diff --git a/src/vue/View.vue b/src/vue/View.vue
index fcea231..fafc2e4 100644
--- a/src/vue/View.vue
+++ b/src/vue/View.vue
@@ -105,22 +105,11 @@
 
 <script setup lang="ts">
 import { computed, inject, ref, watch, onMounted, onUnmounted } from "vue";
-import * as XLSX from "xlsx";
 import { PLUGIN_RUNTIME_KEY, type ToolResult } from "gui-chat-protocol/vue";
-import type { SpreadsheetToolData, SpreadsheetSheet, StorableCell, SpreadsheetCell } from "../core/types";
+import type { SpreadsheetToolData, SpreadsheetSheet } from "../core/types";
 import { isSpreadsheetArtifactPath } from "../core/paths";
-import {
-  SpreadsheetEngine,
-  prefersDayFirst,
-  indexToColumn,
-  extractCellReferences,
-  buildCellFromInput,
-  normalizeData,
-  findCellJsonPosition,
-  type SheetData,
-  type CellValue,
-} from "../engine";
-import { errorMessage as formatErrorMessage, isObj, isRecord } from "../engine/guards";
+import { indexToColumn } from "../engine";
+import { errorMessage as formatErrorMessage } from "../engine/guards";
 import { applyCellHighlights, clearCellHighlights } from "./cellHighlights";
 import {
   APPLY_BUTTON_CLASSES,
@@ -136,14 +125,16 @@ import {
   TABLE_CLASSES,
   sheetTabClasses,
 } from "./viewClasses";
-import { getArrowKeyOffset, isWithinSheetBounds } from "./keyboardNav";
-import { escapeHtml, isCrossOriginHttpUrl } from "./htmlText";
+import { isCrossOriginHttpUrl } from "./htmlText";
 import { useT } from "../lang";
 import { createSheetSession, type LoadOutcome } from "./sheetSession";
 import { readLoadReply, readSaveReply, type LoadedWorkbook, type SaveReply } from "../core/dispatchReplies";
 import { fileChangeAction } from "./fileFollow";
 import { useCustomFunctions } from "./useCustomFunctions";
-import { calculateWith } from "../engine/customFunctions";
+import { useMiniEditor } from "./useMiniEditor";
+import { selectCellInEditor } from "./editorSelection";
+import { downloadWorkbook } from "./excelDownload";
+import { useRenderedTable } from "./useRenderedTable";
 
 // Import all spreadsheet functions to populate the function registry
 import "../engine/functions";
@@ -155,38 +146,6 @@ const t = useT();
 const runtime = inject(PLUGIN_RUNTIME_KEY, undefined);
 const locale = computed(() => runtime?.locale.value ?? "en");
 
-/**
- * Normalize malformed data structures
- * Some models generate flat arrays instead of 2D arrays - fix them
- */
-function normalizeSheetData(data: unknown): unknown[][] {
-  if (!Array.isArray(data) || data.length === 0) {
-    return [];
-  }
-
-  // If data is already a 2D array, return as-is
-  if (Array.isArray(data[0])) {
-    return data;
-  }
-
-  // If data is a flat array of cell objects, convert to 2D by pairing cells
-  // Pattern: [cell1, cell2, cell3, cell4] -> [[cell1, cell2], [cell3, cell4]]
-  if (isObj(data[0])) {
-    const rows: unknown[][] = [];
-    for (let i = 0; i < data.length; i += 2) {
-      const row = [data[i]];
-      if (i + 1 < data.length) {
-        row.push(data[i + 1]);
-      }
-      rows.push(row);
-    }
-    return rows;
-  }
-
-  // Unknown structure - return empty
-  return [];
-}
-
 const props = defineProps<{
   selectedResult: ToolResult<SpreadsheetToolData>;
 }>();
@@ -195,9 +154,6 @@ const emit = defineEmits<{
   updateResult: [result: ToolResult];
 }>();
 
-// Create spreadsheet engine instance
-const engine = new SpreadsheetEngine();
-
 const loading = ref(false);
 const errorMessage = ref("");
 const resolvedSheets = ref<SpreadsheetSheet[]>([]);
@@ -389,17 +345,19 @@ const editorTextarea = ref<HTMLTextAreaElement | null>(null);
 const editorDetails = ref<HTMLDetailsElement | null>(null);
 const tableContainer = ref<HTMLDivElement | null>(null);
 
-// Mini editor state
-const miniEditorOpen = ref(false);
-const miniEditorCell = ref<{ row: number; col: number } | null>(null);
-
-const miniEditorValue = ref<unknown>(null);
-const miniEditorType = ref<"number" | "string" | "object">("string");
-const miniEditorFormula = ref("");
-const miniEditorFormat = ref("");
-
-// Referenced cells state (for formula highlighting)
-const referencedCells = ref<{ row: number; col: number }[]>([]);
+const {
+  miniEditorOpen,
+  miniEditorCell,
+  miniEditorValue,
+  miniEditorType,
+  miniEditorFormula,
+  miniEditorFormat,
+  referencedCells,
+  openMiniEditor,
+  closeMiniEditor,
+  saveMiniEditor,
+  handleKeyboardNavigation,
+} = useMiniEditor({ editableData, activeSheetIndex, persistSheets });
 
 // Check if spreadsheet data has been modified
 const hasChanges = computed(() => {
@@ -414,223 +372,17 @@ const hasChanges = computed(() => {
 // Short alias used in the template column header.
 const indexToCol = indexToColumn;
 
-// `normalizeData` is the engine's own reader for the stored cell forms (bare
-// values, `null` gaps, flat rows); `calculate` runs it internally anyway, so
-// applying it here only meets the engine's declared type at the call site.
-const toEngineSheet = (sheet: SpreadsheetSheet): SheetData => ({ name: sheet.name, data: normalizeData(sheet.data) });
-
-// Calculate formulas in the data using the spreadsheet engine
-const calculateFormulas = (data: StorableCell[][], sheetName?: string): CellValue[][] => {
-  // If we have a sheet name, we need to find all sheets for cross-sheet references
-  const allSheets = resolvedSheets.value.map(toEngineSheet);
-
-  // Create a SheetData object for the engine
-  const sheet: SheetData = {
-    name: sheetName || "Sheet1",
-    data: normalizeData(data),
-  };
-
-  // Read the date order from the current locale on every calculation, so a
-  // locale switch takes effect without rebuilding the engine.
-  engine.setOptions({ preferDDMMYYYY: prefersDayFirst(locale.value) });
-  const result = calculateWith(customFunctions.value, () => engine.calculate(sheet, allSheets));
-
-  return result.data;
-};
-
 // Render the active sheet as HTML table
-const renderedHtml = computed(() => {
-  if (!resolvedSheets.value || resolvedSheets.value.length === 0) {
-    return "";
-  }
-
-  const sheet = resolvedSheets.value[activeSheetIndex.value];
-  if (!sheet || !sheet.data) {
-    return "";
-  }
-
-  try {
-    // Calculate formulas first with sheet name for cross-sheet references
-    const calculatedData = calculateFormulas(sheet.data, sheet.name);
-
-    // Convert data array to worksheet
-    const worksheet = XLSX.utils.aoa_to_sheet(calculatedData);
-
-    // Generate HTML table
-    const html = XLSX.utils.sheet_to_html(worksheet, {
-      id: "spreadsheet-table",
-      editable: false,
-    });
-
-    return html;
-  } catch (error) {
-    console.error("Failed to render spreadsheet:", error);
-    // Fed into v-html, and a caught throw can carry an object whose
-    // `details` / `message` formatErrorMessage surfaces verbatim.
-    return `<div class="error">Failed to render spreadsheet: ${escapeHtml(formatErrorMessage(error, "Unknown error"))}</div>`;
-  }
-});
+const renderedHtml = useRenderedTable({ resolvedSheets, activeSheetIndex, customFunctions, locale });
 
 // Download as Excel file
-const downloadExcel = () => {
-  if (!resolvedSheets.value || resolvedSheets.value.length === 0) return;
-
-  try {
-    const workbook = XLSX.utils.book_new();
-
-    // Add all sheets to workbook
-    resolvedSheets.value.forEach((sheet) => {
-      const worksheet = XLSX.utils.aoa_to_sheet(sheet.data);
-      XLSX.utils.book_append_sheet(workbook, worksheet, sheet.name);
-    });
-
-    // Generate filename
-    const filename = props.selectedResult.title ? `${props.selectedResult.title.replace(/[^a-z0-9]/gi, "_").toLowerCase()}.xlsx` : "spreadsheet.xlsx";
-
-    // Write file
-    XLSX.writeFile(workbook, filename);
-  } catch (error) {
-    console.error("Failed to download Excel:", error);
-    alert(`Failed to download Excel file: ${formatErrorMessage(error, "Unknown error")}`);
-  }
-};
+const downloadExcel = () => downloadWorkbook(resolvedSheets.value, props.selectedResult.title);
 
 function handleDataEdit() {
   // Just update the local state, don't apply yet
   // User needs to click "Apply Changes" button
 }
 
-function openMiniEditor(rowIndex: number, colIndex: number) {
-  try {
-    const sheets = JSON.parse(editableData.value);
-    const currentSheet = sheets[activeSheetIndex.value];
-
-    if (!currentSheet || !currentSheet.data) {
-      return;
-    }
-
-    // Normalize the data in case it's malformed
-    const normalizedData = normalizeSheetData(currentSheet.data);
-
-    if (!normalizedData[rowIndex] || normalizedData[rowIndex][colIndex] === undefined) {
-      return;
-    }
-
-    const cellValue = normalizedData[rowIndex][colIndex];
-
-    // Determine cell type and extract values (new format: {v, f})
-    if (isRecord(cellValue) && "v" in cellValue) {
-      const value = cellValue["v"];
-      const format = typeof cellValue["f"] === "string" ? cellValue["f"] : "";
-
-      // Check if it's a formula (value starts with "=")
-      if (typeof value === "string" && value.startsWith("=")) {
-        miniEditorType.value = "object";
-        miniEditorValue.value = "";
-        miniEditorFormula.value = value.substring(1); // Remove "=" prefix
-        miniEditorFormat.value = format;
-        // Extract and store referenced cells for highlighting
-        referencedCells.value = extractCellReferences(value);
-      } else if (typeof value === "number") {
-        miniEditorType.value = "object";
-        miniEditorValue.value = "";
-        miniEditorFormula.value = String(value);
-        miniEditorFormat.value = format;
-        referencedCells.value = [];
-      } else {
-        miniEditorType.value = "string";
-        miniEditorValue.value = String(value);
-        miniEditorFormula.value = "";
-        miniEditorFormat.value = "";
-        referencedCells.value = [];
-      }
-    } else {
-      // Legacy format or plain value
-      miniEditorType.value = "string";
-      miniEditorValue.value = plainCellText(cellValue);
-      miniEditorFormula.value = "";
-      miniEditorFormat.value = "";
-      referencedCells.value = [];
-    }
-
-    miniEditorCell.value = { row: rowIndex, col: colIndex };
-    miniEditorOpen.value = true;
-  } catch (error) {
-    console.error("Failed to open mini editor:", error);
-  }
-}
-
-// A bare value as the editor shows it. An object without `v` (`{}`, `{ f }`)
-// holds no value, so it reads as empty rather than "[object Object]".
-const plainCellText = (value: unknown): string => (typeof value === "string" || typeof value === "number" || typeof value === "boolean" ? String(value) : "");
-
-function closeMiniEditor() {
-  miniEditorOpen.value = false;
-  miniEditorCell.value = null;
-  miniEditorValue.value = null;
-  miniEditorFormula.value = "";
-  miniEditorFormat.value = "";
-  referencedCells.value = [];
-}
-
-function saveMiniEditor() {
-  if (!miniEditorCell.value) return;
-
-  try {
-    const sheets = JSON.parse(editableData.value);
-    const currentSheet = sheets[activeSheetIndex.value];
-
-    if (!currentSheet || !currentSheet.data) return;
-
-    const { row, col } = miniEditorCell.value;
-
-    // Normalize the data in case it's malformed
-    const normalizedData = normalizeSheetData(currentSheet.data);
-
-    // Ensure the row exists
-    while (normalizedData.length <= row) {
-      normalizedData.push([]);
-    }
-
-    // Ensure the row is an array
-    if (!Array.isArray(normalizedData[row])) {
-      normalizedData[row] = [];
-    }
-
-    // Build the new cell value (delegates formula/number detection
-    // and format attachment to the pure helper).
-    const newCellValue: SpreadsheetCell = buildCellFromInput({
-      type: miniEditorType.value,
-      value: miniEditorValue.value,
-      formula: miniEditorFormula.value,
-      format: miniEditorFormat.value,
-    });
-
-    // Update the cell in normalized data
-    normalizedData[row][col] = newCellValue;
-
-    // Update the sheet with normalized data
-    currentSheet.data = normalizedData;
-
-    // Update editableData
-    editableData.value = JSON.stringify(sheets, null, 2);
-
-    // Persist to disk (if file-backed) and emit update
-    void persistSheets(sheets);
-
-    // Update referenced cells if the saved cell contains a formula
-    if (typeof newCellValue.v === "string" && newCellValue.v.startsWith("=")) {
-      referencedCells.value = extractCellReferences(newCellValue.v);
-    } else {
-      referencedCells.value = [];
-    }
-
-    // Don't close the mini editor - keep it open so user can see the updated references
-  } catch (error) {
-    alert(`Failed to save cell: ${formatErrorMessage(error, "Unknown error")}`);
-  }
-}
-
 // External http(s) links inside cells (XLSX hyperlink fields) open in a new
 // tab instead of navigating the host app away.
 function handleExternalLinkClick(event: MouseEvent): boolean {
@@ -665,28 +417,7 @@ function handleTableClick(event: MouseEvent) {
 
   // If editor is open, try to find and select this cell in the editor.
   if (!editorTextarea.value) return;
-  try {
-    const sheets = JSON.parse(editableData.value);
-    const currentSheet = sheets[activeSheetIndex.value];
-    if (!currentSheet || !currentSheet.data) return;
-    const normalizedData = normalizeSheetData(currentSheet.data);
-    if (!normalizedData[rowIndex] || normalizedData[rowIndex][colIndex] === undefined) {
-      return;
-    }
-    const cellStr = JSON.stringify(normalizedData[rowIndex][colIndex]);
-    const cellStart = findCellJsonPosition(editableData.value, currentSheet.name, rowIndex, colIndex);
-    if (cellStart < 0) return;
-    editorTextarea.value.focus();
-    editorTextarea.value.setSelectionRange(cellStart, cellStart + cellStr.length);
-    // Scroll the textarea to make the selection visible.
-    const textBeforeSelection = editableData.value.substring(0, cellStart);
-    const lineNumber = textBeforeSelection.split("\n").length;
-    const lineHeight = 22;
-    const textarea = editorTextarea.value;
-    textarea.scrollTop = Math.max(0, lineNumber * lineHeight - textarea.clientHeight / 2);
-  } catch (error) {
-    console.error("Failed to select cell in editor:", error);
-  }
+  selectCellInEditor(editorTextarea.value, editableData.value, activeSheetIndex.value, rowIndex, colIndex);
 }
 
 async function applyChanges() {
@@ -742,29 +473,6 @@ watch(
   { flush: "post" },
 );
 
-function isEditableTarget(target: EventTarget | null): boolean {
-  if (!(target instanceof HTMLElement)) return false;
-  return target.tagName === "INPUT" || target.tagName === "TEXTAREA" || target.isContentEditable;
-}
-
-function handleKeyboardNavigation(event: KeyboardEvent) {
-  if (!miniEditorOpen.value || !miniEditorCell.value) return;
-  if (isEditableTarget(event.target)) return;
-
-  const { row, col } = miniEditorCell.value;
-  const next = getArrowKeyOffset(event.key, row, col);
-  if (!next) return;
-
-  try {
-    const sheets = JSON.parse(editableData.value);
-    if (!isWithinSheetBounds(sheets[activeSheetIndex.value], next.row, next.col)) return;
-    event.preventDefault();
-    openMiniEditor(next.row, next.col);
-  } catch (error) {
-    console.error("Failed to navigate cells:", error);
-  }
-}
-
 // Add keyboard event listener on mount
 onMounted(() => {
   document.addEventListener("keydown", handleKeyboardNavigation);
diff --git a/src/vue/editorSelection.ts b/src/vue/editorSelection.ts
new file mode 100644
index 0000000..8101b8c
--- /dev/null
+++ b/src/vue/editorSelection.ts
@@ -0,0 +1,30 @@
+// With the JSON editor open, a click on a table cell selects that cell's JSON in the editor.
+
+import { findCellJsonPosition } from "../engine";
+import { normalizeSheetData } from "./sheetRows";
+
+/** Select, in `textarea` holding `editableJson`, the JSON of the cell at `rowIndex`, `colIndex` of the
+ *  sheet at `sheetIndex`, and scroll it into view; nothing when the cell is not in the JSON. */
+export function selectCellInEditor(textarea: HTMLTextAreaElement, editableJson: string, sheetIndex: number, rowIndex: number, colIndex: number): void {
+  try {
+    const sheets = JSON.parse(editableJson);
+    const currentSheet = sheets[sheetIndex];
+    if (!currentSheet || !currentSheet.data) return;
+    const normalizedData = normalizeSheetData(currentSheet.data);
+    if (!normalizedData[rowIndex] || normalizedData[rowIndex][colIndex] === undefined) {
+      return;
+    }
+    const cellStr = JSON.stringify(normalizedData[rowIndex][colIndex]);
+    const cellStart = findCellJsonPosition(editableJson, currentSheet.name, rowIndex, colIndex);
+    if (cellStart < 0) return;
+    textarea.focus();
+    textarea.setSelectionRange(cellStart, cellStart + cellStr.length);
+    // Scroll the textarea to make the selection visible.
+    const textBeforeSelection = editableJson.substring(0, cellStart);
+    const lineNumber = textBeforeSelection.split("\n").length;
+    const lineHeight = 22;
+    textarea.scrollTop = Math.max(0, lineNumber * lineHeight - textarea.clientHeight / 2);
+  } catch (error) {
+    console.error("Failed to select cell in editor:", error);
+  }
+}
diff --git a/src/vue/excelDownload.ts b/src/vue/excelDownload.ts
new file mode 100644
index 0000000..b82accc
--- /dev/null
+++ b/src/vue/excelDownload.ts
@@ -0,0 +1,29 @@
+// The workbook downloaded as an Excel file, its sheets as written (formulas included).
+
+import * as XLSX from "xlsx";
+import type { SpreadsheetSheet } from "../core/types";
+import { errorMessage as formatErrorMessage } from "../engine/guards";
+
+/** Download `sheets` as an .xlsx file named after `title` (spreadsheet.xlsx without one). */
+export function downloadWorkbook(sheets: SpreadsheetSheet[], title: string | undefined): void {
+  if (!sheets || sheets.length === 0) return;
+
+  try {
+    const workbook = XLSX.utils.book_new();
+
+    // Add all sheets to workbook
+    sheets.forEach((sheet) => {
+      const worksheet = XLSX.utils.aoa_to_sheet(sheet.data);
+      XLSX.utils.book_append_sheet(workbook, worksheet, sheet.name);
+    });
+
+    // Generate filename
+    const filename = title ? `${title.replace(/[^a-z0-9]/gi, "_").toLowerCase()}.xlsx` : "spreadsheet.xlsx";
+
+    // Write file
+    XLSX.writeFile(workbook, filename);
+  } catch (error) {
+    console.error("Failed to download Excel:", error);
+    alert(`Failed to download Excel file: ${formatErrorMessage(error, "Unknown error")}`);
+  }
+}
diff --git a/src/vue/sheetRows.ts b/src/vue/sheetRows.ts
new file mode 100644
index 0000000..a6d0e66
--- /dev/null
+++ b/src/vue/sheetRows.ts
@@ -0,0 +1,35 @@
+// A sheet's rows as the editors read them from the JSON they edit.
+
+import { isObj } from "../engine/guards";
+
+/**
+ * Normalize malformed data structures
+ * Some models generate flat arrays instead of 2D arrays - fix them
+ */
+export function normalizeSheetData(data: unknown): unknown[][] {
+  if (!Array.isArray(data) || data.length === 0) {
+    return [];
+  }
+
+  // If data is already a 2D array, return as-is
+  if (Array.isArray(data[0])) {
+    return data;
+  }
+
+  // If data is a flat array of cell objects, convert to 2D by pairing cells
+  // Pattern: [cell1, cell2, cell3, cell4] -> [[cell1, cell2], [cell3, cell4]]
+  if (isObj(data[0])) {
+    const rows: unknown[][] = [];
+    for (let i = 0; i < data.length; i += 2) {
+      const row = [data[i]];
+      if (i + 1 < data.length) {
+        row.push(data[i + 1]);
+      }
+      rows.push(row);
+    }
+    return rows;
+  }
+
+  // Unknown structure - return empty
+  return [];
+}
diff --git a/src/vue/useMiniEditor.ts b/src/vue/useMiniEditor.ts
new file mode 100644
index 0000000..b13de1a
--- /dev/null
+++ b/src/vue/useMiniEditor.ts
@@ -0,0 +1,199 @@
+// The mini editor below the table: the cell it edits, what it shows for that cell, the cells a formula
+// there refers to, and writing the edited cell back into the sheets.
+
+import { ref, type Ref } from "vue";
+import type { SpreadsheetSheet, SpreadsheetCell } from "../core/types";
+import { extractCellReferences, buildCellFromInput } from "../engine";
+import { errorMessage as formatErrorMessage, isRecord } from "../engine/guards";
+import { normalizeSheetData } from "./sheetRows";
+import { getArrowKeyOffset, isWithinSheetBounds } from "./keyboardNav";
+
+/** What the mini editor works on: the editor's JSON, the sheet shown, and how a change is saved. */
+export interface MiniEditorSources {
+  editableData: Ref<string>;
+  activeSheetIndex: Ref<number>;
+  persistSheets: (sheets: SpreadsheetSheet[]) => Promise<void>;
+}
+
+const plainCellText = (value: unknown): string => (typeof value === "string" || typeof value === "number" || typeof value === "boolean" ? String(value) : "");
+
+function isEditableTarget(target: EventTarget | null): boolean {
+  if (!(target instanceof HTMLElement)) return false;
+  return target.tagName === "INPUT" || target.tagName === "TEXTAREA" || target.isContentEditable;
+}
+
+export function useMiniEditor({ editableData, activeSheetIndex, persistSheets }: MiniEditorSources) {
+  // Mini editor state
+  const miniEditorOpen = ref(false);
+  const miniEditorCell = ref<{ row: number; col: number } | null>(null);
+
+  const miniEditorValue = ref<unknown>(null);
+  const miniEditorType = ref<"number" | "string" | "object">("string");
+  const miniEditorFormula = ref("");
+  const miniEditorFormat = ref("");
+
+  // Referenced cells state (for formula highlighting)
+  const referencedCells = ref<{ row: number; col: number }[]>([]);
+
+  function openMiniEditor(rowIndex: number, colIndex: number) {
+    try {
+      const sheets = JSON.parse(editableData.value);
+      const currentSheet = sheets[activeSheetIndex.value];
+
+      if (!currentSheet || !currentSheet.data) {
+        return;
+      }
+
+      // Normalize the data in case it's malformed
+      const normalizedData = normalizeSheetData(currentSheet.data);
+
+      if (!normalizedData[rowIndex] || normalizedData[rowIndex][colIndex] === undefined) {
+        return;
+      }
+
+      const cellValue = normalizedData[rowIndex][colIndex];
+
+      // Determine cell type and extract values (new format: {v, f})
+      if (isRecord(cellValue) && "v" in cellValue) {
+        const value = cellValue["v"];
+        const format = typeof cellValue["f"] === "string" ? cellValue["f"] : "";
+
+        // Check if it's a formula (value starts with "=")
+        if (typeof value === "string" && value.startsWith("=")) {
+          miniEditorType.value = "object";
+          miniEditorValue.value = "";
+          miniEditorFormula.value = value.substring(1); // Remove "=" prefix
+          miniEditorFormat.value = format;
+          // Extract and store referenced cells for highlighting
+          referencedCells.value = extractCellReferences(value);
+        } else if (typeof value === "number") {
+          miniEditorType.value = "object";
+          miniEditorValue.value = "";
+          miniEditorFormula.value = String(value);
+          miniEditorFormat.value = format;
+          referencedCells.value = [];
+        } else {
+          miniEditorType.value = "string";
+          miniEditorValue.value = String(value);
+          miniEditorFormula.value = "";
+          miniEditorFormat.value = "";
+          referencedCells.value = [];
+        }
+      } else {
+        // Legacy format or plain value
+        miniEditorType.value = "string";
+        miniEditorValue.value = plainCellText(cellValue);
+        miniEditorFormula.value = "";
+        miniEditorFormat.value = "";
+        referencedCells.value = [];
+      }
+
+      miniEditorCell.value = { row: rowIndex, col: colIndex };
+      miniEditorOpen.value = true;
+    } catch (error) {
+      console.error("Failed to open mini editor:", error);
+    }
+  }
+
+  // A bare value as the editor shows it. An object without `v` (`{}`, `{ f }`)
+  // holds no value, so it reads as empty rather than "[object Object]".
+
+  function closeMiniEditor() {
+    miniEditorOpen.value = false;
+    miniEditorCell.value = null;
+    miniEditorValue.value = null;
+    miniEditorFormula.value = "";
+    miniEditorFormat.value = "";
+    referencedCells.value = [];
+  }
+
+  function saveMiniEditor() {
+    if (!miniEditorCell.value) return;
+
+    try {
+      const sheets = JSON.parse(editableData.value);
+      const currentSheet = sheets[activeSheetIndex.value];
+
+      if (!currentSheet || !currentSheet.data) return;
+
+      const { row, col } = miniEditorCell.value;
+
+      // Normalize the data in case it's malformed
+      const normalizedData = normalizeSheetData(currentSheet.data);
+
+      // Ensure the row exists
+      while (normalizedData.length <= row) {
+        normalizedData.push([]);
+      }
+
+      // Ensure the row is an array
+      if (!Array.isArray(normalizedData[row])) {
+        normalizedData[row] = [];
+      }
+
+      // Build the new cell value (delegates formula/number detection
+      // and format attachment to the pure helper).
+      const newCellValue: SpreadsheetCell = buildCellFromInput({
+        type: miniEditorType.value,
+        value: miniEditorValue.value,
+        formula: miniEditorFormula.value,
+        format: miniEditorFormat.value,
+      });
+
+      // Update the cell in normalized data
+      normalizedData[row][col] = newCellValue;
+
+      // Update the sheet with normalized data
+      currentSheet.data = normalizedData;
+
+      // Update editableData
+      editableData.value = JSON.stringify(sheets, null, 2);
+
+      // Persist to disk (if file-backed) and emit update
+      void persistSheets(sheets);
+
+      // Update referenced cells if the saved cell contains a formula
+      if (typeof newCellValue.v === "string" && newCellValue.v.startsWith("=")) {
+        referencedCells.value = extractCellReferences(newCellValue.v);
+      } else {
+        referencedCells.value = [];
+      }
+
+      // Don't close the mini editor - keep it open so user can see the updated references
+    } catch (error) {
+      alert(`Failed to save cell: ${formatErrorMessage(error, "Unknown error")}`);
+    }
+  }
+
+  function handleKeyboardNavigation(event: KeyboardEvent) {
+    if (!miniEditorOpen.value || !miniEditorCell.value) return;
+    if (isEditableTarget(event.target)) return;
+
+    const { row, col } = miniEditorCell.value;
+    const next = getArrowKeyOffset(event.key, row, col);
+    if (!next) return;
+
+    try {
+      const sheets = JSON.parse(editableData.value);
+      if (!isWithinSheetBounds(sheets[activeSheetIndex.value], next.row, next.col)) return;
+      event.preventDefault();
+      openMiniEditor(next.row, next.col);
+    } catch (error) {
+      console.error("Failed to navigate cells:", error);
+    }
+  }
+
+  return {
+    miniEditorOpen,
+    miniEditorCell,
+    miniEditorValue,
+    miniEditorType,
+    miniEditorFormula,
+    miniEditorFormat,
+    referencedCells,
+    openMiniEditor,
+    closeMiniEditor,
+    saveMiniEditor,
+    handleKeyboardNavigation,
+  };
+}
diff --git a/src/vue/useRenderedTable.ts b/src/vue/useRenderedTable.ts
new file mode 100644
index 0000000..f13703b
--- /dev/null
+++ b/src/vue/useRenderedTable.ts
@@ -0,0 +1,82 @@
+// The active sheet calculated and rendered as the HTML table the View shows.
+
+import { computed, type Ref } from "vue";
+import * as XLSX from "xlsx";
+import type { SpreadsheetSheet, StorableCell } from "../core/types";
+import { SpreadsheetEngine, prefersDayFirst, normalizeData, type SheetData, type CellValue } from "../engine";
+import { errorMessage as formatErrorMessage } from "../engine/guards";
+import { calculateWith } from "../engine/customFunctions";
+import { escapeHtml } from "./htmlText";
+import type { useCustomFunctions } from "./useCustomFunctions";
+
+// `normalizeData` is the engine's own reader for the stored cell forms (bare
+// values, `null` gaps, flat rows); `calculate` runs it internally anyway, so
+// applying it here only meets the engine's declared type at the call site.
+const toEngineSheet = (sheet: SpreadsheetSheet): SheetData => ({ name: sheet.name, data: normalizeData(sheet.data) });
+
+/** What the table is rendered from. */
+export interface RenderedTableSources {
+  resolvedSheets: Ref<SpreadsheetSheet[]>;
+  activeSheetIndex: Ref<number>;
+  customFunctions: ReturnType<typeof useCustomFunctions>;
+  locale: Ref<string>;
+}
+
+export function useRenderedTable({ resolvedSheets, activeSheetIndex, customFunctions, locale }: RenderedTableSources) {
+  // Create spreadsheet engine instance
+  const engine = new SpreadsheetEngine();
+
+  // Calculate formulas in the data using the spreadsheet engine
+  const calculateFormulas = (data: StorableCell[][], sheetName?: string): CellValue[][] => {
+    // If we have a sheet name, we need to find all sheets for cross-sheet references
+    const allSheets = resolvedSheets.value.map(toEngineSheet);
+
+    // Create a SheetData object for the engine
+    const sheet: SheetData = {
+      name: sheetName || "Sheet1",
+      data: normalizeData(data),
+    };
+
+    // Read the date order from the current locale on every calculation, so a
+    // locale switch takes effect without rebuilding the engine.
+    engine.setOptions({ preferDDMMYYYY: prefersDayFirst(locale.value) });
+    const result = calculateWith(customFunctions.value, () => engine.calculate(sheet, allSheets));
+
+    return result.data;
+  };
+
+  // Render the active sheet as HTML table
+  const renderedHtml = computed(() => {
+    if (!resolvedSheets.value || resolvedSheets.value.length === 0) {
+      return "";
+    }
+
+    const sheet = resolvedSheets.value[activeSheetIndex.value];
+    if (!sheet || !sheet.data) {
+      return "";
+    }
+
+    try {
+      // Calculate formulas first with sheet name for cross-sheet references
+      const calculatedData = calculateFormulas(sheet.data, sheet.name);
+
+      // Convert data array to worksheet
+      const worksheet = XLSX.utils.aoa_to_sheet(calculatedData);
+
+      // Generate HTML table
+      const html = XLSX.utils.sheet_to_html(worksheet, {
+        id: "spreadsheet-table",
+        editable: false,
+      });
+
+      return html;
+    } catch (error) {
+      console.error("Failed to render spreadsheet:", error);
+      // Fed into v-html, and a caught throw can carry an object whose
+      // `details` / `message` formatErrorMessage surfaces verbatim.
+      return `<div class="error">Failed to render spreadsheet: ${escapeHtml(formatErrorMessage(error, "Unknown error"))}</div>`;
+    }
+  });
+
+  return renderedHtml;
+}