diff --git a/A00_Common/spreadsheet/spreadsheet_grid.ts b/A00_Common/spreadsheet/spreadsheet_grid.ts
index 3dc806f1..7118a752 100644
--- a/A00_Common/spreadsheet/spreadsheet_grid.ts
+++ b/A00_Common/spreadsheet/spreadsheet_grid.ts
@@ -39,11 +39,13 @@ import { formatValue } from "./spreadsheet_numfmt";
 import { MAX_COLS, MAX_ROWS } from "./spreadsheet_types";
 import type {
   CellRange,
+  CellStyle,
   ErrorValue,
   HAlign,
   Scalar,
   Sheet,
   SheetCellAddress,
+  Workbook,
 } from "./spreadsheet_types";
 import type {
   CellBox,
@@ -133,6 +135,25 @@ function buildMergeMap(sheet: Sheet): Map<string, CellRange> {
 }
 
 /** 확대 · 축소 — 밑감(1 배) 자리 재기를 그대로 두고 픽셀만 곱함(수는 그대로 · 화면만 커짐). */
+let measureRuler: CanvasRenderingContext2D | null = null;
+
+/** 글 너비(px) — 칸 재기용(수가 칸 폭보다 길면 `#####`). */
+function measureText(text: string, font: string): number {
+  measureRuler ??= document.createElement("canvas").getContext("2d");
+  if (!measureRuler) return text.length * 7;
+  measureRuler.font = font;
+  return measureRuler.measureText(text).width;
+}
+
+/** 칸 글꼴 CSS 글(캔버스 재기용) — `applyCellStyle` 이 칸에 입히는 글꼴과 같은 차례로 고름. */
+function cellFont(style: CellStyle, book: Workbook, scale: number): string {
+  const family = style.글꼴 || book.기본?.글꼴 || "굴림";
+  const size = (style.크기 ?? book.기본?.크기 ?? 10) * scale;
+  const weight = style.굵게 ? "700" : "400";
+  const italic = style.기울임 ? "italic " : "";
+  return `${italic}${weight} ${size}pt ${family}`;
+}
+
 function scaledGeometry(base: LineGeometry, factor: number): LineGeometry {
   if (factor === 1) return base;
   return {
@@ -148,6 +169,7 @@ interface CellDisplay {
   hAlign: HAlign;
   title: string;
   isError: boolean;
+  isNumeric: boolean;
   color?: string;
 }
 
@@ -181,7 +203,9 @@ function cellDisplay(
   const isError = typeof scalar === "object" && scalar !== null && "error" in scalar;
   const hAlign: HAlign = hAlign0 !== "general" ? hAlign0 : formatted.정렬;
   const title = isError ? ((scalar as ErrorValue).why ?? formatted.글) : "";
-  return { text: formatted.글, hAlign, title, isError, color: formatted.색 };
+  const isNumeric =
+    !isError && scalar !== null && typeof scalar !== "string" && typeof scalar !== "boolean";
+  return { text: formatted.글, hAlign, title, isError, isNumeric, color: formatted.색 };
 }
 
 export function createGrid(ctx: SpreadsheetContext): GridHandle {
@@ -304,7 +328,7 @@ export function createGrid(ctx: SpreadsheetContext): GridHandle {
     paneBR.style.top = `${headRowH() + frozenH}px`;
     paneBR.style.width = `${Math.max(0, w - headColW() - frozenW)}px`;
     paneBR.style.height = `${Math.max(0, h - headRowH() - frozenH)}px`;
-    spacer.style.transform = `translate(${colGeo.total(extent.cols) - frozenW}px, ${rowGeo.total(extent.rows) - frozenH}px)`;
+    resizeSpacer();
     overlay.style.left = `${headColW()}px`;
     overlay.style.top = `${headRowH()}px`;
     overlay.style.right = "0";
@@ -313,7 +337,45 @@ export function createGrid(ctx: SpreadsheetContext): GridHandle {
   }
 
   /** `br` 스크롤 위치 → 세 판(머리 둘 · tr · bl)에 옮겨 그리고 보이는 칸을 다시. */
+  function resizeSpacer(): void {
+    spacer.style.transform = `translate(${colGeo.total(extent.cols) - frozenW}px, ${rowGeo.total(extent.rows) - frozenH}px)`;
+  }
+
+  /** 이름 상자 · Ctrl+방향키 등으로 간 칸이 지금 스크롤 영역 밖이면 그만큼 늘림(엑셀처럼 · 빈 시트도 안 막힘). */
+  function ensureExtent(r: number, c: number): void {
+    let grown = false;
+    if (r >= extent.rows - 1) {
+      extent.rows = Math.min(MAX_ROWS, r + 100);
+      grown = true;
+    }
+    if (c >= extent.cols - 1) {
+      extent.cols = Math.min(MAX_COLS, c + 20);
+      grown = true;
+    }
+    if (grown) resizeSpacer();
+  }
+
+  /** 스크롤이 끝 가까이 닿으면 미리 늘림(휠 · 스크롤바로 끝까지 밀 때도 안 막힘). */
+  function growOnScrollEdge(): void {
+    const edge = 100;
+    if (
+      extent.rows < MAX_ROWS &&
+      paneBR.scrollTop + paneBR.clientHeight >= paneBR.scrollHeight - edge
+    ) {
+      extent.rows = Math.min(MAX_ROWS, extent.rows + 100);
+      resizeSpacer();
+    }
+    if (
+      extent.cols < MAX_COLS &&
+      paneBR.scrollLeft + paneBR.clientWidth >= paneBR.scrollWidth - edge
+    ) {
+      extent.cols = Math.min(MAX_COLS, extent.cols + 20);
+      resizeSpacer();
+    }
+  }
+
   function onScroll(): void {
+    growOnScrollEdge();
     const left = paneBR.scrollLeft;
     const top = paneBR.scrollTop;
     colHeadInnerScroll.style.transform = `translateX(${-left}px)`;
@@ -399,7 +461,17 @@ export function createGrid(ctx: SpreadsheetContext): GridHandle {
         // 조건부 서식 글자색이 이기고(엑셀과 같음) · 없으면 숫자 형식([Red] 등)이 정한 색.
         if (display.color && !condStyle?.글자색) cellEl.style.color = display.color;
         const comment = sheet.comments?.[addr];
-        setCellText(cellEl, display.text, display.title || comment || undefined);
+        // 수는 칸 폭보다 길면 `#####`(엑셀과 같음) · 글은 지금처럼 줄임표.
+        let text = display.text;
+        if (display.isNumeric && !style.줄바꿈) {
+          const font = cellFont(style, book, zoom);
+          const avail = w - 4;
+          if (measureText(text, font) > avail) {
+            const hashW = measureText("#", font) || 1;
+            text = "#".repeat(Math.max(1, Math.floor(avail / hashW)));
+          }
+        }
+        setCellText(cellEl, text, display.title || comment || undefined);
         cellEl.classList.toggle("is-error", display.isError);
         cellEl.classList.toggle("has-comment", !!comment);
         cellEl.classList.toggle(
@@ -576,7 +648,7 @@ export function createGrid(ctx: SpreadsheetContext): GridHandle {
     const h = root.clientHeight;
     const scrollW = Math.max(0, w - headColW() - frozenW);
     const scrollH = Math.max(0, h - headRowH() - frozenH);
-    const frozenColsVisible = visibleIndices(colGeo, 0, Math.max(0, frozenCols - 1));
+    const frozenColsVisible = visibleIndices(colGeo, 0, frozenCols - 1);
     const scrollColFrom = Math.max(frozenCols, colGeo.indexAt(paneBR.scrollLeft));
     const scrollColTo = Math.min(extent.cols - 1, colGeo.indexAt(paneBR.scrollLeft + scrollW) + 1);
     const scrollColsVisible = visibleIndices(
@@ -584,7 +656,7 @@ export function createGrid(ctx: SpreadsheetContext): GridHandle {
       scrollColFrom,
       Math.max(scrollColFrom, scrollColTo),
     );
-    const frozenRowsVisible = visibleIndices(rowGeo, 0, Math.max(0, frozenRows - 1));
+    const frozenRowsVisible = visibleIndices(rowGeo, 0, frozenRows - 1);
     const scrollRowFrom = Math.max(frozenRows, rowGeo.indexAt(paneBR.scrollTop));
     const scrollRowTo = Math.min(extent.rows - 1, rowGeo.indexAt(paneBR.scrollTop + scrollH) + 1);
     const scrollRowsVisible = visibleIndices(
@@ -820,6 +892,7 @@ export function createGrid(ctx: SpreadsheetContext): GridHandle {
   }
 
   function reveal(r: number, c: number): void {
+    ensureExtent(r, c);
     if (r >= frozenRows) {
       const y0 = rowGeo.offset(r) - rowGeo.offset(frozenRows);
       const y1 = y0 + rowGeo.size(r);
diff --git a/A00_Common/spreadsheet/spreadsheet_headers.ts b/A00_Common/spreadsheet/spreadsheet_headers.ts
index 50e4cc0b..1d62e1a5 100644
--- a/A00_Common/spreadsheet/spreadsheet_headers.ts
+++ b/A00_Common/spreadsheet/spreadsheet_headers.ts
@@ -16,8 +16,11 @@ export const DEFAULT_ROW_PT = 15;
 const CHAR_PX = 7;
 const CHAR_PAD_PX = 5;
 const PT_PX = 4 / 3;
+/** 엑셀 열 폭 상한(글자 단위) — 이 위로 재는 값이 들어와도 격자는 여기서 막음(자동 맞춤 폭주 방어). */
+export const MAX_COL_CHARS = 255;
 
-export const colCharsToPx = (chars: number): number => Math.round(chars * CHAR_PX + CHAR_PAD_PX);
+export const colCharsToPx = (chars: number): number =>
+  Math.round(Math.min(chars, MAX_COL_CHARS) * CHAR_PX + CHAR_PAD_PX);
 export const pxToColChars = (px: number): number => Math.max(0, (px - CHAR_PAD_PX) / CHAR_PX);
 export const ptToPx = (pt: number): number => Math.round(pt * PT_PX);
 export const pxToPt = (px: number): number => px / PT_PX;