycle.beginOperation();
     return pendingLargeValueHydrations.run(hydrationKey, sourceResult, async () => {
       try {
@@ -605,6 +610,14 @@ export function useDataGridLargeValues(options: UseDataGridLargeValuesOptions) {
         if (!options.resultLifecycle.isCurrent(operation) || options.result.value !== sourceResult) return false;
         const value = resolved.get(rowId)?.get(columnIndex);
         if (value === undefined && !resolved.get(rowId)?.has(columnIndex)) return false;
+        if (ownsSnapshot && typeof value === "string") {
+          const sizes = materializedSnapshotBytes.get(sourceResult) ?? new Map<string, number>();
+          const bytes = new TextEncoder().encode(value).length;
+          const total = [...sizes.values()].reduce((sum, size) => sum + size, 0) - (sizes.get(hydrationKey) ?? 0) + bytes;
+          if (total > 64 * 1024 * 1024) throw new Error("LOB result exceeds the 64 MiB view/edit limit; use CSV/JSON export or download individual complete values");
+          sizes.set(hydrationKey, bytes);
+          materializedSnapshotBytes.set(sourceResult, sizes);
+        }
         const row = [...(sourceResult.rows[item.sourceIndex!] ?? [])];
         row[columnIndex] = value ?? null;
         const rows = sourceResult.rows.slice();
diff --git a/apps/desktop/src/lib/__tests__/dataGrid/snapshotExport.spec.ts b/apps/desktop/src/lib/__tests__/dataGrid/snapshotExport.spec.ts
new file mode 100644
index 0000000000..ffc4f560bb
--- /dev/null
+++ b/apps/desktop/src/lib/__tests__/dataGrid/snapshotExport.spec.ts
@@ -0,0 +1,47 @@
+import { describe, expect, it } from "vitest";
+import { snapshotExportSelection, assertSnapshotXlsxCellLengths } from "@/lib/dataGrid/snapshotExport";
+import type { QueryResult } from "@/types/database";
+
+const result = {
+  columns: ["ID", "Value", "value"], rows: [[1, "first preview", "second preview"], [2, "third preview", null]],
+  large_value_context: { connectionId: "original", database: "oracletest", clientSessionId: "original-session" },
+  large_value_cells: [
+    { row_index: 0, column_index: 1, value_ref: "first", value_kind: "text" },
+    { row_index: 0, column_index: 2, value_ref: "second", value_kind: "text" },
+    { row_index: 1, column_index: 1, value_ref: "third", value_kind: "text" },
+  ],
+} as QueryResult;
+
+describe("snapshot export selection", () => {
+  it("refuses XLSX truncation while retaining the complete value for other formats", () => {
+    expect(() => assertSnapshotXlsxCellLengths([["a".repeat(32767)]])).not.toThrow();
+    const value = "中🙂".repeat(20000);
+    expect(() => assertSnapshotXlsxCellLengths([[value]])).toThrow("XLSX cannot preserve");
+    expect(Array.from(value)).toHaveLength(40000);
+  });
+  it("remaps sorted rows and projected quoted columns by source positions", () => {
+    const selected = snapshotExportSelection(result, ["value", "Value"], [2, 1], [
+      { sourceIndex: 1, data: [null, "third preview"] },
+      { sourceIndex: 0, data: ["second preview", "first preview"] },
+    ])!;
+    expect(selected.cells).toEqual([
+      { rowIndex: 0, columnIndex: 1, valueRef: "third" },
+      { rowIndex: 1, columnIndex: 0, valueRef: "second" },
+      { rowIndex: 1, columnIndex: 1, valueRef: "first" },
+    ]);
+    expect(selected.context).toEqual({ ...result.large_value_context, valueRef: "" });
+  });
+  it("preserves complete dirty values and new rows rather than substituting their original snapshots", () => {
+    const selected = snapshotExportSelection(result, ["Value", "value"], [1, 2], [
+      { sourceIndex: 0, data: ["edited complete", "second preview"], isDirtyCol: [true, false] },
+      { isNew: true, data: ["new complete", "other complete"] },
+    ])!;
+    expect(selected.cells).toEqual([{ rowIndex: 0, columnIndex: 1, valueRef: "second" }]);
+    expect(selected.rows[0]![0]).toBe("edited complete");
+    expect(result.rows[0]![1]).toBe("first preview");
+  });
+  it("fails before export when original connection context is missing", () => {
+    expect(() => snapshotExportSelection({ ...result, large_value_context: undefined }, ["Value"], [1], [{ sourceIndex: 0, data: ["preview"] }])).toThrow("connection is unavailable");
+    expect(snapshotExportSelection(result, ["ID"], [0], [{ sourceIndex: 0, data: [1] }])).toBeUndefined();
+  });
+});
diff --git a/apps/desktop/src/lib/backend/api.ts b/apps/desktop/src/lib/backend/api.ts
index fcab597f7f..80395f4ea3 100644
--- a/apps/desktop/src/lib/backend/api.ts
+++ b/apps/desktop/src/lib/backend/api.ts
@@ -284,6 +284,7 @@ export const closeQuerySession = forward("closeQuerySession");
 export const readLargeValueChunk = forward("readLargeValueChunk");
 export const releaseLargeValue = forward("releaseLargeValue");
 export const downloadLargeValue = forward("downloadLargeValue");
+export const exportSnapshotResult = forward("exportSnapshotResult");
 export const closeClientConnectionSession = forward("closeClientConnectionSession");
 export const analyzeSqlReferences = forward("analyzeSqlReferences");
 export const findStatementAtCursor = forward("findStatementAtCursor");
diff --git a/apps/desktop/src/lib/backend/http.ts b/apps/desktop/src/lib/backend/http.ts
index 501b712c63..a3c523f57a 100644
--- a/apps/desktop/src/lib/backend/http.ts
+++ b/apps/desktop/src/lib/backend/http.ts
@@ -1624,6 +1624,25 @@ export async function downloadLargeValue(request: LargeValueRequest, filePath: s
   anchor.click();
 }
 
+export interface SnapshotExportRequest {
+  context: LargeValueRequest;
+  format: "csv" | "json";
+  columns: string[];
+  rows: unknown[][];
+  cells: Array<{ rowIndex: number; columnIndex: number; valueRef: string }>;
+  quoteMode?: "all" | "necessary";
+  nullLiteral?: string | null;
+}
+
+export async function exportSnapshotResult(request: SnapshotExportRequest, filePath: string): Promise<void> {
+  const fileName = filePath.split(/[\\/]/).pop() || `result.${request.format}`;
+  const prepared = await post<{ downloadId: string }>("/api/query/large-value/export", { request, fileName });
+  const anchor = document.createElement("a");
+  anchor.href = apiUrl(`/api/query/large-value/download/${encodeURIComponent(prepared.downloadId)}`);
+  anchor.download = fileName;
+  anchor.click();
+}
+
 export async function closeQuerySession(connectionId: string, database: string, sessionId: string, clientSessionId?: string, catalog?: string): Promise<boolean> {
   return post("/api/query/close-session", {
     connectionId,
diff --git a/apps/desktop/src/lib/backend/tauri.ts b/apps/desktop/src/lib/backend/tauri.ts
index 3476cc0df2..9614e8ff1d 100644
--- a/apps/desktop/src/lib/backend/tauri.ts
+++ b/apps/desktop/src/lib/backend/tauri.ts
@@ -2036,6 +2036,10 @@ export async function downloadLargeValue(request: import("./http").LargeValueReq
   await invoke("download_large_value", { request, filePath });
 }
 
+export async function exportSnapshotResult(request: import("./http").SnapshotExportRequest, filePath: string): Promise<void> {
+  await invoke("export_snapshot_result", { request, filePath });
+}
+
 export async function closeQuerySession(connectionId: string, database: string, sessionId: string, clientSessionId?: string, catalog?: string): Promise<boolean> {
   return invoke("close_query_session", {
     connectionId,
diff --git a/apps/desktop/src/lib/dataGrid/snapshotExport.ts b/apps/desktop/src/lib/dataGrid/snapshotExport.ts
new file mode 100644
index 0000000000..9fb8f19269
--- /dev/null
+++ b/apps/desktop/src/lib/dataGrid/snapshotExport.ts
@@ -0,0 +1,41 @@
+import type { QueryResult } from "@/types/database";
+import type { SnapshotExportRequest } from "@/lib/backend/http";
+
+interface SnapshotExportRow {
+  sourceIndex?: number;
+  data: unknown[];
+  isNew?: boolean;
+  isDirtyCol?: boolean[];
+}
+
+/** Projection uses source positions, never labels, so quoted and repeated names remain distinct. */
+export function snapshotExportSelection(
+  result: QueryResult,
+  columns: string[],
+  sourceColumns: number[],
+  items: SnapshotExportRow[],
+): Pick<SnapshotExportRequest, "columns" | "rows" | "cells" | "context"> | undefined {
+  const refs = new Map((result.large_value_cells ?? []).filter((cell) => cell.value_ref).map((cell) => [`${cell.row_index}:${cell.column_index}`, cell.value_ref!]));
+  const cells: SnapshotExportRequest["cells"] = [];
+  items.forEach((item, rowIndex) => {
+    if (item.isNew || item.sourceIndex === undefined) return;
+    sourceColumns.forEach((sourceColumn, columnIndex) => {
+      if (item.isDirtyCol?.[columnIndex]) return;
+      const valueRef = refs.get(`${item.sourceIndex}:${sourceColumn}`);
+      if (valueRef) cells.push({ rowIndex, columnIndex, valueRef });
+    });
+  });
+  if (!cells.length) return undefined;
+  if (!result.large_value_context) throw new Error("LOB result connection is unavailable; execute the query again");
+  return { columns, rows: items.map((item) => item.data), cells, context: { ...result.large_value_context, valueRef: "" } };
+}
+
+export function assertSnapshotXlsxCellLengths(rows: unknown[][]): void {
+  for (const row of rows) for (const value of row) {
+    if (typeof value !== "string") continue;
+    let count = 0;
+    for (const _character of value) if (++count > 32767) {
+      throw new Error("XLSX cannot preserve a LOB longer than 32,767 characters; use CSV/JSON or download the complete value");
+    }
+  }
+}
diff --git a/crates/dbx-core/src/query/mod.rs b/crates/dbx-core/src/query/mod.rs
index 189c0189b4..2f0f9288ce 100644
--- a/crates/dbx-core/src/query/mod.rs
+++ b/crates/dbx-core/src/query/mod.rs
@@ -7,6 +7,7 @@ pub mod plugin_data;
 pub mod plugin_plan;
 pub mod query_cancel;
 pub mod redis_ops;
+pub mod snapshot_export;
 mod sqlserver_agent_batch;
 pub mod sqlserver_manual_transaction;
 pub mod two_phase_commit;
diff --git a/crates/dbx-core/src/query/snapshot_export.rs b/crates/dbx-core/src/query/snapshot_export.rs
new file mode 100644
index 0000000000..bec2543017
--- /dev/null
+++ b/crates/dbx-core/src/query/snapshot_export.rs
@@ -0,0 +1,321 @@
+use super::{is_canceled, canceled_error, request_large_value_with_cancel, LargeValueRequest};
+use crate::connection::AppState;
+use serde::Deserialize;
+use serde_json::Value;
+use std::collections::HashMap;
+use std::io::{BufReader, Read, Seek, SeekFrom, Write};
+
+#[derive(Debug, Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub struct SnapshotExportCell {
+    pub row_index: usize,
+    pub column_index: usize,
+    pub value_ref: String,
+}
+
+#[derive(Debug, Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub struct SnapshotExportRequest {
+    pub context: LargeValueRequest,
+    pub format: String,
+    pub columns: Vec<String>,
+    pub rows: Vec<Vec<Value>>,
+    pub cells: Vec<SnapshotExportCell>,
+    #[serde(default)]
+    pub quote_mode: dbx_formats::csv_export::CsvQuoteMode,
+    pub null_literal: Option<String>,
+}
+
+/// Original result references only. A temporary cell file bounds memory even for
+/// formula-guard inspection; callers publish the output only after success.
+pub async fn write_snapshot_export(state: &AppState, request: SnapshotExportRequest, output: &mut std::fs::File) -> Result<(), String> {
+    let registered = request.context.execution_id.as_ref().map(|id| state.running_queries.register_task(
+        id.clone(), crate::query_cancel::RunningTaskMetadata::query(
+            request.context.connection_id.clone(), request.context.database.clone(), request.context.client_session_id.clone(),
+        ),
+    ));
+    let cancel = registered.as_ref().map(|task| task.token());
+    write_snapshot_export_with_fetch(request, output, cancel.clone(), |chunk_request| {
+        request_large_value_with_cancel(state, chunk_request, false, cancel.clone())
+    }).await
+}
+
+async fn write_snapshot_export_with_fetch<F, Fut>(request: SnapshotExportRequest, output: &mut std::fs::File, cancel: Option<tokio_util::sync::CancellationToken>, mut fetch: F) -> Result<(), String>
+where F: FnMut(LargeValueRequest) -> Fut, Fut: std::future::Future<Output = Result<Value, String>> {
+    let mut buffered = std::io::BufWriter::new(output);
+    let output = &mut buffered;
+    if request.format != "csv" && request.format != "json" { return Err("Unsupported snapshot export format".into()); }
+    if request.rows.iter().any(|row| row.len() != request.columns.len()) { return Err("Invalid snapshot export row".into()); }
+    let mut refs = HashMap::new();
+    for cell in &request.cells {
+        if cell.row_index >= request.rows.len() || cell.column_index >= request.columns.len()
+            || cell.value_ref.is_empty() || cell.value_ref.len() > 128
+            || refs.insert((cell.row_index, cell.column_index), cell.value_ref.as_str()).is_some() {
+            return Err("Invalid snapshot export cell".into());
+        }
+    }
+    // JSON objects cannot preserve duplicate labels. Reject rather than dropping a column.
+    if request.format == "json" {
+        let mut names = std::collections::HashSet::new();
+        if request.columns.iter().any(|name| !names.insert(name)) { return Err("JSON export requires unique column names; use CSV".into()); }
+    }
+    let json = request.format == "json";
+    if json { output.write_all(b"[").map_err(|e| e.to_string())?; }
+    else {
+        let mut header = String::new();
+        for (index, name) in request.columns.iter().enumerate() {
+            if index > 0 { header.push(','); }
+            dbx_formats::csv_export::push_csv_field(&mut header, name, request.quote_mode);
+        }
+        output.write_all(header.as_bytes()).map_err(|e| e.to_string())?;
+    }
+    for (row_index, row) in request.rows.iter().enumerate() {
+        if is_canceled(&cancel) { return Err(canceled_error()); }
+        output.write_all(if json { if row_index == 0 { b"{" } else { b",{" } } else { b"\n" }).map_err(|e| e.to_string())?;
+        for (column_index, value) in row.iter().enumerate() {
+            if column_index > 0 { output.write_all(b",").map_err(|e| e.to_string())?; }
+            if json {
+                serde_json::to_writer(&mut *output, &request.columns[column_index]).map_err(|e| e.to_string())?;
+                output.write_all(b":").map_err(|e| e.to_string())?;
+            }
+            if let Some(value_ref) = refs.get(&(row_index, column_index)) {
+                let mut cell_file = tempfile::tempfile().map_err(|e| e.to_string())?;
+                let mut chunk_request = request.context.clone();
+                chunk_request.value_ref = (*value_ref).to_string();
+                chunk_request.offset = 0;
+                chunk_request.limit = 4096;
+                let mut original_kind: Option<String> = None;
+                loop {
+                    if is_canceled(&cancel) { return Err(canceled_error()); }
+                    let chunk = fetch(chunk_request.clone()).await?;
+                    let (data, next, eof, kind) = checked_chunk(&chunk, chunk_request.offset)?;
+                    if original_kind.as_deref().is_some_and(|original| original != kind) { return Err("LOB chunk type changed".into()); }
+                    if original_kind.is_none() && kind == "binary" { cell_file.write_all(b"0x").map_err(|e| e.to_string())?; }
+                    original_kind = Some(kind.to_string());
+                    cell_file.write_all(data.as_bytes()).map_err(|e| e.to_string())?;
+                    if eof { break; }
+                    chunk_request.offset = next;
+                }
+                cell_file.seek(SeekFrom::Start(0)).map_err(|e| e.to_string())?;
+                let guard = !json && stream_formula_guard(BufReader::new(CancelableReader { reader: &mut cell_file, cancel: &cancel }))?;
+                cell_file.seek(SeekFrom::Start(0)).map_err(|e| e.to_string())?;
+                let quoted = json || request.quote_mode == dbx_formats::csv_export::CsvQuoteMode::All || csv_needs_quotes(CancelableReader { reader: &mut cell_file, cancel: &cancel })?;
+                cell_file.seek(SeekFrom::Start(0)).map_err(|e| e.to_string())?;
+                if quoted { output.write_all(b"\"").map_err(|e| e.to_string())?; }
+                if guard { output.write_all(b"'").map_err(|e| e.to_string())?; }
+                let mut buffer = [0_u8; 8192];
+                loop {
+                    if is_canceled(&cancel) { return Err(canceled_error()); }
+                    let count = cell_file.read(&mut buffer).map_err(|e| e.to_string())?;
+                    if count == 0 { break; }
+                    write_escaped(output, &buffer[..count], json)?;
+                }
+                if quoted { output.write_all(b"\"").map_err(|e| e.to_string())?; }
+            } else if json { serde_json::to_writer(&mut *output, value).map_err(|e| e.to_string())?; }
+            else {
+                let mut cell = String::new();
+                dbx_formats::csv_export::push_query_result_csv_row_with_options(&mut cell, std::slice::from_ref(value), request.quote_mode, request.null_literal.as_deref());
+                output.write_all(cell.as_bytes()).map_err(|e| e.to_string())?;
+            }
+        }
+        if json { output.write_all(b"}").map_err(|e| e.to_string())?; }
+    }
+    if is_canceled(&cancel) { return Err(canceled_error()); }
+    if json { output.write_all(b"]").map_err(|e| e.to_string())?; }
+    output.flush().map_err(|e| e.to_string())
+}
+
+struct CancelableReader<'a, R> { reader: R, cancel: &'a Option<tokio_util::sync::CancellationToken> }
+impl<R: Read> Read for CancelableReader<'_, R> {
+    fn read(&mut self, buffer: &mut [u8]) -> std::io::Result<usize> {
+        if is_canceled(self.cancel) { return Err(std::io::Error::other(canceled_error())); }
+        self.reader.read(buffer)
+    }
+}
+
+fn checked_chunk(chunk: &Value, offset: u64) -> Result<(&str, u64, bool, &str), String> {
+    if chunk.get("status").and_then(Value::as_str) != Some("ok") { return Err("LOB snapshot expired; execute the query again".into()); }
+    let data = chunk.get("data").and_then(Value::as_str).ok_or("Invalid LOB data")?;
+    let next = chunk.get("next_offset").and_then(Value::as_u64).ok_or("Invalid LOB offset")?;
+    let eof = chunk.get("eof").and_then(Value::as_bool).ok_or("Invalid LOB EOF")?;
+    let kind = chunk.get("value_kind").and_then(Value::as_str).ok_or("Invalid LOB type")?;
+    if next < offset || next - offset > 4096 || (!eof && next == offset) { return Err("Invalid LOB offset".into()); }
+    let amount = match kind {
+        "text" => data.chars().count(),
+        "binary" if data.len() <= 8192 && data.len() % 2 == 0 && data.bytes().all(|b| b.is_ascii_hexdigit()) => data.len() / 2,
+        _ => return Err("Invalid LOB chunk encoding".into()),
+    };
+    if amount as u64 != next - offset { return Err("Invalid LOB chunk length".into()); }
+    Ok((data, next, eof, kind))
+}
+
+fn write_escaped(output: &mut impl Write, bytes: &[u8], json: bool) -> Result<(), String> {
+    for &byte in bytes {
+        match byte {
+            b'"' => output.write_all(if json { b"\\\"" } else { b"\"\"" }),
+            b'\\' if json => output.write_all(b"\\\\"),
+            0..=31 if json => write!(output, "\\u{byte:04x}"),
+            _ => output.write_all(&[byte]),
+        }.map_err(|e| e.to_string())?;
+    }
+    Ok(())
+}
+
+fn csv_needs_quotes(mut reader: impl Read) -> Result<bool, String> {
+    let mut buffer = [0_u8; 8192];
+    loop {
+        let count = reader.read(&mut buffer).map_err(|e| e.to_string())?;
+        if count == 0 { return Ok(false); }
+        if buffer[..count].iter().any(|&byte| matches!(byte, b',' | b'"' | b'\n' | b'\r')) { return Ok(true); }
+    }
+}
+
+// Same cell-level guard as dbx-formats, including negative decimals and literal
+// apostrophes, without retaining leading spaces/zeroes or the complete cell.
+fn stream_formula_guard(reader: impl Read) -> Result<bool, String> {
+    let mut bytes = reader.bytes();
+    let mut next = || bytes.next().transpose().map_err(|e| e.to_string());
+    let mut byte = next()?;
+    if byte == Some(b'\'') {
+        byte = next()?;
+        if byte == Some(b'\'') { return Ok(true); }
+    }
+    while byte == Some(b' ') { byte = next()?; }
+    if byte != Some(b'-') { return Ok(byte.is_some_and(|b| b"=+@\t\r".contains(&b))); }
+    byte = next()?;
+    if matches!(byte, Some(b'+') | Some(b'-')) { byte = next()?; }
+    let mut digits = 0_usize;
+    let mut significant = 0;
+    let mut dot = false;
+    loop {
+        match byte {
+            Some(b'0'..=b'9') => {
+                digits += 1;
+                if byte != Some(b'0') || significant > 0 { significant += 1; }
+                if significant > 15 { return Ok(true); }
+            }
+            Some(b'.') if !dot && digits > 0 => { dot = true; digits = 0; significant = 0; }
+            None => return Ok(digits == 0),
+            _ => return Ok(true),
+        }
+        byte = next()?;
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    #[test]
+    fn streamed_guard_matches_existing_cell_semantics() {
+        for value in ["", "plain", "=cmd", "  +86", "-1", "-1.25", "-00000000000000000000000000001", "-1.00000000000000001", "-2+cmd", "-", "'-1", "'=cmd", "''text", "'plain", "  --1", "-.1", "\ttext"] {
+            let mut expected = String::new();
+            dbx_formats::csv_export::push_formula_guard(&mut expected, value);
+            assert_eq!(stream_formula_guard(value.as_bytes()).unwrap(), !expected.is_empty(), "{value}");
+        }
+    }
+    #[test]
+    fn escapes_chunk_boundaries_without_changing_utf8_or_binary_hex() {
+        let text = "中🙂\"\\\n\0";
+        for split in 0..=text.len() {
+            let mut out = Vec::new();
+            write_escaped(&mut out, &text.as_bytes()[..split], true).unwrap();
+            write_escaped(&mut out, &text.as_bytes()[split..], true).unwrap();
+            assert_eq!(serde_json::from_slice::<String>(&[b"\"".as_slice(), &out, b"\""].concat()).unwrap(), text);
+        }
+    }
+    #[test]
+    fn rejects_expiry_invalid_offsets_and_incomplete_hex() {
+        for chunk in [serde_json::json!({"status":"expired"}), serde_json::json!({"status":"ok","data":"0","next_offset":1,"eof":true,"value_kind":"binary"}), serde_json::json!({"status":"ok","data":"a","next_offset":5000,"eof":true,"value_kind":"text"})] {
+            assert!(checked_chunk(&chunk, 0).is_err());
+        }
+        let chunk = serde_json::json!({"status":"ok","data":"🙂","next_offset":1,"eof":true,"value_kind":"text"});
+        assert_eq!(checked_chunk(&chunk, 0).unwrap().1, 1);
+    }
+
+    fn request(format: &str) -> SnapshotExportRequest {
+        serde_json::from_value(serde_json::json!({
+            "context": {"connectionId":"original-connection","database":"oracletest","valueRef":"","clientSessionId":"original-session"},
+            "format":format,"columns":["ID","PAYLOAD"],"rows":[[1,"preview"]],
+            "cells":[{"rowIndex":0,"columnIndex":1,"valueRef":"original-locator"}],"nullLiteral":"\\N"
+        })).unwrap()
+    }
+
+    #[tokio::test]
+    async fn production_writer_preserves_unicode_quotes_and_original_context_in_multiple_chunks() {
+        let original = format!(" =cmd{}\"\\\n", "中🙂".repeat(3000));
+        let chars: Vec<char> = original.chars().collect();
+        for format in ["csv", "json"] {
+            let mut file = tempfile::tempfile().unwrap();
+            let mut offsets = Vec::new();
+            write_snapshot_export_with_fetch(request(format), &mut file, None, |chunk_request| {
+                assert_eq!(chunk_request.value_ref, "original-locator");
+                assert_eq!(chunk_request.connection_id, "original-connection");
+                assert_eq!(chunk_request.client_session_id.as_deref(), Some("original-session"));
+                assert_eq!(chunk_request.limit, 4096);
+                offsets.push(chunk_request.offset);
+                let begin = chunk_request.offset as usize;
+                let end = (begin + 4096).min(chars.len());
+                std::future::ready(Ok(serde_json::json!({"status":"ok","data":chars[begin..end].iter().collect::<String>(),"next_offset":end,"eof":end==chars.len(),"value_kind":"text"})))
+            }).await.unwrap();
+            assert_eq!(offsets, vec![0,4096]);
+            file.seek(SeekFrom::Start(0)).unwrap();
+            let mut text = String::new(); file.read_to_string(&mut text).unwrap();
+            if format == "json" { assert_eq!(serde_json::from_str::<Value>(&text).unwrap()[0]["PAYLOAD"], original); }
+            else { assert_eq!(text, dbx_formats::csv_export::format_query_result_csv_with_options(&["ID".into(),"PAYLOAD".into()], &[vec![Value::from(1), Value::from(original.clone())]], dbx_formats::csv_export::CsvQuoteMode::All, Some("\\N"))); }
+        }
+    }
+
+    #[tokio::test]
+    async fn production_writer_never_completes_on_mid_read_expiry_or_cancel() {
+        for cancel_read in [false, true] {
+            let token = tokio_util::sync::CancellationToken::new();
+            let mut file = tempfile::tempfile().unwrap();
+            let mut calls = 0;
+            let error = write_snapshot_export_with_fetch(request("json"), &mut file, Some(token.clone()), |chunk_request| {
+                calls += 1;
+                if cancel_read { token.cancel(); }
+                std::future::ready(Ok(if chunk_request.offset == 0 {
+                    serde_json::json!({"status":"ok","data":"first","next_offset":5,"eof":false,"value_kind":"text"})
+                } else { serde_json::json!({"status":"expired"}) }))
+            }).await.unwrap_err();
+            assert_eq!(calls, if cancel_read {1} else {2});
+            assert!(!error.is_empty());
+        }
+    }
+
+    #[tokio::test]
+    async fn production_writer_keeps_blob_hex_prefix_once_and_all_byte_values() {
+        let hex: String = (0..=255_u8).map(|byte| format!("{byte:02x}")).collect();
+        let mut file = tempfile::tempfile().unwrap();
+        write_snapshot_export_with_fetch(request("json"), &mut file, None, |chunk_request| {
+            let begin = chunk_request.offset as usize;
+            let end = (begin + 127).min(256);
+            std::future::ready(Ok(serde_json::json!({"status":"ok","data":&hex[begin*2..end*2],"next_offset":end,"eof":end==256,"value_kind":"binary"})))
+        }).await.unwrap();
+        file.seek(SeekFrom::Start(0)).unwrap();
+        let result: Value = serde_json::from_reader(file).unwrap();
+        assert_eq!(result[0]["PAYLOAD"], format!("0x{hex}"));
+    }
+
+    #[tokio::test]
+    async fn necessary_quotes_and_formula_guard_match_existing_export() {
+        for value in ["plain", "", "-000000000000000000001", " =cmd", "'plain", "'=cmd", "a,b", "a\"b"] {
+            let mut req = request("csv");
+            req.quote_mode = dbx_formats::csv_export::CsvQuoteMode::Necessary;
+            let mut file = tempfile::tempfile().unwrap();
+            write_snapshot_export_with_fetch(req, &mut file, None, |_| std::future::ready(Ok(serde_json::json!({
+                "status":"ok","data":value,"next_offset":value.chars().count(),"eof":true,"value_kind":"text"
+            })))).await.unwrap();
+            file.seek(SeekFrom::Start(0)).unwrap();
+            let mut output = String::new(); file.read_to_string(&mut output).unwrap();
+            assert_eq!(output, dbx_formats::csv_export::format_query_result_csv_with_options(&["ID".into(),"PAYLOAD".into()], &[vec![Value::from(1), Value::from(value)]], dbx_formats::csv_export::CsvQuoteMode::Necessary, Some("\\N")));
+        }
+    }
+
+    #[test]
+    fn cancelled_formula_scan_stops_instead_of_retrying_forever() {
+        let token = tokio_util::sync::CancellationToken::new(); token.cancel();
+        let cancel = Some(token);
+        assert!(stream_formula_guard(BufReader::new(CancelableReader { reader: b"   -0000".as_slice(), cancel: &cancel })).is_err());
+    }
+}
diff --git a/crates/dbx-web/src/main.rs b/crates/dbx-web/src/main.rs
index bba528a353..aa8d6dd495 100644
--- a/crates/dbx-web/src/main.rs
+++ b/crates/dbx-web/src/main.rs
@@ -916,6 +916,7 @@ async fn serve() -> Result<(), String> {
         .route("/query/large-value/chunk", post(routes::query::read_large_value_chunk))
         .route("/query/large-value/release", post(routes::query::release_large_value))
         .route("/query/large-value/download", post(routes::query::prepare_large_value_download))
+        .route("/query/large-value/export", post(routes::query::prepare_snapshot_export))
         .route("/query/large-value/download/{id}", get(routes::query::download_large_value))
         .route("/query/close-client-session", post(routes::query::close_client_connection_session))
         .route("/export/query-result-json", post(routes::text_export::export_query_result_json))
diff --git a/crates/dbx-web/src/routes/query.rs b/crates/dbx-web/src/routes/query.rs
index d5bef8581d..42bf24bbb5 100644
--- a/crates/dbx-web/src/routes/query.rs
+++ b/crates/dbx-web/src/routes/query.rs
@@ -732,6 +732,36 @@ pub async fn download_large_value(
     super::mongodb_import_export::export_file_response(file).await
 }
 
+#[derive(Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub struct SnapshotExportDownloadRequest {
+    pub request: dbx_core::query::snapshot_export::SnapshotExportRequest,
+    pub file_name: String,
+}
+
+pub async fn prepare_snapshot_export(
+    State(state): State<Arc<WebState>>,
+    Json(req): Json<SnapshotExportDownloadRequest>,
+) -> Result<Json<serde_json::Value>, AppError> {
+    let mut temporary = tempfile::NamedTempFile::new().map_err(|error| AppError::from(error.to_string()))?;
+    let format = req.request.format.clone();
+    dbx_core::query::snapshot_export::write_snapshot_export(&state.app, req.request, temporary.as_file_mut()).await.map_err(AppError::from)?;
+    let (_, path) = temporary.keep().map_err(|error| AppError::from(error.to_string()))?;
+    let download_id = uuid::Uuid::new_v4().to_string();
+    state.export_files.write().await.insert(download_id.clone(), crate::state::WebExportFile {
+        file_path: path.to_string_lossy().into_owned(), download_filename: req.file_name, format,
+    });
+    let cleanup_state = state.clone();
+    let cleanup_id = download_id.clone();
+    tokio::spawn(async move {
+        tokio::time::sleep(std::time::Duration::from_secs(300)).await;
+        if let Some(file) = cleanup_state.export_files.write().await.remove(&cleanup_id) {
+            let _ = tokio::fs::remove_file(file.file_path).await;
+        }
+    });
+    Ok(Json(serde_json::json!({ "downloadId": download_id })))
+}
+
 pub async fn close_query_session(
     State(state): State<Arc<WebState>>,
     Json(req): Json<CloseSessionRequest>,
diff --git a/src-tauri/src/commands/query.rs b/src-tauri/src/commands/query.rs
index 45116e50a8..5365ce5a6b 100644
--- a/src-tauri/src/commands/query.rs
+++ b/src-tauri/src/commands/query.rs
@@ -376,6 +376,20 @@ pub async fn close_client_connection_session(
     state.close_client_session_pool(&connection_id, database, &client_session_id).await
 }
 
+#[tauri::command]
+pub async fn export_snapshot_result(
+    state: State<'_, Arc<AppState>>,
+    request: dbx_core::query::snapshot_export::SnapshotExportRequest,
+    file_path: String,
+) -> Result<(), String> {
+    let path = std::path::Path::new(&file_path);
+    let parent = path.parent().filter(|parent| !parent.as_os_str().is_empty()).unwrap_or(std::path::Path::new("."));
+    let mut temporary = tempfile::NamedTempFile::new_in(parent).map_err(|error| error.to_string())?;
+    dbx_core::query::snapshot_export::write_snapshot_export(&state, request, temporary.as_file_mut()).await?;
+    temporary.persist(path).map_err(|error| error.to_string())?;
+    Ok(())
+}
+
 fn query_session_database<'a>(database: &'a str, catalog: Option<&str>) -> Option<&'a str> {
     if database.trim().is_empty() || catalog.is_some() {
         None
diff --git a/src-tauri/src/lib.rs b/src-tauri/src/lib.rs
index b6a3c19401..21be43f45e 100644
--- a/src-tauri/src/lib.rs
+++ b/src-tauri/src/lib.rs
@@ -2079,6 +2079,7 @@ pub fn run() {
             commands::query::read_large_value_chunk,
             commands::query::release_large_value,
             commands::query::download_large_value,
+            commands::query::export_snapshot_result,
             commands::query::close_client_connection_session,
             commands::query::execute_batch,
             commands::query::execute_script,