diff --git a/frontend/src/lib/components/HandwriteCanvas.svelte b/frontend/src/lib/components/HandwriteCanvas.svelte
index f6ee202..43e2f0f 100644
--- a/frontend/src/lib/components/HandwriteCanvas.svelte
+++ b/frontend/src/lib/components/HandwriteCanvas.svelte
@@ -61,6 +61,12 @@
   let cssWidth = $state(800);
   let cssHeight = $state(600);
 
+  // 완료된 stroke 들을 캐싱하는 offscreen buffer. iPad 성능 핵심 — 매 frame 마다 모든
+  // stroke 의 perfect-freehand 재계산이 main thread 블록 → pointer event 누락.
+  // strokes 배열 변경 시만 rebuild, 매 frame redraw 는 drawImage + inflight 만.
+  let buffer: HTMLCanvasElement | null = null;
+  let bufferDirty = true;
+
   let strokes = $state<Stroke[]>(initialStrokes?.strokes ?? []);
   let undoStack = $state<Stroke[]>([]); // redo 큐 (clear 또는 undo 로 빠진 stroke)
   let inflight: Stroke | null = $state(null);
@@ -97,7 +103,7 @@
       if (!raw) return;
       const parsed = JSON.parse(raw) as StrokesJson;
       if ((initialStrokes?.strokes?.length ?? 0) === 0 && parsed.strokes.length > 0) {
-        strokes = parsed.strokes;
+        setStrokes(parsed.strokes);
         scheduleSave();
       }
     } catch {
@@ -118,6 +124,11 @@
     canvas.style.height = `${cssHeight}px`;
     const ctx = canvas.getContext('2d');
     if (ctx) ctx.setTransform(dpr, 0, 0, dpr, 0, 0);
+    // buffer 도 같은 internal 크기. transform 은 rebuildBuffer 안에서 별도 적용.
+    if (!buffer) buffer = document.createElement('canvas');
+    buffer.width = canvas.width;
+    buffer.height = canvas.height;
+    bufferDirty = true;
     scheduleRedraw();
   }
 
@@ -177,18 +188,44 @@
     ctx.restore();
   }
 
+  // strokes 배열을 변경할 때 항상 사용 (buffer rebuild 마킹 + 자동 저장 트리거).
+  function setStrokes(next: Stroke[]) {
+    strokes = next;
+    bufferDirty = true;
+  }
+
+  // 완료 stroke 들을 buffer canvas 에 한 번만 그림. strokes 변경 시만 호출.
+  function rebuildBuffer() {
+    if (!canvas || !buffer) return;
+    const bctx = buffer.getContext('2d');
+    if (!bctx) return;
+    const dpr = window.devicePixelRatio || 1;
+    bctx.setTransform(dpr, 0, 0, dpr, 0, 0);
+    bctx.clearRect(0, 0, cssWidth, cssHeight);
+    drawTraceBackground(bctx);
+    for (const s of strokes) {
+      drawStroke(bctx, s);
+    }
+    bufferDirty = false;
+  }
+
   function redraw() {
     if (!canvas) return;
     const ctx = canvas.getContext('2d');
     if (!ctx) return;
+    if (bufferDirty) rebuildBuffer();
+
     ctx.clearRect(0, 0, cssWidth, cssHeight);
-    drawTraceBackground(ctx);
-    for (const s of strokes) {
-      drawStroke(ctx, s);
-    }
-    if (inflight) {
-      drawStroke(ctx, inflight);
+    if (buffer) {
+      // buffer 는 internal pixel (cssWidth*dpr) 크기, canvas 도 같은 크기.
+      // 현재 ctx 는 setTransform(dpr,...) 으로 1 unit = 1 css px 좌표계.
+      // drawImage 의 dst (0, 0, cssWidth, cssHeight) 에 그리면 정확히 매핑됨.
+      ctx.drawImage(buffer, 0, 0, cssWidth, cssHeight);
+    } else {
+      drawTraceBackground(ctx);
+      for (const s of strokes) drawStroke(ctx, s);
     }
+    if (inflight) drawStroke(ctx, inflight);
   }
 
   // RAF throttle — pointermove 가 60Hz 보다 빠르게 들어와도 redraw 는 frame 당 1회.
@@ -253,7 +290,7 @@
       (hit ? removed : keep).push(s);
     }
     if (removed.length === 0) return false;
-    strokes = keep;
+    setStrokes(keep);
     undoStack = [...undoStack, ...removed];
     return true;
   }
@@ -266,7 +303,7 @@
     // 이전 stroke 의 inflight 가 어떤 이유로 살아있다면 강제 finalize (race 방어).
     if (inflight) {
       if (inflight.points.length > 1) {
-        strokes = [...strokes, inflight];
+        setStrokes([...strokes, inflight]);
         isDirty = true;
         backupToLocalStorage();
       }
@@ -344,7 +381,7 @@
     }
 
     if (inflight.points.length > 1) {
-      strokes = [...strokes, inflight];
+      setStrokes([...strokes, inflight]);
       undoStack = [];
       isDirty = true;
       backupToLocalStorage();
@@ -358,7 +395,7 @@
   function undo() {
     if (strokes.length === 0) return;
     const last = strokes[strokes.length - 1];
-    strokes = strokes.slice(0, -1);
+    setStrokes(strokes.slice(0, -1));
     undoStack = [...undoStack, last];
     isDirty = true;
     backupToLocalStorage();
@@ -369,7 +406,7 @@
     if (undoStack.length === 0) return;
     const last = undoStack[undoStack.length - 1];
     undoStack = undoStack.slice(0, -1);
-    strokes = [...strokes, last];
+    setStrokes([...strokes, last]);
     isDirty = true;
     backupToLocalStorage();
     scheduleSave();
@@ -379,7 +416,7 @@
     if (strokes.length === 0) return;
     if (!confirm('이 세션의 모든 stroke 를 지웁니다. 계속할까요?')) return;
     undoStack = [...undoStack, ...strokes];
-    strokes = [];
+    setStrokes([]);
     isDirty = true;
     backupToLocalStorage();
     scheduleSave();
diff --git a/frontend/src/routes/study/write/[id]/+page.svelte b/frontend/src/routes/study/write/[id]/+page.svelte
index f723fda..952962d 100644
--- a/frontend/src/routes/study/write/[id]/+page.svelte
+++ b/frontend/src/routes/study/write/[id]/+page.svelte
@@ -36,17 +36,19 @@
     }
   }
 
-  // iOS Safari 핀치/zoom gesture 차단 — document level 등록 (element-level
-  // ongesturestart 가 일부 iPad Safari 빌드에서 미발화하는 케이스 방어).
-  // 페이지 unmount 시 onDestroy 에서 cleanup.
+  // 페이지 줌 차단 — iOS Safari + 데스크톱 Chrome/Firefox 모두 커버:
+  //   1) gesturestart/change/end (Safari) — iOS / macOS Safari 핀치줌
+  //   2) touchstart/touchmove with > 1 fingers — iOS Safari multi-touch zoom
+  //   3) wheel with ctrlKey/metaKey — Chrome/Firefox 데스크톱 trackpad pinch
+  //      (macOS trackpad 핀치는 wheel + ctrlKey 로 dispatch)
   function blockGesture(e) { e.preventDefault(); }
-  // 추가: touchstart 가 두 손가락이면 preventDefault — 일부 Safari 빌드에서
-  // gesture 이벤트 미발화 시에도 핀치 제스처 자체를 차단.
   function blockMultiTouch(e) {
     if (e.touches && e.touches.length > 1) e.preventDefault();
   }
-  // 추가: button 클릭 직전의 자동 zoom (focus zoom) 차단 — pointerdown 에서
-  // 즉시 blur 처리해 입력 포커스 유발 zoom 발생 안 하도록.
+  function blockPinchWheel(e) {
+    // Mac trackpad 핀치 = wheel event + ctrlKey synthesized. 페이지 줌 차단.
+    if (e.ctrlKey || e.metaKey) e.preventDefault();
+  }
 
   // 모든 button 공통 inline style — 더블탭 줌 / long-press 메뉴 / 텍스트 선택 차단.
   const BTN_STYLE =
@@ -60,6 +62,8 @@
     document.addEventListener('gestureend', blockGesture, { passive: false });
     document.addEventListener('touchstart', blockMultiTouch, { passive: false });
     document.addEventListener('touchmove', blockMultiTouch, { passive: false });
+    // wheel 은 페이지 단위 (target=window) 가 아니라 document — passive: false 필수.
+    document.addEventListener('wheel', blockPinchWheel, { passive: false });
   });
   onDestroy(() => {
     if (typeof document !== 'undefined') {
@@ -68,6 +72,7 @@
       document.removeEventListener('gestureend', blockGesture);
       document.removeEventListener('touchstart', blockMultiTouch);
       document.removeEventListener('touchmove', blockMultiTouch);
+      document.removeEventListener('wheel', blockPinchWheel);
     }
   });